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Asthma

Asthma

Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation causing symptoms and structural changes. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship typically present with wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing, cough, and dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea. Diagnosis is confirmed with a pulmonary function test Pulmonary function test Pulmonary function tests are a group of diagnostic procedures yielding useful, quantifiable information about the rate of the flow of air through the individual's airways, lung capacity, and the efficiency of gas exchange in relation to time. The most commonly utilized tests include spirometry (before and after bronchodilator use), lung volumes, and quantitation of diffusing capacity for carbon monoxide (CO). The tests can be influenced by the individual's effort/fatigue, disease state, or anatomical malformation. Pulmonary Function Tests showing a reversible obstructive pattern. Treatment, based on symptom severity, includes bronchodilators Bronchodilators Asthma Drugs and inhaled corticosteroids Corticosteroids Chorioretinitis for control of inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation. Biologic agents Biologic Agents Immunosuppressants targeting inflammatory mediators have been developed for severe persistent asthma Persistent Asthma Asthma in Children.

Last updated: 1 Apr, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Contents

Definition and Epidemiology

Definition

Asthma is a chronic inflammatory disorder of the airways:

  • Involving many cells and cellular elements ( mast cells Mast cells Granulated cells that are found in almost all tissues, most abundantly in the skin and the gastrointestinal tract. Like the basophils, mast cells contain large amounts of histamine and heparin. Unlike basophils, mast cells normally remain in the tissues and do not circulate in the blood. Mast cells, derived from the bone marrow stem cells, are regulated by the stem cell factor. Innate Immunity: Phagocytes and Antigen Presentation, eosinophils Eosinophils Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin. Innate Immunity: Phagocytes and Antigen Presentation, neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation, T lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology, macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation, and epithelial cells) 
  • Characterized by recurrent episodes of coughing, wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing, breathlessness, and chest tightness 
  • Associated with episodic airflow obstruction, which is often reversible (spontaneously or with treatment)

Epidemiology

  • Affects approximately 8% of the population in the United States
  • Most common chronic disease of childhood with peak presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor at 3 years of age
  • Male-to-female ratio is 2:1 in childhood but this reverses in late adulthood.
  • Some cases of childhood asthma resolve in adolescence, but in those with severe asthma, the condition returns by adulthood.

Etiology

Predisposing factors for asthma

  • Host risk factors:
    • Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics
      • Studies of families show heritability of asthma.
      • Multiple genes Genes A category of nucleic acid sequences that function as units of heredity and which code for the basic instructions for the development, reproduction, and maintenance of organisms. DNA Types and Structure and environmental influence complicate genetic studies.
    • Atopy Atopy Atopic Dermatitis (Eczema)
      • Genetic predisposition to produce immunoglobulin E ( IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions) antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions on allergen exposure Exposure ABCDE Assessment
      • Strong risk factor for asthma
    • Perinatal factors (increased asthma risk)
    • Sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria
      • Asthma is more common in boys before puberty Puberty Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11-19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Puberty. 
      • 1:1 ratio in adulthood, with women affected more by age 40
      • Unclear if sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types are linked to development of asthma
    • Obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity: ↑ risk of asthma 
  • Maternal factors
    • Decreased risk of asthma:
      • Increasing maternal age at delivery (> 30 years)
      • Breastfeeding Breastfeeding Breastfeeding is often the primary source of nutrition for the newborn. During pregnancy, hormonal stimulation causes the number and size of mammary glands in the breast to significantly increase. After delivery, prolactin stimulates milk production, while oxytocin stimulates milk expulsion through the lactiferous ducts, where it is sucked out through the nipple by the infant. Breastfeeding: ↓ wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing in the first 2 years of life
    • Increased risk of asthma:
      • Maternal diet: low in vitamin D Vitamin D A vitamin that includes both cholecalciferols and ergocalciferols, which have the common effect of preventing or curing rickets in animals. It can also be viewed as a hormone since it can be formed in skin by action of ultraviolet rays upon the precursors, 7-dehydrocholesterol and ergosterol, and acts on vitamin D receptors to regulate calcium in opposition to parathyroid hormone. Fat-soluble Vitamins and their Deficiencies and omega-3 polyunsaturated fatty acid
      • Poorly controlled maternal asthma
      • Prenatal exposure Exposure ABCDE Assessment to maternal smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases
  • Environmental factors
    • Respiratory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease early in life: 
      • 40% have asthma/ wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing later in life.
      • Commonly from respiratory syncytial virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology, human rhinovirus Rhinovirus Rhinovirus is an acid-labile, positive-sense RNA virus of the Picornavirus family. The virus, which causes the common cold, is most often acquired through the airway via the inhalation of aerosols containing rhinovirus and fomites. Rhinovirus
    • Pollution: living close to a major road and ↑ nitrogen Nitrogen An element with the atomic symbol n, atomic number 7, and atomic weight [14. 00643; 14. 00728]. Nitrogen exists as a diatomic gas and makes up about 78% of the earth’s atmosphere by volume. It is a constituent of proteins and nucleic acids and found in all living cells. Urea Cycle dioxide → ↑ asthma 
    • Smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases (including secondhand smoke)
    • Occupational exposure Exposure ABCDE Assessment (fires, pesticides, industrial agents) 
    • Allergens ( fungi Fungi A kingdom of eukaryotic, heterotrophic organisms that live parasitically as saprobes, including mushrooms; yeasts; smuts, molds, etc. They reproduce either sexually or asexually, and have life cycles that range from simple to complex. Filamentous fungi, commonly known as molds, refer to those that grow as multicellular colonies. Mycology, dust mite, cockroach allergen)
    • Early exposure Exposure ABCDE Assessment to pet PET An imaging technique that combines a positron-emission tomography (PET) scanner and a ct X ray scanner. This establishes a precise anatomic localization in the same session. Nuclear Imaging allergens: 
      • Varied results
      • Protects by decreasing sensitization to pet PET An imaging technique that combines a positron-emission tomography (PET) scanner and a ct X ray scanner. This establishes a precise anatomic localization in the same session. Nuclear Imaging allergens
      • In some, asthma develops, possibly influenced by other exposures (tobacco, pollution).

Asthma triggers Asthma Triggers Asthma in Children

In established asthma, different triggers Triggers Hereditary Angioedema (C1 Esterase Inhibitor Deficiency) may exacerbate the symptoms. These include the following:

  • Environmental and drug-induced:
    • Allergens
    • Cold air
    • Paints and fumes
    • Irritant gasses
    • Air pollution
    • Drugs (beta blockers and aspirin Aspirin The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. Nonsteroidal Antiinflammatory Drugs (NSAIDs))
  • Endocrine:
    • Premenstrual hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types
    • Thyrotoxicosis Thyrotoxicosis A hypermetabolic syndrome caused by excess thyroid hormones which may come from endogenous or exogenous sources. The endogenous source of hormone may be thyroid hyperplasia; thyroid neoplasms; or hormone-producing extrathyroidal tissue. Thyrotoxicosis is characterized by nervousness; tachycardia; fatigue; weight loss; heat intolerance; and excessive sweating. Thyrotoxicosis and Hyperthyroidism
    • Hypothyroidism Hypothyroidism Hypothyroidism is a condition characterized by a deficiency of thyroid hormones. Iodine deficiency is the most common cause worldwide, but Hashimoto’s disease (autoimmune thyroiditis) is the leading cause in non-iodine-deficient regions. Hypothyroidism
  • Behavioral and psychological:
    • Exercise
    • Hyperventilation Hyperventilation A pulmonary ventilation rate faster than is metabolically necessary for the exchange of gases. It is the result of an increased frequency of breathing, an increased tidal volume, or a combination of both. It causes an excess intake of oxygen and the blowing off of carbon dioxide. Respiratory Alkalosis
    • Stress
  • Other triggers Triggers Hereditary Angioedema (C1 Esterase Inhibitor Deficiency):
    • Upper respiratory tract infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
    • Gastroesophageal reflux

Pathophysiology

Predominant inflammatory response

  • Initial exposure Exposure ABCDE Assessment to antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination:
    • Prompts naive T-cell differentiation to T helper (Th) 2 cells
    • Followed by production of IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions, which bind BIND Hyperbilirubinemia of the Newborn to mast cells Mast cells Granulated cells that are found in almost all tissues, most abundantly in the skin and the gastrointestinal tract. Like the basophils, mast cells contain large amounts of histamine and heparin. Unlike basophils, mast cells normally remain in the tissues and do not circulate in the blood. Mast cells, derived from the bone marrow stem cells, are regulated by the stem cell factor. Innate Immunity: Phagocytes and Antigen Presentation and basophils Basophils Granular leukocytes characterized by a relatively pale-staining, lobate nucleus and cytoplasm containing coarse dark-staining granules of variable size and stainable by basic dyes. Innate Immunity: Phagocytes and Antigen Presentation (ready to respond on antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination rechallenge)
  • Early phase: inhaled antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination (presented by dendritic cells Dendritic cells Specialized cells of the hematopoietic system that have branch-like extensions. They are found throughout the lymphatic system, and in non-lymphoid tissues such as skin and the epithelia of the intestinal, respiratory, and reproductive tracts. They trap and process antigens, and present them to T-cells, thereby stimulating cell-mediated immunity. They are different from the non-hematopoietic follicular dendritic cells, which have a similar morphology and immune system function, but with respect to humoral immunity (antibody production). Skin: Structure and Functions): IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions-bound mast cells Mast cells Granulated cells that are found in almost all tissues, most abundantly in the skin and the gastrointestinal tract. Like the basophils, mast cells contain large amounts of histamine and heparin. Unlike basophils, mast cells normally remain in the tissues and do not circulate in the blood. Mast cells, derived from the bone marrow stem cells, are regulated by the stem cell factor. Innate Immunity: Phagocytes and Antigen Presentation and basophils Basophils Granular leukocytes characterized by a relatively pale-staining, lobate nucleus and cytoplasm containing coarse dark-staining granules of variable size and stainable by basic dyes. Innate Immunity: Phagocytes and Antigen Presentation degranulate (early-phase reaction) → release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology of mediators (prostaglandin Dâ‚‚, histamine, leukotrienes Leukotrienes A family of biologically active compounds derived from arachidonic acid by oxidative metabolism through the 5-lipoxygenase pathway. They participate in host defense reactions and pathophysiological conditions such as immediate hypersensitivity and inflammation. They have potent actions on many essential organs and systems, including the cardiovascular, pulmonary, and central nervous system as well as the gastrointestinal tract and the immune system. Eicosanoids) → airway Airway ABCDE Assessment smooth muscle contraction Smooth muscle contraction Smooth muscle is primarily found in the walls of hollow structures and some visceral organs, including the walls of the vasculature, GI, respiratory, and genitourinary tracts. Smooth muscle contracts more slowly and is regulated differently than skeletal muscle. Smooth muscle can be stimulated by nerve impulses, hormones, metabolic factors (like pH, CO2 or O2 levels), its own intrinsic pacemaker ability, or even mechanical stretch. Smooth Muscle Contraction → airway Airway ABCDE Assessment tightening
  • Late phase Late Phase Sepsis in Children: recruitment Recruitment Skeletal Muscle Contraction of inflammatory cells:  Th2 Th2 A subset of helper-inducer T-lymphocytes which synthesize and secrete the interleukins il-4; il-5; il-6; and il-10. These cytokines influence b-cell development and antibody production as well as augmenting humoral responses. T cells: Types and Functions cells → production of mediators and cytokines Cytokines Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner. Adaptive Immune Response
    • IL-5: ↑ differentiation of eosinophils Eosinophils Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin. Innate Immunity: Phagocytes and Antigen Presentation (which migrate to the lungs Lungs Lungs are the main organs of the respiratory system. Lungs are paired viscera located in the thoracic cavity and are composed of spongy tissue. The primary function of the lungs is to oxygenate blood and eliminate CO2. Lungs: Anatomy) 
    • IL-3, IL-4, and granulocyte- macrophage colony-stimulating factor Macrophage colony-stimulating factor A mononuclear phagocyte colony-stimulating factor (M-CSF) synthesized by mesenchymal cells. The compound stimulates the survival, proliferation, and differentiation of hematopoietic cells of the monocyte-macrophage series. M-CSF is a disulfide-bonded glycoprotein dimer with a mw of 70 kda. It binds to a specific high affinity receptor. White Myeloid Cells: Histology ( GM-CSF GM-CSF An acidic glycoprotein of mw 23 kda with internal disulfide bonds. The protein is produced in response to a number of inflammatory mediators by mesenchymal cells present in the hemopoietic environment and at peripheral sites of inflammation. GM-CSF is able to stimulate the production of neutrophilic granulocytes, macrophages, and mixed granulocyte-macrophage colonies from bone marrow cells and can stimulate the formation of eosinophil colonies from fetal liver progenitor cells. GM-CSF can also stimulate some functional activities in mature granulocytes and macrophages. White Myeloid Cells: Histology) prolong eosinophil survival.
    • IL-4 also helps with T-cell differentiation and IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions production.
    • IL-13 increases mucus glands, airway Airway ABCDE Assessment fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans, and remodeling.
    • Eosinophils Eosinophils Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin. Innate Immunity: Phagocytes and Antigen Presentation (the most prominent cells) increase the release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology of inflammatory mediators.
  • Effects:
    • Cellular response → airway Airway ABCDE Assessment inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation
    • Airway Airway ABCDE Assessment smooth muscle contraction Smooth muscle contraction Smooth muscle is primarily found in the walls of hollow structures and some visceral organs, including the walls of the vasculature, GI, respiratory, and genitourinary tracts. Smooth muscle contracts more slowly and is regulated differently than skeletal muscle. Smooth muscle can be stimulated by nerve impulses, hormones, metabolic factors (like pH, CO2 or O2 levels), its own intrinsic pacemaker ability, or even mechanical stretch. Smooth Muscle Contraction and edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema, with mucus plug formation → airway Airway ABCDE Assessment obstruction
    • Increased histamine, airway Airway ABCDE Assessment smooth muscle mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast, sensitivity Sensitivity Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Blotting Techniques of neural pathways with exaggerated airway Airway ABCDE Assessment constriction → airway Airway ABCDE Assessment hyperresponsiveness
    • Structural changes (smooth muscle hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation and hypertrophy Hypertrophy General increase in bulk of a part or organ due to cell enlargement and accumulation of fluids and secretions, not due to tumor formation, nor to an increase in the number of cells (hyperplasia). Cellular Adaptation, increased extracellular matrix Extracellular matrix A meshwork-like substance found within the extracellular space and in association with the basement membrane of the cell surface. It promotes cellular proliferation and provides a supporting structure to which cells or cell lysates in culture dishes adhere. Hypertrophic and Keloid Scars) affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment reversibility of obstruction → airway Airway ABCDE Assessment remodeling

Other mechanism

  • Non-eosinophilic 
  • Does not involve Th2 Th2 A subset of helper-inducer T-lymphocytes which synthesize and secrete the interleukins il-4; il-5; il-6; and il-10. These cytokines influence b-cell development and antibody production as well as augmenting humoral responses. T cells: Types and Functions cells
  • Environmental factors (pollution, smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, allergens) → involve Th1 Th1 A subset of helper-inducer T-lymphocytes which synthesize and secrete interleukin-2; interferon-gamma; and interleukin-12. Due to their ability to kill antigen-presenting cells and their lymphokine-mediated effector activity, th1 cells are associated with vigorous delayed-type hypersensitivity reactions. T cells: Types and Functions and Th17 Th17 A subset of helper-effector T-lymphocytes which synthesize and secrete interleukins il-17; il-17f; and il-22. These cytokines are involved in host defenses and tissue inflammation in autoimmune diseases. T cells: Types and Functions cell responses → neutrophilic inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and airway Airway ABCDE Assessment hyperresponsiveness
  • Neutrophilic inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation: 

Heterogeneity of asthma

  • Asthma types based on triggers Triggers Hereditary Angioedema (C1 Esterase Inhibitor Deficiency) and etiology:
    • Allergic (atopic) or extrinsic asthma
      • Typically prevalent in childhood
      • Triggered by environmental allergens
    • Non-allergic or intrinsic asthma
  • Asthma is now believed to have more phenotypes, with a classification based on underlying pathophysiologic mechanism:
    • Th2 Th2 A subset of helper-inducer T-lymphocytes which synthesize and secrete the interleukins il-4; il-5; il-6; and il-10. These cytokines influence b-cell development and antibody production as well as augmenting humoral responses. T cells: Types and Functions–mediated (T2 high) inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation: associated with eosinophilia Eosinophilia Abnormal increase of eosinophils in the blood, tissues or organs. Autosomal Dominant Hyperimmunoglobulin E Syndrome and steroid responsiveness
    • Non- Th2 Th2 A subset of helper-inducer T-lymphocytes which synthesize and secrete the interleukins il-4; il-5; il-6; and il-10. These cytokines influence b-cell development and antibody production as well as augmenting humoral responses. T cells: Types and Functions (non-T2): no eosinophilia Eosinophilia Abnormal increase of eosinophils in the blood, tissues or organs. Autosomal Dominant Hyperimmunoglobulin E Syndrome, with sputum neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation (or normal eosinophils Eosinophils Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin. Innate Immunity: Phagocytes and Antigen Presentation and neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation) and non-response to steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors
  • Implication: Treatment options are available and under development based on pathophysiology.
Asthma attack-illustration nih

A: Lung and airway Airway ABCDE Assessment anatomy
B: Cross-section of a normal airway Airway ABCDE Assessment
C: Cross-section of an airway Airway ABCDE Assessment during asthma symptoms: constriction of airway Airway ABCDE Assessment muscles, airway Airway ABCDE Assessment inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation, and increased mucus contribute to the limited airflow

Image: “Asthma attack-illustration” by United States-National Institute of Health. License: Public Domain

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Clinical Presentation

Symptoms

  • Recurrent wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing
  • Dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea: chest tightness/heavy weight on the chest
  • Cough: 
    • Can be dry or productive of sputum
    • Worse at night and in the early morning hours
  • Episodic, can resolve spontaneously or with treatment
  • Symptoms occur with characteristic triggers Triggers Hereditary Angioedema (C1 Esterase Inhibitor Deficiency) (i.e., allergens, cold air).

Signs

  • Asymptomatic when under control
  • When symptomatic:
    • Tachypnea Tachypnea Increased respiratory rate. Pulmonary Examination, tachycardia Tachycardia Abnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia. Sepsis in Children
    • Expiratory ± inspiratory wheezing Inspiratory Wheezing Wheezing and rhonchi
    • Prolonged expiratory phase of respiration Respiration The act of breathing with the lungs, consisting of inhalation, or the taking into the lungs of the ambient air, and of exhalation, or the expelling of the modified air which contains more carbon dioxide than the air taken in. Nose and Nasal Cavity: Anatomy

Classification of asthma based on severity

Component Classification
Intermittent Persistent: mild Persistent: moderate Persistent: severe
Symptoms ≤ 2 days/week > 2 but < 7 days/week Daily Throughout the day
Short-acting bronchodilator use ≤ 2 days/week > 2 days/week Daily Several times/day
Nighttime awakenings ≤ 2/month 3–4/month ≥ 1/week Nightly
Activity limitation None Minor Some Extreme
Lung function FEV1 > 80% FEV1 > 80% FEV1 60%–80% FEV1 < 60%
FEV1: forced expiratory volume in 1 second

Diagnosis

Clinical findings

  • Recurrent episodes of airflow obstruction or airway Airway ABCDE Assessment hyperresponsiveness are present.
  • Airflow obstruction is at least partially reversible. 
  • Alternative diagnoses are excluded.

Pulmonary function tests

  • Spirometry Spirometry Measurement of volume of air inhaled or exhaled by the lung. Pulmonary Function Tests:
    • Maximal inhalation followed by rapid forceful exhalation (at least 6 seconds)
    • Measures: 
      • FEV1 (forced expiratory volume in 1 second)
      • FVC (forced vital capacity Vital capacity The volume of air that is exhaled by a maximal expiration following a maximal inspiration. Ventilation: Mechanics of Breathing or the maximal volume exhaled with maximally forced effort)
    • ↓ FEV1 and FEV1/FVC ratio < 0.70 (suggests airway Airway ABCDE Assessment obstruction)
  • Bronchodilator response:
    • Nebulized or 2–4 puffs of bronchodilator (e.g., albuterol Albuterol A short-acting beta-2 adrenergic agonist that is primarily used as a bronchodilator agent to treat asthma. Sympathomimetic Drugs) given, then spirometry Spirometry Measurement of volume of air inhaled or exhaled by the lung. Pulmonary Function Tests rechecked after 15 minutes
    • Increase in FEV1 by > 12% and 200 mL (bronchodilator responsiveness)
  • Peak expiratory flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure (PEF):
    • Maximal inhalation, then fast forceful exhalation (< 2 seconds) into peak flowmeter
    • A single peak flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure is obtained during symptoms.
    • Results compared with average normal values (based on height and age)
    • Post-bronchodilator administration, improvement of > 20% suggests reversible airway Airway ABCDE Assessment obstruction (favors diagnosis of asthma)
    • Used more for monitoring than for diagnosis
  • Bronchoprovocation testing:
    • A stimulus ( methacholine Methacholine A quaternary ammonium parasympathomimetic agent with the muscarinic actions of acetylcholine. It is used as a parasympathomimetic bronchoconstrictor agent and as a diagnostic aid for bronchial asthma. Cholinomimetic Drugs, exercise, histamine, inhaled mannitol Mannitol A diuretic and renal diagnostic aid related to sorbitol. It has little significant energy value as it is largely eliminated from the body before any metabolism can take place. It can be used to treat oliguria associated with kidney failure or other manifestations of inadequate renal function and has been used for determination of glomerular filtration rate. Mannitol is also commonly used as a research tool in cell biological studies, usually to control osmolarity. Osmotic Diuretics) is tried, to trigger Trigger The type of signal that initiates the inspiratory phase by the ventilator Invasive Mechanical Ventilation bronchoconstriction.
    • ≥ 20% reduction in FEV1 with challenge/testing ( airway Airway ABCDE Assessment hyperresponsiveness)
  • Impulse oscillometry (IOS):
    • For children < 5 years old or those who cannot perform spirometry Spirometry Measurement of volume of air inhaled or exhaled by the lung. Pulmonary Function Tests
    • Passive measurement of lung mechanics
    • Requires minimal patient cooperation, but not available to many clinicians

Exhaled nitric oxide Nitric Oxide A free radical gas produced endogenously by a variety of mammalian cells, synthesized from arginine by nitric oxide synthase. Nitric oxide is one of the endothelium-dependent relaxing factors released by the vascular endothelium and mediates vasodilation. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic guanylate cyclase and thus elevates intracellular levels of cyclic gmp. Pulmonary Hypertension Drugs

  • Nitric oxide Nitric Oxide A free radical gas produced endogenously by a variety of mammalian cells, synthesized from arginine by nitric oxide synthase. Nitric oxide is one of the endothelium-dependent relaxing factors released by the vascular endothelium and mediates vasodilation. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic guanylate cyclase and thus elevates intracellular levels of cyclic gmp. Pulmonary Hypertension Drugs measured in patient’s exhaled breath
  • Basis of test: eosinophilic airway Airway ABCDE Assessment inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation upregulates nitric oxide Nitric Oxide A free radical gas produced endogenously by a variety of mammalian cells, synthesized from arginine by nitric oxide synthase. Nitric oxide is one of the endothelium-dependent relaxing factors released by the vascular endothelium and mediates vasodilation. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic guanylate cyclase and thus elevates intracellular levels of cyclic gmp. Pulmonary Hypertension Drugs synthase → ↑ amount of fraction of exhaled nitric oxide Nitric Oxide A free radical gas produced endogenously by a variety of mammalian cells, synthesized from arginine by nitric oxide synthase. Nitric oxide is one of the endothelium-dependent relaxing factors released by the vascular endothelium and mediates vasodilation. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic guanylate cyclase and thus elevates intracellular levels of cyclic gmp. Pulmonary Hypertension Drugs (FENO)
  • FENO > 50 parts per billion: 
    • Indicates eosinophilic airway Airway ABCDE Assessment inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation 
    • Improves with inhaled corticosteroid (ICS)
  • Limitations Limitations Conflict of Interest:
    • Asthma is not always due to eosinophilic airway Airway ABCDE Assessment inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation.
    • Lower FENO: cannot exclude use of ICS (as it provides benefit even for mild asthma)
    • Affected by smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases, atopy Atopy Atopic Dermatitis (Eczema), age, and sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria

Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests

  • Excludes other diagnosis ( pneumothorax Pneumothorax A pneumothorax is a life-threatening condition in which air collects in the pleural space, causing partial or full collapse of the lung. A pneumothorax can be traumatic or spontaneous. Patients present with a sudden onset of sharp chest pain, dyspnea, and diminished breath sounds on exam. Pneumothorax or pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia in exacerbations)
  • Normal in mild asthma
  • May show hyperinflation Hyperinflation Imaging of the Lungs and Pleura in severe asthma (flattened diaphragm Diaphragm The diaphragm is a large, dome-shaped muscle that separates the thoracic cavity from the abdominal cavity. The diaphragm consists of muscle fibers and a large central tendon, which is divided into right and left parts. As the primary muscle of inspiration, the diaphragm contributes 75% of the total inspiratory muscle force. Diaphragm: Anatomy, wide intercostal spaces Intercostal spaces Chest Wall: Anatomy)
  • Indicated for atypical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor of asthma ( fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, crackles, hypoxemia Hypoxemia Neonatal Respiratory Distress Syndrome)

Additional tests

  • No blood test can confirm diagnosis of asthma.
  • Complete blood count: may show eosinophilia Eosinophilia Abnormal increase of eosinophils in the blood, tissues or organs. Autosomal Dominant Hyperimmunoglobulin E Syndrome (which suggests atopic asthma)
  • IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions level: 
    • Moderate-to-severe asthma
    • When anti- IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions monoclonal antibody treatment is considered
  • Allergy Allergy An abnormal adaptive immune response that may or may not involve antigen-specific IgE Type I Hypersensitivity Reaction tests: may determine allergic triggers Triggers Hereditary Angioedema (C1 Esterase Inhibitor Deficiency) and help provide allergen avoidance measures
  • Alpha-1 antitrypsin Alpha-1 antitrypsin Plasma glycoprotein member of the serpin superfamily which inhibits trypsin; neutrophil elastase; and other proteolytic enzymes. Alpha-1 Antitrypsin (AAT) Deficiency level: detects alpha-1 antitrypsin Alpha-1 antitrypsin Plasma glycoprotein member of the serpin superfamily which inhibits trypsin; neutrophil elastase; and other proteolytic enzymes. Alpha-1 Antitrypsin (AAT) Deficiency deficiency (for patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with persistent airway Airway ABCDE Assessment obstruction)
  • Biomarkers:
    • Sputum eosinophils Eosinophils Granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing coarse, round granules that are uniform in size and stainable by eosin. Innate Immunity: Phagocytes and Antigen Presentation: can be used as biomarker for T2-high asthma
    • Periostin: biomarker for eosinophilic inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation despite use of corticosteroids Corticosteroids Chorioretinitis
  • Sweat chloride Chloride Inorganic compounds derived from hydrochloric acid that contain the Cl- ion. Electrolytes test:
    • In children with persistent respiratory symptoms, to rule out cystic Cystic Fibrocystic Change fibrosis Fibrosis Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury. Bronchiolitis Obliterans
    • Low threshold Threshold Minimum voltage necessary to generate an action potential (an all-or-none response) Skeletal Muscle Contraction in performing test due to lifelong implications of disease
  • Arterial blood gas Arterial blood gas Respiratory Alkalosis (in severe asthma exacerbation):
    • Obtain when oxygen saturation Oxygen Saturation Basic Procedures of < 94%, no bronchodilator response, mental status change(s)
    • Initial finding(s): hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage (reduced oxygen), hypocarbia (due to hyperventilation Hyperventilation A pulmonary ventilation rate faster than is metabolically necessary for the exchange of gases. It is the result of an increased frequency of breathing, an increased tidal volume, or a combination of both. It causes an excess intake of oxygen and the blowing off of carbon dioxide. Respiratory Alkalosis), ↑ pH pH The quantitative measurement of the acidity or basicity of a solution. Acid-Base Balance
    • Respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure: hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage, hypercarbia, ↓ pH pH The quantitative measurement of the acidity or basicity of a solution. Acid-Base Balance ( respiratory acidosis Respiratory acidosis The respiratory system is responsible for eliminating the volatile acid carbon dioxide (CO2), which is produced via aerobic metabolism. In the setting of hypoventilation, this acid load is not adequately blown off, and respiratory acidosis occurs. Renal compensation occurs after 3-5 days, as the kidneys attempt to increase the serum bicarbonate levels. Respiratory Acidosis)
Asthma flow volume

Flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure-volume loop (blue line) showing an obstructive pattern of expiration Expiration Ventilation: Mechanics of Breathing, reduced peak expiratory flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure (approximately 4 L/sec), and lung hyperinflation Hyperinflation Imaging of the Lungs and Pleura (approximately 4 L at residual volume Residual volume The volume of air remaining in the lungs at the end of a maximal expiration. Common abbreviation is rv. Ventilation: Mechanics of Breathing and > 8 L after full inspiration Inspiration Ventilation: Mechanics of Breathing). A normal pattern (green line) and restrictive pattern (red line) are shown for comparison.

Image by Lecturio.

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Management

Non-pharmacologic management

  • Patient education: 
    • Asthma symptoms
    • Indications for and proper technique of bronchodilator and corticosteroid inhaler use
    • Discuss asthma action plan (PEF monitoring and corresponding action)
  • Goals: 
  • Smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases cessation
  • Update influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza and pneumococcal vaccinations.

Pharmacologic and invasive management

  • For rescue treatment of acute exacerbation:
    • Short-acting beta2-agonists (SABA): for exercise-induced asthma or asthma exacerbation
    • Long-acting beta2-agonists (LABA): low-dose inhaled corticosteroids Corticosteroids Chorioretinitis; formoterol Formoterol Asthma Drugs can be used as acute symptom reliever (Global Initiative for Asthma guidelines)
  • Controllers:
    • Inhaled corticosteroids Corticosteroids Chorioretinitis (ICS): most effective anti-inflammatory medications for asthma
    • Systemic corticosteroids Corticosteroids Chorioretinitis:
      • Short-term treatment (< 7 days) recommended
      • Tapering required if > 2 weeks 
    • Leukotriene Leukotriene Asthma Drugs receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors antagonists (LTRA) and 5-lipoxygenase inhibitor:
  • Monoclonal antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions for severe asthma:
    • Anti- IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions or IgE IgE An immunoglobulin associated with mast cells. Overexpression has been associated with allergic hypersensitivity. Immunoglobulins: Types and Functions antibody: omalizumab Omalizumab An anti-ige, recombinant, humanized monoclonal antibody which specifically binds to the c epsilon3 domain of immunoglobulin e, the site of high-affinity ige receptor binding. It inhibits the binding of ige to mast cells and basophils to reduce the severity of the allergic response and is used in the management of persistent allergic asthma. Asthma Drugs
    • IL-5 antagonist: mepolizumab Mepolizumab Asthma Drugs, reslizumab 
    • IL-5 receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors antagonist: benralizumab Benralizumab Asthma Drugs
    • Anti-IL-4 receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors antagonist: dupilumab Dupilumab Asthma Drugs 
  • Bronchial thermoplasty: 
    • Ablates bronchial smooth muscles Smooth muscles Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. Muscle Tissue: Histology through the application of heat Heat Inflammation during bronchoscopy Bronchoscopy Endoscopic examination, therapy or surgery of the bronchi. Laryngomalacia and Tracheomalacia 
    • Carries procedure-related risks; only modest improvement of asthma
    • Strict criteria for selection Selection Lymphocyte activation by a specific antigen thus triggering clonal expansion of lymphocytes already capable of mounting an immune response to the antigen. B cells: Types and Functions (including patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship who are unresponsive to maximum pharmacologic therapy)

Emergency management

Emergency management is for severe asthma exacerbation, not for responding to initial outpatient management.

  • Oxygen therapy goal: 93%–95% oxygen saturation Oxygen Saturation Basic Procedures (adults)
  • Inhaled therapy:
    • High dose of SABA via nebulizer or spacer
    • Nebulized ipratropium Ipratropium A muscarinic antagonist structurally related to atropine but often considered safer and more effective for inhalation use. It is used for various bronchial disorders, in rhinitis, and as an antiarrhythmic. Anticholinergic Drugs if no response to beta2-agonists
    • High-dose ICS given in 1st hour
  • Intravenous medication(s):
    • IV corticosteroids Corticosteroids Chorioretinitis:
      • If asthma does not improve consistently after SABA treatment
      • If exacerbation occurs despite ongoing daily oral steroid therapy 
      • If exacerbation is recurrent after recent discontinuation of systemic steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors
    • Consider IV magnesium sulfate Magnesium Sulfate A small colorless crystal used as an anticonvulsant, a cathartic, and an electrolyte replenisher in the treatment of pre-eclampsia and eclampsia. It causes direct inhibition of action potentials in myometrial muscle cells. Excitation and contraction are uncoupled, which decreases the frequency and force of contractions. Laxatives (1 dose):
  • Endotracheal intubation Intubation Peritonsillar Abscess and mechanical ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing in case of impending respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure: 
    • Mental status changes (confused, agitated, or drowsy)
    • Silent chest on auscultation
    • Respiratory fatigue Fatigue The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli. Fibromyalgia ( respiratory rate Respiratory rate The number of times an organism breathes with the lungs (respiration) per unit time, usually per minute. Pulmonary Examination > 30/min, heart rate Heart rate The number of times the heart ventricles contract per unit of time, usually per minute. Cardiac Physiology > 120/min, use of accessory muscles)
    • Respiratory acidosis Respiratory acidosis The respiratory system is responsible for eliminating the volatile acid carbon dioxide (CO2), which is produced via aerobic metabolism. In the setting of hypoventilation, this acid load is not adequately blown off, and respiratory acidosis occurs. Renal compensation occurs after 3-5 days, as the kidneys attempt to increase the serum bicarbonate levels. Respiratory Acidosis with increasing hypercapnia Hypercapnia A clinical manifestation of abnormal increase in the amount of carbon dioxide in arterial blood. Neonatal Respiratory Distress Syndrome
    • Low oxygen saturation Oxygen Saturation Basic Procedures (< 92%) despite high- flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure oxygen
  • Improved PEF > 80% and resolution of symptoms: discharge

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Asthma: Treatment

Management Guidelines

National Asthma Education and Prevention Program (NAEPP)

Table: NAEPP recommendations by classification
Intermittent Persistent: mild Persistent: moderate Persistent: severe
Controller Preferred: daily low-dose ICS Daily low-dose ICS-LABA Daily medium-dose ICS-LABA +/- LTRA, zileuton Zileuton Asthma Drugs
Alternative controllers and additional therapies Daily LTRA Daily medium-dose ICS or daily low-dose ICS + LTRA More severe symptoms: daily high-dose ICS-LABA +/- omalizumab Omalizumab An anti-ige, recombinant, humanized monoclonal antibody which specifically binds to the c epsilon3 domain of immunoglobulin e, the site of high-affinity ige receptor binding. It inhibits the binding of ige to mast cells and basophils to reduce the severity of the allergic response and is used in the management of persistent allergic asthma. Asthma Drugs +/- oral CS
Reliever SABA, as needed SABA, as needed SABA, as needed

Global Initiative for Asthma (GINA)

  • Updated 2020
  • Basis of severity: level of treatment (steps) needed to control symptoms and exacerbations
  • All patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship given ICS either daily or as needed
  • ICS- formoterol Formoterol Asthma Drugs:
    • 1st-line therapy (reliever) for adults and adolescents > 12 years of age
    • Preferred over SABAs for as-needed relief (except for age < 5 years)
Table: GINA 2019 recommendations by classification
Step 1 (< 2x a month) Step 2 (> 2x a month, not daily) Step 3 (most days) Step 4 (uncontrolled asthma)
Controller See preferred reliever Low-dose ICS- formoterol Formoterol Asthma Drugs as needed or daily low-dose ICS Daily low-dose ICS-LABA
  • Step 4: daily medium-dose ICS-LABA
  • Step 5: daily high-dose ICS-LABA
Alternative controller See alternative reliever Low-dose ICS, if SABA is taken, or daily LTRA Daily medium-dose ICS or daily low-dose ICS with LTRA
  • Daily high-dose ICS
  • More severe symptoms: Add-on tiotropium, LTRA, oral steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors, and other therapy (e.g., zileuton Zileuton Asthma Drugs, anti– Ig Ig X-linked Agammaglobulinemia-E/IL-5/IL-5R/IL-4)
Preferred reliever Low-dose ICS- formoterol Formoterol Asthma Drugs, as needed Low-dose ICS- formoterol Formoterol Asthma Drugs, as needed Low-dose ICS- formoterol Formoterol Asthma Drugs, as needed Low-dose ICS- formoterol Formoterol Asthma Drugs, as needed
Alternative reliever SABA, as needed SABA, as needed SABA, as needed SABA, as needed

Differential Diagnosis

  • Upper airway Airway ABCDE Assessment obstruction by tumor Tumor Inflammation or laryngeal edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema: causes stridor Stridor Laryngomalacia and Tracheomalacia rather than wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing. Flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure-volume loop shows a limitation in flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure in both inspiratory and expiratory curves. Bronchoscopy Bronchoscopy Endoscopic examination, therapy or surgery of the bronchi. Laryngomalacia and Tracheomalacia confirms diagnosis.
  • Foreign-body aspiration: shows localized or generalized wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing. Chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests can be normal or with unilateral hyperinflation Hyperinflation Imaging of the Lungs and Pleura or infiltrate. Bronchoscopy Bronchoscopy Endoscopic examination, therapy or surgery of the bronchi. Laryngomalacia and Tracheomalacia is diagnostic and therapeutic ( foreign body Foreign Body Foreign Body Aspiration retrieval).
  • Left ventricular failure: wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing is accompanied by crackles. History, physical examination with chest X-ray X-ray Penetrating electromagnetic radiation emitted when the inner orbital electrons of an atom are excited and release radiant energy. X-ray wavelengths range from 1 pm to 10 nm. Hard x-rays are the higher energy, shorter wavelength x-rays. Soft x-rays or grenz rays are less energetic and longer in wavelength. The short wavelength end of the x-ray spectrum overlaps the gamma rays wavelength range. The distinction between gamma rays and x-rays is based on their radiation source. Pulmonary Function Tests, echocardiogram Echocardiogram Transposition of the Great Vessels, and ECG ECG An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG) help distinguish congestive heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR).
  • Vocal cord dysfunction: presents with wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing, cough, and dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea. Spirometry Spirometry Measurement of volume of air inhaled or exhaled by the lung. Pulmonary Function Tests would show flattened inspiratory flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure loop suggestive of variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables extrathoracic obstruction. Laryngoscopy (gold standard) is recommended for diagnosis.
  • Eosinophilic granulomatosis with polyangiitis Granulomatosis with Polyangiitis A multisystemic disease of a complex genetic background. It is characterized by inflammation of the blood vessels (vasculitis) leading to damage in any number of organs. The common features include granulomatous inflammation of the respiratory tract and kidneys. Most patients have measurable autoantibodies (antineutrophil cytoplasmic antibodies) against myeloblastin. Granulomatosis with Polyangiitis: may present with cough and wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing. The condition is refractory to usual asthma treatment and has peripheral manifestations of vasculitis Vasculitis Inflammation of any one of the blood vessels, including the arteries; veins; and rest of the vasculature system in the body. Systemic Lupus Erythematosus.
  • Chronic obstructive pulmonary disease Pulmonary disease Diseases involving the respiratory system. Blastomyces/Blastomycosis ( COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD)): manifests with dyspnea Dyspnea Dyspnea is the subjective sensation of breathing discomfort. Dyspnea is a normal manifestation of heavy physical or psychological exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Dyspnea, cough, and wheezing Wheezing Wheezing is an abnormal breath sound characterized by a whistling noise that can be relatively high-pitched and shrill (more common) or coarse. Wheezing is produced by the movement of air through narrowed or compressed small (intrathoracic) airways. Wheezing. The condition has a strong association with smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases history. Pulmonary function test Pulmonary function test Pulmonary function tests are a group of diagnostic procedures yielding useful, quantifiable information about the rate of the flow of air through the individual’s airways, lung capacity, and the efficiency of gas exchange in relation to time. The most commonly utilized tests include spirometry (before and after bronchodilator use), lung volumes, and quantitation of diffusing capacity for carbon monoxide (CO). The tests can be influenced by the individual’s effort/fatigue, disease state, or anatomical malformation. Pulmonary Function Tests will show obstructive pattern without significant reversibility. Emphysema Emphysema Enlargement of air spaces distal to the terminal bronchioles where gas-exchange normally takes place. This is usually due to destruction of the alveolar wall. Pulmonary emphysema can be classified by the location and distribution of the lesions. Chronic Obstructive Pulmonary Disease (COPD), a form of COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD), also has reduced diffusing capacity of the lung for carbon monoxide Carbon monoxide Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. Carbon Monoxide Poisoning ( DLCO DLCO Pulmonary Function Tests).

References

  1. Barnes P.J. (2018). Asthma. Jameson J, & Fauci A.S., & Kasper D.L., & Hauser S.L., & Longo D.L., & Loscalzo J. (Eds.), Harrison’s Principles of Internal Medicine, 20e. McGraw-Hill. 
  2. Bell, M., Busse, W. (2015). The biology of asthma. Grippi, M., Elias, J., Fishman, J., Kotloff, R., Pack, A., Senior, R., Siegel, M. Fishman’s Pulmonary Diseases and disorders (5th Ed). McGraw-Hill.
  3. Carr, T., Zeki, A., Kraft, M. (2018). Eosinophilic and Noneosinophilic Asthma. Am J Respir Crit Care Med 197 (1): 22–37. https://www.atsjournals.org/doi/pdf/10.1164/rccm.201611-2232PP
  4. Esteban-Gorgojo, I., Antolin-Amerigo, D., Dominguez-Ortega, J., Quirce, S. (2018). Non-eosinophilic asthma: current perspectives. J Asthma Allergy. 11: 267–281. doi: 10.2147/JAA.S153097
  5. Fanta, C., Wood, R., Bochner, B., Hollingsworth, H., TePas, E. (Eds.). (2020). An overview of asthma management. UpToDate. Retrieved 28 Oct 2020, from https://www.uptodate.com/contents/an-overview-of-asthma-management
  6. Fanta, C., Barnes, P., Bochner, B., Hollingsworth H. (2020). Asthma in adolescents and adults: Evaluation and diagnosis. UpToDate. Retrieved 7 Sept 2020, from https://www.uptodate.com/contents/asthma-in-adolescents-and-adults-evaluation-and-diagnosis
  7. Kuruvilla, M., Eun-Hyung Lee, F.,  Lee, G. (2019). Understanding asthma phenotypes, endotypes and mechanisms of disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6411459/
  8. National Asthma Education and Prevention Program: Expert Panel Report III: Guidelines for the diagnosis and management of asthma. Bethesda, MD. National Heart, Lung, and Blood Institute, 2007. (NIH publication no. 08-4051). www.nhlbi.nih.gov/guidelines/asthma/asthgdln.htm
  9. Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention. (2020). Retrieved 28 Oct 2020, from www.ginasthma.org
  10. Morris, M., Pearson, D., Mosenifar, Z. (Ed.). (2019) Asthma. Medscape. Retrieved 6 Sept 2020, from https://emedicine.medscape.com/article/296301-overview
  11. Sinyor, B., Perez, L. (2020) Pathophysiology of Asthma. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK551579
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