Noninvasive Ventilation

Indications

Definition

Noninvasive ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing (NIV) is respiratory support that does not require an artificial, invasive airway Airway ABCDE Assessment (such as an endotracheal tube).

Types

• Noninvasive positive pressure ventilation Positive pressure ventilation Application of positive pressure to the inspiratory phase when the patient has an artificial airway in place and is connected to a ventilator. Flail Chest (NIPPV):
  • Can be provided with:
    • Continuous positive airway Airway ABCDE Assessment pressure (CPAP) 
    • Bilevel positive airway Airway ABCDE Assessment pressure (BiPAP).
  • Typically applied with a sealed face mask that covers both the nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose Anatomy (External & Internal) and the mouth. 
  • Can also be used in the form of a helmet
  • Positive airway Airway ABCDE Assessment pressure allows alveolar recruitment Recruitment Skeletal Muscle Contraction to participate in oxygenation. 
• High-flow nasal cannula Nasal Cannula Respiratory Failure (HFNC):
  • Another form of NIV that uses high concentrations of oxygen, which may be delivered at up to 60 L/min via large-bore nasal cannula Nasal Cannula Respiratory Failure
  • At higher 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 rates, HFNC generates positive end-expiratory pressure Positive end-expiratory pressure Pressure remaining in the distal airways of the patient at the end of expiration Invasive Mechanical Ventilation ( PEEP PEEP Pressure remaining in the distal airways of the patient at the end of expiration Invasive Mechanical Ventilation) above the physiologic level.

Indications

The most common indication for use is acute 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:

• Ideally, for conscious patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with spontaneous breathing 
• Moderate to severe hypoxemia Hypoxemia Neonatal Respiratory Distress Syndrome or hypercapnia Hypercapnia A clinical manifestation of abnormal increase in the amount of carbon dioxide in arterial blood. Neonatal Respiratory Distress Syndrome
• Increased respiratory effort and tachypnea Tachypnea Increased respiratory rate. Pulmonary Examination:
  • Accessory muscle use, pursed-lip breathing
  • Goal is to prevent 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.

Common conditions that may be suitable for NIV:

• Acute hypoxic 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:
  • Infection/ 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
  • 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 causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma exacerbation
  • Pulmonary embolism Pulmonary Embolism Pulmonary embolism (PE) is a potentially fatal condition that occurs as a result of intraluminal obstruction of the main pulmonary artery or its branches. The causative factors include thrombi, air, amniotic fluid, and fat. In PE, gas exchange is impaired due to the decreased return of deoxygenated blood to the lungs. Pulmonary Embolism
  • Atelectasis Atelectasis Atelectasis is the partial or complete collapse of a part of the lung. Atelectasis is almost always a secondary phenomenon from conditions causing bronchial obstruction, external compression, surfactant deficiency, or scarring. Atelectasis
  • Posttrauma
• Acute hypercapnic respiratory failure Hypercapnic Respiratory Failure Respiratory Failure +/– acute hypoxic 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:
  • 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 causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma or 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)) exacerbation
  • 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) (HF) exacerbation/ pulmonary edema Pulmonary edema Pulmonary edema is a condition caused by excess fluid within the lung parenchyma and alveoli as a consequence of a disease process. Based on etiology, pulmonary edema is classified as cardiogenic or noncardiogenic. Patients may present with progressive dyspnea, orthopnea, cough, or respiratory failure. Pulmonary Edema
  • Hypoventilation from sedation
  • Progressive obesity hypoventilation syndrome Obesity hypoventilation syndrome Hypoventilation syndrome in very obese persons with excessive adipose tissue around the abdomen and diaphragm. It is characterized by diminished to absent ventilatory chemoresponsiveness; chronic hypoxia; hypercapnia; polycythemia; and long periods of sleep during day and night (hypersomnolence). It is a condition often related to obstructive sleep apnea but can occur separately. Obstructive Sleep Apnea
  • Progressive neuromuscular disorder
• Note: Studies have shown a mortality Mortality All deaths reported in a given population. Measures of Health Status benefit of NIPPV in 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) and HF exacerbations.

Contraindications

While NIV may reduce the need for invasive mechanical ventilation Invasive mechanical ventilation Invasive mechanical ventilation (IMV) is an advanced airway modality used for individuals with immediate or impending respiratory failure and/or in preparation for surgery. The IMV technique involves positive pressure ventilation delivered to the lungs through an endotracheal tube via a ventilator. Invasive Mechanical Ventilation and its associated complications, careful consideration for patient 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 is essential to prevent harm. 

Common contraindications for NIPPV include:

• Cardiac or respiratory arrest
• Poor airway Airway ABCDE Assessment protection:
  • Increased secretions
  • Impaired coughing/ swallowing Swallowing The act of taking solids and liquids into the gastrointestinal tract through the mouth and throat. Gastrointestinal Motility
  • Altered mental status Altered Mental Status Sepsis in Children
• Upper airway Airway ABCDE Assessment trauma/anatomical abnormality
• Unstable hemodynamics Hemodynamics The movement and the forces involved in the movement of the blood through the cardiovascular system. Vascular Resistance, Flow, and Mean Arterial Pressure 
• Recent maxillofacial surgery
• Uncontrollable vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
• Patient refusal 

Contraindications for HFNC:

• There are no clear absolute contraindications at this time, as few studies are available.
• Potential contraindications include:
  • Facial anomalies preventing proper fit
  • After upper airway Airway ABCDE Assessment surgery

Noninvasive Positive Pressure Ventilation

Basic settings controlled by the operator

• PEEP PEEP Pressure remaining in the distal airways of the patient at the end of expiration Invasive Mechanical Ventilation or expiratory positive airway Airway ABCDE Assessment pressure (EPAP):
  • Pressure remaining in the distal airways at the end of expiration Expiration Ventilation: Mechanics of Breathing
  • Keeps the alveoli Alveoli Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place. Acute Respiratory Distress Syndrome (ARDS) open to participate in oxygenation
  • Can be ↑ to improve oxygenation (↑ PaO₂)
  • Can be lowered to ↓ oxygenation (↓ PaO₂)
• Inspiratory positive airway Airway ABCDE Assessment pressure (IPAP; for BiPAP):
  • The amount of positive pressure delivered with each inspiration Inspiration Ventilation: Mechanics of Breathing 
  • ↑ IPAP → ↑ tidal volume Tidal volume The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are tv or V with subscript t. Ventilation: Mechanics of Breathing → ↑ ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing → ↓ PaCO₂
  • ↓ IPAP → ↓ tidal volume Tidal volume The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are tv or V with subscript t. Ventilation: Mechanics of Breathing → ↓ ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing → ↑ PaCO₂  
  • Note: Changes in ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing can occur only if EPAP is not changed in the same proportion.
• Fraction of inspired oxygen (FiO₂):
  • Percentage of oxygen delivered directly to the individual 
  • ↑ FiO₂ → ↑ oxygenation 
  • ↓ FiO₂ → ↓ oxygenation
• Note:
  • In CPAP: a constant PEEP PEEP Pressure remaining in the distal airways of the patient at the end of expiration Invasive Mechanical Ventilation is used → provides continuous positive pressure throughout the breathing cycle
  • In BiPAP: IPAP and EPAP are used → provides different pressures for inhalation and exhalation

Background physiology

• Constant positive airway Airway ABCDE Assessment pressure → improves alveolar recruitment Recruitment Skeletal Muscle Contraction → improves hypoxemia Hypoxemia Neonatal Respiratory Distress Syndrome
• IPAP during inhalation, in addition to the set EPAP/ PEEP PEEP Pressure remaining in the distal airways of the patient at the end of expiration Invasive Mechanical Ventilation, creates bilevel ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing
  • The pressure gradient Pressure gradient Vascular Resistance, Flow, and Mean Arterial Pressure between the IPAP and the EPAP correlates with the tidal volume Tidal volume The volume of air inspired or expired during each normal, quiet respiratory cycle. Common abbreviations are tv or V with subscript t. Ventilation: Mechanics of Breathing delivered.
  • This relationship ultimately regulates CO₂ clearance.
• NIV can be used to:
  • Improve alveolar ventilation Alveolar ventilation Ventilation: Mechanics of Breathing → improve hypercapnia Hypercapnia A clinical manifestation of abnormal increase in the amount of carbon dioxide in arterial blood. Neonatal Respiratory Distress Syndrome and acidosis Acidosis A pathologic condition of acid accumulation or depletion of base in the body. The two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up. Respiratory Acidosis
  • Recruit alveoli Alveoli Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place. Acute Respiratory Distress Syndrome (ARDS) and deliver ↑ FiO₂ → help reverse hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage
    • Maintains open airway Airway ABCDE Assessment and prevents dynamic hyperinflation Hyperinflation Imaging of the Lungs and Pleura of alveoli Alveoli Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place. Acute Respiratory Distress Syndrome (ARDS)
    • Improves ventilation Ventilation The total volume of gas inspired or expired per unit of time, usually measured in liters per minute. Ventilation: Mechanics of Breathing/perfusion (V/Q) mismatch
  • Ameliorate respiratory distress/ work of breathing Work of breathing Respiratory muscle contraction during inhalation. The work is accomplished in three phases: lung compliance work, that required to expand the lungs against its elastic forces; tissue resistance work, that required to overcome the viscosity of the lung and chest wall structures; and airway resistance work, that required to overcome airway resistance during the movement of air into the lungs. Work of breathing does not refer to expiration, which is entirely a passive process caused by elastic recoil of the lung and chest cage. Pulmonary Examination
  • Reduce left ventricular preload Preload Cardiac Mechanics and afterload Afterload Afterload is the resistance in the aorta that prevents blood from leaving the heart. Afterload represents the pressure the LV needs to overcome to eject blood into the aorta. Cardiac Mechanics:
    • Consequently, increasing right ventricular (RV) afterload Afterload Afterload is the resistance in the aorta that prevents blood from leaving the heart. Afterload represents the pressure the LV needs to overcome to eject blood into the aorta. Cardiac Mechanics and reducing RV preload Preload Cardiac Mechanics
    • Can be beneficial in left-sided 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), but should be used with caution in right-sided heart failure Right-Sided Heart Failure Ebstein’s Anomaly

High-Flow Nasal Cannula

Basic settings controlled by the operator

There are 2 parameters that affect oxygenation:

• Flow rate Flow rate maximum flow the ventilator will deliver a set tidal volume in liters per minute Invasive Mechanical Ventilation (generally optimized first to avoid FiO₂ levels > 60%, when possible)
• FiO₂

Background physiology

• HFNC delivers heated and humidified oxygen for the following physiologic effects:
  • Washes out CO₂ from the anatomical dead space Dead space That part of the respiratory tract or the air within the respiratory tract that does not exchange oxygen and carbon dioxide with pulmonary capillary blood. Ventilation: Mechanics of Breathing
  • Can generate a moderate level of PEEP PEEP Pressure remaining in the distal airways of the patient at the end of expiration Invasive Mechanical Ventilation → ↑ recruitment Recruitment Skeletal Muscle Contraction of collapsed alveoli Alveoli Small polyhedral outpouchings along the walls of the alveolar sacs, alveolar ducts and terminal bronchioles through the walls of which gas exchange between alveolar air and pulmonary capillary blood takes place. Acute Respiratory Distress Syndrome (ARDS) 
  • Improved comfort (improves compliance Compliance Distensibility measure of a chamber such as the lungs (lung compliance) or bladder. Compliance is expressed as a change in volume per unit change in pressure. Veins: Histology) through:
    • Humidification and warming of oxygen 
    • No mask
  • May have fewer hemodynamic effects than NIPPV
  • Can ↓ work of breathing Work of breathing Respiratory muscle contraction during inhalation. The work is accomplished in three phases: lung compliance work, that required to expand the lungs against its elastic forces; tissue resistance work, that required to overcome the viscosity of the lung and chest wall structures; and airway resistance work, that required to overcome airway resistance during the movement of air into the lungs. Work of breathing does not refer to expiration, which is entirely a passive process caused by elastic recoil of the lung and chest cage. Pulmonary Examination
• Best used in acute hypoxic 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:
  • May have a role in mild or moderate hypercapnic respiratory failure Hypercapnic Respiratory Failure Respiratory Failure
  • May be able to prevent intubation Intubation Peritonsillar Abscess in select individuals
  • Can be combined easily with inhaled vasodilators Vasodilators Drugs used to cause dilation of the blood vessels. Thromboangiitis Obliterans (Buerger’s Disease) 
  • Sometimes use preintubation for oxygen delivery

Complications

The most feared complication for NIV is delaying a potentially lifesaving intervention because of poor patient 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. 

• Intubation Intubation Peritonsillar Abscess is not without risk, but it is often necessary in the critical care setting. 
• Delaying intubation Intubation Peritonsillar Abscess in a rapidly deteriorating individual may result in increased mortality Mortality All deaths reported in a given population. Measures of Health Status.

Major complications for noninvasive positive pressure ventilation Positive pressure ventilation Application of positive pressure to the inspiratory phase when the patient has an artificial airway in place and is connected to a ventilator. Flail Chest

• Barotrauma Barotrauma Injury following pressure changes; includes injury to the eustachian tube, ear drum, lung and stomach. Invasive Mechanical Ventilation (rare)
• Pressure ulcers/ necrosis Necrosis The death of cells in an organ or tissue due to disease, injury or failure of the blood supply. Ischemic Cell Damage of the nasal bridge (from the mask)
• Claustrophobia Claustrophobia Magnetic Resonance Imaging (MRI) or anxiety Anxiety Feelings or emotions of dread, apprehension, and impending disaster but not disabling as with anxiety disorders. Generalized Anxiety Disorder
• Aspiration from vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia
• Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension in right 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) or hypovolemia Hypovolemia Sepsis in Children 
• Reduced communication Communication The exchange or transmission of ideas, attitudes, or beliefs between individuals or groups. Decision-making Capacity and Legal Competence

Major complication for high-flow nasal cannula Nasal Cannula Respiratory Failure

• Epistaxis Epistaxis Bleeding from the nose. Granulomatosis with Polyangiitis
• Abdominal distention Abdominal distention Megacolon 
• Aspiration
• Barotrauma Barotrauma Injury following pressure changes; includes injury to the eustachian tube, ear drum, lung and stomach. Invasive Mechanical Ventilation (rare, and lower risk than NIPPV 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)