Loading...Dyspnea is the subjective sensation of breathing discomfort. It is a normal manifestation of heavy exertion, but also may be caused by underlying conditions (both pulmonary and extrapulmonary). Management focuses on treating the underlying condition. Wheezes are high-pitched, continuous loud sounds that are often louder than breath sounds. They can be heard on inspiration or expiration. They are caused by a narrowing of the airways, resulting in the oscillation of opposing airway walls. The most common causes of wheezing are asthma and COPD exacerbations (often from viral respiratory infections).
Table of Contents
Image: “Asthma inhaler.” by NIAID. License: CC BY 2.0
Dyspnea – Introduction and Pathophysiology
Definition
Dyspnea is the subjective sensation of breathing discomfort (chest tightness or shortness of breath).
Pathophysiology
Dyspnea occurs due to an imbalance between the required gas exchange and the acid-base status of an individual. This sensation is often due to a combination of factors including
Layout presenting the pathophysiology of dyspnea. Image by Lecturio.
- Changes in lung physiology:
- Increased airway resistance
- Increased dead space
- Ventilation-perfusion mismatch
- Decrease in lung/chest wall compliance
- Stimulates chest wall and pulmonary mechanoreceptors
- Vagus nerve
- Muscle spindles and tendons of the chest wall
- Stimulates chest wall and pulmonary mechanoreceptors
- Acute hypercapnia, hypoxemia, or metabolic acidosis
- Stimulation of chemoreceptors (by PaO₂, pH, and PaCO₂)
- Peripheral: aortic arch and carotid bodies
- Central: medulla
- Stimulation of chemoreceptors (by PaO₂, pH, and PaCO₂)
- Impaired oxygen delivery/utilization
- May be due to reduced oxygen-carrying capacity of the blood
- May be due to deconditioning
Dyspnea – Etiology
- Can be broken down into
- Pulmonary or extrapulmonary causes
- 5 most common causes of chronic dyspnea:
- Asthma
- COPD
- Interstitial lung disease
- Myocardial dysfunction
- Obesity/deconditioning
- See chart below for a summary of the conditions in each category.
|
Pulmonary Causes of Dyspnea |
||
| Clinical presentation | Associated conditions | |
| Obstructive lung disease | Characterized by air trapping in the lungs
Findings
|
COPD
Chronic bronchitis Emphysema |
| Restrictive lung disease | Characterized by decreased lung compliance:
Findings
|
Poor breathing mechanics
Interstitial lung diseases
|
| Upper airway obstruction | Often caused by infection or foreign body obstruction
Findings
|
Epiglottitis
Foreign body obstruction |
| Others | Characterization and findings vary. | Pulmonary embolism
Metastatic disease Pulmonary edema |
|
Extrapulmonary Causes of Dyspnea |
||
| Clinical presentation | Associated conditions | |
| Cardiac dyspnea | Often a complication of left-sided heart failure
Findings
|
Hypertensive or valvular heart disease
Cardiomyopathy Ischemic heart disease: Heart failure with reduced or preserved ejection fraction Arrhythmia |
| Anemia | Impaired tissue oxygenation
Findings
|
Hypovolemic shock
Acute hemorrhage |
| Psychogenic dyspnea | Hyperventilation associated with anxiety may lead to acute respiratory alkalosis manifested as
|
Panic disorder
Anxiety Pain Somatization disorder |
| Endocrine dyspnea | Changes in pH and PaCO₂ stimulate the brain stem
|
Metabolic acidosis:
Medications:
|
| Central dyspnea | Variable causes | Neuromuscular disease
|
Important elements in clinical history
- Duration, onset, severity, and progression of dyspnea
- Sudden acute dyspnea is more concerning than chronic dyspnea.
- Triggers relation to
- Exertion
- Body position
- Cold air
- Animal dander
- Stress/anxiety
- Associated symptoms:
- Cough
- Sputum production
- Orthopnea
- Paroxysmal nocturnal dyspnea
- Chest pain
- Peripheral edema
- Joint swelling
- Palpitations
- Effects of medications (such as albuterol, beta-blockers)
- Tobacco history
- Thrombosis risk factors
Important elements in physical exam
Due to the wide array of differential diagnoses, it is important to take different considerations during physical exam.
| Vital signs |
|
Red flag vital signs
Red flags exam findings
|
| Pulmonary |
|
|
| Cardiovascular |
|
|
| Abdominal |
|
|
| Musculoskeletal |
|
Labs
- CBS and BMP, especially in patients who have fever, sputum production, or anemia
- BNP if heart failure is suspected
- D-dimer if pulmonary embolism is suspected
- Arterial blood gas
Imaging and other tests
- Chest X-ray may detect cardiopulmonary disease (e.g., congestive heart failure, COPD, cor pulmonale, pulmonary hypertension)
- Lateral neck radiography
- If suspected upper airway obstruction
- ECG
- May detect ischemia, arrhythmia, or ventricular hypertrophy
- CT – pulmonary angiogram or VQ lung scan
- If pulmonary embolism is suspected
- Spirometry
- Used in outpatient setting to differentiate obstructive vs. restrictive lung disease
- Used with a bronchodilator to differentiate asthma from COPD
- Other tests to consider in specific situations
- Echocardiography
- Chest CT
- Cardiac stress testing
Video Gallery
Dyspnea by Charles Vega, MD
Dyspnea: Diagnosis by Charles Vega, MD
Dyspnea – Management
- Oxygen supplementation if O₂ saturation is < 90%.
- Treatment of the underlying cause
- Asthma and COPD
- Bronchodilators or inhaled corticosteroids
- Dyspnea associated with heart failure
- Diuretics
- Pneumonia/infectious causes
- Antibiotics
- Supplemental oxygen
- Pulmonary embolism
- Thrombolytics
- Asthma and COPD
Wheezing
Definition
- High-pitched, continuous loud sounds
- Generally louder than normal breath sounds
- May be inspiratory or expiratory
Pathophysiology
- Caused by a narrowing of the airways, resulting in the oscillation of opposing airway walls
Etiology
- Viral respiratory tract infections
- Most common cause of wheezing in children and adults
- Most common cause of asthma exacerbations in children and adults
- May also be associated with COPD and airway obstruction
Differential Diagnosis
- Symmetric wheezing
- Asthma
- COPD
- Unilateral wheezing:
- Foreign body aspiration
- Airway compression from a tumor or mass
It is important to differentiate wheezing from stridor, as acute stridor needs rapid medical intervention.
- Stridor is a specific kind of wheezing that has a constant pitch.
- Most commonly heard in upper respiratory obstruction
- Inspiratory stridor is usually related to laryngeal obstruction.
- Expiratory stridor is associated with tracheobronchial obstruction.
Diagnostics
-
- Dependent on history, exam findings, and extrapulmonary findings
- Pulmonary function testing
- With pre and post-bronchodilator
- Evaluation of the flow-volume loop
- Chest X-ray
Video Gallery
Wheezing by Carlo Raj, MD
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