From the Guidelines
Dyspnea, or shortness of breath, can be caused by numerous conditions beyond the common cardiac and pulmonary disorders, including asthma, bronchitis, chronic obstructive pulmonary disease (COPD), and interstitial lung disease (ILD), as well as non-cardiopulmonary causes such as anemia, obesity, neuromuscular disorders, anxiety disorders, metabolic acidosis, high altitude exposure, pregnancy, deconditioning, and certain medications 1.
Causes of Dyspnea
The causes of dyspnea can be broadly categorized into:
- Cardiopulmonary disorders, such as asthma, bronchitis, COPD, and ILD 1
- Non-cardiopulmonary disorders, such as:
- Anemia, which reduces oxygen-carrying capacity in the blood
- Obesity, which increases the work of breathing
- Neuromuscular disorders like myasthenia gravis or ALS that weaken respiratory muscles
- Anxiety disorders that can trigger hyperventilation
- Metabolic acidosis, which stimulates increased respiratory rate
- High altitude exposure due to lower oxygen levels
- Pregnancy, especially in later stages when the uterus compresses the diaphragm
- Deconditioning from prolonged inactivity
- Certain medications like beta-blockers or NSAIDs in sensitive individuals
- Thyroid disorders (both hyper- and hypothyroidism)
- Severe pain
- Carbon monoxide poisoning
Evaluation of Dyspnea
When evaluating unexplained shortness of breath, it's essential to consider these non-cardiopulmonary causes, especially when typical treatments for heart or lung conditions aren't effective 1. The underlying mechanism varies by cause - from reduced oxygen transport capacity to mechanical limitations of breathing to neurological signaling issues - highlighting why a comprehensive approach to diagnosis is essential.
Key Considerations
- A multifactorial etiology is reported in up to a third of patients with chronic dyspnea 1
- The presence of dyspnea is a potent predictor of mortality, often surpassing common physiological measurements in predicting the clinical course of a patient 1
- Dyspnea is a common problem affecting up to half of patients admitted to acute, tertiary care hospitals and one quarter of ambulatory patients 1
From the Research
Other Causes of Dyspnea
Other causes of dyspnea include:
- Cardiovascular etiologies, such as heart failure 2
- Pulmonary embolism, which requires expeditious diagnosis and management 2
- Chronic obstructive pulmonary disease (COPD) exacerbations, which can lead to hypercapnic failure 2, 3, 4, 5
- Asthma, which can cause intermittent and reversible airway obstruction 6
- Overlap syndrome, which combines components of asthma and COPD 6
- Other morbidities, such as pneumonia, coronary artery disease, arrhythmias, interstitial lung diseases, bronchiectasis, anxiety, and depression, which can mimic or aggravate COPD exacerbations 5
Respiratory and Cardiovascular Etiologies
Respiratory and cardiovascular etiologies are the most common causes of dyspnea, and differentiating between the two can be challenging 2.
- B-type natriuretic peptide (BNP) and N-terminal proB-type natriuretic peptide (NT-proBNP) can be used to identify patients with dyspnea who do not have heart failure 2
- Clinical decision rules, such as the Wells rule and the Geneva rule, can be used to establish the probability of pulmonary embolism 2
COPD Exacerbations
COPD exacerbations can cause dyspnea, and management of these exacerbations is crucial to prevent hospitalization and improve health outcomes 3, 4, 5.
- Interventions that reduce inspiratory neural drive, improve respiratory mechanics and muscle function, or address the affective dimension of dyspnea can achieve measurable benefits 4
- A structured multidisciplinary approach, carefully tailored to meet the specific needs of the individual, is necessary for effective dyspnea amelioration 4