What investigations are recommended for a patient with shortness of breath and a history of asthma, Chronic Obstructive Pulmonary Disease (COPD), or heart failure?

Investigations for Shortness of Breath in Patients with Asthma, COPD, or Heart Failure

Begin with chest radiography as the initial imaging study for all patients with shortness of breath, followed by spirometry to assess airflow obstruction, and consider B-type natriuretic peptide (BNP) testing when cardiac causes cannot be clinically excluded. 1, 2

Initial Diagnostic Workup

Essential First-Line Investigations

• Chest X-ray is the mandatory initial imaging study and should be performed in all patients presenting with chronic dyspnea (>4-8 weeks duration), as it provides diagnostic information in approximately one-third of cases when combined with clinical evaluation 1, 2

• Spirometry must be performed to assess for airflow obstruction, particularly in patients >50 years who are long-term smokers with chronic breathlessness on minor exertion, as physical examination alone has poor sensitivity for detecting moderately severe COPD 1, 2, 3

• Pulse oximetry should be measured in all breathless patients and recorded as the "fifth vital sign" along with the inspired oxygen device and flow rate 2, 3

• Basic laboratory panel including complete blood count, basic metabolic panel, and electrocardiography should be obtained as part of the initial evaluation 4

Critical Biomarker Testing

• BNP measurement is particularly valuable in patients with known COPD or asthma presenting with dyspnea, as approximately 20% will have undiagnosed heart failure that emergency physicians miss in 63% of cases 5

• BNP >100 pg/mL has 93.1% sensitivity and 77.3% specificity for identifying heart failure in patients with pulmonary disease history, with a negative predictive value of 97.7% 5

• D-dimer testing may help rule out pulmonary embolism when clinically suspected 4

Advanced Imaging Based on Clinical Context

When Chest X-ray is Abnormal or Clinical Suspicion Persists

• CT chest without IV contrast is appropriate when a radiographic abnormality requires further characterization or when clinical findings necessitate additional imaging despite a normal chest radiograph 1, 2

• Inspiratory and expiratory CT chest should be considered specifically to evaluate for air trapping in patients with small airways disease, including asthma and COPD, as air trapping correlates with lung function impairment 1

• CT chest with IV contrast (rating 7 by ACR) is indicated when pulmonary vascular disease or pulmonary embolism is suspected 6, 2

Cardiac Evaluation

• Transthoracic echocardiography should be performed in all patients with dyspnea of suspected cardiac origin to evaluate cardiac structure and function 6, 2

• Echocardiography with bubble study (agitated saline contrast) is rated as appropriate (rating 7-9) for unexplained dyspnea to evaluate for right-to-left shunt 6

Specialized Testing for Specific Clinical Scenarios

Exercise-Related Dyspnea

• Exercise challenge testing or surrogate testing (eucapnic voluntary hyperpnea or mannitol challenge) should be performed instead of methacholine challenge when exercise-induced bronchoconstriction is suspected, as indirect challenges are more sensitive for detecting EIB 1

• Cardiopulmonary exercise testing should be performed to determine whether exercise-induced dyspnea and hyperventilation are masquerading as asthma, especially in children and adolescents 1

• Flexible laryngoscopy during exercise may be needed to differentiate exercise-induced bronchoconstriction from exercise-induced laryngeal dysfunction 1

Emerging Technologies

• Hyperpolarized xenon gas MRI (Xenon-MRI) has recently received FDA approval and may show impaired ventilation in patients with COPD and small airways disease, though its role is still being defined 1

Common Diagnostic Pitfalls to Avoid

• Do not assume relief with nitroglycerin is diagnostic of myocardial ischemia, as this should not be used as a diagnostic criterion 2

• Do not overlook cardiac causes in women, who may present with atypical symptoms and are at risk for underdiagnosis 2

• Do not rely on clinical judgment alone in patients with pulmonary disease history, as emergency physicians correctly identify only 36.8% of concurrent heart failure cases without BNP testing 5

• Do not prescribe inhalers without confirmatory pulmonary function testing, as studies show 28.4% of patients treated with inhalers for presumed obstructive airway disease have no evidence of lung disease 7

• Do not administer high-concentration oxygen to patients with COPD or others at risk of hypercapnic respiratory failure, as this can worsen respiratory acidosis; target oxygen saturation should be 88-92% in these patients pending blood gas results 2, 3

Algorithmic Approach

1. Measure vital signs including oxygen saturation, respiratory rate, pulse, blood pressure, and temperature in all patients 2

2. Obtain chest X-ray as the initial imaging study 1, 2

3. Perform spirometry to assess airflow obstruction 1, 2

4. Measure BNP if cardiac cause cannot be clinically excluded, particularly in patients with known pulmonary disease 5

5. If chest X-ray is abnormal or BNP is elevated (>100 pg/mL), proceed to echocardiography 6, 2, 5

6. If chest X-ray is normal but clinical suspicion persists, proceed to CT chest (with or without contrast based on suspected etiology) 1, 2

7. If initial workup is unrevealing, consider specialized testing such as exercise challenge, cardiopulmonary exercise testing, or advanced imaging 1