Approach to dyspnea: Clinical sciences

Acute dyspnea is the sensation of difficult or uncomfortable breathing that develops over hours to days. Dyspnea is a common symptom with a wide range of causes including respiratory, cardiovascular, metabolic, neuromuscular, and neurologic conditions. Many causes of acute dyspnea are life-threatening, so it is important to have a systematic approach to evaluating these patients.

When approaching a patient with dyspnea, first you should perform an ABCDE assessment, to determine if your patient is unstable or stable. If they are unstable, first check for alarm signs and symptoms! Check for upper airway obstruction by auscultating for stridor, a high-pitched breathing sound, and by directly examining the airway for oropharyngeal swelling or the presence of a foreign body.

If the airway is clear, evaluate the patient’s breathing by assessing respiratory rate and oxygen saturation. A respiratory rate less than 10 or greater than 20 breaths per minute, or oxygen saturation less than 90% requires acute management.

You should also look for red flag features that signal impending respiratory failure such as confusion, inability to speak in complete sentences, and the use of accessory respiratory muscles, such as the scalenes and intercostals.

In this case, stabilize the airway, breathing, and circulation, which may require removing any airway obstruction, endotracheal intubation and mechanical ventilation. Some patients might require supplemental oxygen only, but, in both cases, don’t forget to obtain IV access and put your patient on continuous vital sign monitoring.

Now, here’s a high-yield fact to keep in mind! Causes of acute airway obstruction, that might present with stridor, include anaphylaxis, epiglottitis, and the presence of a foreign body.

Suspect anaphylaxis if the patient reports exposure to a known allergen, such as an insect sting, and presents with urticaria, stridor, or wheezing.

On the other hand, epiglottitis most commonly presents with hoarseness and dysphagia in the setting of upper respiratory infection caused by Haemophilus influenzae, as well as Streptococcal and Staphylococcal species.

Finally, the presence of a foreign body is usually via accidental aspiration and can range from a child that inhaled a small toy to an unconscious patient that has vomited and obstructed their airway.

Now that unstable patients are taken care of, let’s go back to the ABCDE assessment and take a look at stable patients.

If your patient is stable, proceed with a focused history and physical examination, and order labs including CBC, BMP, BNP, D-dimer, and cardiac enzymes. Additionally, order imaging, like a chest x-ray, and possibly point of care ultrasound, or POCUS for short. You’ll also want to get an ECG on all patients with dyspnea.

First, let's discuss the primary respiratory causes of acute dyspnea, which include pneumothorax, pneumonia, asthma, and COPD exacerbation.

Let’s look at pneumothorax,

Consider pneumothorax in a patient with acute dyspnea that reports pleuritic chest pain.

On physical exam, decreased breath sounds and hyperresonance to percussion on the affected side are consistent with pneumothorax.

Chest x-ray will show a distinct visceral pleural edge with an absence of distal lung markings, and, in the case of a tension pneumothorax, may show tracheal deviation and mediastinal shift away from the side of the collapsed lung.

POCUS will show absent lung sliding.

Keep in mind that patients with tension pneumothorax are usually unstable, so you should skip imaging and perform immediate needle decompression.

Another primary respiratory cause of acute dyspnea is pneumonia.

A person with pneumonia might report pleuritic chest pain, productive cough, and fever. Their labs will show leukocytosis with left shift, while chest x-ray could show lobar consolidation or diffuse infiltrates.

Common POCUS findings include subpleural consolidation, liver-like echogenicity of the lung, and dynamic air bronchograms. All these findings are suggestive of pneumonia!

Next, let’s look at obstructive lung disease as a cause of acute dyspnea.

Bronchoconstriction during an asthma or COPD exacerbation can cause wheezing, diminished air entry, and a prolonged expiratory phase on physical exam. Chest x-ray may show lung hyperinflation and flattened diaphragms.

History can help distinguish between asthma and COPD. Patients with asthma are typically younger and have episodic dyspnea triggered by allergens or exercise but breathe normally between episodes. Individuals with COPD tend to be older, often have a productive cough that worsens over time, and have a history of smoking.

Next, let’s move on to cardiovascular causes of acute dyspnea, which include cardiac tamponade, pulmonary embolism, myocardial infarction, arrhythmia, and decompensated heart failure.

Let’s start with cardiac tamponade.

In these individuals, history finding typically includes chest pain, and the physical findings include pulsus paradoxus and Beck triad, which is hypotension, jugular venous distention, and muffled heart sounds.

ECG often shows sinus tachycardia with low voltage QRS complexes or electrical alternans.

Chest X-ray might reveal a widened mediastinum and a water bottle sign, where the cardiac silhouette appears enlarged and stretched.

Diagnosis of cardiac tamponade can be confirmed via POCUS or transthoracic echocardiogram or TTE, which typically shows pericardial effusion, as well as diastolic collapse of the right atrium and ventricle.

Next up is pulmonary embolism.

Suspect pulmonary embolism in patients with pleuritic chest pain and hemoptysis that have a history of deep vein thrombosis or DVT. Chest x-ray is usually normal.

On the other hand, ECG often shows sinus tachycardia, and less frequently the S1Q3T3 pattern, where there’s a large S wave in lead I, and a Q wave and inverted T wave in lead III.

Since massive PE causes strain to the right heart, labs may show elevated cardiac enzymes. The likelihood of PE can be determined by the Wells criteria. A high-probability Wells score or an intermediate score plus elevated D-dimer should prompt you to order CT pulmonary angiography or CTPA.

If the CTPA reveals a filling defect in a pulmonary artery, the diagnosis of pulmonary embolism is confirmed.

Another important cardiac cause of acute dyspnea is myocardial infarction.

Suspect myocardial infarction in a person with risk factors for cardiovascular disease who presents with anginal chest pain and diaphoresis.

ECG might reveal ST segment elevations or depressions, T wave inversions, and new onset left bundle branch block, while labs will usually show elevated cardiac enzymes from myocardial damage. All of these findings are suggestive of myocardial infarction!

Next, let’s look at arrhythmia.