20: Dyspnea

Key Points

• Determine whether an immediate life threat is present.

• Answer 3 key questions when approaching patients in moderate to severe respiratory distress.

• Diagnose causes of dyspnea by using a structured step-by-step anatomic approach.

• Do not hesitate. Initiate treatment in cases of respiratory distress immediately, even if the diagnostic work-up is incomplete.

Introduction

Dyspnea, from the patient's perspective, is known as “shortness of breath.” This is a sensation of breathlessness or “air hunger” manifested by signs of difficult or labored breathing, often owing to a physiologic aberration. Tachypnea is rapid breathing. Dyspnea may or may not involve tachypnea. Hyperventilation is ventilation that exceeds metabolic demands, such as can be caused by a psychological stressor (eg, anxiety attack).

From the physician's perspective, dyspnea is caused by impaired oxygen delivery to tissues. This can begin at the mechanical level, with any possible cause of airway obstruction, and can end at the cellular level, with any chemical inability to offload oxygen to tissues. If time permits, a systematic walk-through from airway to tissue can help elucidate the more difficult diagnoses. However, treatment for life-threatening severe respiratory distress must be initiated during, or even before, the diagnostic work-up.

Clinical Presentation

Start your initial assessment of the severity of the presentation with these 3 questions:

1. Does the patient need to be intubated immediately? This may be demonstrated by the patient's:

   1. Failure to oxygenate

   2. Failure to ventilate

   3. Failure to protect the airway

If “yes” to any of the above, intubate immediately. If the patient cannot oxygenate, there will be anoxic injury, especially brain injury, within seconds to minutes. The inability to perform the act of breathing (failure to ventilate) leads to carbon dioxide buildup, and the ensuing acidosis can lead to cardiac dysfunction. Finally, if the patient cannot maintain an open airway (due to brain injury, mechanical occlusion, etc.), there will be threat to both oxygenation and ventilation, warranting immediate intubation.

2. Is the respiratory distress rapidly reversible? Recognizing and promptly intervening on the rapidly reversible causes of severe respiratory distress can prevent the need for intubation. Delays in therapy may cause the patient to quickly decompensate. Some of these reversible causes (and their solutions) are as follows:

   Hypoxia (administer oxygen)

   Bronchospasm (beta-agonists/steroids/epinephrine)

   Hypertensive pulmonary edema (nitrates/diuresis)

   Pneumothorax (needle decompression/chest tube)

   Allergic reaction (steroids/epinephrine/antihistamine)

3. Can he run?

   Imagine the patient had to run for his or her life (in many ways, this is what the patient is doing). How long could the patient go before he or she collapsed? What is the patient's physiologic reserve? For example, is the patient young and healthy or elderly with comorbidities? Consider all of the following in this assessment: airway, chest wall/musculature, diaphragmatic excursion, posture, age, body mass index, cardiopulmonary status, and baseline exercise tolerance. The decision to intubate or to wait is based on the patient's ability to maintain the ...