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The term respiratory distress includes both symptoms of dyspnea and signs indicating difficulty breathing. The cause of respiratory distress is often multifactorial and may include the findings of hypoxia, hypercapnia, and cyanosis.
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Dyspnea is the subjective feeling of difficult, labored, or uncomfortable breathing. There is no single pathophysiologic mechanism that causes dyspnea and its etiology may be secondary to pulmonary, cardiac, or neurological dysfunction.
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The initial assessment of any patient with dyspnea should be directed toward identifying respiratory failure, which requires more immediate action. Dyspnea alone is a subjective complaint often difficult to quantify; therefore, objective findings are often needed to aid in diagnosis. Assess for signs of impending respiratory failure which include tachycardia, tachypnea, stridor, the use of accessory respiratory muscles (intercostals, sternocleidomastoid), stridor, lethargy, agitation, altered mental status, and inability to speak due to breathlessness. If present, oxygen should be administered immediately. Early use of noninvasive ventilation is often helpful in reversing the downward trajectory, although the need for aggressive airway management and mechanical ventilation should be anticipated. Lesser degrees of distress allow for a more detailed approach.
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Diagnosis and Differential
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The history and physical examination, together with ancillary testing, will help identify the etiology of dyspnea (Table 29-1).
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It can be challenging to differentiate cardiac (CHF) and pulmonary causes. Signs such as an S3 gallop, edema, jugular venous distention, a history of orthopnea, an elevated brain natriuretic peptide (BNP), or troponin and chest radiograph findings of edema and cardiomegaly may point to cardiac causes. Pulse oximetry is a rapid but insensitive screen for disorders of gas exchange as it may be falsely elevated as in methemoglobinemia. Arterial blood gas (ABG) analysis is more sensitive, detects both hypoxia and hypercarbia, and is useful for identifying metabolic causes, such as acidosis with compensatory tachypnea, but does not take into account work of breathing and fatigue. A peak expiratory flow rate may indicate reactive airway disease and a negative inspiratory force (NIF) may identify neurological causes of dyspnea. Additional ancillary tests that may prove helpful include a complete blood count to look for anemia, d-dimer assay when used with clinical decision rules to look for pulmonary embolus (PE), chest radiograph, electrocardiogram, and computed tomography of the chest. Bedside cardiopulmonary ultrasound is increasingly being used to look for ...