Differential Diagnosis of Dyspnea
1Department of Emergency Medicine, National Cheng Kung University, Taiwan
Acute dyspnea is a common presentation in the setting of emergency department (ED) practice. Dyspnea in the ED could be attributed to several possible differential diagnoses: pulmonary, cardiovascular, obstruction of upper airway, compensatory (metabolic or hematological) or psychological (anxiety, panic) factors. The etiologies could be assessed by investigating the clinical characteristics, physical examination findings, environmental exposures, imaging modalities, and laboratory studies.
Biomarkers are useful in dyspnea both for diagnosis, prognosis and risk prediction. Many require age or co-morbidity-adjusted stratification in determining optimal cut-off values for ruling-in or ruling-out certain diagnoses. Plasma natriuretic peptides are applied for exclusion of the heart failure when diagnostic uncertainty exists. Troponins could also serve as indicators of mortality in patients with acute decompensated heart failure. An age-adjusted D-dimer threshold for ED patients with suspected pulmonary embolism is more accurate than a standard cut-point of 500 ng/dL.
Approach to patients with dyspnea should be thorough and comprehensive. Critical etiologies could be masked by other differential diagnoses in some circumstances. A young age patient presenting with dyspnea is frequently diagnosed as hyperventilation in the ED. Although hyperventilation is usually anxiety or panic attack related, it could be resulted from other underlying causes and must be excluded before labeling it as hysteria or panic. In conditions when panic attack was preceded by shortness of breath and intense restlessness and anxiety, with decreased saturation by pulse oximetry, pulmonary embolism should be speculated. Central neurogenic hyperventilation is usually due to midbrain and upper pons damage. Head injury, severe brain hypoxia, or lack of cerebral perfusion should be taken into consideration in the presence of persistent hyperventilation.
The use of point-of-care ultrasonography (POCUS) has taken an important role in the daily practice of modern emergency medicine. Bedside lung ultrasound in emergency (BLUE) protocol provides a rapid, more sensitive and specific evaluation for conditions including pneumothorax, pleural effusions, consolidation, and interstitial fluid. Study showed that utilizing the BLUE protocol in cases of acute respiratory distress in the ED will significantly shorten the time in patient management and identification of cause, and decrease the gap in carrying out definite treatments. The main limitations of POCUS in the ED lie in the context of training and operator dependency. Emergency physician should gain experience and expertise in ultrasound skills as core competence during residency training.