CO2 measurement for the early differential diagnosis of pulmonary embolism-related shock at the emergency department: A case series

Objective: An early differential diagnosis is mandatory when facing a patient with clinical shock of unclear aetiology, in order to guide proper treatment. We assessed if the expired CO2 measurement and alveolar-arterial CO2 calculation could improve the differential diagnosis of shock during its initial presentation, particularly in separating pulmonary embolism from other causes of shock. Methods: We analysed the charts of 12 patients who presented with clinical shock and had end-tidal CO2 (EtCO2) and arterial CO2 partial pressure (PaCO2) measurements. Results: In cases with pulmonary embolism-related shock (n = 3), the gradient between PaCO2 and EtCO2 was increased (37 vs 0.2 mmHg). There was a similar trend for a higher PaCO2 value (60 vs 32.2 mmHg) and a lower EtCO2 value (23 vs 32 mmHg). Conclusion: An initial CO2 measurement might be an easily available tool for the early diagnostic work-up of clinical shock.