Objective: Application of a new method for analysis of exhaled gas in critically ill patients.
Design: Open study.
Setting: Surgical intensive care unit of an university hospital.
Patients: Thirty-seven consecutive, critically ill, mechanically ventilated patients.
Interventions: None.
Measurements and results: Chemical analysis of the patient's exhaled gas was based upon substance adsorption and concentration onto activated charcoal, microwave desorption and gas chromatographic separation. Patients with acute respiratory distress syndrome (ARDS) exhaled less isoprene than those without ARDS [9.8 (8.2-21.6) vs 21.8 (13.9-41.4) nmol/m2 per min [median (95% confidence interval)], p = 0.04]. In patients who developed pulmonary infection, pentane elimination increased from 0.4 (0.0-5.4) to 2.7 (0.6-6.1, p = 0.05) nmol/m2 per min and isoprene elimination decreased from 5.2 (0-33) to 5.0 (0-17, p = 0.05) nmol/m2 per min, resulting in a significant increase in pentane/isoprene ratio from 0.1 (0-0.3) to 0.4 (0-15, p = 0.007) when compared to patients without pulmonary infection.
Conclusions: The new method allows quantitative analysis of human gas samples with low substance concentrations and is well suited for clinical studies which involve the investigation of metabolic processes in the lung and the body.