Objective: To determine lung compliance in patients who had out-of-hospital cardiac arrests.
Methods: A prospective, observational study of patients suffering nontraumatic cardiopulmonary arrest and requiring CPR at one university hospital ED. Following termination of resuscitation efforts, lung compliance was measured. Measurements were made while inflating the lung from 250 mL to 2,000 mL (in 250-mL increments) using a calibrated supersyringe. Airway flow and pressure were measured at the endotracheal tube with a pneumotachograph and a pressure transducer. Flow and pressure signals were recorded by a respiratory monitor and used to construct pressure-volume curves for calculation of lung compliance.
Results: The 25 cardiac arrest patients (17 men, eight women) had a mean (+/- SD) age of 65 +/- 7 years. Mean lung compliance was 0.051 +/- 0.011 L/cm H2O. Lung compliance was smaller at low lung volumes, suggesting the presence of alveolar collapse. Compliance values from 500 mL to 1,500 mL were similar. Compliance also diminished with increasing duration of CPR.
Conclusions: One previous publication suggested that lung compliance following resuscitation is 0.022 L/cm H2O. The results of this study, using the accepted standard measurements of static lung compliance, suggest that true compliance is twice this value. This finding has important ramifications for future research on ventilation during resuscitation and current ventilation standards.