A new automated method versus continuous positive airway pressure method for measuring pressure-volume curves in patients with acute lung injury

Objective: To compare pressure-volume (P-V) curves obtained with the Galileo ventilator with those obtained with the CPAP method in patients with acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Design: Prospective, observational study. Setting: General critical care center. Patients and participants: Patients with ALI/ARDS and receiving mechanical ventilation. Interventions: Pressure-volume curves were obtained in random order with the CPAP technique and with the software PV Tool-2 (Galileo ventilator). Measurements and results: In ten consecutive patients, airway pressure was measured by a pressure transducer and changes in lung volume were measured by respiratory inductive plethysmography. P-V curves were fitted to a sigmoidal equation with a mean R 2 of 0.994 ± 0.003. Intraclass correlation coefficients were all >0.75 (P < 0.001 at all pressure levels). Lower (LIP) and upper inflection (UIP), and deflation maximum curvature (PMC) points calculated from the fitted variables showed a good correlation between methods with intraclass correlation coefficients of 0.98 (0.92, 0.99), 0.92 (0.69, 0.98), and 0.97 (0.86, 0.98), respectively (P < 0.001 in all cases). Bias and limits of agreement for LIP (0.51 ± 0.95 cmH 2O; -1.36 to 2.38 cmH2O), UIP (0.53 ± 1.52 cmH 2O; -2.44 to 3.50 cmH2O), and PMC (-0.62 ± 0.89 cmH2O; -2.35 to 1.12 cmH2O) obtained with the two methods in the same patient were clinically acceptable. No adverse effects were observed. Conclusion: The PV Tool-2 built into the Galileo ventilator is equivalent to the CPAP method for tracing static P-V curves of the respiratory system in critically ill patients receiving mechanical ventilation.