Pressure-volume curves with and without muscle paralysis in acute respiratory distress syndrome

OBJECTIVE: Pressure-volume (PV) curves are recorded after induction of complete muscle paralysis, which may limit their clinical use. The feasibility of recording PV curves without paralysis has not been tested. In 19 patients with acute respiratory distress syndrome (ARDS) and no hemodynamic instability we prospectively evaluated whether PV curves can be safely and reliably recorded under deep sedation without neuromuscular blockade. METHODS: After standardized sedation (continuous infusion of midazolam and fentanyl) PV curves were recorded during apneic sedation, defined as absence of respiratory effort during a 6-s expiratory pause and during paralysis induced by cis-atracurium. MEASUREMENTS AND RESULTS: Agreement between PV curve parameters in the two conditions was evaluated. Curves were obtained from 10 cmH2O and from zero end-expiratory pressure in all patients under apneic sedation. In five patients propofol was given in addition to midazolam and fentanyl, and in two of them fluid resuscitation was needed. A strong agreement was found for respiratory system compliance and the lower inflection point and for chest wall compliance in the five patients whose esophageal pressure was measured. The variability of the measurements, however, should be taken into account in clinical practice. CONCLUSION: Neuromuscular blockade can be dispensed with when recording PV curves in many ARDS patients. Reliable PV curves can be obtained under anesthesia alone, with no serious adverse effects.