Short time efficacy and safety of modified pressure-controlled ventilation recruitment maneuver in a group of patients with acute respiratory distress syndrome

Introduction

Recruitment maneuvers (RM) attempt mechanical homogenization and improvement of V/Q matching in the heterogeneous acute respiratory distress syndrome (ARDS) lung in a short time. Apart from the postulated beneficial effect, their performance carries a risk for serious adverse events.

Methods

The study included 17 consecutive ARDS patients placed on baseline ventilation with standardized ventilatory parameters. Pressure-controlled ventilation RM was then applied for 2 minutes and consisted of: peak inspiratory pressure = 45 mbar, respiratory rate = 10/min, I:E = 1:1, positive end-expiratory pressure (PEEP) = 20 mbar for the first minute, 25 mbar for the remaining time. Predefined safety criteria were used for premature RM termination. Patients with a minimum of 30% PaO₂/FiO₂ increment on the fifth minute after the RM completion were judged responders. Those with prematurely terminated RM and non-responders were excluded from the subsequent study. In the remaining group, a decremental PEEP trial was then conducted. ECG, SpO₂, invasive systemic arterial pressures, Paw, exhaled Vt/MV and total respiratory system compliance (Ctot) were continuously monitored and their representative values were recorded for different time periods. Arterial blood samples for blood gas analysis were taken immediately before the RM, on the fifth minute and on the sixth hour after the RM completion. Twenty-four hours after the RM, a bedside chest X-ray was conducted for extraalveolar air detection.

Results

Six patients (35.3%) were considered nonresponders, and in one of them RM was prematurely terminated. In the responders' group there was statistically significant PaO₂/FiO₂ increment on the fifth minute after the RM, which was preserved on the sixth hour. The PaO₂/FiO₂ increment was significant in the nonresponders' group too, but with smaller magnitude. There was also a significant increase in Ctot and PaCO₂ decrement in the responders' group on the sixth hour. No significant changes in PaCO₂ and Ctot in the nonresponders' group were noted. PaO₂/FiO₂ in the fifth minute after the RM was not significantly different between responders and nonresponders, but PaCO₂ and Ctot were. None of the monitored hemodynamic parameters changed significantly at any time in both groups. Clinical or radiographic signs of barotrauma were not found.

Conclusion

The described pressure-controlled ventilation RM and decremental PEEP titration increased arterial oxygenation efficacy in the short term. Surrogate markers for alveolar recruitment were also influenced. RM showed good tolerability regarding hemodynamic stability and barotrauma potential.