Effects of periodic lung recruitment maneuvers on gas exchange and respiratory mechanics in mechanically ventilated acute respiratory distress syndrome (ARDS) patients

Objective: We wished to investigate whether volume recruitment maneuvers (VRMs) could improve alveolar recruitment and oxygenation in acute respiratory distress syndrome (ARDS) patients, ventilated at relatively low positive end-expiratory pressure (PEEP). Setting: General intensive care unit (ICU) located in a teaching hospital. Patients: 15 PEEP responder ARDS patients undergoing continuous positive pressure ventilation (CPPV) with sedation and muscle paralysis. Interventions: We identified a low (9.4 ± 3 cmH2O) and a high (16.0 ± 2 cmH2O) level of PEEP associated with target oxygenation values. Using a custom modified mechanical ventilator, we applied in random order three steps lasting 30 min: (1) CPPV at the low PEEP level (CPPV LO); (2) CPPV at the high PEEP level (CPPV HI); (3) CPPV at low PEEP with the superimposition of periodic VRMs (CPPV VRM). VRMs were performed twice a minute by increasing PEEP to the high level for two breaths. Each brace of two breaths was spaced 30 seconds from the preceding one. Measurements and results: We measured gas exchange, hemodynamics, respiratory mechanics, and the end expiratory lung volume (EELV). Compared to CPPV LO, CPPV VRM resulted in higher PaO2 (117.9 ± 40.6 vs 79.4 ± 13.6 mmHg, P < 0.01) and EELV (1.50 ± 0.62 vs 1.26 ± 0.50 l, P < 0.05), and in lower venous admixture (Q VA/Q T) (0.42 ± 0.07 vs 0.48 ± 0.07, P < 0.01). During CPPV HI, we observed significantly higher PaO2 (139.3 ± 32.5 mmHg) and lower Q VA/Q T (0.37 ± 0.08) compared to CPPV LO (P < 0.01) and to CPPV VRM (P < 0.05). Conclusions: VRMs can improve oxygenation and alveolar recruitment during CPPV at relatively low PEEP, but are relatively less effective than a continuous high PEEP level.