• Massimiliano Pirrone, Daniel Fisher, Daniel Chipman, David A E Imber, Javier Corona, Cristina Mietto, Robert M Kacmarek, and Lorenzo Berra.
• 1Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, MA. 2Dipartimento di Anestesiologia, Terapia Intensiva e Scienze Dermatologiche, Università degli Studi di Milano, Milan, Italy. 3Respiratory Care Services, Massachusetts General Hospital, Boston, MA. 4Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain.
• Crit. Care Med. 2016 Feb 1; 44 (2): 300-7.

ObjectiveThe approach to applying positive end-expiratory pressure in morbidly obese patients is not well defined. These patients frequently require prolonged mechanical ventilation, increasing the risk for failed liberation from ventilatory support. We hypothesized that lung recruitment maneuvers and titration of positive end-expiratory pressure were both necessary to improve lung volumes and the elastic properties of the lungs, leading to improved gas exchange.DesignProspective, crossover, nonrandomized interventional study.SettingMedical and surgical ICUs at Massachusetts General Hospital.PatientsCritically ill, mechanically ventilated morbidly obese (body mass index > 35 kg/m(2)) patients (n = 14).InterventionsThis study evaluated two methods of titrating positive end-expiratory pressure; both trials were done utilizing positive end-expiratory pressure titration and recruitment maneuvers while measuring hemodynamics and respiratory mechanics. Measurements were obtained at the baseline positive end-expiratory pressure set by the clinicians, at zero positive end-expiratory pressure, at best positive end-expiratory pressure identified through esophageal pressure measurement before and after a recruitment maneuver, and at best positive end-expiratory pressure identified through a best decremental positive end-expiratory pressure trial.Measurements And Main ResultsThe average body mass index was 50.7 ± 16.0 kg/m(2). The two methods of evaluating positive end-expiratory pressure identified similar optimal positive end-expiratory pressure levels (20.7 ± 4.0 vs 21.3 ± 3.8 cm H2O; p = 0.40). End-expiratory pressure titration increased end-expiratory lung volumes (Δ11 ± 7 mL/kg; p < 0.01) and oxygenation (Δ86 ± 50 torr; p < 0.01) and decreased lung elastance (Δ5 ± 5 cm H2O/L; p < 0.01). Recruitment maneuvers followed by titrated positive end-expiratory pressure were effective at increasing end-expiratory lung volumes while decreasing end-inspiratory transpulmonary pressure, suggesting an improved distribution of lung aeration and reduction of overdistension. The positive end-expiratory pressure levels set by the clinicians (11.6 ± 2.9 cm H2O) were associated with lower lung volumes, worse elastic properties of the lung, and lower oxygenation.ConclusionsCommonly used positive end-expiratory pressure by clinicians is inadequate for optimal mechanical ventilation of morbidly obese patients. A recruitment maneuver followed by end-expiratory pressure titration was found to significantly improve lung volumes, respiratory system elastance, and oxygenation.

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