Résumé
Background No study has evaluated the inspiratory effort in patients with obesity immediately after extubation according to the noninvasive ventilatory support used. We aimed to determine, in critically ill patients with morbid obesity, whether Non Invasive Ventilation applied with facial mask with Pressure Support above Positive End-Expiratory Pressure (PSV-PEEP) may reduce patient inspiratory efforts to a greater extent than Continuous Positive Airway Pressure (CPAP) after extubation. Methods We conducted a post-hoc analysis based on data from a physiological study involving consecutive patients with morbid obesity prior to extubation. Flow, airway, esophageal, and gastric pressure signals were then recorded 20 min after extubation under three distinct conditions: (1) standard oxygen, (2) CPAP and (3) PSV-PEEP. Inspiratory efforts were assessed by calculation of the trans-diaphragmatic pressure (Pdi) and work-of-breathing (WOB). Results Fifteen patients with mean body mass index of 45 kg/m 2 (± 8 kg/m 2 ) were enrolled. WOB and Swing Pdi were lower with PSV-PEEP than with CPAP and standard oxygen respectively 5.3 [3.6–6.0] vs 8.4 [7.4–10.0] and 14.9 [11.1–22.1] J/min (p < 0.001), and 5.9 [4.0–7.8] vs 11.4 [10.1–13.1] and 19.6 [18.5–23.6] cmH2O (p < 0.001). We also observed a significant decrease of respiratory rate (RR) and RR/V T (tidal volume) ratio with the use of PSV-PEEP (24.4 [21.9–27.7] breaths/min and 65.7 [45.1–78.5] min/mL, respectively), and with the use of CPAP (24.6 [24.1–34.5] breaths/min and 75.3 [57.2–108.0] min/mL), compared with standard oxygen (29.0 [24.2–34.9] breaths/min and 81.1 [73.5–108.9] min/mL), p < 0.05. Conclusion In critically ill post extubation patients with morbid obesity, both PSV-PEEP and CPAP reduced the inspiratory effort indexes including inspiratory work-of-breathing, traducing an unload of inspiratory muscles. This effect was more important when PSV-PEEP was used in comparison to CPAP, suggesting a more pronounced effect of inspiratory muscle unloading.