Recruitability of the lung estimated by the pressure volume curve hysteresis in ARDS patients

Objective: To assess the hysteresis of the pressure-volume curve (PV curve) as to estimate, easily and at the bedside, the recruitability of the lung in ARDS patients. Design: Prospective study. Setting: Twelve medico-surgical ICU beds of a general hospital. Patients: Twenty-six patients within the first 24 h from meeting ARDS criteria. Intervention: A Quasi-static inflation and deflation PV curve from 0 to 40 cmH(2)O and a 40 cmH(2)O recruitment maneuver (RM) maintained for 10 s were successively done with an interval of 30 min in between. Recordings and calculation: Hysteresis of the PV curve (H (PV)) was calculated as the ratio of the area enclosed by the pressure volume loop divided by the predicted body weight (PBW). The volume increase during the RM (V (RM)) was measured by integration of the flow required to maintain the pressure at 40 cmH(2)O and divided by PBW, as an estimation of the volume recruited during the RM. Results: A positive linear correlation was found between H (PV) and V (RM) (r = 0.81, P < 0.0001). Conclusions: The results suggest using the hysteresis of the PV curve to assess the recruitability of the lung.