The following parameters were calculated from ventilatory variables and the corresponding arterial blood gas values collected immediately before the first SBT (Fig. 1 ): ∆Paw (dynamic driving pressure, defined as Pmax—PEEP in the pressure-controlled ventilation mode), dynamic lung-thorax compliance (LTCdyn)15 (link), mechanical power11 (link) using the simplified formula proposed by Becher and colleagues16 (link),17 (link), and ventilatory ratio (VR, a surrogate for dead space ventilation)18 (link).
Total MP was further normalized to (1) the predicted body weight (a surrogate of the total lung capacity of a healthy individual, PBW-MP)19 (link) and (2) LTCdyn (indicating actual ventilated lung volume, LTCdyn-MP)12 (link). To allow comparability between individual respiratory rate and ventilator pressure settings, LTCdyn-MP was ultimately corrected for corresponding mechanical ventilation PaCO2 (simulating isocapnic conditions), called the Power index of the respiratory system13 (link). Further details can be found in the Supplementary information.
Total MP was further normalized to (1) the predicted body weight (a surrogate of the total lung capacity of a healthy individual, PBW-MP)19 (link) and (2) LTCdyn (indicating actual ventilated lung volume, LTCdyn-MP)12 (link). To allow comparability between individual respiratory rate and ventilator pressure settings, LTCdyn-MP was ultimately corrected for corresponding mechanical ventilation PaCO2 (simulating isocapnic conditions), called the Power index of the respiratory system13 (link). Further details can be found in the Supplementary information.
Free full text: Click here
