Fig. 3
Pressure-volume loops obtained from intratracheal pressure measurement. a, represents the pressure-volume loop at the beginning of FCV with a peak inspiratory pressure (Ppeak) set to 28 cm H2O and a positive end-expiratory pressure (PEEP) of 10 cm H20. Considering the measured resistance of 11.7 cm H2O/l/s and the set flow of 12 l/min and applying Ohm’s law, the alveolar Ppeak calculates to only 25.7 cm H2O and the alveolar PEEP to 12.3 cm H2O. b, after compliance-guided pressure settings Ppeak was reduced to 23 cm H2O (alveolar 21 cm H2O) and PEEP 7 cm H2O (alveolar 9 cm H2O) resulting in an almost linear relation of pressure and volume during in- and expiration. The steeper course of the PV loop in B compared to A indicates the increased compliance after individualized pressure settings. c, two hours after first compliance-guided pressure setting, re-evaluation showed a slight decline in lung mechanics. Therefore, Ppeak was adjusted to 22 cm H2O (alveolar 20 cm H2O) and PEEP to 5 cm H2O (alveolar 7 cm H2O). The initial kinking of the inspiratory pressure volume curve in C is an indicator for intratidal recruitment