Abstract
IntroductionFunctional residual capacity (FRC) measurement is now available on new ventilators as an automated procedure. We compared FRC, static thoracopulmonary compliance (Crs) and PaO2 evolution in an experimental model of acute respiratory distress syndrome (ARDS) during a reversed, sequential ramp procedure of positive end-expiratory pressure (PEEP) changes to investigate the potential interest of combined FRC and Crs measurement in such a pathologic state.MethodsARDS was induced by oleic acid injection in six anesthetised pigs. FRC and Crs were measured, and arterial blood samples were taken after induction of ARDS during a sequential ramp change of PEEP from 20 cm H2O to 0 cm H2O by steps of 5 cm H2O.ResultsARDS was responsible for significant decreases in FRC, Crs and PaO2 values. During ARDS, 20 cm H2O of PEEP was associated with FRC values that increased from 6.2 ± 1.3 to 19.7 ± 2.9 ml/kg and a significant improvement in PaO2. The maximal value of Crs was reached at a PEEP of 15 cm H2O, and the maximal value of FRC at a PEEP of 20 cm H2O. From a PEEP value of 15 to 0 cm H2O, FRC and Crs decreased progressively.ConclusionOur results indicate that combined FRC and Crs measurements may help to identify the optimal level of PEEP. Indeed, by taking into account the value of both parameters during a sequential ramp change of PEEP from 20 cm H2O to 0 cm H2O by steps of 5 cm H2O, the end of overdistension may be identified by an increase in Crs and the start of derecruitment by an abrupt decrease in FRC.
Highlights
Functional residual capacity (FRC) measurement is available on new ventilators as an automated procedure
During acute respiratory distress syndrome (ARDS), 20 cm H2O of positive end-expiratory pressure (PEEP) was associated with FRC values that increased from 6.2 ± 1.3 to 19.7 ± 2.9 ml/kg and a significant improvement in PaO2
Our results indicate that combined FRC and compliance of the respiratory system (Crs) measurements may help to identify the optimal level of PEEP
Summary
Functional residual capacity (FRC) measurement is available on new ventilators as an automated procedure. We compared FRC, static thoracopulmonary compliance (Crs) and PaO2 evolution in an experimental model of acute respiratory distress syndrome (ARDS) during a reversed, sequential ramp procedure of positive end-expiratory pressure (PEEP) changes to investigate the potential interest of combined FRC and Crs measurement in such a pathologic state. Functional residual capacity (FRC), which reflects the amount of gas present in the lungs, has been suggested to be a better indicator than Crs to assess the state of recruitment and derecruitment caused by ARDS = acute respiratory distress syndrome; Crs = static thoracopulmonary compliance of the respiratory system; FRC = functional residual capacity, PEEP = positive end-expiratory pressure; Pexp = expiratory plateau airway pressure; Pins = inspiratory plateau airway pressure; Vt = tidal volume. We compared FRC, Crs and PaO2 evolution in an experimental model of ARDS during a reversed sequential ramp procedure of PEEP changes to investigate the potential interest of combining FRC and Crs measurements in such a pathologic state
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