Effect of Positive End Expiratory Pressure and Mean Airway Pressure on Respiratory Compliance and Gas Exchange in Children with Liver Disease

The effect of positive end expiratory pressure (PEEP) and mean airway pressure (MAP) on respiratory compliance and gas exchange was assessed in children with liver disease. In the first study of 12 patients, PEEP was decreased either by 3 cmH2O below the baseline level (the child's original level) or to 0 cmH2O and then increased to 3 cmH2O above the baseline. Decreasing PEEP impaired compliance (P < 0.01), and oxygenation (P < 0.05), whereas increasing PEEP improved compliance (P < 0.05) and oxygenation (P < 0.05). Neither increasing nor decreasing PEEP caused significant changes in the carbon dioxide levels. In the second study, 24 children were studied at their baseline settings and then after increasing the PEEP by 3 cm H2O while simultaneously lowering the peak inspiratory pressure (PIP) to maintain MAP constant (12 children had lung function measurements). In the group overall increasing PEEP while decreasing PIP resulted in an insignificant change in paO2, but a significant increase paCO2 (P < 0.01) and reduction in tidal volume (P < 0.01), the change in compliance was not significant. After a second period at the baseline settings, in 12 children inspiratory time (TI) was increased while keeping MAP constant by reducing PIP. No significant change in paO2 or compliance was experienced, but paCO2 increased (P < 0.05) and tidal volume decreased (P < 0.01). In the other 12 children MAP was increased by prolonging TI. Increasing MAP had a variable effect and the changes in paO2 and paCO2 were not significant. No critical MAP level with regard to oxygenation was demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)