Impact of positive end-expiratory pressure on systemic hemodynamics in patients with central respiratory failure

Abstract

Objective To evaluate the impact of positive end-expiratory pressure (PEEP) on hemodynamic variables including central venous pressure (CVP),mean arterial pressure (MAP) and heart rate (HR) in patients with central respiratory failure treated by mechanical ventilation.Methods Thirty two neurosurgical patients with central respiratory failure,male 19,female 13,mean age (58.8 ± 13.9)years,GCS ≤ 8 points,were enrolled in this prospective,self-control study between June 1,2009,and May 31,2011.Patients were excluded in cases of severe cardiopulmonary disorders,pericardial diseases,person machine confrontation,administration of vasoactive drugs,and hypervolemia or hypovolemia.On admission to neurosurgical intensive care unit,all patients were mechanically ventilated in the mode of synchronized intermittent mandatory ventilation.Hemodynamic effects of six randomly set levels of end-expiratory pressures (0,3,6,9,12,15 cm H2O,every 10 min,1cm H2O =0.098 kPa) were studied in all patients.CVP,MAP and HR were recorded at each of the six end-expiratory pressure levels.One-way analysis of variance and simple linear regression model were used for data analysis.Results The levels of central venous pressure were elevated with increase in end-expiratory pressures.CVP levels were positively correlated with the levels of PEEP (R =0.468,P =0.000),with a simple linear regression equation expressed as:CVP (cm H2O) =7.870 +0.344 ×PEEP (cm H2O),The levels of MAP showed no statistically significant changes at different PEEP levels (F =1.390,P =0.227).No linear correlation between MAP,HR and PEEP levels was found (R =0.042 and 0.160,P =0.413 and 0.002).Conclusions CVP values would be overestimated during mechanical ventilation at different PEEP levels in mechanically ventilated patients due to central respiratory failure,positive correlation existed between CVP values and PEEP levels,whereas MAP was unaffected by different PEEP levels.This study could probably offer a quantitative reference for correct assessment of such a hemodynamic variable as CVP for mechanically ventilated patients without discontinuance of PEEP.Further studies are needed to determine whether these findings could be confirmed in a prospective manner. Key words: Positive end-expiratory pressure; Central venous pressure; Central respiratory failure; Mechanical ventilation