[The effects of positive end-expiratory pressure on central venous pressure in patients with different chest wall elastic resistance].

Objective: To investigate the role of chest wall elastic resistance in determining the effects of positive end-expiratory pressure (PEEP) on central venous pressure (CVP) in patients with mechanical ventilation (MV). Methods: In this prospective study, according to the median of ratio of chest wall elastic resistance to respiratory system elastic resistance (Ers), patients were divided into high chest wall elastic resistance group (Ecw/Ers≥0.24) and low chest wall elastic resistance group [elastance of chest wall (Ecw)/Ers<0.24]. PEEP was set at 5, 10, 15 cmH2O (1 cmH2O=0.098 kPa) respectively. Clinical data including CVP, heart rate (HR), blood pressure (BP) and respiratory mechanics were recorded. Results: Seventy patients receiving MV were included from November 2017 to December 2018. Clinical characteristics including age, BP, HR, baseline PEEP, the ratio of arterial oxygen partial pressure to fractional inspired oxygen (P/F) and comorbidities were comparable in two groups. However, patients with high Ecw/Ers ratio presented higher body mass index (BMI) than those with low Ecw/Ers ratio[ (25.4±3.2) kg/m2 vs. (23.4±3.2) kg/m2, P=0.011]. As PEEP increased from 5 cmH2O to 10 cmH2O, CVP in high Ecw/Ers group increased significantly compared with that in low Ecw/Ers group [1.75(1.00, 2.13) mmHg (1 mmHg=0.133kPa) vs. 1.50(0.50, 2.00)mmHg,P=0.038], which was the same as PEEP increased from 10 cmH2O to 15 cmH2O [2.00(1.50, 3.00)mmHg vs. 1.50(1.00, 2.00)mmHg,P=0.041] or PEEP increased from 5 cmH2O to 15 cmH2O [ 3.75(3.00,4.63)mmHg vs. 3.00(1.63, 4.00)mmHg, P=0.012]. When PEEP increased from 5 cmH2O to 10 cmH2O, 10 cmH2O to 15 cmH2O and 10 cmH2O to 15 cmH2O, there were significant correlations between Ecw/Ers and CVP elevation (r=0.29, P=0.016; r=0.31, P=0.011; r=0.31, P=0.01 respectively). Conclusions: In patients receiving mechanical ventilation, elevation of PEEP leads to a synchronous change of CVP, which is corelated with patients' chest wall elastic resistances.