[Effect of different transpulmonary pressures guided mechanical ventilation on respiratory and hemodynamics of patients with ARDS: a prospective randomized controlled trial]

Abstract

Objective: To assess the effect of different transpulmonary pressures (Ptp) guided mechanical ventilation (MV) on respiratory function and hemodynamics parameters of patients with acute respiratory distress syndrome (ARDS), and to find out a more optimized Ptp.

Methods: A prospective randomized controlled trial (RCT) was conducted. The ventilated patients with ARDS admitted to Department of Critical Care Medicine (ICU) of Shenzhen Shajing Affiliated Hospital of Guangzhou Medical University and Department of Emergency and Critical Care Medicine (EICU) of Shenzhen Hospital of South Medical University from February 2013 to August 2016 were enrolled. According to random number table method, all patients were divided into control group and observation group. The patients in observation group was subdivided into three subgroups according to the different setting of Ptp, namely Ptp 10, 15, 20 cmH₂O (1 cmH₂O = 0.098 kPa) subgroups. The patients in all groups received standard treatment in accordance with the international guidelines for ARDS. The patients in control group were ventilated by guidance of ARDSNet, and the patients in observation group were ventilated by guidance of different Ptp. After setting different Ptp at 1, 24, 48 hours in the process of MV, respiratory function parameters of patients in all groups were determined. The hemodynamic parameters were determined by using pulse indicating continuous cardiac output (PiCCO) technology. The duration of MV, length of ICU stay and 28-day mortality were recorded.

Results: A total of 67 patients with ARDS were enrolled, among whom 2 patients died within 48 hours, and 1 case was lost to follow-up. Finally, 64 patients completed the study, 43 patients in observation group, and 21 in control group. There were no significant differences in gender composition, age, oxygenation index (PaO₂/FiO₂) within 4 hours after hospital admission and acute physiology and chronic health evaluation II (APACHE II) score between the two groups, which showed the baseline was equivalent and comparable. The respiratory function and hemodynamic parameters showed no obvious change in control group at different time points of MV; but with the extension of ventilation, the respiratory function was improved significantly in observation group, and the gradually rising of Ptp had obvious adverse effects on hemodynamics parameters. Compared with control group, at 48 hours of ventilation after setting Ptp, the respiratory function in Ptp 20 cmH₂O subgroup was improved significantly, PaO₂/FiO₂, arterial partial pressure of carbon dioxide (PaCO₂), positive end-expiratory pressure (PEEP), airway platform pressure (Pplat), and lung compliance (Cst) were significantly increased [PaO₂/FiO₂ (mmHg, 1 mmHg = 0.133 kPa): 220.9±30.8 vs. 178.5±42.9, PaCO₂ (mmHg): 55.1±7.6 vs. 38.6±4.8, PEEP (cmH₂O): 24.7±4.8 vs. 6.6±2.2, Pplat (cmH₂O): 34.4±3.7 vs. 20.7±3.5, Cst (mL/cmH₂O): 23.8±3.6 vs. 13.1±4.6; all P < 0.05], and extravascular lung water index (ELWI) was significantly decreased (mL/kg: 6.8±1.7 vs. 10.8±2.6, P < 0.05), but mean artery pressure (MAP), cardiac index (CI), global end-diastolic volume index (GEDVI) such as hemodynamics parameters were also significantly reduced [MAP (mmHg): 58.8±6.7 vs. 69.7±4.7, CI (mL×s^-1×m^-2): 46.7±23.3 vs. 73.3±30.0, GEDVI (mL/m²): 633.2±45.2 vs. 702.6±55.7; all P < 0.05]; the PaO₂/FiO₂, PEEP, Pplat, and Cst in Ptp 10 cmH₂O subgroup were significantly increased [PaO₂/FiO₂ (mmHg): 183.4±45.5 vs. 178.5±42.9, PEEP (cmH₂O): 14.4±3.6 vs. 6.6±2.2, Pplat (cmH₂O): 25.7±5.6 vs. 20.7±3.5, Cst (mL/cmH₂O): 16.2±4.3 vs. 13.1±4.6; all P < 0.05], and ELWI was significantly reduced (mL/kg: 8.7±1.8 vs. 10.8±2.6, P < 0.05), but the MAP, CI and GEDVI showed no significant difference [MAP (mmHg): 65.8±4.6 vs. 69.7±4.7, CI (mL×s^-1×m^-2): 65.0±35.0 vs. 73.3±30.0, GEDVI (mL/m²): 706.7±54.4 vs. 702.6±55.7; all P > 0.05]. The above illustrated that 10 cmH₂O Ptp could act as the same as 20 cmH₂O did to improve oxygenation and respiratory function, but had no obvious effect on hemodynamics. Compared with control group, the duration of MV and the length of ICU stay showed no significant differences in Ptp 10 cmH₂O and 15 cmH₂O subgroups, but those in 20 cmH₂O subgroup were significantly shortened [duration of MV (days): 95.5±21.5 vs. 130.8±23.6, length of ICU stay (days): 8.1±2.2 vs. 12.8±2.8, both P > 0.05]. There was no significant difference in 28-day mortality among the groups.

Conclusions: MV guided by Ptp of 10 cmH₂O could improve oxygenation and respiratory mechanics, while has less hemodynamic influence. It was a safe and effective cardiopulmonary protection ventilation method.