Dynamic evaluation of the pulmonary protective effects of prone position ventilation via respiratory mechanics for patients with moderate to severe acute respiratory distress syndrome

Background: Patients with moderate to severe acute respiratory distress syndrome (ARDS) have been recommended to receive prone position ventilation (PPV). However, the dynamic changes in respiratory mechanics during PPV and their relationship with the prognosis have not been sufficiently evaluated. In addition, the impact of using neuromuscular blocking agents (NMBAs) during PPV on respiratory mechanics is not clear enough. Thus, the study aims to investigate the above-mentioned issues. Methods: A prospective cohort study was conducted on 22 patients with moderate to severe ARDS who received PPV in the intensive care unit (ICU) of the First Affiliated Hospital of Guangzhou Medical University. A multifunctional gastric tube was used to measure the patients' respiratory mechanics during supine position ventilation (SPV), early PPV (PPV within 4 h of initiation), and middle/late PPV (more than 6 h after the initiation of PPV). Longitudinal data were analyzed with generalized estimating equations (GEE). Results: Compared with SPV, the esophageal pressure swings (APes) measured during the PPV was significantly higher (SPV 7.46 vs. early PPV 8.00 vs. middle/late PPV 8.30 cmH2O respectively; PSPVvs. middle/late PPV =0.025 < 0.05). A stratified analysis by patients' outcome showed that the peak airway pressure (Ppeak), APes and respiration rate (RR) in the death group were significantly higher than survival group. On the contrary, the tidal volume (Vt), diaphragmatic electromyogram (EMGdi) and PaO2/FiO2 ratio (PFR) in the death group were significantly lower than survival group. Notably, the APes and transpulmonary driving pressure (DPL) were significantly lower in the patients treated with NMBAs (7.08 vs. 8.76 cmH2O APes; P < 0.01), (14.82 vs. 18.08 cmH2O DPL; P < 0.001). Conclusions: During the transition from SPV to early PPV and then to middle/late PPV, the APes in the PPV were greater than SPV and it fluctuated within a normal range while oxygenation improved significantly in all patients. The Ppeak, APes and RR in the death group were significantly higher than survival group. When NMBAs were used, the APes, inspiratory transpulmonary pressure (PLei), driving pressure (DP) and DPL were significantly decreased, suggesting that the rational combination of NMBAs and PPV may exert a synergistic protective effect on the lungs.

Automated summary

This study found that APes during PPV in patients with moderate to severe ARDS was significantly higher than during SPV, and the use of neuromuscular blocking agents could reduce changes in respiratory mechanics, suggesting a protective effect on the lungs.