[Correlation between functional residual capacity and trans-pulmonary pressure in acute respiratory distress syndrome patients and their prognostic value].

Objective: To analyze the application of functional residual capacity (FRC)-guided optimal positive end-expiratory pressure (PEEP) in pulmonary retention in patients with acute respiratory distress syndrome (ARDS), and to explore the correlation between FRC and trans-pulmonary pressure and their predictive value for prognosis.

Methods: Seventy-eight ARDS patients on mechanical ventilation admitted to department of critical care medicine of the First Affiliated Hospital of Jinzhou Medical University from March 2018 to May 2019 were enrolled. According to random number table method, the patients were divided into experimental group and the control group. PEEP of all patients were gradually increased in recruitment after fully sedation and analgesia. The best PEEP was set by monitoring FRC in the experimental group, and by monitoring maximum oxygen in the control group set. The differences before and after 30 minutes and 2 hours recruitment manoeuvres in dynamic compliance (Cdyn), oxygenation index (PaO/FiO), and mechanical power (MP) were compared between the two groups. Pearson method was used to analyze the correlation between FRC and trans-pulmonary pressure. The predictive value of FRC and trans-pulmonary pressure for 28-day mortality in patients with ARDS was analyzed by receiver operating characteristic (ROC) curve.

Results: The optimal PEEP was (16.24±1.57) cmHO (1 cmHO = 0.098 kPa) in the experimental group and (14.11±1.15) cmHO in the control group in recruitment maneuvres, with statistically significant difference between the two groups (t = 5.678, P = 0.000). Pearson correlation analysis showed that there was a significant correlation between FRC and trans-pulmonary pressure in ARDS patients (r = 0.759, P = 0.000). Cdyn and PaO/FiO in the experimental group were higher than the control group at 30 minutes and 2 hours after recruitment maneuvres [Cdyn (mL/cmHO): 61.16±3.55 vs. 58.54±5.25, 58.59±2.82 vs. 56.86±3.40; PaO/FiO (mmHg, 1 mmHg = 0.133 kPa): 245.27±14.86 vs. 239.00±5.34, 192.25±5.11 vs. 188.86±5.07], MP was lower than the control group (J/min: 16.32±1.11 vs. 17.05±1.22, 15.22±1.25 vs. 17.03±1.50), the difference was statistically significant (all P < 0.05). The ROC curve analysis showed that both FRC and trans-pulmonary pressure had predictive value for the 28-day mortality of ARDS patients, and the area under the ROC curve (AUC) was 0.868, and 0.828 respectively (both P < 0.01).

Conclusions: Measuring FRC in patients with ARDS during recruitment maneuvres can guide optimal PEEP. FRC was significantly correlated with trans-pulmonary pressure, and both of them had predictive value for 28-day mortality in ARDS patients.