Prediction of static compliance of the respiratory system based on anthropometric measurements in patients on mechanical ventilation: a cross-sectional study

Abstract

Standard Crs reference values (50–70 ml/cmH2O) lack population-specific data and might be influenced by anthropometry. This study aimed to establish practical Crs values, explore the Crs/Predicted Body Weight (PBW) relationship, and develop a predictive model for Crs. A multicenter, cross-sectional study involving mechanically ventilated patients was conducted across Brazil. Patients with hemodynamic instability, chest wall deformities, or intrathoracic limitations were excluded. Data collected included PBW, plateau pressure, Crs, and Driving Pressure (DP). Patients were categorized into three PBW groups (G1 < 59kg, G2 59-68kg, G3 > 68kg) and further stratified by the presence/absence of pulmonary disease. The study included 159 patients with median values of Crs (38.0 ml/cmH2O), DP (9.0 cmH2O), and Crs/PBW (0.65 ml/cmH2O/kg). Statistically significant differences in Crs were observed between G1 vs. G2 (p = 0.03) and G1 vs. G3 (p < 0.01). However, the presence/absence of pulmonary disease did not significantly affect Crs (p = 0.59). The formulated predictive model for Crs yielded an R² of 0.157. Our study indicated that Crs in mechanically ventilated patients with near-normal elastance appears influenced by anthropometric data, particularly height and sex. A Crs/PBW cutoff of 0.6 ml/cmH2O/kg was established. The study also presents a preliminary model for Crs prediction.