Prone position as a protective strategy during the onset of spontaneous effort in patients with ARDS on mechanical ventilation

To evaluate its impact on the transition of patients with acute respiratory distress syndrome (ARDS) under spontaneous ventilation, on the level of effort, drive, and magnitude of pendelluft, as well as on the homogenization of ventilation.

A clinical study approved by an ethical-scientific committee (N.012/2022) included patients on mechanical ventilation (MV) with ARDS in the resolution phase who were hemodynamically stable and had RASS -2 to -3. Pregnant women, patients with neuromuscular disease, new episodes of sepsis, and contraindications to monitoring devices were excluded. After individualizing the PEEP level (crossing point between least overdistension and collapse according to electrical impedance tomography (EIT) during downward titration) and pressure support (for VT 6-8 ml/kg and esophageal pressure swing (Pes) -10 cmH2O), each patient randomly received pressure support ventilation (PSV) in the supine position 35º-45º and prone position for one hour. At 30 (T1) and 60 (T2) minutes, respiratory variables (diaphragmatic electrical activity [EAdi], transdiaphragmatic pressure [Pdi=Pga-Pes], neuromuscular coupling [NMC=Pdi/EAdi], and pressure-time-minute product [PTPmin]) were recorded, as well as parameters derived from TIE (Pendellut and global inhomogeneity (GI) index). These variables were compared between supine and prone at T1 and T2 with paired t-tests and Spearman's test was used for correlations.

Seven patients were included (56±14 years; PaO2/FiO2 210 [200-217] mmHg, 4±2 days of MV at the time of the study). A lower EAdi and better NMC were observed in prone compared to supine (Figure 1). There were no changes in Pes or PTPmin. The decrease in the magnitude of pendelluft and ventilatory heterogeneity with the prone position were inversely correlated with their values in the supine position (r=-0.864 and r=-0.827, respectively

The prone position at the beginning of spontaneous ventilation could reduce the respiratory drive and improve neuromechanical coupling, as well as homogenize ventilation and reduce the magnitude of the pendelluft when its value is high in the supine position, representing a potential strategy to prevent damage associated with spontaneous ventilation. New studies are required to confirm these findings.

Using the prone position during the transition from controlled mechanical ventilation to spontaneous ventilation could reduce the risks of lung damage and allow safer ventilation in patients at risk of VILI.