PEEP Titration Is Markedly Affected by Trunk Inclination in Mechanically Ventilated Patients with COVID-19 ARDS: A Physiologic, Cross-Over Study

Abstract

Background: Changing trunk inclination affects lung function in patients with ARDS. However, its impacts on PEEP titration remain unknown. The primary aim of this study was to assess, in mechanically ventilated patients with COVID-19 ARDS, the effects of trunk inclination on PEEP titration. The secondary aim was to compare respiratory mechanics and gas exchange in the semi-recumbent (40° head-of-the-bed) and supine-flat (0°) positions following PEEP titration. Methods: Twelve patients were positioned both at 40° and 0° trunk inclination (randomized order). The PEEP associated with the best compromise between overdistension and collapse guided by Electrical Impedance Tomography (PEEPEIT) was set. After 30 min of controlled mechanical ventilation, data regarding respiratory mechanics, gas exchange, and EIT parameters were collected. The same procedure was repeated for the other trunk inclination. Results: PEEPEIT was lower in the semi-recumbent than in the supine-flat position (8 ± 2 vs. 13 ± 2 cmH2O, p < 0.001). A semi-recumbent position with optimized PEEP resulted in higher PaO2:FiO2 (141 ± 46 vs. 196 ± 99, p = 0.02) and a lower global inhomogeneity index (46 ± 10 vs. 53 ± 11, p = 0.008). After 30 min of observation, a loss of aeration (measured by EIT) was observed only in the supine-flat position (−153 ± 162 vs. 27 ± 203 mL, p = 0.007). Conclusions: A semi-recumbent position is associated with lower PEEPEIT and results in better oxygenation, less derecruitment, and more homogenous ventilation compared to the supine-flat position.

Comment on: Effects of changes in trunk inclination on ventilatory efficiency in ARDS patients: quasi‑experimental study

“…We have read with great interest the study conducted by Benites et al, which explores the impact of trunk inclination on ventilator efficiency in patients with ARDS [ 1 ]. Similarly to our own studies [ 2 – 4 ], and understandably given the historical period, most studied patients (18/22) had COVID-related ARDS. However, some results presented by Benites differ from what we have described and hypothesized [ 2 – 4 ] and might, therefore, deserve further discussion.…”

“…Similarly to our own studies [ 2 – 4 ], and understandably given the historical period, most studied patients (18/22) had COVID-related ARDS. However, some results presented by Benites differ from what we have described and hypothesized [ 2 – 4 ] and might, therefore, deserve further discussion.…”

“…The first key issue is the potential influence of trunk inclination on PEEP titration. Our recent work revealed that the “best PEEP”, balancing overdistension and collapse (identified with electrical impedance tomography-EIT), varies by an average of 5 cmH 2 O, depending on trunk inclination (semi-recumbent at 40° vs. supine-flat), with lower values identified in semi-recumbent position [ 4 ].…”

Monitoring lung recruitment

“…Lung recruitability varied from 0.3 to 66.9% regardless of ARDS severity, and EIT-based PEEP ranged from 10 cmH 2 O in low recruiters to 15.5 cmH 2 O in high recruiters. The EIT-based PEEP approach, as the best compromise between the lowest collapse and atelectasis, was shown to ensure lower de-recruitment, inhomogeneity of ventilation, and better oxygenation in a semi-recumbent position (40° head-of-the-bed) compared with a supine-flat position [51 ▪ ].…”

Setting positive end-expiratory pressure by using electrical impedance tomography

“…Several studies utilized the calculation of regional C rs using EIT. The effect of the head-up body tilt on the crossover point PEEP value determined from a decremental PEEP trial was examined in patients with ARDS showing lower PEEP values, better oxygenation and lower GI values in comparison with the flat supine posture [17]. Regional overdistension and collapse was determined based on a decremental PEEP trial in patients with ARDS and compared with a new approach based on the calculation of regional peak inspiratory flows, showing comparable results between the two methods [18].…”