Effect of prone positioning on end-expiratory lung volume, strain and oxygenation change over time in COVID-19 acute respiratory distress syndrome: A prospective physiological study

Abstract

BackgroundProne position (PP) is a recommended intervention in severe classical acute respiratory distress syndrome (ARDS). Changes in lung resting volume, respiratory mechanics and gas exchange during a 16-h cycle of PP in COVID-19 ARDS has not been yet elucidated.MethodsPatients with severe COVID-19 ARDS were enrolled between May and September 2021 in a prospective cohort study in a University Teaching Hospital. Lung resting volume was quantitatively assessed by multiple breath nitrogen wash-in/wash-out technique to measure the end-expiratory lung volume (EELV). Timepoints included the following: Baseline, Supine Position (S1); start of PP (P0), and every 4-h (P4; P8; P12) until the end of PP (P16); and Supine Position (S2). Respiratory mechanics and gas exchange were assessed at each timepoint.Measurements and main results40 mechanically ventilated patients were included. EELV/predicted body weight (PBW) increased significantly over time. The highest increase was observed at P4. The highest absolute EELV/PBW values were observed at the end of the PP (P16 vs S1; median 33.5 ml/kg [InterQuartileRange, 28.2–38.7] vs 23.4 ml/kg [18.5–26.4], p < 0.001). Strain decreased immediately after PP and remained stable between P4 and P16. PaO2/FiO2 increased during PP reaching the highest level at P12 (P12 vs S1; 163 [138–217] vs 81 [65–97], p < 0.001). EELV/PBW, strain and PaO2/FiO2 decreased at S2 although EELV/PBW and PaO2/FiO2 were still significantly higher as compared to S1. Both absolute values over time and changes of strain and PaO2/FiO2 at P16 and S2 versus S1 were strongly associated with EELV/PBW levels.ConclusionIn severe COVID-19 ARDS, EELV steadily increased over a 16-h cycle of PP peaking at P16. Strain gradually decreased, and oxygenation improved over time. Changes in strain and oxygenation at the end of PP and back to SP were strongly associated with changes in EELV/PBW. Whether the change in EELV and oxygenation during PP may play a role on outcomes in COVID-ARDS deserves further investigation.Clinical trial registration[www.ClinicalTrials.gov], identifier [NCT 04818164].

Magnitude and time to peak oxygenation effect of prone positioning in ventilated adults with COVID‐19 related acute hypoxemic respiratory failure

“…Importantly, while recommendations advocate for prolonged prone position episodes, its optimal duration has not been determined 21 . A major finding from our study is that the peak effect on oxygenation occurred in the first episode and peaked at 9 h, earlier than similar reports 37 . While it is feasible to extend prone sessions beyond 24 24 or even 48 23 h, this carries risks of prone‐related complications including ocular, nerve or pressure injuries 2,38,39 …”

“…21 A major finding from our study is that the peak effect on oxygenation occurred in the first episode and peaked at 9 h, earlier than similar reports. 37 While it is feasible to extend prone sessions beyond 24 24 or even 48 23 h, this carries risks of prone-related complications including ocular, nerve or pressure injuries. 2,38,39 Prone position therapy is generally recommended to be continued until the criteria to stop are met; that is, a PaO 2 :FiO 2 ratio of ≥150 with positive end expiratory pressure ≤10 cmH 2 0 and an FiO 2 of ≤0.6.…”

End-expiratory lung volumes as a potential indicator for COVID-19 associated acute respiratory distress syndrome: a retrospective study

“…Dilken et al conducted a study on 40 intubated COVID-19 patients to examine the variations in EELV while in supine and prone positions. Their study monitored changes over a single day, and reported median values of 1444 ml for EELV, 23.4 ml/kg for EELV/PBW, and 0.31 for strain in the supine position, but did not assess patient outcomes [ 32 ]. In our study, we found median values of 1287 ml for EELV, 19.96 ml/kg for EELV/PBW, and 0.30 for strain.…”