In patients with acute respiratory distress syndrome (ARDS) receiving venovenous extracorporeal oxygenation (ECMO), the use of prone positioning (PP) improved oxygenation and was associated with reduced rates of hospital mortality, according to the results of a multicenter, retrospective cohort study published in the Annals of the American Thoracic Society.
Investigators sought to evaluate the feasibility, safety, and effect on oxygenation and lung mechanics of PP during ECMO. Additionally, they assessed the link between PP and hospital mortality. Patients from 6 Italian centers involved in the analysis were managed with either PP (prone group; 4 centers) or with supine positioning (control group; 2 centers). Physiologic variables were examined at 4 time points: supine prior to PP (one hour before); start of PP; end of PP; and supine after PP (one hour after supination). The relationship between PP and hospital mortality was evaluated with the use of multivariate analysis and propensity score matching.
A total of 240 patients were enrolled in the study — 107 in the prone group and 133 in the control group. The average participant age was almost the same in the prone and control groups (48±13 years vs 49±13 years, respectively). The majority of participants in both of the groups were men — 68.2% (73 of 107) of those in the prone group compared with 62.4% (83 of 133) of those in the control group.
In participants who underwent PP, the time from ECMO initiation to the first PP session was 4 days (range, 2-7 days). Overall, a total of 326 PP maneuvers were examined, and the mean duration of the pronation cycles was 15 hours (range, 12-18 hours). There were no major complications recorded. Minor reversible complications were reported in 6% (21 of 326) of the PP cycles. Overall, 6 of the procedures were aborted because of respiratory or hemodynamic instability during PP.
Results of the study showed that the intrapulmonary shunt fraction and the PaO2/FiO2 ratio significantly improved during PP, with that improvement maintained following resupination (P <.05). Moreover, static compliance of the respiratory system improved significantly following the PP cycle (P <.05).
Hospital mortality was significantly lower in the prone group compared with the control group (34% vs 50%, respectively; P =.017). Following adjustment for covariates, PP remained significantly associated with decreased hospital mortality (odds ratio, 0.50; 95% CI, 0.29-0.87). Patients in the prone group had longer durations of ECMO than those in the control group (16 days vs 10 days, respectively; P =.0344) but lower rates of hospital mortality (30% vs 53%, respectively; P =.0241).
Several study limitations were noted, including the retrospective design, the relatively small population, the possibility of selection bias, and the specificity of the ventilatory strategy applied which means that the findings may not be generalizable to facilities with different strategies.
The investigators concluded that prospective, controlled studies are warranted to confirm the effect of PP during ECMO in patients with ARDS.
Giani M, Martucci G, Madotto F, et al. Prone positioning during venovenous extracorporeal membrane oxygenation in acute respiratory distress syndrome: a multicentre cohort study and propensity-matched analysis. Ann Am Thorac Soc. Published online September 17, 2020. doi:10.1513/AnnalsATS.202006-625OC