Effect of head-end of bed elevation on respiratory mechanics in mechanically ventilated patients with moderate-to-severe COVID-19 ARDS – A cohort study

BACKGROUND: Head-end elevation (HEE) is known to improve oxygenation and respiratory mechanics. In ARDS, poor lung compliance limits positive pressure ventilation causing delivery of inadequate minute ventilation (MVe). We observed that, in moderate-to-severe COVID-19 ARDS, the respiratory system compliance (Crs) reduces upon elevating the head-end of the bed, and vice-versa, which can be utilized to improve ventilation and avoid respiratory acidosis. We hypothesized that increasing the degree of HEE reduces Crs. METHODS: We included 20 consecutive mechanically ventilated, moderate-to-severe COVID-19 ARDS patients in this pilot study (CTRI/2021/06/034,182). The Crs, Mve and Rinsp were recorded at 0°, 10°, 20° and 30° HEE. Repeated measures ANOVA was used to determine significant differences in measurements with increasing degrees and repeated measures correlation (rmcorr) for correlation. RESULTS: Repeated measures ANOVA showed a significant difference (p < 0.0001) between values of Crs, MVe and Rinsp. Rmcorr showed a strong negative correlation between increasing degrees and Crs and Mve (r-0.87 [95% CI -0.79 to −0.92, p < 0.0001 and r-0.77 [95% CI -0.64 to −0.85, p < 0.0001]) and a moderate negative correlation for Rinsp (r-0.67; 95% CI -0.79 to −0.50; p < 0.0001). CONCLUSIONS: Increasing degree of HEE reduces compliance in moderate-to-severe COVID-19 ARDS. Reducing HEE may optimize ventilation and mitigate ventilator induced lung injury.