Effect of awake prone position on diaphragmatic thickening fraction in patients assisted by noninvasive ventilation for hypoxemic acute respiratory failure related to novel coronavirus disease

Abstract

Background: Awake prone position is an emerging rescue therapy applied in patients undergoing noninvasive ventilation (NIV) for acute hypoxemic respiratory failure (ARF) related to novel coronavirus disease (COVID-19). Although applied to stabilize respiratory status, in awake patients, the application of prone position may reduce comfort with a consequent increase in the workload imposed on respiratory muscles. Thus, we primarily ascertained the effect of awake prone position on diaphragmatic thickening fraction, assessed through ultrasound, in COVID-19 patients undergoing NIV.

Methods: We enrolled all COVID-19 adult critically ill patients, admitted to intensive care unit (ICU) for hypoxemic ARF and undergoing NIV, deserving of awake prone positioning as a rescue therapy. Exclusion criteria were pregnancy and any contraindication to awake prone position and NIV. On ICU admission, after NIV onset, in supine position, and at 1 h following awake prone position application, diaphragmatic thickening fraction was obtained on the right side. Across all the study phases, NIV was maintained with the same setting present at study entry. Vital signs were monitored throughout the entire study period. Comfort was assessed through numerical rating scale (0 the worst comfort and 10 the highest comfort level). Data were presented in median and 25th-75th percentile range.

Results: From February to May 2021, 20 patients were enrolled and finally analyzed. Despite peripheral oxygen saturation improvement [96 (94-97)% supine vs 98 (96-99)% prone, p = 0.008], turning to prone position induced a worsening in comfort score from 7.0 (6.0-8.0) to 6.0 (5.0-7.0) (p = 0.012) and an increase in diaphragmatic thickening fraction from 33.3 (25.7-40.5)% to 41.5 (29.8-50.0)% (p = 0.025).

Conclusions: In our COVID-19 patients assisted by NIV in ICU, the application of awake prone position improved the oxygenation at the expense of a greater diaphragmatic thickening fraction compared to supine position. Trial registration ClinicalTrials.gov, number NCT04904731. Registered on 05/25/2021, retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT04904731 .

Fig. 1

Enrollment flow diagram. COVID-19, novel coronavirus disease; ICU, intensive care unit; NIV, noninvasive ventilation

Fig. 2

Generalized linear mixed model predicted diaphragmatic thickening fractions according to comfort scores, adjusted for body position, i.e., supine versus prone. Generalized linear mixed model predicted diaphragmatic thickening fractions according to comfort scores with 95% confidence intervals, adjusted for body position, i.e., supine (green) versus prone (red), are depicted. Fixed effect comfort score estimate (95% CI) =  − 2.9 (− 5.5 to − 0.4); p = 0.025

Fig. 3

Impact of body position on diaphragmatic thickening fraction in the patients who experienced or not noninvasive ventilation failure within 48 h following study completion. Boxes and whiskers represent median, 25th–75th percentile, and minimum-to-maximum interval of diaphragmatic thickening fractions acquired in supine and prone position. Hollow boxes refer to patients who experienced NIV failure while grey boxes refer to patients with NIV success. *p = 0.008, NIV failure versus NIV success, refers to mixed model analysis carried out with Satterthwaite methods of degrees of freedom. NIV, noninvasive ventilation