Prone positioning improves oxygenation and lung recruitment in patients with SARS-CoV-2 acute respiratory distress syndrome; a single centre cohort study of 20 consecutive patients

Abstract

Objective: We aimed to characterize the effects of prone positioning on respiratory mechanics and oxygenation in invasively ventilated patients with SARS-CoV-2 ARDS.

Results: This was a prospective cohort study in the Intensive Care Unit (ICU) of a tertiary referral centre. We included 20 consecutive, invasively ventilated patients with laboratory confirmed SARS-CoV-2 related ARDS who underwent prone positioning in ICU as part of their management. The main outcome was the effect of prone positioning on gas exchange and respiratory mechanics. There was a median improvement in the PaO2/FiO2 ratio of 132 in the prone position compared to the supine position (IQR 67-228). We observed lower PaO2/FiO2 ratios in those with low (< median) baseline respiratory system static compliance, compared to those with higher (> median) static compliance (P < 0.05). There was no significant difference in respiratory system static compliance with prone positioning. Prone positioning was effective in improving oxygenation in SARS-CoV-2 ARDS. Furthermore, poor respiratory system static compliance was common and was associated with disease severity. Improvements in oxygenation were partly due to lung recruitment. Prone positioning should be considered in patients with SARS-CoV-2 ARDS.

Keywords: Adult; Prone position; Respiratory distress syndrome; Severe acute respiratory syndrome coronavirus 2.

Conflict of interest statement

The authors declare they have no competing interests.

Figures

Fig. 1

The effect of prone positioning on gas exchange and respiratory mechanics are shown in (a–c). a Line graph representing mean PaO2/FiO2 ratio before, during, and after prone positioning, n=20, b Line graph representing mean Aa gradient before, during, and after prone positioning, n = 20, (c) Line graph representing mean respiratory system static compliance (CRS) before, during, and after prone positioning, n = 15, (d) shows the association between respiratory system static compliance (CRS) and severity of SARS-CoV-2 ARDS. It displays a box plot representing the difference in baseline PF ratio between patients with <median CRS and > median CRS, n = 19. PF = PaO2/FiO2 ratio, Aa = Alveolar-arterial gradient, CRS = respiratory system static compliance. Pre-Prone = immediately prior to prone positioning, Prone 1 = following prone positioning, Prone 2 = the mid-point of prone positioning, Prone 3 = prior to supination, and Post-Prone = following supination. Statistical Analysis: Analyzed by repeated measures two-way ANOVA with Tukey’s post-hoc test for multiple comparisons for line graphs and Mann-Whitney U test for box plot. ****P<0.0001, ** P<0.01, * P<0.05. Patients with incomplete data sets were excluded from analysis. a–c: error bars represent standard deviation. d: box plot with bars representing range.

Fig. 2

Electrical impedance tomographs (PulmoVista 500, Dräger) are shown above for 3 adult patients with SARS-CoV-2 ARDS who were invasively ventilated and underwent prone positioning. a represents the end-inspiratory trend view prior to prone positioning. b represents the end-inspiratory trend view following prone positioning. In (a, b), areas of increasing impedance variation (corresponding to greater ventilation) are represented in order of increasing variation in black (none), blue (intermediate) and white (greatest) colors. c represents the difference between the images in a, b, displaying loss of regional ventilation (areas in orange) which represent ventral regions being over-distended in the supine position and gain of regional ventilation (areas in blue) which represent recruitment of the dorsal regions upon prone positioning. Patients 1 and 3 showed an increase in tidal impedance variation in dorsal regions in the prone position and a decrease in tidal impedance variation in the ventral regions, which is consistent with lung recruitment dorsally.