TOPIC: Respiratory Care
TYPE: Original Investigations
PURPOSE: To date, multiple large randomized trials investigating the effects of prone positioning on both oxygenation and mortality in ARDS have shown positive results. By reversing the vertical pleural pressure gradient and reducing the superimposed pressure of both the heart and the abdomen, prone positioning improves oxygenation in patients with severe ARDS. Although trial results have demonstrated the benefit of prone positioning, all patients were either placed flat or in the reverse Trendelenburg position. No studies are available to compare the effects of positioning the bed in different angles during proning. In this observational study, we examine the effect of Trendelenburg position during prone position ventilation in patients with severe ARDS secondary to COVID-19 pneumonia.
METHODS: This is an observational study of adult patients admitted to MICU with severe ARDS secondary to COVID-19 pneumonia requiring prone position ventilation. Prone positioning was started within 48 hours of developing severe ARDS and the bed was positioned in Trendelenburg’s position within 3-6 hours after prone position was achieved. All patients were mechanically ventilated in pressure-controlled mode with various PEEP depending on their lung mechanics. Patients were paralyzed using Cisatracurium drips to eliminate spontaneous effort and patient-ventilator dyssynchrony. Tidal volumes were recorded 15 minutes prior to Trendelenburg positioning and 60 minutes after. Respiratory system compliance was calculated using the formula VT/(Pplat-PEEP), and no changes were made to the patient’s ventilator settings between the recordings. T-test was done to compare the values.
RESULTS: Seven adult patients aged 38-70 years were included in this study. Patient BMI’s ranged from 27 to 42kg/m2with two patients in the overweight range and five in the obesity range. Increased tidal volumes were observed in all patients by an average of 72 ml/breath (18%) after Trendelenburg positioning. This increase was statistically significant (p <.01). Respiratory system compliance ranged from 19.28 +/- 6 ml/cmH2O prior to Trendelenburg positioning and 23.3 +/-5 ml/cmH2O after, with an average increase of 4 ml/cmH2O (18%); although this change was not statistically significant (P 0.2).
CONCLUSIONS: In this study, statistically significant increase in tidal volume without increased pressure support was observed in patients placed in Trendelenburg position during prone position ventilation which may indicate improvement in lung compliance and thereby improve alveolar ventilation. These effects may be the reflection of change in pleural pressure and trans-pulmonary pressure during body positioning. Although improvement in respiratory system compliance was not found to be statistically significant, this is likely due to small sample size and body habitus of the participants as large pannus may decrease diaphragmatic excursion during Trendelenburg position thereby masking the effect of respiratory system compliance from the positioning itself.
CLINICAL IMPLICATIONS: This is a unique study examining the effect of Trendelenburg positioning on lung mechanics. More studies need to be done to evaluate different bed positioning in augmenting ventilation for patients with ARDS. Patient BMI as well as comorbidities should be taken into account as the observed benefits from different positioning may be correlated to their physiology.
DISCLOSURES: No relevant relationships by ehab daoud, source=Web Response
No relevant relationships by Marissa Su, source=Web Response
© 2021 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.