Ultrasound variations of diaphragm activity between prone position versus supine position in ventilated patients: a cross-sectional comparative study

Abstract

Purpose To evaluate the effect of the positioning from the supine position (SP) to the prone position (PP) on the diaphragm activity in ventilated patients; using the ultrasound (US) imaging. Methods A cross-sectional comparative study before/after PP was conducted on 40 ICU patients over 18 years who received invasive ventilation (IV) for at least 48 h. The considered ventilator modes were: assisted control volume with a low trigger flow (between − 2 and 2 L/mn) and pressure support mode. US diaphragmatic assessments were performed at SP and at 60 min of PP. Both End-inspiratory and End-expiratory diameters (EID/EED) were taken at 3 levels of axillary lines and determined by the average values of multiple measures. Diaphragmatic thickening fraction (DTF) was calculated as: DTF = (EID − EED/EED) × 100. Pairing and ANOVA tests were used for comparisons. Results Forty ventilated patients (42 years of median age) at 4 days [2-7] of median duration of ventilation were examined during the two positions: SP versus PP. EID decreased from the SP to the PP (2.8 mm in SP vs. 2.4 mm in PP, p = 0.001). No difference was showed regarding the expiratory thickness. Overall, DTF didn't change in PP (37.4 vs. 42.05%, p = 0.36). When the patient was placed in PP, the best DTF value was showed at the posterior part of diaphragm (posterior: 45%, median: 31% and anterior: 38%, p = 0.049). Conclusion The ventral placement in ventilated patients reduced end-inspiratory diameter and tended to decrease DTF. In PP, the best contractile activity was detected at the posterior region of diaphragm.

Prone Positioning Decreases Inhomogeneity and Improves Dorsal Compliance in Invasively Ventilated Spontaneously Breathing COVID-19 Patients—A Study Using Electrical Impedance Tomography

“…Given that we evaluated changes in aeration in patients who did not receive neuromuscular blocking agents, it can be speculated that the observed improvements were related to the patient’s respiratory effort. Notwithstanding, prone position in invasively ventilated patients is associated with less respiratory effort [ 35 ] and less diaphragmatic function [ 36 ], which would decrease apparent compliance and not improve it. We also observed a decrease in the global inhomogeneity index, which is opposite to the effect expected after an increase in the respiratory effort [ 37 ], and no increase in the pendelluft phenomenon incidence.…”

Review of Physiological Rationale of Physiotherapy in Covid-19 Patients: A Case Series

“…Prone position reduces alveolar trauma thereby eliminating the deterioration to the need for invasive mechanical ventilation. Ventilation in the prone position may not be as effective as in the supine, but the V/Q matching is optimized [13]. The duration of prone position recommended is minimum of 2 hours for the effect to take place [14].…”

“…In prone, the Diaphragm shows increased motility in the dorsal regions, freeing the posterior basal segments, enabling expansion [13]. The heart and mediastinum also shift ventrally in prone, reducing the weight on the lungs, recruiting more alveoli [15].…”

Diaphragm and Phrenic Nerve Ultrasound in COVID‐19 Patients and Beyond

“…Diaphragm ultrasound variations between prone and supine positioning have been described, which is an important consideration given the common practice of prone positioning of COVID-19 patients to improve oxygenation. 17,29 In our practice, we perform all imaging with the patient in the supine position. If patient effort is not deemed as appropriate at baseline, imaging of both neutral (i.e., unprompted) respiration as well as prompted deep breathing is obtained.…”