key: cord-1007130-qlbn0gg3
authors: Stavi, Dekel; Goffi, Alberto; Al Shalabi, Mufid; Piraino, Thomas; Chen, Lu; Jackson, Robert; Brochard, Laurent
title: The Pressure Paradox: Abdominal Compression to Detect Lung Hyperinflation in COVID-19 Acute Respiratory Distress Syndrome
date: 2021-11-08
journal: Am. j. respir. crit. care med
DOI: 10.1164/rccm.202104-1062im
sha: efacf9e677715eae251de1776e1a4a609f832c3e
doc_id: 1007130
cord_uid: qlbn0gg3

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A 57-year-old male with respiratory failure secondary to coronavirus disease (COVID-19) pneumonia was intubated for worsening hypoxemia 22 days after onset of symptoms. Past medical history was significant for type 2 diabetes mellitus, hypertension, mild asthma, distal pancreatectomy in the context of severe necrotizing pancreatitis (2003), small hiatal hernia, and 20-pack-year smoking. His body mass index was 20.7 kg/m 2 . He was ventilated with ultraprotective volume-control ventilation (VT of 4.5 ml/kg predicted body weight) and, owing to lack of recruitability as assessed by the recruitment-to-inflation ratio (0.2) (1), positive end-expiratory pressure (PEEP) of 6 cm H 2 O. Chest radiography demonstrated dense bilateral consolidations to the lower lobes and periphery of the mid-lung zones associated with mild to moderate interstitial edema and pulmonary vascular prominence. A computed tomographic scan confirmed bilateral widespread subpleural consolidations associated with patchy peripheral ground-glass opacities with areas of lobular sparing.

On Day 4 after intubation, while the patient was sedated and paralyzed, and in supine semirecumbent position, we noticed that a moderate sustained manual compression at the level of the patient's mesogastrium was associated with a paradoxical and almost immediate drop in both peak and plateau pressures that persisted for the entire duration of abdominal compression (see Figure 1 and Video 1) (2) . Pressure values returned to baseline as soon as compression was released. This phenomenon was reproducible over the course of several days.

The measured quasistatic (3) airway and static esophageal and bladder pressures (and their derived parameters of lung and chest wall respiratory mechanics; https://rtmaven.com) are shown in Table 1 and Video 1. Visual observation of pressure-time curve profiles revealed a reduction of the pressure over time concavity during abdominal compression (see Figure 1 and Video 1) (2). This observation suggests that the pressure applied to the patient's abdomen, by increasing intrathoracic pressure, caused a reduction in the end-expiratory lung volume and a downward shift of the pressure-volume curve, with reduction in tidal hyperinflation and possibly increase in tidal recruitment. The combination of these two effects led to the paradoxical improvement of lung and respiratory system compliance, and of lung stress (4, 5) .

Since our original observation in June 2020, we and other groups (5) have identified several patients with severe COVID-19 acute respiratory distress syndrome displaying similar paradoxical improvements of respiratory mechanics during abdominal compression. Such a simple bedside maneuver can detect lung hyperinflation even in patients mechanically ventilated with ultraprotective lung strategies and low PEEP. 

Potential for lung recruitment estimated by the recruitment-to-inflation ratio in acute respiratory distress syndrome. A clinical trial

Airway pressure-time curve profile (stress index) detects tidal recruitment/hyperinflation in experimental acute lung injury

Fifty years of research in ARDS. Respiratory mechanics in acute respiratory distress syndrome

Improving lung compliance by external compression of the chest wall

Paradoxically Improved Respiratory Compliance With Abdominal Compression in COVID-19 ARDS

Video 1. Video demonstrating the paradoxical effect of a moderate sustained manual abdominal compression and its release on airway pressures and respiratory mechanics in a sedated and paralyzed patient with severe respiratory failure secondary to coronavirus disease (COVID-19) infection