Related Experiment Video
Updated: Jul 13, 2025

An Educational Video Demonstration of How to Prone a Critically Ill Intubated Patient
Published on: November 30, 2022
Changes in Respiratory Mechanics With Trunk Inclination Differs Between Patients With ARDS With and Without Obesity
Shailesh Bihari1, Ubbo F Wiersema2
1Department of ICCU, Flinders Medical Centre, Bedford Park, SA, Australia; College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.
Background:
Studies investigating the effect of trunk inclination on respiratory mechanics in mechanically ventilated patients with ARDS have reported postural differences in partition respiratory mechanics. Compared with more upright positions, the supine-flat position provided lower lung and chest wall elastance, allowing reduced driving pressures and end-inspiratory transpulmonary pressure. However, the effect of trunk inclination on respiratory mechanics in patients with obesity and ARDS is uncertain.
Research Question:
Does the effect of change in posture on partition respiratory mechanics differ between patients with ARDS with and without obesity?
Study Design And Methods:
In this single-center study, patients with ARDS with and without obesity were randomized into two 15-minute steps in which trunk inclination was changed from semi-recumbent (40° head up) to supine-flat (0°), or vice versa. At the end of each step partition respiratory mechanics, airway opening pressure and arterial blood gases were measured. Paired t test was used to examine respiratory mechanics and blood gas variables in each group.
Results:
Forty consecutive patients were enrolled. Twenty were obese (BMI, 38.4 [34.5-42.3]), and 20 were non-obese (BMI, 26.6 [25.2-28.5]). In the patients with obesity, lung and chest wall elastance, driving pressure, inspiratory transpulmonary pressure, Paco2, and ventilatory ratio were lower supine than semi-recumbent (P < .001). Airways resistance was greater supine (P = .006). In the patients without obesity, only chest wall elastance was lower in supine vs semi-recumbent (P < .001).
Interpretation:
In mechanically ventilated patients with ARDS and obesity, supine posture provided lower lung and chest wall elastance, and better CO2 clearance, than the semi-recumbent posture.
Clinical Trial Registration:
This study was registered with Australian New Zealand Clinical Trials Registry (ACTRN12623000794606).
More Related Videos
06:22Surfactant Depletion Combined with Injurious Ventilation Results in a Reproducible Model of the Acute Respiratory Distress Syndrome ARDS
Published on: April 7, 2021
08:30Intraperitoneal Glucose Tolerance Test, Measurement of Lung Function, and Fixation of the Lung to Study the Impact of Obesity and Impaired Metabolism on Pulmonary Outcomes
Published on: March 15, 2018
Related Concept Videos
Physical Assessment of the Respiratory Tract II: Inspection
Chest Configuration
The chest configuration...
Acute Respiratory Failure-IV
Respiratory System Abnormal Finding I: Inspection and Percussion
Inspection Findings
During an inspection, several findings may suggest the presence of respiratory distress or disease. Pursed-lip breathing, where exhalation is slowed by...
Alterations in Respiration II
In Biot's breathing, the respiratory rate and depth are irregular, alternating between periods of deep gasping and apnea. Common causes...
Assessment of Airway, Skin Color, and Use of Accessory Muscles
Introduction
The initial evaluation of a patient's respiratory system...
Pressure Relationships in Thoracic Cavity
Breathing Mechanisms
Both intra-alveolar and intrapleural pressures rely on specific lung properties. The ability to breathe—allowing air to enter the lungs...