Emily Gerson’s MSc Thesis Defence

Title: The effect of proportional assist ventilation on diaphragm electrical activity

Thesis Supervisor: Dr. Bill Sheel
Committee Members: Dr. Paolo Dominelli, Dr. Jordan Guenette, Dr. Tania Lam
Dr Cameron Mitchell

Abstract: The diaphragm is the largest contributing muscle in a spontaneous breath. Classically, when failure in this muscle occurs, mechanical ventilation is implemented to reduce acute respiratory failure. The proportional assist ventilator (PAV) is a type of mechanical ventilator that can maintain gas homeostasis in dynamic exercise. However, PAV’s effect on the diaphragm, accessory respiratory muscles, and effectiveness during lower intensity exercise is still unclear. PURPOSE: To investigate the diaphragm electrical activity during low exercise intensity (10% below gas exchange threshold (GET)) while reducing the work of breathing via a proportional assist ventilator (PAV). METHODS: 8 participants (n = 4 male, n = 4 female; 26.8 ± 1 years) completed two days of testing. On day one, subjects performed a maximal VO2 exercise test on a cycle ergometer. On day 2, subjects cycled at 10% below gas exchange threshold (GET) while alternating breathing on the PAV and spontaneously. Electromyography of the diaphragm (EMGdi), scalenes (EMGSCA), and sternocleidomastoids (EMGSCM), and work of breathing (WOB) were measured throughout the experimental protocol. RESULTS: WOB was lower while breathing on the PAV during medium (76.7 ± 41.9 J/min vs. 93.5 ± 39.4 J/min, p < 0.05) and high (72.2 ± 34.0 J/min vs. 114 ± 48.1 J/min, p < 0.01) unloading conditions. EMGdi was lowered while breathing during all PAV unloading levels (low, medium, and high)