A proportional assist ventilator to experimentally unload respiratory muscles during exercise in humans

New Findings

What is the central question of this study?

Can a modern proportional assist ventilator (PAV) function to sufficiently unload the respiratory muscles during exercise?

What is the main finding and its importance?

A PAV can be constructed with contemporary hardware and software and be used during all exercise intensities to unload the respiratory muscles by up to 70%. Previously, PAVs have allowed researchers to address many fundamental physiological problems in clinical and healthy populations, but those versions are no longer functional or available. We describe the creation of a PAV that permits researchers to use it as an experimental tool.

Manipulating the normally occurring work of breathing (WOB) during exercise can provide insights into whole-body regulatory mechanisms in clinical and healthy subjects. One method to reduce the WOB utilizes a proportional assist ventilator (PAV). Suitable commercially available units are not capable for used during heavy exercise. This investigation was undertaken in order to create a PAV and assess the degree to which the WOB could be reduced during exercise. A PAV works by creating a positive mouth pressure (P_m) during inspiration which consequently reduces the WOB. Spontaneous breathing patterns can be maintained and the amplitude of P_m is calculated using the equation of motion and predetermined proportionality constants. We generated positive P_m using a breathing apparatus consisting of rigid tubing, solenoid valves to control airflow direction and a proportional valve connected to compressed gas. Healthy male and female subjects were able to successfully use the PAV while performing cycle exercise over a range of intensities (50–100% maximum workload) for different durations (30 s to 20 min) and different protocols (constant vs. progressive workload). Inspiratory WOB was reduced up to 90%, while total WOB was be reduced 70%. The greatest reduction in WOB (50–75%) occurred during submaximal exercise, but at maximal ventilations (>180 l min⁻¹) a 50% reduction was still possible. The calculated change in WOB and subsequent reduction in respiratory muscle oxygen consumption resulted in equivalent reductions in whole-body oxygen consumption. With adequate familiarization and practice, our PAV can consistently reduce the WOB across a range of exercise intensities.

This article is protected by copyright. All rights reserved

from Physiology via xlomafota13 on Inoreader http://ift.tt/1V5AGW0
via IFTTT