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Related Experiment Video

Updated: Oct 4, 2025

Supramaximal Intensity Hypoxic Exercise and Vascular Function Assessment in Mice

Supramaximal Intensity Hypoxic Exercise and Vascular Function Assessment in Mice

Published on: March 15, 2019

Parasternal intercostal function during sustained hypoxia.

Michael Ji¹, Tetsunori Ikegami², Estifanos Debru¹

¹Department of Critical Care Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.

Journal of Applied Physiology (Bethesda, Md. : 1985)

|February 3, 2022

Summary

Sustained hypoxia causes a biphasic ventilatory response in canines, with parasternal intercostal muscle activity initially increasing then decreasing. This suggests reduced respiratory drive extends to chest wall muscles during prolonged low oxygen.

Keywords:

EMG activity hypoxia hypoxic ventilatory response parasternal intercostal respiratory muscle

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Published on: February 20, 2017

Area of Science:

Respiratory Physiology
Neuroscience

Background:

The ventilatory response to hypoxia is biphasic, with reduced diaphragm drive.
The role of chest wall muscles, like the parasternal intercostal, during sustained hypoxia is poorly understood.
Parasternal intercostal muscles are clinically relevant as surrogates for diaphragm function.

Purpose of the Study:

To investigate parasternal intercostal muscle function during sustained isocapnic hypoxia.
To determine if hypoxia-induced attenuation of respiratory drive affects chest wall muscles.

Main Methods:

Simultaneous recording of parasternal intercostal muscle length, shortening, and electromyogram (EMG) activity in awake canines.
Measurements were taken during sustained moderate isocapnic hypoxia (20-25 min).
Breathing patterns were monitored alongside muscle activity.

Main Results:

Parasternal intercostal muscle exhibited phasic inspiratory shortening and EMG activity during both room air and hypoxic conditions.
Muscle shortening and EMG activity significantly increased with initial hypoxia.
These parameters markedly declined with sustained hypoxia, mirroring the biphasic ventilatory response.

Conclusions:

Attenuation of central neural respiratory drive during sustained hypoxia extends to the parasternal intercostal muscle.
This decline in parasternal intercostal activity directly contributes to the biphasic changes in ventilation.
Findings highlight the parasternal intercostal's role in the complex respiratory response to prolonged hypoxia.