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Parasternal intercostal muscle activity during methacholine-induced bronchoconstriction
Victoria MacBean1, Claire L Pringle1, Alan C Lunt1
1Division of Asthma, Allergy and Lung Biology, King's College London, London, UK.
Experimental Physiology
|February 15, 2017
Summary
The parasternal intercostal electromyogram (EMGpara) reflects respiratory load. Airway obstruction, not lung hyperinflation, significantly impacts EMGpara during methacholine challenges, indicating its sensitivity to bronchoconstriction.
Area of Science:
- Respiratory Physiology
- Pulmonary Medicine
- Neuroscience
Background:
- The parasternal intercostal electromyogram (EMGpara) serves as a non-invasive measure of respiratory load-capacity balance.
- Previous research indicates relationships between EMGpara and airflow obstruction/hyperinflation in obstructive lung diseases.
- The independent contributions of airflow obstruction and hyperinflation to EMGpara have not been fully elucidated.
Purpose of the Study:
- To investigate the independent effects of airway obstruction and changes in lung volume on EMGpara.
- To determine whether airway calibre or end-expiratory lung volume is a stronger determinant of EMGpara during induced bronchoconstriction.
Main Methods:
- Methacholine challenge was administered to 25 adult humans to induce airflow obstruction.
- Forced expiratory volume in 1 second (FEV1) and EMGpara were measured at each dose.
- Inspiratory capacity (IC) was measured in 20 participants to assess lung volumes.
Main Results:
- Methacholine challenge significantly reduced FEV1 and increased EMGpara.
- A strong inverse relationship was found between EMGpara and airway obstruction (FEV1).
- Changes in inspiratory capacity did not significantly influence EMGpara, suggesting airway calibre is the primary driver.
Conclusions:
- EMGpara is more sensitive to changes in airway calibre than to alterations in end-expiratory lung volume during methacholine-induced airway challenge.
- These findings highlight the influence of bronchoconstriction on neural respiratory drive.
- EMGpara can serve as a valuable tool for assessing the impact of airway obstruction on respiratory muscle effort.
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