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Respiratory muscle activity in the assessment of bronchial responsiveness in asthmatic children
A B Sprikkelman1, L A Van Eykern, M S Lourens
1Beatrix Children's Hospital, University Hospital Groningen, 9700 RB Groningen, The Netherlands.
Insights
In asthmatic children, increased diaphragm and intercostal muscle electrical activity closely correlates with a 20% fall in forced expiratory volume (FEV1) during histamine challenge. This finding links respiratory muscle response to airway obstruction severity.
Area of Science:
- Respiratory Physiology
- Pediatric Pulmonology
- Clinical Electromyography
Background:
- Asthma involves airway hyperresponsiveness, leading to bronchoconstriction.
- Assessing the severity of asthma exacerbations often relies on lung function tests like forced expiratory volume in one second (FEV1).
- The role of respiratory muscle electrical activity during histamine-induced bronchoconstriction in children is not fully understood.
Purpose of the Study:
- To investigate the correlation between transcutaneous electromyographic (EMG) activity of respiratory muscles and the concentration of histamine causing a 20% fall in FEV1 (PC20) in asthmatic children.
- To determine if increased EMG activity precedes or coincides with significant bronchoconstriction.
Main Methods:
- Eleven asthmatic children underwent histamine challenge testing.
- Transcutaneous electromyography (EMG) recorded diaphragm and intercostal muscle activity.
- EMG activity ratio (EMGAR) was calculated by comparing activity at PC20 or highest histamine dose to baseline.
- EMGAR was analyzed in relation to FEV1 changes.
Main Results:
- All children who reached PC20 showed an increased diaphragmatic and intercostal EMGAR.
- No increase in EMGAR was observed at histamine doses below PC20.
- In challenges where no significant FEV1 fall occurred, EMGAR did not increase.
- In two instances, EMGAR increased without a significant FEV1 fall, suggesting subclinical changes.
Conclusions:
- Increased electrical activity of the diaphragm and intercostal muscles in asthmatic children closely corresponds to a 20% fall in FEV1 induced by histamine challenge.
- Respiratory muscle EMG activity may serve as a sensitive indicator of airway narrowing in pediatric asthma.
- EMG monitoring could offer insights into the dynamic respiratory effort during bronchoconstriction in children.
Abstract:
We investigated whether an increase in transcutaneous electromyographic (EMG) activity of the diaphragm and intercostal muscles corresponds with the concentration of histamine that induces a 20% fall in the forced expiratory volume in one second (FEV1; PC20). Eleven asthmatic children (mean age 11.9 yr) were studied after they were given histamine challenge. EMG activity at PC20 or at the highest histamine concentration was compared with activity at baseline by calculating the ratio of the mean peak-to-peak excursion at the highest histamine dose to that at baseline [EMG activity ratio (EMGAR)]. In all children reaching PC20, an increase in diaphragmatic and intercostal EMGAR was observed. No increase was found at the dose step before PC20 was reached. In six challenges, no fall in FEV1 was induced, and no increase in EMGAR was seen. In two challenges, no fall in FEV1 was induced, but increase in diaphragmatic or intercostal EMGAR was observed. Increase in the electrical activity of the diaphragm and intercostal muscles in asthmatic children corresponds closely to a 20% fall in FEV1 induced by histamine challenge.