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Published on: July 10, 2018
Avoiding deep inspirations increases the maximal response to methacholine without altering sensitivity in
David G Chapman1, Gregory G King, Norbert Berend
1Woolcock Institute of Medical Research, PO Box M77 Missenden Road, Sydney, NSW 2050, Australia. dcha7069@woolcock.org.au
Respiratory Physiology & Neurobiology
|August 7, 2010
Summary
Deep inspiration (DI) avoidance increases airway hyperresponsiveness in non-asthmatic individuals by enhancing maximal bronchoconstriction, but not sensitivity. This effect was not observed in asthmatic subjects, suggesting DI
Area of Science:
- Pulmonary Physiology
- Respiratory Medicine
- Clinical Investigation
Background:
- Airway hyperresponsiveness (AHR) is a hallmark of asthma, characterized by increased sensitivity and maximal bronchoconstriction.
- Deep inspiration (DI) is known to modulate airway responsiveness, but its specific role in asthma remains debated.
- Previous studies suggest DI avoidance impacts responsiveness differently in asthmatic versus non-asthmatic individuals.
Purpose of the Study:
- To investigate the effect of deep inspiration (DI) avoidance on the sensitivity and maximal response of the FEV(1) dose-response curve (DRC) to methacholine.
- To compare these effects in non-asthmatic and asthmatic subjects.
Main Methods:
- A cumulative high-dose methacholine challenge was performed in 13 non-asthmatic and 10 asthmatic subjects.
- Methacholine challenges were repeated after a 10-minute period of DI avoidance.
- Airway responsiveness was assessed by fitting sigmoidal equations to the FEV(1) DRC to determine sensitivity (α) and measuring maximal FEV(1) fall.
Main Results:
- In non-asthmatic subjects, DI avoidance significantly increased the maximal fall in FEV(1) (p=0.0001) but did not alter sensitivity (α) (p=0.75).
- DI avoidance did not affect the bronchodilator effect of DI (BD(DI)) in non-asthmatic subjects (p=0.13).
- DI avoidance had no significant impact on airway responsiveness in asthmatic subjects.
Conclusions:
- Deep inspiration (DI) avoidance exacerbates airway hyperresponsiveness in non-asthmatic individuals primarily by increasing maximal bronchoconstriction, not sensitivity.
- The findings suggest that the loss of DI's bronchodilator effect in asthma may contribute to excessive bronchoconstriction.
- Understanding the role of DI in modulating airway responsiveness is crucial for asthma management.
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