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Assessment of Pulmonary Capillary Blood Volume, Membrane Diffusing Capacity, and Intrapulmonary Arteriovenous Anastomoses During Exercise
Published on: February 20, 2017
Diaphragm activation during exercise in chronic obstructive pulmonary disease.
C Sinderby1, J Spahija, J Beck
1Guy-Bernier Research Center, Maisonneuve-Rosemont Hospital, Department of Medicine, and Ste Justine Research Center, Ste Justine Hospital, Montreal, Quebec, Canada. SINDERBY@COMPUSERVE.COM
Summary
Dynamic hyperinflation in chronic obstructive pulmonary disease (COPD) patients during exercise significantly impairs diaphragm function. This leads to increased diaphragm electrical activation (EAdi) as lung volumes expand.
Area of Science:
- Respiratory Physiology
- Pulmonary Medicine
Background:
- Central inhibition of respiratory drive is theorized to prevent diaphragm fatigue in COPD patients during exercise.
- This hypothesis lacks empirical validation in individuals with chronic obstructive pulmonary disease (COPD).
Purpose of the Study:
- To investigate diaphragm electrical activation (EAdi) relative to maximal capacity in COPD patients during incremental exhaustive exercise.
- To assess the relationship between dynamic hyperinflation and diaphragm function during exercise in COPD.
Main Methods:
- Evaluated 10 moderately severe COPD patients at rest and during exhaustive bicycle exercise.
- Measured EAdi, transdiaphragmatic pressures (Pdi), and end-expiratory lung volume (EELV) using esophageal catheter and inspiratory capacity maneuvers.
- Assessed minute ventilation (VE) and lung volumes relative to total lung capacity (TLC).
Main Results:
- Minute ventilation increased from 12.2 L/min at rest to 31.0 L/min at end-exercise.
- End-expiratory lung volume increased significantly, leading to end-inspiratory lung volumes near TLC (97%).
- Diaphragm electrical activation (EAdi) rose from 24% at rest to 81% of maximal capacity at end-exercise, while Pdi plateaued.
Conclusions:
- Dynamic hyperinflation during exhaustive exercise in COPD patients reduces the diaphragm's pressure-generating capacity.
- High levels of diaphragm activation are promoted by dynamic hyperinflation, potentially contributing to respiratory muscle fatigue.
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