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Diaphragm fatigue following maximal ventilation in man
C H Hamnegård1, S Wragg, D Kyroussis
1Respiratory Muscle Laboratory, Brompton Hospital, London, UK.
The European Respiratory Journal
|February 1, 1996
Summary
Maximal isocapnic ventilation significantly reduces diaphragmatic contractility in healthy individuals. This diaphragmatic fatigue may limit maximal ventilation capacity.
Area of Science:
- Respiratory Physiology
- Exercise Physiology
- Muscle Physiology
Background:
- Maximal voluntary ventilation involves significant inspiratory muscle loading.
- A rapid fall in ventilation and reduced relaxation rates suggest inspiratory muscle dysfunction.
- Diaphragmatic contractile failure is a potential cause of this dysfunction.
Purpose of the Study:
- To investigate the impact of maximal isocapnic ventilation on diaphragmatic contractility.
- To determine if diaphragmatic fatigue occurs after intense ventilation.
Main Methods:
- Nine healthy subjects performed 2 minutes of maximal isocapnic ventilation (MIV).
- Twitch transdiaphragmatic pressure (Pdi,Tw) was measured via cervical magnetic stimulation before and after MIV.
- Control studies were conducted without MIV.
Main Results:
- Ventilation decreased by 35% within the first minute of MIV.
- Pdi,Tw was reduced by 24% at 10 minutes post-MIV and remained significantly lower at 90 minutes.
- No changes in Pdi,Tw were observed in control conditions.
Conclusions:
- Two minutes of MIV significantly reduces diaphragmatic contractility.
- Diaphragmatic fatigue is a likely contributor to the observed reduction in maximal ventilation.
- These findings highlight the role of diaphragmatic function in limiting ventilatory capacity.