Related Experiment Videos
Dynamic changes in human diaphragm length: maximal inspiratory and expulsive efforts studied with sequential
S C Gandevia1, R B Gorman, D K McKenzie
1Department of Clinical Neurophysiology, Prince Henry Hospital, Sydney, Australia.
The Journal of Physiology
|November 1, 1992
Summary
Diaphragm muscle length changes explain differences in maximal voluntary pressure. Inspiratory efforts shorten the diaphragm, reducing force, while expulsive efforts lengthen it, increasing force.
Area of Science:
- Respiratory Physiology
- Biomechanics
- Muscle Physiology
Background:
- Maximal voluntary pressure generation by the diaphragm differs significantly between inspiratory and expulsive efforts.
- Neural drive is unlikely to be the sole factor responsible for this pressure difference.
Purpose of the Study:
- To investigate the role of dynamic changes in diaphragm length during inspiratory and expulsive efforts.
- To explain the observed difference in maximal voluntary pressure between these effort types.
Main Methods:
- Digital sequential radiography at 6 frames per second was used to measure diaphragm length.
- Transdiaphragmatic pressure (Pdi) was measured during maximal inspiratory and expulsive efforts.
Main Results:
- During maximal inspiratory efforts, diaphragm length decreased by approximately 20%.
- During maximal expulsive efforts, the diaphragm initially shortened but then lengthened before peak pressure development.
- Muscle force is known to increase with lengthening and decrease with shortening.
Conclusions:
- Dynamic changes in diaphragm length, specifically lengthening during expulsive efforts, provide a definitive explanation for increased maximal voluntary pressure.
- The findings highlight the importance of muscle mechanics in respiratory force generation.