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Adverse effect of hyperinflation on parasternal intercostals
1Respiratory Research Unit, Erasme University Hospital, Brussels School of Medicine, Belgium.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|November 1, 1994
Summary
Hyperinflation reduces the lung inflation ability of parasternal intercostal muscles in dogs. Their rib-elevating action decreases while sternal action increases, impairing breathing mechanics.
Area of Science:
- Respiratory Physiology
- Muscle Mechanics
- Pulmonary Function
Background:
- The parasternal intercostal muscles are crucial for rib cage expansion and lung inflation.
- Previous studies suggested their force-generating capacity is maintained during hyperinflation.
Purpose of the Study:
- To investigate if the parasternal intercostals' ability to expand the rib cage and inflate lungs is maintained during hyperinflation.
- To analyze the effects of positive airway pressure on parasternal intercostal muscle function and rib cage mechanics.
Main Methods:
- Measurements included electromyogram, muscle length changes, sternal and rib motion, pleural pressure, and tidal volume in anesthetized dogs.
- Experiments involved selective parasternal stimulation and spontaneous breathing at varying positive airway pressures (0-15 cmH2O).
Main Results:
- Hyperinflation (15 cmH2O) decreased parasternal muscle shortening and cranial rib motion but increased sternal caudal displacement.
- Similar changes in muscle and rib/sternal motion were observed during spontaneous breathing, with a marked reduction in tidal volume.
- These findings indicate altered parasternal intercostal muscle actions on the rib cage during hyperinflation.
Conclusions:
- Hyperinflation impairs the parasternal intercostals' rib-elevating action while enhancing their sternal action.
- The overall ability of parasternal intercostals to inflate the lungs is reduced by hyperinflation.
- Both diaphragm and parasternal intercostal muscles' inflationary actions are diminished by hyperinflation.