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Diaphragm metabolism during supramaximal phrenic nerve stimulation
1Pulmonary Section, Brockton/West Roxbury Veterans Administration Medical Center, Boston 02132.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1989
Summary
Diaphragm fatigue during phrenic nerve stimulation shows decreased oxygen consumption, not anaerobic metabolism, despite reduced force generation. Lactate production occurred early in pacing but not during the second period.
Area of Science:
- Physiology
- Metabolic research
Background:
- Diaphragm fatigue mechanisms, especially metabolic changes, are not fully understood.
- The link between anaerobic metabolism and force decline during fatigue is unclear.
Purpose of the Study:
- To investigate metabolic changes during diaphragm fatigue induced by phrenic nerve stimulation.
- To determine if anaerobic metabolism correlates with force generation decline.
Main Methods:
- Anesthetized dogs underwent bilateral phrenic nerve pacing.
- Measurements included transdiaphragmatic pressure, phrenic blood flow, blood gases, and lactate.
- Diaphragm oxygen consumption and lactate production were calculated.
Main Results:
- Diaphragm force (Pdi) decreased significantly during pacing.
- Oxygen consumption (VO2) initially increased then decreased, indicating altered O2 extraction.
- Lactate production was observed early in the first pacing period but absent in the second.
Conclusions:
- Diaphragm fatigue under these conditions is not primarily driven by anaerobic metabolism.
- Changes in oxygen extraction, not anaerobic glycolysis, characterize metabolic shifts during fatigue.
- Force decline occurs independently of significant lactate production in repeated stimulation bouts.