Effects of uncompensated and compensated metabolic acidosis on canine diaphragm

S. Howell, R. S. Fitzgerald, C. Roussos

Research output: Contribution to journalArticle

Abstract

We investigated the effects of metabolic acidosis and compensated metabolic acidosis on force of contraction of the diaphragm in anesthetized dogs. Mechanically ventilated animals were prepared with an open thorax. A balloon was positioned beneath the diaphragm to measure transdiaphragmatic pressure (Pdi), an a plaster cast was placed around the abdomen to maintain length and geometry of the diaphragm. The force of contraction was evaluated by measuring Pdi during supramaximal phrenic stimulation at different frequencies and also during spontaneous inspiratory efforts. In 13 dogs with an arterial pH (pH(a)) of 7.38 and arterial Pco2 (Pa(co2)) of 36.5 Torr, metabolic acidosis was produced by infusion of HCl until pH(a) equaled 6.98 and Pa(co2) equaled 36.4 Torr. Pdi at all frequencies > 10 Hz was significantly reduced (P < 0.05). The dogs were then hyperventilated until pH(a) was 7.34 and Pa(co2) was 12.8 Torr. Pdi was significantly reduced again at all frequencies (P < 0.05) except 5 Hz. The percent reduction in Pdi by compensated acidosis was significantly greater at low-frequency stimulation than at high (P < 0.05). Similar qualitative results were observed during spontaneous inspiratory efforts where Pdi was compared at constant magnitudes of diaphragmatic electromyograms. Twitch characteristics revealed that metabolic acidosis led to a significant shortening of twitch relaxation time (P < 0.05), and compensated metabolic acidosis added to this effect a significant decrease in twitch amplitude (P < 0.05).

Original languageEnglish (US)
Pages (from-to)1376-1382
Number of pages7
JournalJournal of applied physiology
Volume59
Issue number5
DOIs
StatePublished - 1985

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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