Inspiratory action of separate external and parasternal intercostal muscle contraction

K. Budzinska, G. Supinski, A. F. DiMarco

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


We have previously shown that electrical stimulation of the thoracic spinal cord produces near maximal activation of the inspiratory intercostal muscles. In the present investigation, we used this technique to evaluate the relative capacity of separate external (EI) and parasternal intercostal (PA) muscle contraction to produce changes in airway pressure and inspired volume. Studies were performed in 23 anesthetized phrenicotomized dogs. Electrical stimuli were applied to the spinal cord after hyperventilation-induced apnea, before and after sequentially severing either the PA or EI muscles from the first through sixth intercostal spaces. During spinal cord stimulation (SCS), measurements were made of inspired volume (ΔV) with the airway open and negative airway pressure (ΔP) during tracheal occlusion. Compared with control values, sectioning of the PA muscles resulted in a 40.9% reduction in ΔP and 35.7% reduction in ΔV during SCS. In other animals, initial sectioning of the EI muscles produced reductions in ΔP and ΔV of 67.4 and 63.0, respectively, during SCS. After subsequent section of the PA muscles, SCS produced only negligible inspired volumes and changes in airway pressure. We conclude that 1) the EI and PA muscles are each capable of generating substantial changes in airway pressure and large inspired volumes and 2) the ventilatory capacity of the EI muscles exceeds that of the PA muscles.

Original languageEnglish
Pages (from-to)1395-1400
Number of pages6
JournalJournal of Applied Physiology
Issue number4
StatePublished - 1989

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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