Effects of continuous low-frequency pacing on immature canine diaphragm

M. Marzocchi, R. T. Brouillette, L. M. Klemka-Walden, S. L. Heller, D. E. Weese-Mayer, B. S. Brozanski, J. Caliendo, M. Daood, M. N. Ilbawi, C. E. Hunt

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14 Scopus citations


Although diaphragm pacing has been shown to be a practical method of supporting ventilation in children, its usefulness has been limited because of concern that continuous (24 h/day) diaphragm pacing would fatigue and damage the diaphragm. We examined the functional and structural effects of continuous low-frequency diaphragm pacing on the left hemidiaphragm of five immature dogs aged 65 ± 2 (SD) days at onset of pacing. Stimulus parameters approximated those required to pace infants: frequency 11.1 Hz, inspiratory time 810 ms, and respiratory rate 20 breaths/min. Animals were paced 24 h/day for 24-28 days. Paced tidal volumes and airway occlusion pressures were unchanged at low (<15 Hz) stimulus frequencies but were reduced at high (>20 Hz) stimulus frequencies. Although histologically the paced hemidiaphragms appeared normal, histochemical studies showed a conversion from a mixture of type I (54%) and type II (46%) fibers to a uniform population of type I fibers with high oxidative enzyme activity. Transformation of muscle type was also demonstrated by pyrophosphate gel electrophoresis; fast and slow isomyosin bands were noted in control specimens, whereas only slow isomyosin was identified in paced specimens. Thus, in immature dogs, continuous low-frequency pacing affects both function and structure of the diaphragm.

Original languageEnglish
Pages (from-to)892-898
Number of pages7
JournalJournal of Applied Physiology
Issue number3
StatePublished - 1990


  • diaphragmatic pacing
  • dogs
  • electrical stimulation
  • muscle fiber type
  • phrenic nerve pacing


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