Influence of phasic volume feedback on abdominal expiratory nerve activity

Ralph F. Fregosi, Donald Bartlett, Walter M. St.John

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Our purpose was to examine the influence of phasic lung volume feedbackon the activities of motor nerves innervating the dia[phragm and transversus abdominis muscles during hypercapnia and hypoxia. We studied seventeen decerebrate cats that were paralyzed and ventilated with a servo-respirator controlled by the integrated phrenic neurogram. The effects of phasic lung volume feedback were assessed by withholding pulmonary inflation during the central inspiratory period. Withholding lung inflation for a single respiratory cycle under hyperoxic, normocapnic conditions consistently prolonged the durations of the inspiratory and expiratory periods, and caused marked increases in the peak electrical activities of both phrenic and abdominal nerves. Hyperoxic hypercapnia (PACO2 50-80 mmHg) and isocapnic hypoxia (PaO2 60-35 mmHg) increased peak phrenic and abdominal neural activities, and withholding pulmonary inflation under these conditions caused even greater augmentations of inspiratory and expiratory motor output. The augmentation of expiratory activity by withholding lung inflation was proportionately greater than the concomitant prolongation of the central expiratory period. All responses to non-inflation maneuvers were abolished following bilateral cervical vagotomy. The results indicate that vagally mediated volume feedback during inspiration can attenuate the output of abdominal motoneurons in the subsequent expratory period. Moreover, hypoxia, which attenuates abdominal motor activity in vagotomized animals, enhances this activity when the vagi are intact.

Original languageEnglish (US)
Pages (from-to)189-200
Number of pages12
JournalRespiration Physiology
Issue number2
StatePublished - Nov 1990


  • Animal
  • Control of breathing
  • Diaphragm
  • Expiratory muscles
  • Hypercapnia
  • Hypopxia
  • Motoneurons of respiratory muscles
  • cat
  • expiratory muscles
  • lung feedback
  • respiratory muscles

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine


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