These investigations examined the relative function of costal and crural diaphragm segments. This work produced the first direct measurements of length and electromyogram (EMG) of the diaphragm in an awake, intact animal. / Examination of diaphragm function following laparotomy revealed a consistent pattern of postoperative segmental recovery, and showed the inadequacy of EMG alone as an indicator of diaphragm activity. Segmental contraction during airway occlusion was confirmed to be non-isometric and different per segment. The basic relation between segmental velocity of shortening and mean inspiratory flow, was confirmed for diaphragm but not for intercostal musculature. Anesthesia produced a distinctive alteration in the resting length of crural compared to costal segment, suggesting a difference in inherent segmental tonic activity. Costal and crural activity during hypoxic and hypercapnic stimulated breathing revealed different, stimulant-specific activities of the segments; hypoxia elicited prominent crural post inspiratory activity (PIIA). During thermal panting, peak crural shortening was out of phase with costal shortening and inspiratory airflow. This unique segmental asynchrony may represent a natural analog to high frequency ventilation. / We conclude that costal and crural diaphragm segments can function as individual segment-muscles, exhibiting distinctive, differential activities under certain conditions of respiration.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41004 |
| Date | January 1992 |
| Creators | Easton, Paul A. |
| Contributors | Grassino, Alex (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Division of Experimental Medicine.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001327523, proquestno: NN87793, Theses scanned by UMI/ProQuest. |
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