The fatigue of the human diaphragm during resting ventilation^was found to be determined by the fraction of the maximal trans-^diaphragmatic pressure used at each inspiration (Pdi/Pdi(' )max) and the fraction of the breathing cycle time spent in inspiration (T(,I)/T(,TOT)). A fatigue threshold relation was found between the Pdi/Pdi(' )max and the T(,I)/T(,TOT). This fatigue threshold corresponds to a quadratic hyperbola function given by the product (Pdi/Pdi(' )max) times (T(,I)/T(,TOT)). This product was termed the diaphragmatic tension-time index (TTdi) and at the fatigue threshold is equal to .15 (TTdi crit). Above TTdi crit the endurance time is limited and is accompanied by a progressive shift of the EMG power spectrum towards lower frequencies. The rate of shift of the EMG power spectrum is proportional to the endurance time. Patients with chronic obstructive lung disease breathe at rest closer to the fatigue threshold than normals secondary to an increased airway resistance and a decreased Pdi max. Minor modifications of the breathing cycle in those patients were found to cause diaphragmatic fatigue. / Diaphragmatic blood flow (Qdi)(' )in dogs was measured during static continuous and intermittent stimulated contractions. Qdi(' )was found to be related to the TTdi and to be maximal at a TTdi of .20. At higher and lower TTdi,(' )Qdi decreases and is zero at TTdi of .75. When the TTdi was greater than .20, a post contraction hyperaemia was present and increased as a function of TTdi, thus indicating that the(' )Qdi was limited in the preceding contractions.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.77137 |
| Date | January 1982 |
| Creators | Bellemare, François. |
| 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 (Department of Physiology) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000137896, proquestno: AAINK58048, Theses scanned by UMI/ProQuest. |
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