This thesis examines changes in the mechanical behaviour of the canine and human respiratory systems to changes in lung volume below normal functional residual capacity (FRC). In open chested dogs lung elastance (E$ sb{ rm L}$) increased and lung resistance (R$ sb{ rm L}$) changed little with decreases in positive end-expiratory pressure (PEEP) of the ventilatory circuit. The dominance of plastoelastic lung tissue properties at low lung volumes was used to interpret the lack of change in R$ sb{ rm L}$. Computed tomography demonstrated that pleural effusion (PE) created atelectasis in dependent caudal lung regions which contributed to the overall lung volume loss. PE produced a decrease in only lung vertical height while chest wall dimensions changed both vertically and horizontally. E$ sb{ rm L}$ and R$ sb{ rm L}$ increased while elastance and resistance of the chest wall were little affected by these shape and density changes. In close-chested, anesthetised, paralysed, ventilated humans a decrease in PEEP below normal FRC caused an increase in R$ sb{ rm L}$, E$ sb{ rm L}$ and both chest wall elastance and resistance. Median sternotomy caused E$ sb{ rm L}$ to increase with increasing PEEP while the negative volume dependence of R$ sb{ rm L}$ remained. Most of the difference between open-chested and closed-chested E$ sb{ rm L}$ was presumably due to lung collapse in the open-chested state.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.41568 |
| Date | January 1993 |
| Creators | Dechman, Gail Sterns |
| Contributors | Bates, J. H. T. (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 (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001397569, proquestno: NN94605, Theses scanned by UMI/ProQuest. |
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