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Title: Studies of lung function
Author: Davies, Andrew
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2000
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This thesis outlines the candidate's contribution to the study of Respiratory Physiology in two main areas 1. The effect of lung morphometry on lung function and 2. Reflex control of pattern of breathing. The work that makes up this thesis is laid out in largely chronological order describing the evolution of the investigations. The effect of bronchial tree structure on function was investigated using a number of new techniques developed by the author. These include a method of modelling the bronchial tree to previously unobtained detail in the form of a hollow cast. This enabled gas transit times to airways of 2-3 mm diameter to be measured and the contribution made by architecture, tissue compliance and the gradient of pleural pressure to the distribution of ventilation to be apportioned. This was the first time transit times to individual airways had been measured. Using these techniques the effect of bronchial tree structure on the phenomenon of separation of gas mixtures into their components during breathing, and the effect of the beating heart on the mixing of gases during breathing was quantified. The author's contributions to the investigation of neural control of breathing follow. A fortuitous observation that S02 blocks pulmonary stretch receptors (PSR) in rabbits, which took place while developing an animal model of bronchitis, lead to the observation of a non PSR mechanism determining inspiratory time (ti). Investigation of the action of rapidly adapting pulmonary receptors (RAR) using S02 confirmed their role in provoking sighs or augmented breaths and demonstrated that they terminated expiratory duration (tn) with a constant latency. A consistent effect of RARs on inspiration proved elusive until it was discovered that after provoking an augmented breath ft is refractory to the direct effects of RAR activity for about 2 minutes. This observation lead to the development of a theoretical model of control of ft via a central linking. This explained our observation of a non-PSR effect restricting ft after S02 block. Further investigations confirmed a role for RAR in control of breathing in conscious dogs. The action of RAR in initiating inspiration was demonstrated using PSR block. The same technique was used to elucidate the role played by PSR in shifts in functional residual capacity during changes in posture. An interesting observation made at this time is that although cough is primarily associated with RAR activity it can not be triggered from the lungs. The results of experiments demonstrating a similar role for RAR in conscious animals are presented. The influence of high frequency ventilation, on pulmonary receptors, the reflexes they produce and on the non-Newtonian properties of bronchial mucus is described. The way in which different species control their very different frequencies of breathing is included and the way pulmonary receptor activity is changed in some models of lung disease. The effects of modern anaesthetics on receptor activity and the effect of acupuncture as a respiratory stimulant are reported. The results of some investigations of human movement and tremor are presented. The candidates contributions to books and books published are described.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Sc.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available