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Title: Respiratory drive in a rabbit model of pulmonary emphysema
Author: Dallak, Mohammad A. M.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1999
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This thesis describes an investigation of the respiratory drive to breathe in a rabbit model of pulmonary emphysema. I propose that an altered respiratory drive in emphysematous rabbits may model the origin of the sensation of dyspnoea experienced by many human patients with emphysema. Pulmonary emphysema was induced in Dutch rabbits by endotracheal administration of type IV porcine pancreatic elastase. In rats it was induced by endotracheal administration of papain. Respiratory drive was measured as phrenic activity (phrenic slope, G and phrenic height, H). since emphysema changes the mechanical properties of the lungs and ventilation will be changed for a given respiratory drive. Rats' and rabbits' conscious pattern of breathing (expiratory time, tE; inspiratory time, tl and tital volume. VT) was measured barometrically to investigate the role of sensation in changed conscious pattern of breathing. To elucidate the role of pulmonary receptors in changing the pattern of breathing and respiratory drive, the respiratory variables were measured during 3 stages: 1) preSO2: when all pulmonary receptors were intact 2) post SO2: when pulmonary stretch receptors (SARs) were blocked by inhaled sulphur dioxide 3) postvagotomy: when all pulmonary receptors input was removed by bilateral vagotomy. Emphysema increased static lung compliance in rabbits (normal (N): 4.12± .49 ml/cmH2O, n=25 vs. emphysematous (E): 4.61±0.31. n=35) and rats (N: 0.61±0.02 ml/cmH2O, n=10 vs. E: 0.82±0.03, n=10). It also increased mean linear intercept in rabbits (N: 79.71±8.42μm, n=25 vs. E: 99.62±2.32n, n=35) and rats (N: 80.5±2.9, n=10 vs. 108.4±3.2, n=10). Breathing accelerated by 6% CO2 inhalation in all three stages (calculated as Δ %) showed that emphysematous rabbits have a stronger respiratory drive indicating the relative importance of vagal and extravagal inputs (preSO2, G (N): 30.9±3 vs. E: 37.6±1.8; postSO2, G(N): 24.4±2.3 vs. E: 33.92±1.5; postvagotomy, GN(N): 27.95±3.2 vs. E: 45.61±2.08). It is concluded from this study that it is this stronger respiratory drive in eupnoea and in response to CO2, that patients with pulmonary emphysema perceive as dyspnoea.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available