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Respiratory Part 5
Question | Answer |
---|---|
Airway Resistance due to size of airway | Neurohormonal; Parasym makes bronchi constrict and increases resistance. Epi makes bronchi dilate and decreases resistance. |
Airway Resistance due to mechanical | Reisitance is least at apex, end of inspiration and total lung capacity |
Nature of Airflow | Bulk flow which is turbulent: Large airways and laminar: up to terminal bronchiole. There is diffusion |
The resistance in relation to the radius | Resistance= 1/radius to the 4th power |
Turbulent flow | Requires lot of work/high energy expenditure. Molecules swirl in eddy currents. Pressure gradient responsible for flow is related to the square of the pressure. Doubling the flow requires a fourfold increase in driving pressure. |
Laminar flow | Gas molecules travel in cocentric layers. The friction created as these layers slide over one another is responsible for gas viscosity. Doubling the flow only requires doubling of pressure gradient. Velocity= flow/x-sec area |
Reynold's number= [(Velocity)(Diameter)(Density)]/Viscosity | Determines whether flow will be laminar or turbulent. Less than 2000, it will be laminar. Greater than 2000, it will be turbulent. Viscosity is constant in respiratory system |
Name ways to prevent turbulent breathing | Breath slowly, lower density by giving patients Heliox (60%helium & 40% oxygen) to breath |
Diffusion | At level of smallest airways bulk flow ceases. Movement of O2 molecule to the alveolar surface via diffusion. Velocity=0 therefore no way to create turbulence. Silent zones |
Obstructive Pulmonary Disease | Increase in airway resistance & measured as decrease in expiratory flow rate. |
Chronic Bronchitis | Hypertrophied smooth muscle and mucus glands, increased mucus secretion=narrow airways |
Asthma | Hyperreactive airways, inflammation(cellular infiltrates, tissue edema)=narrow airways |
Emphysema | Loss of tissue elasticity=loss of support for small airways=easily distorted airways |
Spirometry characteristics of Obstructive Pulmonary Disease | FVC-decreased, FEV1sec-decreased more than FVC, FEV1sec/FVC-decreased, FEF25-75% decreased. Lung volumes: FRC increased, RV increased and TLC, increased or normal. |