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Respiratory Homeostasis And Abnormalities Notes

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Lecture 9 Respiratory homeostasis and abnormalities


Apply Fick's principle to solve problems involving CO and oxygen consumption o Blood flow to organ can be calculated using marker substance if following is known
? Amount of marker substance taken up by the organ per unit time
? Concentration of marker substance in arterial blood supplying the

organ Concentration of marker substance in venous blood leaving the organ






*o Oxygen Consumption Rate (Vo2)
? Measured using spirometer or calculated using Fick principle:

* Vo2 = Cardiac output x (CaO2 - CvO2)
? Depends upon cardiac function (ETT) andability of tissues to extract oxygen. Describe & explain changes in respiratory rate, tidal volume, CO, oxygen consumption & CO2 that occur during exercise o PAO2, PaO2, CO2 & oxygen saturation all unchanged o Increased ventilation (tidal volume, respiratory rate, CO & O2 consumption increase) Outline theories regarding alteration to control of ventilation during exercise o Chemoreceptors in veins that haven't been found yet o Increase in body temperature (not much evidence) o Activity in motor cortex= increased respiratory centre activity o Receptors in muscle spindles and joints (tandem bike test, one pedalling but both ventilation goes up) o Chemoreceptors more sensitive in exercise so sense small changes Define and explain VO2 max. Using Fick principle to explain determining factors o Maximum capacity of an individual's body to transport and use oxygen during incremental exercise, which reflects the physical fitness of the individual o Factors affecting VO2 are often divided into supply and demand factors
? Supply (usually limiting one)

* Transport of oxygen from the lungs to the mitochondria

* Lung diffusion, stroke volume, blood volume, & capillary density of muscle
? Demand

* Rate at which the mitochondria can reduce O2 in the process of oxidative phosphorylation Describe and explain anaerobic threshold stating the effect upon plasma lactate concentration and minute ventilation o Calculate the rate of oxygen delivery to systemic tissues o Greater delivery than consumption o So, if arterial levels drop, there is no real danger o Factors that determine oxygen delivery to tissue
? Blood flow (in terms of CO)
? Oxygen content in arterial blood (amount of O2 dissolved & bound to haemoglobin can be calculated) List the symptoms and signs of acute hypoxia

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