ch9 Respiration-notes

ch9 Respiration-notes - Respiratory System Under Stress...

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Respiratory System Under Stress Questions: 1. What is anaerobic threshold? 2. How is PaCO2 regulated in exercise? 3. What is absorption atelectasis? Exercise Normal human responses to graded exercise are shown below. Arterial blood PaCO2 is maintained at about 38 mm Hg until work rate exceeds 75 watts and then a progressive decrease is seen. The decrease in PaCO2 is coupled with a fall in arterial pH, fall in bicarbonate, and rise in lactate(lactic acid). The “P” in the plot is pyruvate which is a metabolic factor involved in glycolysis. These changes are consistent with the onset of anaerobic metabolism beginning at 75 watts in this subject( Wasserman- Harbor General Hospital-Torrance, Ca ). The respiratory measurements for this subject are also shown. Note that the plot of minute ventilation versus work rate(power) can be fitted with a line until 75 watts where the response becomes steeper. This then justifies a simpler method of estimating the anaerobic threshold which is a fitness index. The higher the threshold the better. A patient with breathing or heart problems would have a much lower threshold.
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The normal human exercise cardiovascular responses are shown below(Circulation 69:203-213, 1984). Although not explicitly plotted, the data are consistent with a linear relationship between cardiac output and work rate. There is some degradation due to age indicated in the plot. Note that the maximum
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ch9 Respiration-notes - Respiratory System Under Stress...

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