1. At a PO2 of 40, which condition has the greatest saturation? a. Pco2 = 20 b.
ID: 3523081 • Letter: 1
Question
1. At a PO2 of 40, which condition has the greatest saturation?
a. Pco2 = 20
b. Pco2 = 40
c. Pco2 = 80
Explain the physiology as to why the right answer is right and the wrong answer is wrong.
I got this question wrong. My answer was: PCO2 is normally between 35 and 45 mm mercury. high PCO2 means that the patient is hyperventilating (sometimes to compensate for the blood being acidic), and a low PCO2 means they are under ventilating.
My teacher responded with:
incorrect your physiology regarding changes in PCO2 values in how it relates to ventilation is correct; but how can you link this to the physiology for gas exchange. next can you challenge yourself to explain the physiology and shifts occurring at the various curves? and why it's a benefit that there is a shift
Please help answer it correctly with her questions.
100 80 60 Pco 20 Pco240 Poo2 80 40 20 20 40 60 80 100 Po: (mmHg)Explanation / Answer
The most important factor that determines how much oxygen binds to hemoglobin is PO2. At 40 mmHg of partial pressure of oxygen saturation won't be 100% and 75% saturation can be seen. The higher PCO2 value the curve shifts to right denoting less saturation and less affinity to oxy- hemoglobin binding. This implies a reduction in the affinity of blood for oxygen . For a given PO2 value , venous blood contains less oxygen than arterial blood and it facilitates the unloading of oxygen from hemoglobin in the tissues. The converse occurs during passage through the pulmonary capillaries with the greater affinity accompanying a shift of the curve to the left aiding the uptake of oxygen. According to the question curve, when PCO2 is 80 mmHg the saturation is the lowest as the curve shifted to the right whereas our question was to denote the maximum saturation. The PCO2 at 20 mmHg showed maximum shift to the left and thus predicts maximum saturation.
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