Question

for subject a at rest: map = 83 mm hg and co = 4.2 l · min⁻¹. for subject a at 125 watts: map = 105 mm hg and co = 18.0 l · min⁻¹. what is the ratio of tpr at rest and tpr at 125 watts? you can click the view image button to get some help with the question. a) about ⅓, tpr is lower at rest than during exercise. b) about 3, tpr is higher at rest than during exercise c) about 5, tpr is higher at rest than during exercise d) about 1, tpr doesnt change much with exercise

Explanation:

Step1: Recall the formula for TPR

TPR (Total Peripheral Resistance) is calculated by the formula $TPR=\frac{MAP}{CO}\times80$ (where MAP is Mean - Arterial Pressure in mmHg, CO is Cardiac Output in L/min, and the factor 80 is a conversion factor to get the units in dyne $\cdot$ s $\cdot$ $cm^{- 5}$). But for the ratio, the 80 will cancel out.

Step2: Calculate TPR at rest

Let $TPR_{rest}=\frac{MAP_{rest}}{CO_{rest}}$, with $MAP_{rest} = 83$ mmHg and $CO_{rest}=4.2$ L/min. So $TPR_{rest}=\frac{83}{4.2}$.

Step3: Calculate TPR during exercise

Let $TPR_{exercise}=\frac{MAP_{exercise}}{CO_{exercise}}$, with $MAP_{exercise}=105$ mmHg and $CO_{exercise}=18.0$ L/min. So $TPR_{exercise}=\frac{105}{18.0}$.

Step4: Calculate the ratio of TPR at rest to TPR during exercise

The ratio $R=\frac{TPR_{rest}}{TPR_{exercise}}=\frac{\frac{83}{4.2}}{\frac{105}{18.0}}=\frac{83\times18.0}{4.2\times105}$.
$83\times18.0 = 1494$ and $4.2\times105=441$.
$R=\frac{1494}{441}\approx3.39\approx3$.

Answer:

b) About 3, TPR is higher at rest than during exercise