Question

You have been contracted by a triathlete to determine their maximal aerobic capacity. As the athlete arrived at your laboratory, you realized that your metabolic chart had stopped functioning, and you need to measure blood gasses to perform the test. The data you obtain are as follow:

-Age: 35 years old

-Height: 1.75m

-Weight: 73kg

-Speed at VO_2max: 16.2 km/h

-Heart Rate at VO_2max: 192 bpm

-End Diastolic Volume: 242mL

-End Systolic Volume: 90mL

-Hemoglobin concentration: 163g/L (16.3 g/100mL)

-Arterial PO₂: 95mmHg (O2 sat: 97%)

-Venous PO₂: 20mmHg (O2 sat: 35%)

-Arterial PCO₂: 35mmHg

-Venous PCO₂: 40mmHg

Can you provide your triathlete with their maximal aerobic capacity? Include all your calculations (20 points) (Fick's equation)

Answer 1

According to Fick's Euation,

where,

CO = cardiac output

VO2 = aerobic capacity

pvO2 = pulmonary vein O2 concentration

paO2 = pulmonary artery O2 concentration

Given,

End diastolic volume (EDV) = 242 mL

End systolic volume (ESV) = 90 mL

Heart rate (HR) = 192 bpm

We have,

Therefore, CO = (242 - 90) X 192 = 29,184 mL = 29.2 L

We know that 1 gram of hemoglobin can bind 1.34 mL of oxygen.

Given, 0.163 gram of hemoglobin is present in 1mL of blood.

Now, pvO2 = 95 mmHg (97% Hb saturation) = 0.163X (97/100) X 1.34 = 0.21 mlO2 / ml blood

paO2 = 20 mmHg (35% Hb saturation) = 0.163 X (35/100) X 1.34 = 0.08 mlO2 / ml blood

Hence, maximum aerobic capacity VO2max. = CO X (pvO2 - paO2) = 29,184 X (0.21 - 0.08) = 29,184 X 0.13 = 3,793.92 mL/min

Given, body weight = 73 kg

Hence, VO2max. = 3,793.92 / 73 = 51.97 mL/kg/min

So, we have the maximal aerobic velocity of this triathlete as nearly 52 mL/kg/min