Question

help please!

32. Extra credit, no penalty if wrong. Within the context of the Fick equation, I am a patient with heart disease. My doctor puts me on beta blockers (a drug that decreases HRmax and blood pressure and makes my symptoms better). My HRmax decreases from 160 to 130 bpm, my stroke volume stays at 80 ml/beat. My arterial and venous saturations stay at 97 and 30% respectively, and my hemoglobin stays at 13 gm%. What is my VO2max (in ml/kg) before and after drug therapy if I weigh 95 kg? (30 pts)

Answer 1

FICK EQUATION:

Maximum oxygen uptake or VO2 max is considered as the recognised standard of cardiovascular , pulmonary and muscular aerobic fitness. VO2 max is the maximum oxygen consumption that can be used per minute, representing any individuals upper limit of aerobic metabolism. The equation is VO2 max = Q(CaO2- CvO2). In this Q is the cardiac output, CaO2 is the arterial oxygen content , CvO2 is the venous oxygen content.

The cardiac output is the amount of blood pumped from the heart in 1 minute. It can be calculated by Q= HR max (stroke volume).

In this case our patient is on  beta-blocker drugs.

BEFORE THERAPY:

HR max = 160 bpm

stroke volume = 80 ml/bt

CaO2 = 97%

CvO2 = 30%

hb = 13 gm%

weight = 95 kg

Cardiac output (Q) = Max HR ( stroke volume) = 160 bpm (80 ml/bt)= 12800ml/mt

CaO2 - CvO2 = 97 - 30 = 97 - 30 = 67 ml of O2/100 ml of blood

VO2 max = Q(CaO2 - CvO2) = 12800(67)/100 = 8576 ml of O2/mt = 8.576L/mt.

converting into ml/kg = 8.576/95(1000) = 90.28 ml/kg.

AFTER THERAPY:

HR max = 130 bpm . Rest of all the values remain same as before therapy.

VO2 max = Q(CaO2 - CvO2)

Q = HR max (stroke volume) = 130 bpm (80 ml/bt) = 10400 ml/mt

CaO2 -CvO2 = 67 ml O2/ 100 ml of blood

VO2 max = 10400(67)/ 100 = 6968 ml of O2/mt = 6.968L/ mt

Converting into ml/kg = 6.968/95(1000) = 73.35 ml/kg