Summary
Highlights
The video introduces Adolf Fick, born in 1829 in Kassel, Germany, who originally studied math and physics before transitioning to medicine. Fick was the first to measure cardiac output using the technique that would become known as the Fick equation.
The Fick method calculates O2 uptake by sampling arterial and venous pressures. This involves measuring O2 taken into the lungs, its arterial value, O2 released at tissues based on metabolic demand, and the post-artery oxygen, providing a differential between O2 taken in and expired.
VO2 is calculated using Cardiac Output (stroke volume multiplied by heart rate, representing total blood pumped per minute) and the A-VO2 difference (the differential in oxygen between arterial blood supplied to tissues and venous oxygen remaining in the blood). This results in total oxygen consumption.
Heart rate is beats per minute, stroke volume is liters of blood pumped per beat, making cardiac output liters of blood per minute. The arterio-venous O2 difference is in milliliters of oxygen per liter of blood, representing the difference in oxygen concentration. Body oxygen consumption (VO2) is total oxygen processed per minute in liters of O2 per minute.
An example demonstrates calculating VO2 for a person at rest with 4 liters/minute cardiac output. Arterial blood has 20 ml O2/100 ml blood, and venous blood has 15 ml O2/100 ml blood. The calculation involves converting liters to milliliters, finding the O2 difference (5 ml O2/100 ml blood), and then multiplying by cardiac output to find a resting VO2 of 0.2 liters of O2 per minute.
The video concludes by stating that the calculated resting VO2 is low, which is expected for someone not exercising. It sets up the concept that exercise would significantly change these values, increasing VO2.