08 July, 2011
How to Calculate Cardiac Output During Exercise
Cardiac output is a measure of how much blood your heart is pumping per minute of time. Although the most accurate measures of cardiac output are highly invasive, one simpler and fairly accurate way to measure it is to multiply your heart rate by your pulse pressure, then convert that to liters per minutes. Cardiac output is one important measure of cardiovascular functioning and it can help indicate the condition of the heart.
Determining Cardiac Output
Place a heart rate monitor around your chest and place a mobile blood pressure cuff around your upper arm.
Step onto the treadmill.
Write down your heart rate when you have reached the point at which you want to measure your cardiac output. Heart rate increases proportionally to the difficulty of the exercise you are performing.
Turn on the blood pressure cuff to check your blood pressure reading for the heart rate you have reached. The device will display your systolic blood pressure -- the larger number, on top -- and your diastolic blood pressure -- the smaller number, on the bottom.
Stop the treadmill and step off.
Calculate the difference between your systolic and diastolic blood pressure to get a value for your pulse pressure. For instance, if your blood pressure reads 130/70, your pulse pressure is 60. Because pulse pressure can be used to approximate the heart's stroke volume, you give describe it in units of mL/beat, or in this case, 60 mL/beat.
Multiply heart rate by stroke volume to determine your cardiac output in milliliters, and then divide by 1000 to convert to liters. For instance, if your stroke volume was 60 mL/beat with a heart rate of 150 bpm, cardiac output equals about 9,000 mL/min or about 9 L of blood circulating per minute.
Having a partner check your heart rate and blood pressure readings will ensure your safety while you operate the treadmill.
- Critical Care Nurse; Measuring Cardiac Output: Intermittent Bolus Thermodilution Method; Anna Gawlinski
- Toronto General Hospital of Anesthesia: Cardiac Physiology
- Computers in Cardiology; Estimating Cardiac Output from Arterial Blood Pressure Waveforms: a Critical Evaluation using the MIMIC II Database; J.X. Sun, et al.
- University of Maryland Medical Center: High Blood Pressure
- Centers for Disease Control and Prevention: Pulse and Blood Pressure Procedures for Household Interviewers
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