3.4 Calculate cardiac output and discuss the importance of this value.

Cardiac output is the volume of blood that the heart is able to pump. When the ventricles contract, about 70-90 cm3 of blood is ejected into the pulmonary artery and aorta. This represents the volume of blood being pumped round the body; this is an important factor in determining the effectiveness of the heart. It may indicate problems such as heart failure or poor circulation. There are two major factors that contribute to the cardiac output and that is heart rate (number of heat loads being pumped round the body per unit of time) and the stroke volume (the volume of blood the heart can fill with per contraction). Cardiac output = heart rate x stroke volume. The stroke volume is regulated by stimulation from the sympathetic nervous system.By increasing the heart rate effectively increases the cardiac output by increasing the volume of blood released in the body. As long as the heart is given enough time at diastole the effective volume that the heart outputs will increase.If the cardiac output is too low then this means that the body is not being supplied with enough blood which could lead to heart failure of other life threatening problems.Problems are usually recorded by attaching electrodes to a machine that can amplify and record an ECG (electrocardiogram). As the cardiac impulse travels across the atria and ventricular walls its electrical activity produces a recorded trace.(http://bme.usc.edu/bme403/Section_3/cardiac_output.html)