Cardiac output

The primary function of the cardiovascular system is to transport oxygen, nutrients and substrates around the body, thus ensuring that the appropriate amounts of these products are present to meet the metabolic demands within the cells.

The prime determinant of efficacy of the transport system is cardiac output. Cardiac output is the amount of blood that is ejected from the heart every minute and is the product of the equation:

Stroke volume is the amount of blood that is ejected from the heart with each beat. Stroke volume is determined by three factors:

1. 1 Preload: affected by the volume status of a patient
   
2. 2 Afterload: impacted by the systemic vascular resistance
   
3. 3 Contractility: the power created by the heart muscle to pump the blood around the body.

An analogy to describe this is a hosepipe with an adjustable nozzle.