330x330px<unk>  <unk> , also known as heart<unk>  denoted by the symbols , or , is a term used in cardiac physiology that describes the volume of blood being pumped by both ventricles of the heart, per unit time (usually measured per minute).<unk>  <unk>  is the product of the heart rate (HR), i.e. the number of heartbeats per minute (bpm), and the stroke volume (SV), which is the volume of blood pumped from the left ventricle per beat; thus giving the formula: :CO = HR × SV Values for<unk>  are usually denoted as L/min. For a healthy individual weighing 70 kg, the<unk>  at rest averages about 5 L/min; assuming a heart rate of 70 beats/min, the stroke volume would be approximately 70 mL. Because<unk>  is related to the<unk> uantity of blood delivered to various parts of the body, it is an important<unk> mponent of how efficiently the heart can meet the body's demands for the maintenance of adequate tissue perfusion. Body tissues require<unk> ntinuous oxygen delivery which requires the sustained transport of oxygen to the tissues by systemic circulation of oxygenated blood at an adequate pressure from the left ventricle of the heart via the aorta and arteries. Oxygen delivery (DO2 mL/min) is the resultant of blood flow<unk> <unk>  times the blood oxygen<unk> ntent (CaO2). Mathematically this is calculated as follows: oxygen delivery =<unk>  × arterial oxygen<unk> ntent, giving the formula :DO2 =<unk>  × CaO2. With a resting<unk>  of 5 L/min, a 'normal' oxygen delivery is around 1 L/min. The amount/percentage of the circulated oxygen<unk> nsumed (VO2) per minute through metabolism varies depending on the activity level but at rest is circa 25% of the DO2. Physical exercise requires a higher than resting-level of oxygen<unk> nsumption to support increased muscle activity. In the case of heart failure, actual<unk>  may be insufficient to support even simple activities of daily living; nor can it increase sufficiently to meet the higher metabolic demands stemming from even moderate exercise.<unk>  is a global blood flow parameter of interest in hemodynamics, the study of the flow of blood. The factors affecting stroke volume and heart rate also affect<unk> . The figure at the right margin illustrates this dependency and lists some of these factors. A detailed hierarchical illustration is provided in a subsequent figure. There are many methods of measuring<unk> , both invasively and non-invasively; each has advantages and drawbacks as described below.
Cardiac output
Coronary perfusion pressure
Vagal tone
Mean arterial pressure
Mean systemic pressure
Cerebral perfusion pressure
Cardiac reserve
Respiratory rate