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Major factors influencing cardiac output – heart rate and stroke volume, both of which are variable. [1]In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols , ˙, or ˙, [2] is the volumetric flow rate of the heart's pumping output: that is, the volume of blood being pumped by a single ventricle of the heart, per unit time (usually measured ...
In the determination of cardiac output, the substance most commonly measured is the oxygen content of blood thus giving the arteriovenous oxygen difference, and the flow calculated is the flow across the pulmonary system. This gives a simple way to calculate the cardiac output: [citation needed]
Here Q is the cardiac output of the heart, C a O 2 is the arterial oxygen content, and C v O 2 is the venous oxygen content. (C a O 2 – C v O 2) is also known as the arteriovenous oxygen difference. The Fick equation may be used to measure V̇O 2 in critically ill patients, but its usefulness is low even in non-exerted cases. [8]
In order to do so oxygen consumption (VO 2) may be measured using a spirometer to detect gaseous concentrations in exhaled air compared to inhaled air, while cardiac output can be determined using a Doppler ultrasound. [3] Arterial blood will generally contain an oxygen concentration of around 20 mL/100 mL. [1]
Stroke volume is an important determinant of cardiac output, which is the product of stroke volume and heart rate, and is also used to calculate ejection fraction, which is stroke volume divided by end-diastolic volume. Because stroke volume decreases in certain conditions and disease states, stroke volume itself correlates with cardiac function.
Cardiac output as shown on an ECG. Cardiac output (CO) is a measurement of the amount of blood pumped by each ventricle (stroke volume, SV) in one minute. To calculate this, multiply stroke volume (SV), by heart rate (HR), in beats per minute. [1] It can be represented by the equation: CO = HR x SV [1]
The Frank-Starling mechanism allows the cardiac output to be synchronized with the venous return, arterial blood supply and humoral length, [2] without depending upon external regulation to make alterations. The physiological importance of the mechanism lies mainly in maintaining left and right ventricular output equality. [1] [3]
The cardiac index (CI) is a hemodynamic measure that represents the cardiac output (CO) of an individual divided by their body surface area (BSA), expressed in liters per minute per square meter (L/min/m²). This parameter provides a more accurate assessment of heart function relative to the size of the individual, as opposed to absolute ...