|
Cardiac output (CO, also denoted by the symbols and ), is a term used in cardiac physiology that describes the volume of blood being pumped by the heart, in particular by a left or right ventricle, per unit time. CO values can be represented using many physical units, such as dm3/min and L/min.. Because cardiac output is related to the quantity of blood delivered to various parts of the body, it is an important indicator of how efficiently the heart can meet the demands of the body. For instance, infections are correlated with high CO and heart failure with low CO. Along with stroke volume (SV), cardiac output is a global blood flow parameter of interest in hæmodynamics – the study of the flow of blood under external forces. The factors affecting stroke volume and heart rate also affect cardiac output. The figure to the right 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 CO, both invasively and non-invasively, each with its own advantages and drawbacks. No standard or reference measurement against which all of these methods can be compared exists. ==Definition== The function of the heart is to drive blood through the circulatory system in a cycle that delivers oxygen, nutrients and chemicals to the body's cells and removes cellular waste. Because it pumps out whatever blood comes back into it from the venous system, the quantity of blood returning to the heart effectively determines the quantity of blood the heart pumps out – its cardiac output, ''Q''. Cardiac output is classically defined alongside stroke volume (SV) and the heart rate (HR) as: In standardizing what CO values are considered to be within normal range independent of the size of the subject's body, the accepted convention is to further index equation () using Body surface area (BSA), giving rise to the Cardiac index (CI). This is detailed in equation () below. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cardiac output」の詳細全文を読む スポンサード リンク
|