Estimation of Cardiac Output.

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Exercise Physiology

Estimation of Cardiac Output

Introduction

To investigate the measurements of cardiac output by a non invasive indirect Flick method and to examine the effects of posture on cardiac output.

Cardiac output refers to the amount of blood pumped by the heart, usually during a 1 minute period. The maximal value for cardiac output reflects the functional capacity of the circulation to meet the demands of physical activity. (Exercise Physiology, William Mcardle, Frank I. Katch, Victor L. Katch 1996)

        Output from the heart , as with any pump depends on its rate of pumping (Heart rate) and the quanity of blood ejected with each stroke (stroke volume). (Exercise Physiology, William Mcardle, Frank I. Katch, Victor L. Katch 1996)

        The cardiac output is worked out by the following equation:-

Cardiac Output =Heart Rate X Stroke Volume.

The heart is composed mainly of cardiac muscle: a specialised tissue that can contract automatically, powerfully and without fatigue, throughout the life. The heart is situated in the mid-centre of the chest cavity behind the sternum and the ribs.

        The thickness of the walls in the different heart chambers reflects their function. The atria are thinly muscled because they only pump blood the short distance to the ventricles directly below them. (Biology, Marcus Barbor, Mike Boyle, Mike Cassidy, Kathryn Senior 1997). The ventricle is more heavily muscled than either of the atria because it has to force blood a further distance to the lungs. The left ventricle has the thickest wall because it has to force blood all the way around the body.  

        The heart has two atria acting as receiving chambers, the right atrium receives blood returning from all parts of the body and the left atrium receives oxygenated blood from the lungs. The heart also has two ventricles acting as sending units. The right ventricle pumps the blood to the lungs for aeration by way of the pulmonary circulation. The left ventricle pumps the oxygenated blood into the aorta for distribution throughout the body in the systemic circulation. (Wilmore et al. 1994) 

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The heart can be divided into two sides, the left and the right. The division is important for the heart to carry out its function effectively. Each of the sides has slightly different roles; the right side is responsible for pumping deoxygenated blood to the lungs where it can be deoxygenated. The left side of the heart is responsible for pumping the oxygenated blood to the various parts of the body. (Wesson et al, 1998)

The sequence of events in a single heartbeat is known as the cardiac output cycle. The cycle involves systole, or contraction ...

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