Cardiac Output: Definition, Formula, Normal Range And Examples

Cardiac Output Definition

Cardiac output can be defined as the amount of blood the heart produces per ventricle every minute. It is, therefore, this form of measurement that is vital for an individual to know how the heart supplies the body effectively.Cardiac output is the product of heart rate and stroke volume. Heart rate is defined as the number of beats per minute, and stroke volume is the volume of blood pumped out with each beat from each ventricle. The resting cardiac output in a normal, healthy adult is approximately 5.0 litres per minute.Cardiac output ensures that an acceptable quantity of blood, along with the supply of oxygen and nutrients, reaches the tissues and organs. It also helps to deal with an elimination system within the system of waste products.

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This Story also Contains

1. Cardiac Output Definition
2. Factors Regulating Cardiac Output
3. Measurement Of Cardiac Output
4. Regulation Of Cardiac Output
5. Normal Values And Variations Of Cardiac Output
6. Clinical Importance
7. Use in Practice
8. Recommended video on Cardiac Output

Factors Regulating Cardiac Output

• Heart Rate: It is the number of times the heart beats in one entire minute and is used as a quantitative measure of cardiac activity. Increased heart rate generally results in improved cardiac output.

• Stroke Volume: It is the quantity of blood pumped out at each contraction of the heart and can be calculated as:

• Preload: The EDV or volume of blood entering the ventricles.

• Afterload: The arterial pressure or the resistance in the arteries which the heart must overcome to eject blood.

• Contractility: The forcefulness of each heart contraction.

• Venous Return: The volume of blood returning to the heart by the veins. It will be approximately equal to the CO over time.

• Physical Exercise: Exercise increases HR and SV leading to raised CO.

• Pathological Conditions: Pathologic conditions of the heart, such as heart failure, tachycardia, or hypertension will alter the CO.

Measurement Of Cardiac Output

The measurement of cardiac output can be done in several ways:

Direct Methods:

Fick Principle

Thermodilution

Indirect Methods:

Echocardiography

Doppler Ultrasound

Each method bears an advantage and a limitation in terms of accuracy and invasiveness.

Regulation Of Cardiac Output

• The cardiac output is regulated through:

• Intrinsic Regulation: The Frank-Starling mechanism, where the increased venous return stretches the ventricles, due to which stronger contractions take place.

• Extrinsic Regulation: Nervous and hormonal methods of control; for example, the autonomic nervous system and adrenaline.

Normal Values And Variations Of Cardiac Output

The general normal range of cardiac output in most adults is about 4-8 litres per minute. Age, sex, and physical condition are other factors that could influence this. Abnormal cardiac output could mean something terrible in health.

Clinical Importance

Cardiac output values play a critical and surgically important role in the clinical process. The abnormal value can diagnose heart failure, infections, and so on.

Use in Practice

Cardiac output measurements are also used in sports medicine to assess athletic performance and in medical settings to guide treatment decisions.

Conclusion

Cardiac blood flow is an important index of the functional efficiency of the heart and, more generally, of overall cardiovascular health. An understanding of the determinants and regulation of cardiac output provides a basis for the management of health and disease diagnosis.

Recommended video on Cardiac Output