Cardiac output

Cardiac output (CO) is a measure of the volume of blood pumped by the heart in one minute.

It is a crucial indicator of the efficiency of the heart and the circulatory system in delivering oxygen and nutrients to the body’s tissues.

Factors Determining Cardiac Output

CO is determined by two primary factors:

1. Heart Rate (HR)

   • Definition: The number of times the heart beats per minute.
   • Influencing Factors: Age, fitness level, emotional state, and the balance between the sympathetic and parasympathetic nervous systems.

2. Stroke Volume (SV)

   • Definition: The volume of blood pumped by the heart with each beat.
   • Influencing Factors:
     • Preload: The amount of blood in the ventricles before contraction.
     • Afterload: The resistance the ventricles must overcome to pump blood.
     • Contractility: The strength of the heart muscle’s contractions.

Formula for Cardiac output

Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV)

• Units: CO is typically expressed in liters per minute (L/min).

Average Cardiac Output

• For a healthy adult at rest, the average CO is approximately 5 to 6 liters per minute.
• This value can vary based on factors such as age, gender, body size, and physical fitness.

Importance of CO

• CO is vital for maintaining adequate blood flow to the body’s tissues and organs.
• It can increase during exercise or stress and decrease during rest or changes in posture.
• The heart and circulatory system continuously adapt to ensure optimal CO, ensuring the body’s tissues receive sufficient oxygen and nutrients for proper function.

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