What is a normal cardiac output (CO) for an average adult?

From the Guidelines

The normal cardiac output for an average adult at rest is approximately 5 to 6 liters per minute. This value is supported by the Fick equation, which states that for every 1 L/min increase in oxygen uptake, there is an obligate requirement for a 5 to 6 L/min increase in cardiac output, as noted in a scientific statement from the American Heart Association and American College of Cardiology 1. Cardiac output can vary based on several factors including body size, with larger individuals typically having higher cardiac outputs. During exercise, cardiac output can increase significantly, reaching up to 20-25 liters per minute in trained athletes. Some key points to consider when evaluating cardiac output include:

• Cardiac output is calculated by multiplying heart rate (normally 60-100 beats per minute at rest) by stroke volume (approximately 70-80 mL per beat in a typical adult)
• Maintaining normal cardiac output is essential for adequate tissue perfusion and oxygen delivery throughout the body
• Cardiac output is an important measurement in clinical settings, as it helps assess heart function and can guide treatment decisions for conditions like heart failure, shock, or during critical care management. The increase in cardiac output during exercise is independent of age, sex, or fitness, as stated in the study published in Circulation 1.

From the Research

Normal Cardiac Output

• Cardiac output (CO) is a fundamental measure of the adequacy of myocardial function to meet the perfusion needs of tissue at any time 2.
• Normal cardiac output values can vary depending on factors such as age, gender, and body size.

Factors Influencing Cardiac Output

• Age: some studies suggest a weak relation between CO and age, observed only in women 3, while others report a yearly decline in cardiac index (between 3.5 and 8 mL/min/m2 per year) 4.
• Gender: CO normal limits are lower in females than in males (lower limit: 3.3 vs 3.5 L/min, upper limit: 7.3 vs 8.2 L/min) 3.
• Body size: CO of obese patients is significantly greater than that of their nonobese counterparts, but cardiac index (CI) is not influenced by body size 3.

Normal Reference Values

• Normative reference CO values for nonobese adults: lower limit 3.3-3.5 L/min, upper limit 7.3-8.2 L/min 3.
• Normative reference CI values for nonobese adults: lower limit 1.9 L/min/m2, upper limit 4.3 L/min/m2 3.
• Mean cardiac index in healthy volunteers over 60 years of age: between 2.1 and 3.2 L/min/m2 4.
• Mean cardiac output in healthy volunteers over 60 years of age: between 3.1 and 6.4 L/min 4.