Maximum cardiac output related to sex and age.

Maximum cardiac output (Qmax) was determined for 233 males (aged 9 through 53 years) and 102 females (aged 9 through 20 years) by the carbon dioxide rebreathing technique during bicycle exercise. Maximum cardiac output of the males progressively increased from 12.5 to 22.0 liter/min until age 17 through 18 years and was maintained at this level until age 24 years. From age 25 years a decrease in Qmax to 16.7 liter/min by age 53 years was observed. Qmax of the females increased from a level of 10.5 liter/min at age 9 years to a Qmaximum of 15.5 liter/min at age 18 years, maintaining this level through age 20 years. Male Qmax for comparable ages above 18 years was 30 % higher than female Qmax . Using the average Qmax value of males of 23-24 years as an optimum value, the decrement in Qmax with each year was approximately 0.9 %.