Cardiac output of Indian men by a non-invasive method the Indirect Fick Principle

The cardiac-output (Q) of seven young healthy Indians with common physical characteristics at rest and after a single bout of exercise of 600 kpm for 10 min on a bicycle ergometer was ascertained by the Indirect Fick Principle. The end tidal alveolar Co2 pressure was obtained at the end of a normal expiration and PvCo2 was obtained by the help of the exponential rise (Defares method) in Co2 concentration during rebreathing from an initially low Co2 in O2 mixture (3-4%). The standard Co2 dissociation curve of oxygenated blood was used to find out the corresponding arterial and venous Co2 content, assuming the Hb content of these individuals to be normal. The mean value of the Cardiac-Output so obtained during rest is 4.21 liters/min when Co2 rebreathing time does not exceed 10 secs, and 17.33 litres/min., 2 to 3 breaths after exercise, when rebreathing time did not exceed 5 to 7 secs. Repeated studies and better training of the subjects will perhaps improve the resting values, while after exercise and during recovery our values are better reproducible.