Saturday, 30 October 2010

Cardiac Output Measurement Techniques (Dye Dilution, Fick, Thermodilution Methods)

Cardiac Output Measurement Techniques:
  • Dye dilution method
  • Fick method
  • Thermodilution method
Dye Dilution Method:
  • Based on principle that if a known amount of indictor dye is mixed into an unknown volume of blood, & its concentration is then measured, the volume of blood can be calculated from the dilution factor.
  • The flow of blood can be measured if the mean concentration of the indicator is assessed for the time required for that indicator to pass a given site.
Fick Method:
  • Based on principle that the amount of oxygen delivered to the peripheral tissues must equal the oxygen uptake by the lungs, plus the oxygen delivered to the lungs in the pulmonary artery.
  • Equals = (oxygen consumption) / (Arterial O2 content - Venous O2 content).
  • Equals = [ml O2/min]/ [ml O2 per L blood] = L/min
Thermodilution Method:
  • Based on principle that cold saline injected at the proximal end of a catheter in the right ventricle, mixes with blood in the right ventricle & a temperature change can measured by a thermistor in the pulmonary artery.

Sunday, 17 October 2010