Which catheter is used to measure cardiac output via thermodilution?

• A. Bronchoscopy
• B. Thermodilution catheter
• C. CVP line
• D. Balloon catheter

Answer: (B)

Measuring cardiac output by thermodilution relies on a catheter with a distal temperature sensor—the thermodilution catheter. A cold saline bolus is injected, typically via a central venous port, and the sensor in the pulmonary artery detects the resulting temperature drop over time. The temperature-time curve is analyzed using the Stewart-Hamilton principle to calculate cardiac output. This is the setup used in a Swan-Ganz pulmonary artery catheter, which is specifically designed for thermodilution CO measurement. Other options aren’t used for this purpose: bronchoscopy is an airway procedure, a CVP line measures central venous pressure, and a balloon catheter is used for occlusion or dilation rather than CO assessment by thermodilution.