This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Medicine
Which of the following is not useful in measuring cardiac output? 
Select and explain. 
A. Transthoracic echocardiogram, B. Central venous catheter, C. Thermodilution pulmonary catheter, D. Continuous cardiac output pulmonary catheter
B: Central venous catheter
Answer: B: Central venous catheter 
Explanation: Ans. B. Central venous catheter* Central venous catheter alone is not useful for measuring cardiac output.* Various methods to measure cardiac output are as follows:- Pulmonary artery flotation catheter (PAFC): Use dye dilution and thermodilution techniques (bolus and continuous thermodilution cardiac output monitoring)- Arterial waveform analysis- Thoracic electrical bioimpedance- Fick partial rebreathing method (uses CO2 )- Aortic Doppler (transesophageal and transcutaneous)- Point-of-care Echo (transthoracic as well as transesophageal)--LVOT is analyzed for cross-sectional area (CSA) and velocity time integral (VTI). Cardiac output (CO) is measured by the formula CO=CSAxVTIxHR- Lithium dilution (uses peripheral vein)- Combined lithium dilution and pulse contour analysis