Problems in Cardiac Output Measurement and Clinical Understanding

Cardiac output measurement is so important that it is widely used in anesthesia and intensive care practice.However, the basic principles for the measurement of each device are not taught for clinicians.This review article describes considerable points for each device; 1) temperature sensors and integration problem for pulmonary artery catheter, 2) angle of ultrasonic probe and meaning of turbulent flow for transesophageal echocardiography, 3) angle of ultrasonic probe and meaning of pulsatile laminar flow for CarioQ, 4) end-tidal and arterial carbon dioxide concentration for Noninvasive cardiac output, 5) the concept of convolution for the arterial pulse wave and arterial resistance for Vigileo, and 6) effect size as a statistical viewpoint of comparison in device effectiveness.As a clinician we should not interpret the value of cardiac output as an absolute meaning, but do as a relative trend considering these theoretical errors.