What does an indwelling arterial catheter measure?

An indwelling arterial catheter measures arterial blood pressure, which includes the determination of mean arterial pressure (MAP). MAP is a significant indicator of perfusion pressure and provides insight into the overall circulatory status of a patient. The catheter is placed in an artery, typically in the radial or femoral area, allowing for continuous blood pressure monitoring, which is essential in critically ill patients or during surgeries.

The measurement of MAP is obtained by integrating the systolic and diastolic pressures over time, reflecting the average blood pressure in a person's arteries during one cardiac cycle. This measurement is vital in assessing blood flow to the organs and can help guide treatment decisions.

While central venous pressure is measured using a different type of catheter placed in the central venous system, pulmonary artery pressures require a specialized catheter (pulmonary artery catheter) and are not measured with a standard arterial line. Cardiac output is often estimated through other means, such as thermodilution or echocardiography, rather than being directly measured by an indwelling arterial catheter. Thus, the primary function of this catheter is to accurately assess mean arterial pressure among other arterial pressures.