Final answer:
A pulmonary artery catheter is used to measure a patient's hemodynamic status, an invasive procedure usually done in surgery or intensive care settings.
Step-by-step explanation:
A pulmonary artery catheter is used to monitor the hemodynamic status of a patient. This involves measuring the pressures within the heart and lungs, including the major veins and the pulmonary artery itself. These invasive procedures are typically performed during surgery or for patients in intensive care. To measure these pressures, health care workers insert catheters into the relevant areas, transmitting the pressures to external measuring devices.