The pulmonary artery is the artery that carries blood from the right side of the heart into the lungs. In pulmonary artery catheterization, a catheter is passed through the right atrium and ventricle and into the pulmonary artery. This procedure is sometimes a useful measure of overall heart function in people who are critically ill, particularly when fluids are being given intravenously. Such people include those who have severe heart or lung disorders (such as heart failure Heart Failure (HF) Heart failure is a disorder in which the heart is unable to keep up with the demands of the body, leading to reduced blood flow, back-up (congestion) of blood in the veins and lungs, and/or... read more 
, heart attack Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) Acute coronary syndromes result from a sudden blockage in a coronary artery. This blockage causes unstable angina or a heart attack (myocardial infarction), depending on the location and amount... read more 
, abnormal heart rhythms Overview of Abnormal Heart Rhythms Abnormal heart rhythms (arrhythmias) are sequences of heartbeats that are irregular, too fast, too slow, or conducted via an abnormal electrical pathway through the heart. Heart disorders are... read more 
, or pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism is the blocking of an artery of the lung (pulmonary artery) by a collection of solid material brought through the bloodstream (embolus)—usually a blood clot (thrombus) or... read more when these disorders are accompanied by complications), those who have just undergone heart surgery, those who are in shock Shock Shock is a life-threatening condition in which blood flow to the organs is low, decreasing delivery of oxygen and thus causing organ damage and sometimes death. Blood pressure is usually low... read more , and those who have severe burns.
Pulmonary artery catheterization is also done to measure pressure in the right heart chambers and to estimate pressure in the left heart chambers, the amount of blood the heart pumps per minute (cardiac output), resistance to blood flow in the arteries that carry blood from the heart (peripheral resistance), and the volume of blood. This procedure can provide useful information about why a person's blood pressure may be low (such as in cardiac tamponade Cardiac Tamponade Cardiac tamponade is pressure on the heart by blood or fluid that accumulates in the two-layered sac around the heart (pericardium). This disorder interferes with the heart's ability to pump... read more ) or to help determine why the person is having difficulty breathing (such as in heart failure or pulmonary hypertension Pulmonary Hypertension Pulmonary hypertension is a condition in which blood pressure in the arteries of the lungs (the pulmonary arteries) is abnormally high. Many disorders can cause pulmonary hypertension. People... read more ).
The procedure may cause complications, but they are usually rare. They include an air pocket between the layers of membranes covering the lungs (pneumothorax Pneumothorax A pneumothorax is the presence of air between the two layers of pleura (thin, transparent, two-layered membrane that covers the lungs and also lines the inside of the chest wall), resulting... read more 
), abnormal heart rhythms (arrhythmias), infection, damage or clotting in the pulmonary artery, and injury to an artery or vein.
How pulmonary artery catheterization is done
As in right heart catheterization Cardiac catheterization Cardiac catheterization and coronary angiography are minimally invasive methods of studying the heart and the blood vessels that supply the heart (coronary arteries) without doing surgery. These... read more 
, a catheter with a balloon at its tip is inserted into a vein, usually in the neck , under the collarbone, groin, or an arm, and is threaded toward the heart. The tip of the catheter passes through the superior vena cava or inferior vena cava (the large veins that return blood to the heart from the upper and lower parts of the body) and through the right atrium and right ventricle to the pulmonary artery. The balloon at the catheter's tip is lodged in the pulmonary artery. A chest x-ray is taken or fluoroscopy (a continuous x-ray procedure) may be used to make sure the tip is placed correctly.
The balloon is inflated to temporarily block the pulmonary artery, so that pressure in the capillaries of the lungs (pulmonary capillary wedge pressure) can be measured. This measurement is an indirect way to determine pressure in the left atrium. Blood samples can be taken through the catheter, so that the oxygen and carbon dioxide levels in the blood can be measured.
