What are pulmonary artery pressures and the role of a pulmonary artery catheter (PAC) in measuring them?

From the Guidelines

Pulmonary artery pressures are a critical measurement in assessing pulmonary hypertension, with a mean pulmonary arterial pressure (mPAP) >20 mm Hg at rest indicating pulmonary hypertension, as defined in the 2022 update of the ACR Appropriateness Criteria for suspected pulmonary hypertension 1. Pulmonary artery pressures are important hemodynamic measurements that reflect the pressure within the pulmonary circulation, providing critical information about right heart function and pulmonary vascular resistance. These pressures are typically measured using a pulmonary artery catheter (PAC), also known as a Swan-Ganz catheter.

Key Points About Pulmonary Artery Catheter

• The PAC is a balloon-tipped, flow-directed catheter that is inserted through a central vein (usually the internal jugular, subclavian, or femoral vein) and advanced through the right atrium, right ventricle, and into the pulmonary artery.
• Normal pulmonary artery systolic pressure ranges from 15-30 mmHg, diastolic pressure from 4-12 mmHg, and mean pressure from 9-18 mmHg.
• The catheter also measures pulmonary artery wedge pressure (PAWP), which reflects left atrial pressure and serves as an indirect measure of left ventricular end-diastolic pressure (normal range 4-12 mmHg).

Uses and Complications of Pulmonary Artery Catheter

• PACs are used in critically ill patients to guide fluid management, assess cardiac function, monitor response to therapies, and diagnose conditions like pulmonary hypertension, heart failure, and cardiogenic shock.
• The catheter can also measure cardiac output using thermodilution techniques, mixed venous oxygen saturation, and core body temperature.
• Potential complications include arrhythmias, pulmonary artery rupture, thrombosis, infection, and pulmonary infarction, so PACs should be used judiciously when less invasive monitoring is insufficient, as recommended by the 2022 update of the ACR Appropriateness Criteria for suspected pulmonary hypertension 1.

Classification of Pulmonary Hypertension

• The 2018 updated clinical classification of pulmonary hypertension includes group 1, PAH; group 2, PH due to left heart disease; group 3, PH due to lung diseases and/or hypoxia; group 4, PH due to PA obstructions; and group 5, PH with unclear and/or multifactorial mechanisms, as defined in the 2022 update of the ACR Appropriateness Criteria for suspected pulmonary hypertension 1.
• The sixth World Symposium on Pulmonary Hypertension also defined specific criteria for precapillary PH, isolated postcapillary PH, and combined pre- and postcapillary PH using an mPAP >20 mm Hg in combination with pulmonary arterial wedge pressure (PAWP) and peripheral vascular resistance (PVR) measurements, as reported in the 2022 update of the ACR Appropriateness Criteria for suspected pulmonary hypertension 1.

From the Research

Pulmonary Artery Pressures

• Pulmonary artery pressure refers to the blood pressure in the pulmonary artery, which carries deoxygenated blood from the heart to the lungs 2.
• Increased pulmonary artery pressure can lead to pulmonary hypertension, a progressive and often fatal disease that can result in right ventricular failure 2, 3.
• Pulmonary hypertension can be caused by various factors, including congenital heart disease, left ventricular diastolic dysfunction, and pulmonary vascular disease 2, 3.

Pulmonary Artery Catheter

• A pulmonary artery catheter is a medical device used to measure the pressure in the pulmonary artery and to assess the function of the right heart 4, 5.
• Right heart catheterization (RHC) is the gold standard for the diagnosis and classification of pulmonary hypertension, and it involves the insertion of a catheter into the pulmonary artery to measure pressure and other parameters 4, 5.
• The procedure requires significant expertise and training to perform safely and accurately, and it can be used to assess various parameters, including pulmonary artery wedge pressure (PAWP) and cardiac output (CO) 4, 5.
• Errors in assessing PAWP can significantly affect the accurate classification of patients with pulmonary hypertension and can lead to potentially deleterious treatment decisions 5.

Diagnosis and Management

• The diagnosis and management of pulmonary hypertension rely on an integrated clinical assessment of the patient's physiology and right heart function 3.
• Echocardiography and other non-invasive methods can be used to estimate pulmonary artery pressure and to assess right heart function, but RHC remains the gold standard for diagnosis and classification 2, 6.
• The management of pulmonary hypertension and right ventricular failure requires consideration of the individual's hemodynamic phenotype and physiologic circumstances, particularly in the intensive care setting 3.