Measuring Pulmonary Artery Pressure with Swan-Ganz Catheter
Right heart catheterization using a Swan-Ganz (pulmonary artery) catheter is the gold standard for measuring PA pressure, requiring systematic advancement through the right heart chambers with pressure measurements at each location, and normal mean PA pressure is 9-18 mm Hg (systolic 15-25 mm Hg, diastolic 8-15 mm Hg). 1
Catheter Insertion and Advancement Technique
The Swan-Ganz catheter is a flow-directed balloon catheter that advances through the venous system into the pulmonary artery. 2, 3
Key technical steps:
- Insert the catheter through a central vein (internal jugular, subclavian, or femoral) and advance it with the balloon deflated until reaching the right atrium 4
- Inflate the balloon in the right atrium, then advance the catheter sequentially through the right ventricle and into the pulmonary artery, using the flow of blood to guide the balloon-tipped catheter forward 4, 2
- Avoid repeated balloon inflations and deflations in the distal pulmonary arteries, as this increases risk of pulmonary artery rupture 4
Pressure Measurement Protocol
Zero the external pressure transducer at the mid-thoracic line in a supine patient, halfway between the anterior sternum and the bed surface—this represents the level of the left atrium. 4
Measure pressures sequentially at each location:
- Right atrial pressure (RA): Normal 2-8 mm Hg 5
- Right ventricular pressure (RV): Normal systolic 15-25 mm Hg, diastolic 0-8 mm Hg 5
- Pulmonary artery pressure (PA): Systolic, diastolic, and mean values 4, 5
- Pulmonary artery wedge pressure (PAWP): With balloon inflated in wedge position, representing left atrial pressure 4
Record all pressure measurements at end-expiration to minimize respiratory artifact. 4 Alternatively, average pressures over several respiratory cycles, except in patients with dynamic hyperinflation. 4
Normal Pulmonary Artery Pressure Values
Normal PA pressures are:
- Mean PA pressure: 9-18 mm Hg (typically cited as <20 mm Hg) 1
- Systolic PA pressure: 15-25 mm Hg 5
- Diastolic PA pressure: 8-15 mm Hg 5
Pulmonary hypertension is defined as mean PA pressure >20 mm Hg on right heart catheterization. 1
Additional Essential Measurements
Beyond pressure measurements, the Swan-Ganz catheter enables comprehensive hemodynamic assessment: 5, 6, 1
- Cardiac output: Measured by thermodilution (inject cold saline in triplicate) or direct Fick method 4
- Oxygen saturations: Sample from superior vena cava, inferior vena cava, pulmonary artery, and systemic artery 4, 5
- Pulmonary vascular resistance: Calculated from (mean PA pressure - PAWP) / cardiac output 5, 6
- Mixed venous oxygen saturation: Obtained from pulmonary artery sample 5, 6
Use thermodilution measured in triplicate as the preferred method for cardiac output, as it provides reliable measurements even with low cardiac output or severe tricuspid regurgitation. 4
Critical Technical Considerations
Confirm true wedge position by obtaining blood sample with balloon inflated—this should have the same oxygen saturation as systemic arterial blood. 4
Record PAWP as the mean of three measurements to ensure accuracy. 4
Use high-fidelity tracings printed on paper rather than small moving traces on a cardiac monitor for optimal waveform interpretation. 4
Perform stepwise oxygen saturation assessment in every patient with pulmonary arterial O2 saturation >75% or when left-to-right shunt is suspected. 4
Safety Profile
When performed at expert centers, right heart catheterization has low complication rates: 1.1% serious events and 0.055% mortality. 4 The most frequent complications are venous access-related (hematoma, pneumothorax), followed by arrhythmias and hypotensive episodes. 5
This procedure should be limited to expert centers due to its technically demanding nature and need for meticulous attention to detail. 4
Important Pitfalls to Avoid
Spontaneous variability in PA pressure can reach 20 mm Hg in individual patients, with mean coefficient of variability of 8%. 6 Single measurements may not reflect true baseline hemodynamics.
Measurements obtained during catheterization represent resting supine conditions only and may not reflect hemodynamic responses during upright posture, activity, or sleep. 6
In patients with intracardiac shunts, thermodilution may be inaccurate due to early recirculation of the injectate—use direct Fick method instead. 4