Pulmonary Artery Catheter (PAC) 

1. Introduction

The Pulmonary Artery Catheter (PAC), commonly known as the Swan–Ganz catheter, is an advanced invasive hemodynamic monitoring tool that allows direct measurement of right-sided, pulmonary, and indirectly left-sided cardiac pressures, along with cardiac output and mixed venous oxygen saturation (SvO₂).

Although its routine use has declined, PAC remains invaluable in selected complex shock states, advanced heart failure, pulmonary hypertension, and post-cardiac surgery patients.

2. Historical Perspective

• Developed in 1970 by Swan and Ganz
• Revolutionized bedside hemodynamic assessment
• Initially widely used → later decline due to:
• Invasive nature
• Complication risk
• No proven mortality benefit in unselected ICU populations

Key exam point: PAC does not improve mortality, but improves diagnostic accuracy and physiological understanding.

3. Structure of Pulmonary Artery Catheter

Length and Size

• Length: 110 cm
• Size: 7–8.5 Fr

Lumens and Ports

4. Route of Insertion

Venous Access

• Right Internal Jugular vein (preferred)
• Subclavian vein
• Femoral vein (least preferred)

Pressure Waveform-Guided Advancement

5. Parameters Measured by PAC

A. Directly Measured

1. Right Atrial Pressure (RAP / CVP)
2. Right Ventricular Pressure
3. Pulmonary Artery Pressure (PAP)
4. Pulmonary Artery Occlusion Pressure (PAOP / PCWP)
5. Cardiac Output (CO) – Thermodilution
6. Mixed Venous Oxygen Saturation (SvO₂)

B. Derived Hemodynamic Variables

6. Pulmonary Artery Occlusion Pressure (PAOP / PCWP)

What It Reflects

• Indirect estimate of Left Atrial Pressure
• Surrogate for LV end-diastolic pressure (LVEDP) only if conditions are ideal

Normal Value

• 6–12 mmHg

Conditions Where PAOP ≠ LVEDP

• Mitral stenosis/regurgitation
• Pulmonary venous disease
• High PEEP
• ARDS
• Diastolic dysfunction
• Elevated intra-thoracic pressure

Exam Pearl: PAOP ≠ preload in many ICU conditions.

7. Cardiac Output Measurement (Thermodilution)

Principle

• Injection of cold saline → temperature change detected by thermistor

Factors Affecting Accuracy

• Tricuspid regurgitation
• Intracardiac shunts
• Rapid infusions
• Mechanical ventilation
• Arrhythmias

8. Mixed Venous Oxygen Saturation (SvO₂)

Normal Value

• 65–75%

Physiological Determinants

• Oxygen delivery
• Oxygen consumption
• Hemoglobin
• Cardiac output

Interpretation

Key concept: SvO₂ reflects global oxygen balance, not tissue perfusion.

9. Clinical Indications for PAC (Selective Use)

A. Cardiogenic Shock

• Post-MI
• Severe LV failure
• Mechanical complications

B. Complex Shock States

• Mixed septic + cardiogenic shock
• Refractory shock despite echo and dynamic indices

C. Severe Pulmonary Hypertension

• RV failure
• Pre-transplant evaluation

D. Advanced Heart Failure

• Transplant/LVAD work-up
• Inotrope titration

E. Post-Cardiac Surgery

• Unstable hemodynamics
• RV dysfunction

Not for routine sepsis management

10. PAC in Shock – Hemodynamic Profiles

11. Complications of PAC

Mechanical

• Pneumothorax
• Arterial puncture
• Arrhythmias (RV irritation)

Catheter-Related

• Pulmonary artery rupture (fatal)
• Thrombosis
• Infection
• Knotting
• Valve injury

Pressure-Related

• Over-wedging → pulmonary infarction

Never inflate balloon with >1.5 mL air

12. PAC vs Echocardiography vs Dynamic Indices

Modern ICU approach: Echo first → PAC only if uncertainty persists.

13. Evidence & Controversies

• ESCAPE Trial: No mortality benefit
• PAC does not worsen outcomes when used by experienced clinicians
• Poor outcomes often due to misinterpretation, not the device