Pulmonary Artery Wedge Pressure


Pulmonary Artery Wedge Pressure (PAWP) is also known as Pulmonary Artery Occlusion Pressure (PAOP)


  • PAOP or PAWP is pressure within the pulmonary arterial system when catheter tip ‘wedged’ in the tapering branch of one of the pulmonary arteries
  • in most patients this estimates LVEDP thus is an indicator of LVEDV (preload of the left ventricle)
  • normally 6-12mmHg (1-5mmHg less than the pulmonary artery diastolic pressure)
  • PCWP >18 mmHg in the context of normal oncotic pressure suggests left heart failure


“Wedging” is measurement of PAOP (pulmonary artery occlusion measurement)

  • PA catheter tip advanced into a small pulmonary artery (usually in RML or RLL)
  • PAWP measured by convention at end-expiration at end-diastole (ECG p wave)
  • phasic blood flow and pressure ceases
  • static column of blood between catheter tip in pulmonary artery and the left atrium
  • must be in West Zone III otherwise trace will show respiratory swing (reflects alveolar pressure in West Zones I and II)


5 indicators that PAC tip is in West Zone III:

  • PAWP < PADP by 1-5 mmHg
  • PAWP alters < than 50% of increase in PEEP
  • PAWP increases by < 50% of changes in alveolar pressure (Pplat)
  • O2 saturation in wedged position greater than unwedged position (sucking back of oxygenated blood)
  • CXR: below level of LA


Situations when PAWP > LVEDP

  • mitral stenosis
  • atrial myxoma
  • pulmonary venous obstruction (e.g. fibrosis, vasculitis)
  • MR
  • non-zone III placement
  • L to R shunt
  • COPD
  • IPPV +/- PEEP

Situations when PAWP < LVEDP

  • left ventricular failure
  • raised intra-thoracic pressure (high PEEP)
  • non-compliant left ventricle (e.g. hypertensive cardiomyopathy)
  • aortic regurgitation

References and Links


CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.