Pressure versus Time Graph


Pressure versus Time Graph. Information obtained

  • peak inspiratory pressure
  • plateau pressure
  • compliance = gradient between PIP and Pplat (small = decreased)
  • type of ventilation (volume vs pressure controlled)
  • get a sense of flow rate
  • CPAP level = pressure at beginning of inspiration
  • patient triggering = negative deflection into CPAP just before inspiration



  • normal PIP, Pplat, PTA (transairway pressure) and Ti (inspiratory time)
  • pressure controlled ventilation shown below

High Raw

  • raised PTA with increased airways resistance

High Flow

  • inspiratory time short with high peak inspiratory pressure -> high inspiratory gas flow

Inadequate inspiratory flow

  • scooped appearance to the synchronized breaths

Decreased Lung Compliance

  • increased plateau pressure and increased PIP -> poor compliance


  • expiratory hold -> pressure-time waveform doesn’t return to base line

Dynamic Hyperinflation

  • inspiratory hold -> plateau pressure > 25cmH20

Cardiac oscillations

  • base line of pressure time wave forms moves up and down with the heart beat -> triggering synchronized breaths

Circuit leaks

  • wave form drifts downwards (expired volume < inspired volume)

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

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