Safe Pressure Support ventilation

3 min readNov 1, 2020

Patient Self Inflicted Lung Injury (PSILI) is a relatively new concept within mechanical ventilation. It implies that a patient can cause harm to their own lungs, creating barotrauma due to excessive transpulmonary pressure as a result of increased patient respiratory effort.

In Pressure Support mechanical ventilation it's not always easy to identify patients at risk of PSILI. This page will attempt to show you how.

Intensivist Dr. Bertoni proposed a method to estimate respiratory effort: he proposed that by performing an expiratory hold and determining the nadir of the pressure curve, you could determine the force that the patient is applying to the ventilator in order to receive an inspiration, i.e. the predicted muscular pressure or Pmus. Despite seemingly adequate respiratory support by the ventilator, some patients still show signs of increased respiratory effort. The predicted force applied specifically to the lungs, i.e. the predicted transpulmonary pressure or Ptp, is derived from this as well.

How to perform the measurement

  • Press record on your ventilator
  • Perform an expiratory hold
  • Retroactively, note the peak pressure, total PEEP and Pnadir (the lowest point of the inspiratory effort of the patient)

How to calculate Pmus and Ptp

Or… use VentICalc to make this a whole lot easier!

Refresher: P0.1

The airway occlusion pressure can also be described by the P0.1 value, i.e. the pressure drop in the first 0.1 seconds (i.e. 100 ms) of the inspiration. This pressure is always negative (as it is an inspiratory effort), but is sometimes depicted as positive…


I'm an intensivist and clinical pharmacologist, spreading the love for and knowledge of acute and critical care medicine on YouTube