Ventilatory Waveform Analysis and Troubleshooting

Auto-PEEP

This is present when there is persistent non-zero flow at end-expiration. Suggests obstructive defect. Perform an expiratory hold maneuver to determine the degree of auto-PEEP in addition to the set PEEP, and therefore the total PEEP.

How to address it? Consider lowering the RR (to increase expiratory time), increasing flow (to decrease inspiratory time and therefore increase I:E ratio), bronchodilators, etc. Watch out for hemodynamic instability. In severe cases, disconnect the patient from the ventilatory and allow for thoracic decompression and full ventilation before re-connecting.

High PIP

Perform an inspiratory hold maneuver to isolate the issue to the airway/tube (high PIP, normal Pplat) or the lung compliance (elevated Pplat).

Resources

1. Chapter 32. Ventilator Waveforms: Clinical Interpretation | Principles of Critical Care, 3e | AccessAnesthesiology | McGraw Hill Medical
2. https://www.stritch.luc.edu/lumen/MedEd/MEDICINE/subint/icu/Basic%20modes.pdf