Flow, volume, and expiratory-hold clues
The pressure-time trace usually returns to set PEEP; intrinsic PEEP is quantified with a valid expiratory hold, not by eyeballing airway pressure alone.
Ventilator pattern lesson
Recognize auto-PEEP — case discussion
Fictional cue set: The key waveform clue is expiratory flow that has not returned to zero before the next breath starts.
Hemodynamic branchDynamic hyperinflation can cause shock.Expiratory-time conceptsCompare strategies that lengthen exhalation.
Original Airway of the Month teaching diagrams redrawn from standard ventilator scalar and loop conventions. Interpretation is anchored to the AARC 2024 Patient–Ventilator Assessment guideline, the peer-reviewed Basics of Ventilator Waveforms review, the 2026 SYNAPsE asynchrony consensus, and the University of Pennsylvania Ventilator Overview and Troubleshooting tip sheet. Waveforms are pattern-recognition aids, not diagnoses; display colors, labels, and orientation vary by ventilator brand.
Look for
- Expiratory flow remains below zero when the next inspiration begins.
- Volume-time may not return to baseline.
- Rising chest volume, increasing difficulty bagging, hypotension, or worsening hypercapnia may accompany severe dynamic hyperinflation.
Evidence and use limits
Last reviewed: 2026-07-17. Designed for: emergency medicine learners, clinicians, EMS, RT, and airway educators.
This fictional ventilator discussion supports pattern-recognition teaching. It does not select settings or recommend a time-critical action. Verify current evidence, equipment instructions, and local policy before clinical application.
Full references · Editorial policy · AARC 2024 ventilator assessment · ATS/ESICM/SCCM lung-protective ventilation · ATS 2024 ARDS update