The Peak Inspiration Podcast
The Peak Inspiration Podcast

Reading Abnormal Ventilator Waveforms Part 3

September 12, 2026

AI Summary

5 min read

A patient in his 60s with COPD and pneumonia was intubated, sedated to a RASS of minus four, and still double-triggering on volume control ventilation. The team’s first instinct was more sedation. The ventilator waveforms, however, told a different story: the patient was doing nearly all the work of breathing himself.

During inspiration, the pressure waveform dropped to negative three cmH₂O. That means the ventilator was barely contributing; the patient’s own inspiratory effort was generating the negative pressure needed to pull air in. The flow waveform, meanwhile, stayed fixed in a decelerating pattern — a telltale sign of volume control (where the ventilator controls flow but not pressure). The expected pressure rise for a passive patient on volume control was simply absent.

Why sedation won’t fix a strong respiratory drive

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What you'll learn

  • 1 (00:00) **Case Introduction: The Double-Triggering COPD Patient** - A 65-year-old COPD patient with pneumonia was found down, intubated, and is double-triggering on volume control ventilation, undermining lung-protective goals.
  • 2 (02:14) **Why More Sedation Won't Fix This** - The speaker argues that increasing sedation is ineffective for blunting respiratory drive in critically ill patients.
  • 3 (03:08) **Diagnostic Approach: Fixed vs. Unfixed Variables** - The speaker outlines his method for analyzing dyssynchrony by identifying what stays constant during a breath.
  • 4 (03:48) **Expected Waveforms for a Passive Patient** - The speaker draws what normal volume control waveforms should look like to establish a baseline for comparison.
  • 5 (06:54) **Comparing Expected vs. Actual: Where Did the Pressure Go?** - The actual waveform shows nearly no pressure during inspiration, meaning the patient is generating all the inspiratory effort.
  • 6 (08:04) **Expiration: Active Exhalation and Timing Issues** - The expiratory flow curve is abnormal, showing active exhalation and a "scoopy" pattern that suggests cycling mismatches.
  • 7 (10:06) **Triggering: No Major Issues** - The patient triggers each breath without significant delay or ineffective efforts, ruling out auto-PEEP as a primary driver.

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Show Notes

In this episode, we move beyond normal waveforms and break down the abnormal patterns you’ll actually encounter at the bedside.

Learn how changes in pressure, flow, and volume can reveal problems with resistance, compliance, flow delivery, air trapping--lets move beyond just sedating!!


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Attendings

Critical Access

CRNA

APPs, PharmD, and Rehab Services

Medics/RNs/RTs/Flight Crew

All Trainees & First Responders



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