Compliance and Auto-PEEP

Why measuring total PEEP with an expiratory hold is essential before judging compliance from an elevated plateau.

MechanicsM3M4⤢ before / after

Fig 1.This waveform demonstrates a patient on APVcmv with elevated airway pressures. An inspiratory hold maneuver reveals an elevated plateau, suggesting reduced respiratory system compliance. To further evaluate this, total PEEP must be measured.

Fig 2.To measure the total PEEP, we need to perform an expiratory hold maneuver on the ventilator. In the absence of flows, alveolar pressures will equilibrate with airway pressures. The pressure measured at the airway opening (Paw) during an expiratory hold is our surrogate for end expiratory alveolar pressure, or total PEEP. This patient’s total PEEP is 11cmH2O, which is higher than the set PEEP of 5cmH2O. Had we used set PEEP to calculate compliance, we would have significantly underestimated it.

Learn the concept behind this case

Comprehensive · M3 — Measuring auto-PEEP

Comprehensive · M3 — Plateau pressure

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