What is SIMV?

In a recent episode of The Peak Inspiration Podcast, the host tackles a persistent misunderstanding about SIMV (Synchronized Intermittent Mandatory Ventilation), a mode of mechanical ventilation widely considered suboptimal in critical care. The central argument is clear: many clinicians incorrectly believe that SIMV does not support a patient’s spontaneous breaths, but this is a misconception rooted in operator settings, not the mode itself. The episode clarifies the technical architecture of SIMV, contrasts it with Assist Control (AC), and explains why SIMV remains a poor choice for patient care despite this correction.

The Core Misunderstanding About SIMV

The host begins by quoting a common description from social media: that SIMV delivers a set number of mandatory breaths synchronized to the patient’s effort, and between those breaths, the patient can breathe spontaneously but the ventilator “does not fully support those breaths” (though it may add pressure support). This, the host states flatly, is “fundamentally not correct.” The confusion stems from conflating the mode’s design with how operators often set it. In SIMV, spontaneous breaths are always handled as pressure-supported breaths—not unsupported. The key distinction is that the level of support during spontaneous breaths is determined by the clinician’s pressure support setting, not by the mode itself. If