Intermittent mandatory ventilation

Intermittent Mandatory Ventilation (IMV) is any mode of mechanical ventilation where a regular series of breaths is scheduled, but the ventilator senses patient effort and reschedules mandatory breaths based on the calculated need of the patient. Similar to continuous mandatory ventilation in parameters set for the patient's pressures and volumes, but distinct in its ability to support a patient by either supporting their effort or providing support when patient effort is not sensed. IMV is frequently paired with additional strategies to improve weaning from ventilator support or to improve cardiovascular stability in patients who may need full life support.

To help illustrate the use of the different types of ventilation, it is helpful to think of a continuum of the common ventilator settings: assist control or continuous mechanical ventilation (AC/CMV), to SIMV, to pressure support (PS). The lungs require a certain amount of oxygen to fill them, the volume, and a certain amount of force to get the oxygen into the lungs, the pressure. In assist control, one of those variables will be controlled by the ventilator, either pressure or volume. Typically, in AC/CMV, it is volume.

In AC/CMV, the ventilator delivers a set volume whenever the patient triggers a breath. In contrast, pressure support delivers a set pressure for every triggered breath, rather than a set volume. SIMV works between AC and PS; it will deliver a set volume only when the patient reaches the breath threshold, instead of just triggering a breath.