Describe Intemittent Mandatory Ventilation (IMV)

Mandatory breaths are delivered at set tidal volumes and rates, and the patient can breathe on his own in between through a unidirectional valve in between (Fig 5). Unlike in ACV, a machine breath is not initated with each patient effort - thus the risk of overventilation is reduced. A refinement of this mode is Synchronous Intermittent Mandatory Ventilation (SIMV) - here the machine breaths are synchronized to patient efforts if it falls within a "window period" of the cycle.

Figure: The IMV Circuit