Characteristics of the Five Different Types of Intermittent Mandatory Ventilation

Intermittent mandatory ventilation (IMV) has evolved substantially from its original form, developing into 5 distinct types intended to enhance patient safety, comfort, and liberation from mechanical ventilation. Each form of IMV has different potential advantages and disadvantages that should be considered when selecting the mode of ventilation. IMV(1): the set mandatory breath rate is always delivered. IMV(2): mandatory breaths may be suppressed by spontaneous breaths if their frequency is high enough. IMV(3): mandatory breaths may be suppressed by spontaneous breaths if they achieve some pre-set goal (eg, minute ventilation threshold). IMV(4): individual mandatory breaths may be suppressed if inspiratory effort is high enough to change volume cycling into flow cycling for patient-triggered breaths. IMV(5): in Pressure Support, individual mandatory breaths are suppressed if the flow cycle threshold is met after the Ti-min setting has elapsed. This article offers a comprehensive review of the definitions and characteristics of these 5 IMV types, providing guidance on their identification based on information from ventilator manufacturers' information and by examining the actual ventilator waveforms produced by ventilating a high-fidelity lung simulator. The purpose is to clarify how the breath sequences called IMV are implemented in current ventilators and to build the reader's skill in identifying them. This skill is essential for clinical application, education, and research in mechanical ventilation. Ultimately, the goal is to improve the knowledge and application of IMV in clinical practice education and research.