CMV (Continuous Mandatory Ventilation)

Controlled ventilation and assisted constant volume ventilation that may be flow triggered. Flow triggering is accessed via the Extra Settings Menu. CMV parameters include VT, T insp, flow, frequency, and PEEP. Without AutoFlow, if the tidal volume is delivered before the end of the inspiratory time, the inspiratory valve closes and an inspiratory plateau fills the remaining inspiratory time.

Pressure Limited Ventilation

This mode is for manually limiting pressure peaks using the Pmax pressure limit. The machine automatically figures this pressure level, and is used on all controlled breaths. The inspiratory flow is reduced when the set Pmax value is reached. The tidal volume remains constant as long as the pressure waveform shows a plateau and the inspiratory flow waveform show a brief flow pause between inspiration and expiration.

If the VT cannot be achieved, the alarm "Volume not constant" is activated. In the graphic on the right, the Pmax pressure limit is established on the third breath.

SIMV (Synchronized Intermittent Mandatory Ventilation)

The number of mandatory ventilator breaths is fixed by the f setting. The Evita 4 allows a 5 second trigger window for these breaths to be synchronized with the patient's inspiratory effort. If expiratory time is less than 5 seconds, the trigger window equals the entire expiratory time. Additional breaths may be taken spontaneously by the patient. To prevent an increase in SIMV rate for breaths synchronized at the beginning of the trigger window, the ventilator adds the difference in time to the period allowed for spontaneous breathing. If the patient has taken in a large volume when triggering a mandatory breath, the mandatory volume delivery is reduced to maintain the set tidal volume.

MMV (Mandatory Minute Ventilation)

Allows spontaneous breathing with automatic adjustments of mandatory ventilation to the meet the patient’s preset minimum minute volume requirement. If the patient maintains the minute volume settings for VT x f, no mandatory breaths are delivered. If the patient's minute volume is insufficient, mandatory delivery of the preset tidal volume will occur until the minute volume is achieved. Should apnea follow a period in which the spontaneous minute volume was high, the Evita 4 will wait a maximum of 7.5 seconds plus one cycle time before beginning mandatory breaths.

SB (Spontaneous Breathing)

Allows spontaneous breathing at ambient pressure.

CPAP (Continuous Positive Airway Pressure)

Spontaneous breathing with positive airway pressure.

PS (Pressure Support)

Assists spontaneous breathing with positive pressure during inspiration. PS is initiated when the flow trigger is reached or when the inspiratory volume is 25 mL (12 mL in pediatric mode). PS ends when inspiratory flow returns to zero before the PS level has been reached, or when flow falls to 25% (6% peds) of the peak flow after reaching PS. A maximum time of 4 seconds (1.5 sec for peds) is allowed per pressure supported breath if neither criteria for flow occurs. If PS is time cycled for three consecutive breaths, an alarm sounds warning of a possible leak in the system.

PCV+ (BIPAP)

Traditional pressure controlled ventilation, combined with spontaneous breathing during the complete breathing cycle. Spontaneous breathing is allowed at two different levels of pressure. P insp sets the pressure control level and PEEP sets the expiratory pressure. Inspiration is time cycled. The change from expiration to inspiration is synchronized with the patient's inspiratory efforts.