PB840 Ventilator: BiLEVEL VENTILATION MODE

·         Mixed mode of ventilation that allows both spontaneous and mandatory breaths.

·         Mandatory breaths are always Pressure Control Ventilation (PCV).

·         Spontaneous breaths may use Pressure Support Ventilation (PSV).

·         BiLevel is essentially having 2 different levels of PEEP; High PEEP (PEEP_H) and Low PEEP (PEEP_L).

·         The ventilator cycles between these two levels according to either the BiLevel Time setting or a patient's respiratory efforts.

·         The patient is free to breathe spontaneously at either PEEP level with or without Pressure Support (PS).

·         BiLevel tries to synchronize transitions between the two PEEP levels with the patient's breathing pattern.

·         Time High (T_H) and Time Low (T_L) are the time intervals set at each PEEP level.

·         In order to synchronize the PEEP levels with the patient, the T_H and T_L intervals can either increase or decrease depending on the phase of the breath the patient is in.  

·         The T_H and T_L settings each have a spontaneous and a synchronous interval.

·         During the spontaneous interval, the ventilator will deliver either spontaneous or mandatory breaths at the PEEP level it is in.

·         During T_L synchronous intervals a patient's inspiratory effort will cause the ventilator to cycle from PEEP_L to PEEP_H.

·         During the TH synchronous interval, a patient's expiratory effort will cause the ventilator to cycle from PEEP_H to PEEP_L.

·         If there are no spontaneous breathing efforts made during the synchronization interval the ventilator will cycle between PEEP_H and PEEPL according to the time intervals set.

·         Overall, BiLevel allows the extension of T_H and T_L intervals to prevent the transition to PEEP_L during inspiration or to PEEP_H during expiration.

Set-up

·         BiLevel is accessed under MODES.

·         Once BiLevel is selected, a PC breath type is selected automatically and PSV can be optionally set for spontaneous breathing.

·         Spontaneous breaths can be either flow or pressure triggered in this mode.

·         The PEEP_H level must always be set at least 5 cmH₂O higher than the PEEP_L level.

·         Setting the Flow Acceleration% determines the amount of time required to reach the target pressure when switching from PEEP_L to PEEP_H.

·         Expiratory Sensitivity must be set appropriately to ensure proper synchronization with the patient's spontaneous respiratory efforts.

 

PSV and BiLEVEL

·         PS level is always set relative to the PEEP_L level.

·         No PS is given at PEEP_H if the level is less than PEEP_H - PEEP_L.

·         Also, if PS + PEEP_L is greater than the PEEP_H level, all spontaneous breaths at both levels are pressure supported.

Reference:  840 Operator's and Technical Reference Manual

By: Kelly Wallis SRCP and Carol Stallaert SRCP