All versions of Op-Vent with an explict exhalation valve and all software releases since the June 20, 2020 release support electronic PEEP (positve end expiratory pressure). By timing the close of the exhalation valve, Op-Vent can regulate the pressure at the end of the expiratory period to a pre-set value.
The pressure at which the exhalation valve needs to close depends on lung parameters. With high lung resistance, the pressure in the lung may be considerably higher than the pressure in the patient circuit and the ventiator must wait for the measured pressure to drop far below the set PEEP value before closing the valve.
Op-Vent uses an adapative algorithm where it adjusts the timing of exhalation valve closing for each breath based on the previous breaths. Depending on settings and lung parameters it may take 10 breaths before the set PEEP is achieved.
Figure P1: Pressure-mode operation with electronic PEEP. Pressure is set at 200mm H2O and PEEP is set at 100mm H2O.
Figure P1 shows flow and pressure waveforms for three breaths using electronic PEEP. At the beginning of each expiratory period pressure is allowed to fall to 50 mmH2O before the exhale valve is closed. This results in the pressure settling at almost exactly 100 mmH2O at the end of the expiratory period.