Ventilator Assisted Pre-Oxygenation (VAPOX) is a protocol developed for using a ventilator during the peri-intubation period primarily for pre-oxygenation.
- To deliver PEEP + machine controlled ventilation during the following peri-intubation periods:
- Pre-Oxygenation – prior to administration of sedative and paralytic drugs
- Apnoea – post onset of drugs until attempt at intubation
- Re-Oxygenation – post an unsuccessful intubation attempt
While it could be used in any patient, it has particular proposed benefit for patients who require PEEP during the pre-oxygenation phase to achieve normal/near-normal oxygenation saturations.
- Provides PEEP through the whole pre-intubation period (except during attempts at intubation)
- Provides machine controlled assisted ventilation
- This is an alternative to human delivered bag-valve mask ventilations which frequently result in excessive ventilation that increase risk of gastric insufflation and aspiration.
- It has been designed to provide a maximum positive inspiratory pressure of 15cm H20. It is thought that the lower oesophageal sphincter is unlikely to allow gastric insufflation below pressures of 20cm H20. By this rationale it is expected to allow safe ventilations during the apnoea period where traditionally in Rapid Sequence Intubation the patient receives no external ventilation.
- Protocol designed for Hamilton T1 Ventilator
- Select NIV-ST Mode
- Key settings:
- RR 6-8 breaths/minute
- Pressure support = 10cm H20
- PEEP = 5cm H20
- FiO2 = 1.0 (100%)
- Other settings
- Expiratory trigger sensitivity = 50%
- Inspiratory Flow trigger = 2L/min
- Inspiratory Time (Ti) = 2 sec
- P-ramp = 50ms
Note this protocol has been proposed based on case series and has not been subject to randomised controlled trials. Clinicians need to consider individual risk/benefit analysis for their patients if considering using this protocol.
For more information consult the original publication:
Grant S, Khan F, Keijzers G, Shirran M, Marneros L. Ventilator-assisted preoxygenation: Protocol for combining non-invasive ventilation and apnoeic oxygenation using a portable ventilator. Emerg Med Australas. 2016;28:67-72.
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VAPOX for COVID-19 Patients
Options for preoxygenation of COVID-19 are discussed here. While VAPOX protocol is ideal for the preoxygenation of patients with hypoxia despite treatment with a non-rebreather mask, there are several required modifications to maximise staff safety that both increase cognitive load and reduce the benefits of the VAPOX protocol. Consequently it is not recommended for COVID-19 patients.
The modifications for COVID-19 patients that are required include:
- Requirement to use a closed-circuit NIV set up where a high efficiency viral filter is placed between a non-vented mask and the expiratory limb of the circuit (before it vents to room air)
- Isolation of patient in a negative pressure room ideally and staff wearing Tier 2 PPE for Aerosol Generating Procedures.
- Minimise mask leak with a well fitting mask with straps or 2 handed mask holding technique by intubator
- CPAP only – dial down pressure support to zero.
- During the apnoeic period the circuit needs to be depressurised before the face mask is removed and the intubation is attempted as this will prevent viral dispersal from air flow through the mask when it is removed.
- One option to achieve this is to turn the CPAP to zero. However most ventilators have a back up mode that kicks in after an extended period of apnoea which could cause significant viral dispersal to the room.
- A safer option is disconnection of the ventilator circuit which can be achieved in 2 ways:
- Disconnect the ventilator just proximal to the viral filter. This carries the attendant safety risk of accidental disconnection of the viral filter.
- Disconnect the inspiratory limb from the ventilator entirely. This is the safest approach but it then mitigates some of the benefits of VAPOX such as the easy ability to reoxygenate/ventilate patients during failed intubation and post intubation.
- Turn pressure support back on
- In the event intubation is unsuccessful and the patient requires re-oxygenation (positive pressure ventilation), pressure support needs to be immediately turned back up (in a mode with a mandatory respiratory rate).
- After successful intubation pressure support (in a mode with a mandatory respiratory rate) needs to be turned back up to ventilate patient or changed to a different ventilator mode.