Preparation
- Only be performed once the absence of brainstem reflex activity has been confirmed
- Ensure cardiovascular stability maintained
- Ensure utilization of end tidal carbon dioxide (EtCO2) monitoring, pulse oximetry, blood pressure monitoring and blood gas analysis:
- Prevents the development of significant hypoxia
- Prevents the development of excessive hypercarbia
- Minimizes the development of hypotension which could risk further injury to potentially recoverable brain tissue
- Preoxygenate with an FiO2 1.0.
- Ensure mild hypercarbia (PaCO2 >6.0 kPa) and acidosis (pH <7.4) prior to testing:
- Reduce the minute ventilation to allow PaCO2 to rise
- A PaCO2 >6.5 kPa should be targeted in:
- Patients with chronic CO2 retention
- Patients receiving intravenous bicarbonate
Performance
- Remove patient from ventilator - cardiac pulsation may be sufficient to trigger supportive breaths
- Ensure oxygenation - options include:
- Connect the patient to CPAP circuit (e.g. Mapleson C)
- Administer oxygen via a catheter in the trachea at a rate of >6L/minute
- Perform a pre-test arterial blood gas to confirm PaCO2 is at least 6.0 kPa and pH <7.4
- Observe for respiratory activity for 5 min, confirming the start time
- Perform a confirmatory blood test to ensure an increase in PaCO2 of more than 0.5 kPa
- After completion of the apnoea, test reconnect the ventilator