- RSI is a high-risk procedure in the prehospital environment and is currently undertaken by single-operator CCPs
- Reported complication rate in ED is around 40% and serious hypoxia in up to 22% of intubations, which is associated with increased morbidity and mortality1.
- Preoxygenation allows a safety buffer during periods of hypoventilation and apnoea, which, in critically unwell patients is often poorly tolerated2.
- In this setting, the risk of hypoxia outweighs the risk of gastric aspiration and therefore avoidance of ventilation during the apnoea phase may be detrimental 3. 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 H2O. It is thought that the lower oesophageal sphincter is unlikely to allow gastric insufflation below pressures of 20cm H2O. 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.
- Studies have shown that in critically hypoxic patients, use of NIV as a preoxygenation technique leads to higher mean SpO2 prior to intubation and maintenance of higher SpO2 levels during intubation4. No negative cardiovascular effects or appreciable gastric distension were noted 5,6.
- Ventilator-assisted preoxygenation (VAPOX) in patients who remain hypoxic on high flow O2
- The use of NIV for preoxygenation should be observed in patients who cannot achieve acceptable saturations with high flow 02 via non-rebreather mask (>93%)
- If intubation is attempted with saturations below 90%, these patients can critically desaturate in seconds7.
- If this is required as a method of preoxygenation then it may be of benefit to have them on this device until the moment of intubation, as PEEP also prevents absorption atelectasis caused by breathing high Fi02, increasing the efficacy of apnoeic oxygenation 8. (see table 1)
- Facial Trauma or deformity
- Upper airway obstruction
Table 1: Risk categorization of patients during preoxygenation
Risk Category Based on pulse oximetry whilst receiving high flow oxygen | Preoxygenation Period (3 minutes) | Onset of muscle relaxation (~ 60 seconds) | Apnoeic period (Variable duration dependent on airway difficulty, ideally <30 seconds) |
|---|---|---|---|
| Low risk (SpO2 96-100%) |
|
|
|
| High risk (SpO2 91-95%) |
|
|
|
| HYPOXAEMIC (SpO2 <91%) |
|
|
|
- This patient group should receive preoxygenation in a head-elevated position wherever possible (minimum ~ 20 degree head elevation)
- For potential spinal injury patients, reverse Trendelenberg position can be used (figure 1)
Figure 1: reverse Trendelenberg positioning
- Turn Hamilton T1 Ventilator on to NIV-ST mode with the following settings:
- RR 6-8 breaths/min
- Pinsp 10mmH20
- PEEP 5cmH20
- O2 100%
- ETS (expiratory trigger sensitivity) 50%
- Inspiratory flow trigger 2L/min
- Ti: 2seconds
- P-ramp 50ms
Figure 2: Hamilton T1 Ventilator settings for VAPOX
- Place NP on patient but do not turn on 02 at this point
- Size NIV mask (from bridge of nose to crease between bottom lip and chin – see below)
- Place mask on patients face and secure straps ensuring no obvious leaks
- Insert Etc02 between mask and flow sensor
- Titrate PEEP between 5-15cmH20 to achieve Sp02 >98%
- Allow patient to breathe at tidal volume for 3 minutes
- Agitated or combative patients may require small aliquots of ketamine to tolerate the process (titrate up to 1mg/kg)
- Push sedative and paralytic
- Leave NIV mask in situ for this period (it will transition to PCV+ once apnoea ensues)
- Turn NP 02 on to 15L/min
- Leave high flow NP in situ throughout intubation period to maintain apnoeic oxygenation
Simpson GD, Ross MJ, McKeown DW, Ray DC. 2012. Tracheal intubation in the critically ill: a multi-centre national study of practice and complications. Br J Anaesth; 108:792-9
Farmery AD, Roe PG. 1996. A model to describe the rate of oxyhaemoglobin desaturation during apnoea. Br J Anaesth; 76:284-91
Grant S, Khan F et al. 2016. Ventilator-assisted preoxygenation: Protocol for combining non-invasive ventilation and apnoeic oxygenation using a portable ventilator. EMJ; 28:67-72
Baillard C, Fosse JP Sebbane M et al. 2006. Noninvasive ventilation improves preoxygenation before intubation of hypoxic patients. Am J Respir Crit Care Med; 174:171-77
Cressey DM, Berthoud MC, Reilly CS. 2001. Effectiveness of continuous positive airway pressure to enhance pre-oxygenation in morbidly obese women. Anaesthesia; 56:680-684
Jaber S, Jung B, Corne P et al. 2010. An intervention to decrease complications related to endotracheal intubation in the intensive care unit: a prospective, multi-centre study. Intensive Care Med; 36:248-255
Weingart S, Levitan RM. 2012. Preoxygenation and Prevention of Desaturation During Emergency Airway Management. Annals of Emergency Medicine; 59:165-75
Rothen HU, Sporre B, Engberg G et al. 1995. Prevention of atelectasis during general anaesthesia. Lancet; 345: 1533-1543
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