- Technique to prolongs "safe apnea time" (time until desaturation to SaO2=88-90% after induction of apnea). This increases time for laryngoscopy/intubation.
- Used as an adjunct to preoxygenation: used to prolong oxygenation after optimal preoxygenation
- Low cost in terms of resources and set-up
- Gas exchange during apnea creates subatmopsheric pressure in the alveoli
- In healthy lungs, 200-250mL O2 per minute can be drawn into blood stream
- In the absence of ventilation (i.e. during apnea), only 10-20mL CO2 enters alveoli from bloodstream per minute, due to increased CO2 tension
- This causes a net decrease in gas in the alveoli
- This gradient can draw air into the lungs, even absent diaphragmatic movement
- Increases safe apnea time in healthy volunteers from 1 minute (room air) to 8-9 minutes
- Severe maxillofacial trauma
- Obstructed nares
- Nasal cannula
- Second oxygen source, e.g. mobile O2 tank
- Start pre-oxygenation while sitting upright, only lay back once RSI drugs pushed.
- During preoxygenation, keep the nasal cannula on underneath your primary preoxygenation technique.
- This can be achieved whether you use a mask, NPPV, or BVM; a good seal can still be obtained. Alternatively, you can use the high flow nasal cannula technique for preoxygenation.
- Normal adjunctive airway techniques/equipment (jaw thrust, oropharyngeal airway) remain useful. In particular, nasal trumpet can maintain patencny of at least one nare.
- Attach the nasal cannula to a separate oxygen source at 15L.
- After preoxygenation, leave the nasal cannula on after removing mask/NPPV/BVM. It should not get in the way of laryngoscopy.
- Consider taping cannula to face to prevent dislodgement.
- Complications are limited and most can be quickly remedied by removing nasal cannula
- If not well-positioned/attached, may complicate laryngoscopy
- High flow oxygen from nasal cannula is cold and dry; may not be well-tolerated by patient
- Extremely high flow oxygen (>70 L/M) may cause barotrauma
- Increased apnea time increases respiratory acidosis
- Not shown to improve saturation in critically ill patients
- Surgical airways