Apneic oxygenation

Revision as of 08:41, 24 February 2019 by Mholtz (talk | contribs)

Overview

  • 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

Physiology

  • 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

Indications

Contraindications

  • Severe maxillofacial trauma
  • Obstructed nares

Equipment Needed

  • Nasal cannula
  • Second oxygen source, e.g. mobile O2 tank

Procedure

  1. Start pre-oxygenation while sitting upright, only lay back once RSI drugs pushed.
  2. 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.
  3. Attach the nasal cannula to a separate oxygen source at 15L.
  4. 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/Limitations

  • 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

See Also

External Links

References