Comparison of 2 Apneic Oxygen Studies

Effectiveness of Apneic Oxygenation during Intubation:  A systemic review and meta-analysis by Silva et al 2017

  • Population:  ED and ICU patients; both RCT and observational studies included.
    • Not OR or outside hospital patients
  • Intervention:
    • Some received High Flow at 60L/min -Transnasal Humidified rapid insufflation ventilator exchange (THRIVE technique).  Some PEEP.
    • Some received Nasal cannula at 15L/Min (Nasal Oxygen during efforts securing a tube- NO DESAT).  No PEEP.
  • Comparison; no apneic ox although 3 studies did not have comparison groups
  • Outcome
    • Lowest SpO2 peri-intubation; usually measured from time of drug injection until mechanical ventilation but not available for all studies
      • In 6 studies, the lowest SpO2 was higher for the ApOx group than for standard ox (difference of 2.21%; 95% CI 0.81-3.61)
        • Crosses 1 but scale set so zero is the dividing line rather than the typical 1
    • First Pass success
      • In 6 studies, ApOx had increased first pass success OR 1.59; 95% CI 1.04-2.44)
    • Incidence of hypoxemia less than 93%
      • OR 0.66; 95%CI 0.52-0.84
    • Severe hypoxemia <80% - not significant
    • Life threatening hypoxemia <70%  - not significant
    • ICU length of stay – only 368 pts but statistically significant with mean decrease in length  of stay of 2.88 days in ap ox group
    • Mortality- not significant
  1. 14 studies for qualitative review
  2. 8 studies for quantitative review (out of the 14)
    1. 1837 patients.  932 pts had apneic oxygenation, 855 did not
    2. Apneic Ox had increased peri-intubation ox saturation difference of 2.21%; 95% CI 0.81-3.61
    3. Decreased rates of hypoxemia OR 0.66; 95%CI 0.52-0.84
      1. Not significant beneficial for cases of severe hypoxemia OR 0.86; 95% CI 0.47-1.57
    4. Increased first pass success OR 1.59; 95% CI 1.04-2.44
  3. Rationale:  apneic oxygenation revolves around physiologic capacity of continuous oxygen capture by alveoli through passive process without providing ventilation
  4. Used several tools to limit bias
  5. Only had a moderate kappa between 2 coders over which studies to include
  6. Limitations:
    1. moderate to low level of certainty in estimates
    2. different methods of Ap Ox (HF vs NC)
    3. Does higher rates of first pass success also mean less oxygen desaturation, affecting that result?
    4. When only using low risk of bias studies, none of the outcomes showed improvement with ApOx but the sample sizes were small/not enough power.

Emergency Department use of Apneic Oxygenation vs usual care during rapid sequence intubation:  a randomized controlled trial (The ENDAO Trial) by Caputo et al 2016

  • Population:  206 ED adult patients requiring intubation but excluding cardiac/traumatic arrest or people who didn’t get pre-oxygenation via NRB/bipap/bvm or awake intubation
  • Intervention:  Apneic oxygenation received nasal cannula oxygen and ETCO2 NC both at flush flow rates of >15L/min
  • Comparison:  Usual Care (just pre-oxygenation)
  • Primary Outcome:  Avg lowest O2 saturation during apnea period or in 2 minutes following intubation
    • Looked for a difference of 5% (Cohen’s D statistic of 0.4 for moderate effect size)
  • No difference between the 2 groups 92% Oxygen saturation; 95% CI 91-93 in AO vs 93, 95% CI 92-94in UC, p=0.11)
    • Secondary:
      • Increased first pass success?  Everyone except 22 patients.  Even these didn’t desat below 90 however 15 of them weren’t intubated for pulmonary reasons.
      • Decreased rates of desaturation below 90?  80?  No significant difference
      • Time to desaturation?  No significant difference
      • Mortality? No significant difference
  1. Pre-oxygenation is providing supplemental O2 w/ goal of 100% FiO2 for at least 3 minutes prior to RSI to increase amount of O2 in the functional residual capacity of the lungs
  2. Apneic oxygenation- leave the NC on after RSI and while visualizing the vocal corts/placing the ETTube.
  3. FELLOW trial showed no difference in desaturation rates between ApOx and usual practice in ICU patients; other studies refute these results
  4. Pre-oxygenation technique at discretion of attending (BVM vs Bipap vs NRB)
  5. Video vs DL and RSI meds at attending discretion
  6. Apnea time from first look (not Med push) to EtCO2 confirmation (not being placed on the vent)- this is a shorter time than the meta-analysis.
    1. Used this because you KNOW the patient is paralyzed/apneic
  7. Subgroup w/ prolonged apnea time of 130+seconds did not desaturate to less than 90%
  8. Limitations:  real time data collection may underestimate AE and time to intubation.  Also single center study in academic center.
  9. Similar results as FELLOW study but different in that everyone received pre-oxygenation.
  10. Perhaps Ap Ox would be useful in those who have not been pre-oxygenated?  E.g. crash intubations




Looking at both of these and how the conflict, consider the following:  Does it apply to your population?  Do you have the resources?  Any harms?  Any benefits that  you've seen?