Journal Club June 2017. Drs. Alan Ko & Nauman Khankhel Tackle Apneic Oxygenation

FELLOW Trial

Summary by Dr. Nauman Khankhel

• Overview
  • Apneic oxygenation via high-flow NC does not improve the lowest arterial saturation measured during MICU intubations.
  • Apneic oxygenation does not lower the risk of hypoxemia, does not improve efficiency/success rate of the intubation itself, and does not affect morbidity/mortality during hospital stay.
• Study design:
  • Randomized: Permuted blocks of unequal length used to randomize and keep the number of patients in each group equal or very similar
  • Open-label: Blinding was not possible as physician will see oxygen source. Nasal canal providing room air could not be used as a placebo for control group because it is not an accurate portrayal of “usual care”, creates a safety hazard by disrupting mask seal, provides misinformation regarding treatment response.
  • Parallel-group: Pt only receives the care assigned to his/her group without any “crossover” of treatment protocol
  • Pragmatic: Study takes place in normal clinical circumstances so that the results are more pertinent in a broad clinical setting. This is in contrast to the classic RCT which takes place in an ideal, tightly controlled environment.
• Population
  • Inclusion (196 pts)- all patients older than 18 intubated by a pulmonary or critical care fellow in the medical ICU
  • Exclusion (46 pts)
    • If awake intubation planned
    • In emergent situations with insufficient time to randomize patient
    • If the physician did not want to use the randomized group assignment (in regards to laryngoscopy type and whether to use apneic oxygenation)
  • Methods
    • Patients that met inclusion criteria were enrolled between feb 2014 and feb 2015 and randomized to either receive apneic oxygenation (n=77) during intubation with high flow NC (15L/min at 100% FIO2) or to not receive any supplemental oxygen (n=73) during the laryngoscopy. Each case was also randomized to either use video vs direct laryngoscopy. Preoxygenation was allowed in both groups and choice of induction meds was not specified. Data collection was performed by independent observers who did not know the study hypothesis. Statistical analysis was done with Mann-Whitney rank sum test, two-sided P value <.05 as cutoff for significance, and using intent-to-treat principle.
  • Results
    • Primary Outcome– Lowest measured pulse oximetry value between induction and 2min after ET tube placement
      • 92% (apneic oxygenation) vs 90% (usual care) but not statistically significant
    • Secondary outcomes (No statistically significant differences in any of the following)
      • On oxygenation: incidence of hypoxemia (SpO2<90%), incidence of severe hypoxemia (SpO2 <80%), incidence of desat >3% from baseline, overall change in saturation.
      • On procedural outcome: first-pass success rate, number of attempts, time elapsed between induction and secured airway
    • Tertiary outcomes- No significant difference on clinical outcomes: Mortality, length of hospital stay, duration of ventilation
  • Criticism
    • Higher use of propofol in usual care group (2.5 vs 13.7%)
    • Median O2 sat. at induction was 98% in apneic oxygenation vs 99% in usual care
    • 5 pts in usual care group received apneic oxygenation and 2 pts in apneic oxygenation group did not
    • Unclear if optimal settings (15L/min at 100%) were used on high-flow NC. Previous studies observed higher intubation sat. with 60L/min
    • Over 50% of pts in each group were intubated for respiratory where supplemental oxygen might be ineffective

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First Pass Success Without Hypoxemia is Increased With the Use of Apneic Oxygenation During Rapid Sequence Intubation in the Emergency Department

Summary by Dr. Alan Ko

Background

• Emergent intubations are associated with a high incidence of adverse events (hypoxemia, hypotension, dysrhythmias, aspiration, cardiac arrest).
• Multiple intubation attempts during emergency airway management are associated with an increase in adverse events. Even after a single failed attempt, the incidence of adverse events increases drastically. Hypoxemia is also associated with adverse outcomes, including mortality, in critically ill patients.
• Apneic oxygenation prior to intubation has been studied for decades in the operating room; these studies have demonstrated that the use of apneic oxygenation can significantly delay the onset of oxygen desaturation, effectively extending the period of safe apnea.

Study question

• What is the effect of apneic oxygenation (AP OX) on first pass success without hypoxemia (FPS-H) in adult patients undergoing rapid sequence intubation (RSI) in the Emergency Department (ED)?

Study design and setting

• Setting: Single-center observational study of ED intubations over a 2 year period (July 1, 2013 to June 30, 2015).
• Intubators: All intubations were performed by ED residents.
• Laryngoscopes: Direct laryngoscope, GlideScope video laryngoscope, and the C-MAC video laryngoscope.
• Recommended preoxygenation technique: standard nasal cannula at 15 L/min AND a nonrebreather face mask at 15 L/min.
• Duration of preoxygenation: 3+ minutes

Study population

• Adult patients 18 years of age and older who underwent RSI in the ED by an emergency medicine resident.
• Only patients that had complete oxygen saturation data documented.
• Patients must have had a starting oxygen saturation of at least 90%.
• Of all the intubations performed at this site in the two year period, 635 patients were eligible for analyses in this study.

Methods and measurements

• After each ED intubation, the resident who performed the intubation filled out a paper form documenting:
  • patient age, sex, and diagnosis
  • operator PGY level
  • reason for intubation
  • presence of difficult airway characteristics (blood/vomit in the airway, presence of a cervical collar or immobility, airway edema, facial/neck trauma, small mandible, short neck, large tongue, restricted mouth opening, obesity)
  • drugs used for intubation
  • device used on each attempt
  • outcome of each attempt
  • the starting oxygen saturation
  • the lowest oxygen saturation during the intubation
  • oxygenation methods used before and during the intubation
  • the estimated duration of preoxygenation before intubation
  • the oxygen flow rate used during intubation
• A senior investigator then reviewed all data forms in real time, cross-referenced with the EMR, entered the data into Excel, then transferred the data into STAT 13 for statistical analysis.

Outcome measures

• Primary outcome: first pass success without hypoxemia (defined as successful tracheal intubation on a single laryngoscope insertion without oxygen saturations falling below 90%)
• Secondary outcome: incidence of hypoxemia (defined as oxygen saturation falling below 90% at any time during intubation)

Analyses

• Patients were categorized into two cohorts: those that had apneic oxygenation utilized (AP OX cohort), and those who did not have apneic oxygenation utilized (no AP OX cohort).
• 380 patients (59.8%) were in the AP OX cohort.
• 255 patients (40.2%) were in the no AP OX cohort.
• Standard multivariate logistic regression analysis was performed to evaluate the association between AP OX and FPS-H.

Results

• In the AP OX cohort, the FPS-H was 312/380 (82.1%).
• In the no AP OX cohort, the FPS-H was 176/255 (69.0%; difference = 13.1%; 95% confidence interval [CI = 6.2% to 19.9%).
• In the AP OX cohort, the overall incidence of hypoxemia was 48/380 (12.6%).
• In the no AP OX cohort, the overall incidence of hypoxemia was 51/255 (20.0%; difference = -7.4%, 95% CI = -13.3% to -1.4%).
• In the multivariate logistic regression analysis, the use of AP OX was associated with an increased odds of FPS-H (adjusted odds ratio [aOR] = 2.2, 95% CI = 1.5 to 3.3).

Conclusions

• The use of apneic oxygenation during RSI of adult patients in the ED is associated with an increase in first pass success without hypoxemia (in the multivariate logistic regression analysis, it was seen that EM residents who utilized AP OX were twice as likely to achieve FPS-H).
• The improvement in FPS-H was due to both an increase in the FPS (+7.6%) and a decrease in the incidence of oxygen desaturation in patients with FPS (-7.4%) in patients who had AP OX utilized.

Criticisms

• This was an observational study. Patients were not randomized into the AP OX vs no AP OX cohorts. There were more trauma patients as well as more difficult airways in the no AP OX cohort. There may have been other unidentified confounders that may have affected the results.
• All the data collected in the study were self-reported by the EM residents who performed the intubations. There may have been over-reporting of FPS and under-reporting of adverse events.
• The majority of intubations in this study were performed using video laryngoscopes, thus the results may not be generalizable to other ED clinical settings.