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Date: January 9th, 2020

Reference: Casey et al. Bag-Mask Ventilation during Tracheal Intubation of Critically Ill Adults. NEJM February 2019

Guest Skeptic: Andrew Merelman is a critical care paramedic and second year medical student at Rocky Vista University in Colorado. His primary interests are resuscitation, critical care, airway management, and point-of-care ultrasound.

Case: A 60-year-old male is in your emergency department with sepsis from pneumonia. He has worsening work of breathing and a decreasing level of consciousness. You decide based on his clinical presentation that he needs to be intubated. Due to his already poor oxygenation, you are concerned about him desaturating during intubation and wonder if there is anything you can do to help prevent it.

Background: Emergency medicine is often referred to as the ABC (Airway, Breathing and Circulation) specialty. We have covered airway a few times on the SGEM:

  • SGEM#75: Video Killed Direct Laryngoscopy?
  • SGEM#96: Machine Head – NIPPV for Out of Hospital Respiratory Distress
  • SGEM#247:Supraglottic Airways Gonna Save You for an OHCA?
  • SGEM#249: Ace in the Hole – Confirming Endotracheal Tube Placement with POCUS
  • SGEM#271: Bougie Wonderland for First Pass Success

Rapid Sequence Intubation (RSI) has been a mainstay of emergency airway management for years. However, there are aspects of the procedure that have been debated, one of which is how best to oxygenate the patient during the apneic period while not increasing rates of aspiration.

Clinical Question: Is bag-mask ventilation (BMV) performed during the apneic period of RSI (defined as the time between administration of RSI medications and intubation) in critically ill adults safe and effective?

Reference: Casey et al. Bag-Mask Ventilation during Tracheal Intubation of Critically Ill Adults. NEJM February 2019

  • Population: Adults patients (older than 17 years of age) undergoing induction and tracheal intubation in the intensive care unit.
    • Exclusions: Patients who were pregnant, incarcerated, had immediate need for intubation or if the treating clinicians felt that ventilation was indicated or contraindicated between induction and laryngoscopy.
  • Intervention: Bag-mask ventilation (BMV) during the time between administration of sedation/paralysis and insertion of the laryngoscope into the mouth for intubation.
  • Comparison: Apnea with or without nasal cannula oxygen during the time between administration of sedation/paralysis and insertion of the laryngoscope into the mouth for intubation.
  • Outcome:
    • Primary Outcome: The lowest oxygen saturation observed during the interval between induction and two minutes after tracheal intubation.
    • Secondary Outcome: The incidence of severe hypoxemia (oxygen saturation of less than 80%).

Authors’ Conclusions: “Among critically ill adults undergoing tracheal intubation, patients receiving bag-mask ventilation had higher oxygen saturations and a lower incidence of severe hypoxemia than those receiving no ventilation.”

Quality Checklist for Randomized Clinical Trials:

  1. The study population included or focused on those in the emergency department. No
  2. The patients were adequately randomized. Yes
  3. The randomization process was concealed. Yes
  4. The patients were analyzed in the groups to which they were randomized. Yes
  5. The study patients were recruited consecutively (i.e. no selection bias). Unsure
  6. The patients in both groups were similar with respect to prognostic factors. No
  7. All participants (patients, clinicians, outcome assessors) were unaware of group allocation. No
  8. All groups were treated equally except for the intervention. No
  9. Follow-up was complete (i.e. at least 80% for both groups). Yes
  10. All patient-important outcomes were considered. No
  11. The treatment effect was large enough and precise enough to be clinically significant. Unsure

Key Results: They screened 667 patients and enrolled 401. The median age was 60 years, 56% were male and half the patients had sepsis or septic shock.

Bag-mask ventilation group had higher oxygen saturations and less severe hypoxemia compared to the control group.

  • Primary Outcome: Lowest oxygen saturation
    • 96% (interquartile range, 87% to 99%) in the BMV group vs. 93% (interquartile range, 81% to 99%) in the no-ventilation group (P = 0.01).
  • Secondary Outcome: 
    • 21 patients (11%) in the BMV group had severe hypoxemia vs. 45 patients (23%) in the no-ventilation group (relative risk, 0.48; 95% CI: 0.30 to 0.77).

1. Patients: Patients in this study were recruited from seven academic intensive care units (ICUs) in the United States. Eighty percent of the patients were intubated for respiratory failure. While many adult patients in the emergency department are intubated for the same reason many others are intubated of cardiac arrest and trauma depending on your place of practice. It is unclear if this study population has external validity outside the ICU and to the emergency department.

Another thing about the patients who were excluded. The study did not enroll those patients judged to be a very high risk of desaturation or aspiration, had hypoxemia, or had acidemia. These patients are ones that we potentially care more about when it comes to peri-intubation oxygenation and ventilation, so it is difficult to say if these results are generalizable to this population.

2. Consecutive Patients: They claim that patients were recruited consecutively. However, selection bias could have been introduced. Patients could be excluded if they required immediate intub ation or if the treating clinicians felt that ventilation was indicated or contraindicated between induction and laryngoscopy.

This is pragmatic but it does introduce subjectivity into the process and could have resulted in bias. It is unclear if this would have any meaningful impact on the results.

3. Prognostic Factors: A quality indicator for an RCT is that both the intervention group and control group are similar with regards to prognostic factors. There were statistical differences between the two groups with 10% more patients having pneumonia and 6% less having a gastrointestinal bleeding in the control group.

4. Treated Equally: Another quality indicator is that both groups are treated equally except for the intervention. That was not the case in this trial. The BMV group was more likely to be preoxygenated with a BMV (40% vs 11%) while the no ventilation group was more likely to be preoxygenated with NiPPV (24% vs 16%). Preoxygenation can have an impact on likelihood of desaturation during intubation.

  • Note: The BMV ventilation in this trial was extremely well done. The providers in the trial were trained to provide appropriate rates, volumes, and adequate mask seal. This is not typical in most emergency departments.

5. DOOs, MOO and POO: Their primary and secondary outcomes were disease-oriented outcomes (DOOs) or monitor-oriented outcomes (MOOs). The median lowest oxygen saturation and incidence of severe hypoxia are surrogate markers and do not represent a patient-oriented outcome (POO).

They did look at a number of exploratory-oriented outcomes (EOO) for safety (ex. aspiration, new opacity on chest x-ray and cardiac arrest) and efficacy (ex. mortality, days in ICU and ventilator-free days). However, they did not include what could be considered the most important POO, survival with good neurologic outcome.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We generally agree with the authors’ conclusions but would also add that a statistical difference in a DOO does not necessarily translate into a clinically important POO.

SGEM Bottom Line: It is unclear if bag-mask ventilation in critically ill adult patients requiring intubation provides a clinically important benefit or is safe.

Case Resolution: Because the patient is at high risk of desaturation during intubation, you make a plan that optimizes preoxygenation. You use your clinical judgment and provide gentle, controlled bag-mask ventilation during the apneic period to prevent desaturation.

Clinical Application: Due to the multiple limitations identified in this trial it is difficult to know how to clinically apply this data.This is a common problem faced by clinicians practicing evidence-based medicine. The literature informs and guides our care but should not dictate our care. When we do not have definitive literature for efficacy or safety we must rely more upon our clinical judgement. In addition, we do not know if BMV will result in a clinically important outcome (survival with good neurologic outcome). This does not mean we should not perform very good preoxygenation prior to intubation.

What Do I Tell My Patient? You have pneumonia and it is making it difficult for you to breath. We can help by putting a tube in your throat. This will make it easier to breath and give time for the antibiotics to work. This can be scary. Before we would put the tube down your throat you would get some extra oxygen. Then, if you say OK to the tube, you will get some medicine to relax you and so you will not remember the experience. We will do everything possible to make sure this is successful and there are no complications.

Keener Kontest: There was no winner last week. The correct answer is Michigan is a Native American word meaning Great Water.

Listen to the podcast this week. If you know the answer to the trivia question then send me an email to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

Other FOAMed:

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.