You are working an ED shift with an experienced EM resident. As the resident prepares to intubate a 100kg patient with pneumonia you suggest that the head of the bed be elevated to aid in first pass success and avoidance of peri-intubation hypoxia. The resident thanks you for your kind suggestion and states ‘I just read an article in Annals of EM suggesting there was no benefit to non-supine position in ED patients.’ This is news to you. You give the resident the benefit of the doubt and ask them to send you a copy of their evidence.
In Emergency Department intubations, does head of bed elevation improve intubating conditions, and improve patient oriented outcomes?
From a physiologic perspective it makes sense to intubate patients in a Head Of Bed (HOB) elevated position. Anecdotally, all patients in respiratory distress (and most patients with severe anxiety) seem to prefer to sit up rather than lay supine.
Sitting up has the potential to both decrease compressive atelectasis in the posterior lung zones, improve functional residual capacity, and especially in our obese patients, improve diaphragm function by alleviating some of the compression from abdominal contents and increased abdominal girth.
Operating Room Evidence:
Two small operating-room based studies show proof of concept with improved safe apnea duration in both obese, and non-obese populations.
Lane and colleagues took 40 elective anesthesia patients and randomized them to pre-oxygenation in 20 degrees HOB elevation vs supine, they were then intubated supine, and the time until sats dropped to < 90% was measured. PMID: 16229689
- HOB elevation: 386 seconds.
- Supine: 283 seconds.
- Absolute difference: 103 seconds.
Populations had no significant differences in age, BMI (26.3 vs 27.9), or smoking status. The times to desaturation are far longer in elective surgery patients than can be expected in critically ill patients in the ED / ICU.
Dixon and colleagues took 40 obese patients with BMI >40 and randomized them to pre-oxygenation with head of bed elevated to 25 degrees vs supine. They were intubated and then time to desaturation <92% was measured. The patients were intubated, and then re-oxygenated in their assigned positions. PMID:15915022
- Arterial PaO2 Upright: 442 +/- 104 mmHg
- Arterial PaO2 Supine: 360 +/- 99 mmHg (P = 0.012)
- Safe apnea duration Upright: 201 +/- 55 seconds
- Safe apnea duration Supine: 155 +/- 69 seconds (P= 0.023)
When the effects of head of bed elevation are studied prospectively in randomized trials, and in airway registry reviews there are variable reports of benefit in the prehospital, emergency department, and ICU setting.
OR Bottom Line:
Pre-oxygenating obese and non-obese patients undergoing elective surgery in HOB elevated position can prolong the non patient oriented outcome of safe apnea duration by over 1 minute. This supports the physiologic plausibility of HOB elevation improving respiratory dynamics.
Murphy and colleagues assessed the effect HOB elevation had on first pass success and laryngoscopic view in a retrospectively analyzed prospectively collected airway registry in Seattle. PMID: 30826211
13,353 patients were intubated by experienced paramedics (12 intubations per year). Trauma patients, pediatric patients, and cardiac arrest patients were excluded.
4879 Intubations were analyzed with 39.4% performed in the inclined (HOB elevation) position. Peri-intubation hypoxia, and duration of safe apnea was not assessed.
Most common indications for intubation:
- Airway protection: 66.8%
- Respiratory failure: 49.1%
- (these were non exclusive categories, thus sum >100%)
First pass success (Primary Outcome):
- Inclined: 86.3%
- Supine: 82.5%
- 3.8% difference, (CI 1.5-6.1)
First attempt grade I view:
- Inclined: 62.9%
- Supine: 57.1%
- (CI: 2.0-9.6)
Challenges to intubation:
Challenges to intubation (secretions, obesity, patient position) were more frequent in the supine group
- Inclined: 38.8%
- Supine: 42.3%
- Difference 3.5% (95% CI: 0.6-6.3)
The only modifiable challenge to intubation of the three that were assessed (presence of airway secretions, emesis, or blood) was lower in the inclined population:
- Inclined: 11.4%
- Supine: 18.5%
- 7.1% difference (95% CI 5.0-9.1)
Limitations of this study:
- This was a large urban-suburban RSI capable EMS system which is a setting and circumstance that may limit the generalizability of the findings to different EMS systems with different scopes of practice.
- Data for the registry is provided by self-report from a paramedic airway operator and thus is subject to recall bias.
- This study cannot report on specific clinical context or patient outcomes beyond what is gathered in the registry.
- As an observational study this trial cannot establish causality but only association of the inclined position and improved first pass success rate.
- The study excluded cardiac arrest and trauma patients, therefore no conclusions can be made about these patient populations as to the most optimal intubation position.
Pre-hospital Bottom Line:
Intubating non trauma and non cardiac arrest patients in a pre-hospital setting in a HOB elevated position is associated with improved first pass success, improved glottic visualization, and a decrease in the presence of airway secretions during laryngoscopy.
Emergency Department Studies:
Two studies have examined the effect of HOB elevation in an ED setting. The first was by Turner and colleagues in 2017. PMID: 28202295 They performed a prospective observational study of ED intubations performed by Emergency Medicine Residents. Head of bed elevation angle was divided into supine (0-10 degrees), inclined (11-44 degrees), or upright (>45 degrees).
Prior to the start of the study period all residents practiced intubating manikins in a HOB elevated position. For a patient to be entered in the study both the treating resident and attending had to have watched a demonstration video and had to have voluntarily agreed to participate in the study. Patient positioning was at the discretion of the treating providers.
231 non-trauma intubations were included in the analysis. 16% were in the supine position, 29% inclined, and 54% upright. The primary outcome was first pass success. First pass success was 65.8% for the supine group, 77.9% for the inclined group, and 85.6% for the upright group. For every 5 degree increase in HOB angle, there was increased likelihood of first pass success. (AOR = 1.11; 95% CI 1.01-1.22 p = 0.043).
No significant difference in:
- Rates of esophageal intubation
- Cormack-Lehane (CL) view obtained
- 5 day mortality
- Development of new pneumonia
- Oxygen saturation decrease
- Time to intubation
This was a rather sick population with a post intubation cardiac arrest rate of 1.7%. Post intubation cardiac arrest occurred in 7.9% of the supine, 0% of the inclined, and 0.8% of the upright intubations.
Peri-intubation hypoxia was associated with increased BMI, (p=0.031) pre-procedural hypoxia (p=0.034) and decreased resident experience (p=0.051).
Patient oriented outcomes of mortality and new pneumonia rates did not differ between groups.
The authors identified several potential confounders in this study:
- Residents / attendings were able to choose patient position. This may create a selection bias for sicker patients to be intubated in the supine position.
- A larger percentage of patients in the supine group were intubated for cardiovascular dysfunction, and may have been more unstable
- Not all eligible intubations were included. Based on resident procedure logs the authors estimate that approximately half of all eligible intubations were captured. It is possible that many of the urgent / unstable patients were not included in the analysis. This dilutes the results of this trial as it may decease the generalizability of the results to other facilities.
- Six patients who were intubated while receiving CPR were included in the analysis. When these patients were excluded patient position was still associated with first pass success (p = 0.034) however when adjusting for demographics first pass success association with position was not statistically significant (p = 0.062)
- Residents had limited training in HOB elevated positioning. It is possible that with more training the rates of HOB elevated first pass success may have been higher.
The most recent ED based study on HOB elevation for intubation was a secondary analysis of the National Emergency Airway Registry (NEAR), a prospectively collected database of ED intubations from an international network of 25 academic and community hospitals. PMID: 31116893 NEAR participation requires 90% of all intubations to be captured.
Patients who underwent intubation with a flexible fiberoptic or video device and those who underwent an “awake intubation” with topical anesthesia alone or in combination with sub-induction doses of sedative agents (ie non RSI cases) were excluded.
The primary outcome was first pass success. Secondary outcomes included CL grade glottic view, and a composite adverse event rate that included physiologic deterioration (saturations <90%, or a drop of >10%, HR <60, BP <100mmHg) emesis / aspiration, mainstem intubation, and peri-intubation arrest.
11,480 patients were included in the analysis, 5.8% were intubated in non-supine position.
- Overall first pass success rate was 87%, with no difference between HOB elevated or supine positioning.
- Adverse event rates were higher in the non-supine position group. (18.3% vs 11.9%)
- Hypoxia (10.5% vs 7.2%), Post intubation bradycardia (1.2% vs 0.6%) and Hypotension (7.1% vs 3.3%) all occurred more frequently in the non-supine group.
- There was an overall low rate or peri-intubation arrest of 0.84%, with a higher rate in the non-supine group (1.5% vs 0.8%)
Fewer than 10% of patients had the lowest peri-intubation saturation recorded, so despite no difference in first pass success, it is impossible to determine whether the physiological plausibility of improved peri-intubation oxygenation played out with HOB elevation.
The non-supine group had higher rates of peri-intubation pressor use, higher rates of peri-intubation hypotension, more obese patients, and more patients with suspected difficult airways. It is possible that this was a sicker group than the supine positioned group, contributing to the higher rates of adverse events.
- Non supine position: 0.5%
- Supine position: 0.7%
- Odds ratio: 0.6 (0.2-2.0)
This was the only individual adverse event that was less likely in the NSP group. Back elevated positioning may be beneficial when treating patients in whom the risk of emesis and aspiration are increased such as massive hemoptysis, significant upper gastrointestinal bleeds, or severe bowel obstruction.
The authors identify several limitations:
- Retrospective reporting can lead to recall bias and degradation of the quality of information input into the data registry. This is noted with the low rate of nadir oxygen saturation recording.
- Despite the improved attention paid to peri-intubation cardiopulmonary optimization in recent years, there was still a very low rate of non supine positioning for data collected Jan 2016 through December 2017. This is important because providers may not have had as much comfort with the HOB elevated position, which could cause non-supine results to appear worse when compared to supine position.
- The ‘dealer’s choice’ option for airway providers to select the position of their patients may have biased sicker patients to be placed in non supine position.
- Both groups include patients with variable cervical spine positions including neutral position, simple extension, and full sniffing position. This means that anatomic alignment may have been suboptimal in many scenarios and may explain the lack of difference in glottic views between the two populations.
- The composite outcome of airway adverse events was necessary due to low overall rates of these events however the composite outcome was not weighted, giving mainstem intubation the same importance as peri-intubation cardiac arrest which are not equal patient oriented outcomes.
Four questions with Hill Stoecklein MD (Lead author of the NEAR registry study):
- Do the results of this study change your practice?
- NO, I still intubate all medical patients at 30 degrees HOB elevation
- If you had a do-over, what would your preferred balance of HOB elevation : supine patients be?
- 50:50 in a randomized controlled study
- Do you think the HOB elevated cohort were sicker?
- YES. This is why hypoxia rates were higher.
- IF you were intubating your favorite (older) sibling, how would you position them?
- HOB elevated to 30 degrees, with reluctant use of peri-intubation sedation.
ED Bottom Line:
ED studies show mixed results with one study showing improved first pass success without a difference in peri-intubation hypoxia or rates of post intubation pneumonia. A larger registry-based study showed no difference in first pass success, but a higher incidence of peri-intubation hypoxia in the HOB elevated group that may have been a sicker population.
ICU / In-hospital studies:
To date the study that has shown the biggest benefit to HOB elevation is the 2016 study performed by Khandelwal and colleagues in a teaching hospital system in Seattle, WA. PMID: 26866753
528 patients managed by anesthesiologists outside of the operating room (ICU, floor) were randomized to Back up, Head elevated to 30 degrees vs supine. Any intubation performed at a HOB angle of <30 degrees was determined to be supine, so there could have been some 20 degree HOB elevation intubations performed. This dilutes the difference between HOB elevation vs supine results as 20 degree HOB elevation is not supine.
The authors assessed for 1 or more airway complications: difficult intubation with >3 looks, or >10min tube placement, esophageal intubation, hypoxia <90%, or aspiration.
The incidence of at least 1 airway complication was lower in the HOB elevated group: 9.3% vs 22.6%. This difference was driven by fewer episodes of hypoxemia (6.3% vs 17%) and pulmonary aspiration (1% vs 2.3%).
NNT to reduce peri-intubation complications:
- At least one airway complication: 7.5
- Hypoxemia: 9
- Pulmonary aspiration: 77
There were a total of 3 surgical airways performed in this cohort.
The most recent ICU study to evaluate HOB elevation was performed by Semler and colleagues in 2017. PMID: 28487139 This was a multicenter randomized trial comparing HOB elevation to 25 degrees versus supine positioning with neck flexed, and head extended.
- Primary outcome was lowest arterial oxygen saturation between induction and 2 minutes after intubation.
- Secondary outcomes were CL grade glottic view, difficulty of intubation, and number of intubation attempts.
The median lowest arterial saturation was 93% (IQR 84%-99%) in the ramped position vs 92% (IQR 79%-98%) in the supine position. (p = 0.27)
The authors correctly state that time to desaturation is a good metric for proof of concept, but offers no significant patient-oriented benefit, other than in a difficult airway where time to first pass success is longer.
Grade of glottic view, difficulty of intubation, and number of attempts were worse in the ramped position than the sniffing position.
First pass success was lower in the ramped position (76.2% vs 85.4% p = 0.02)
This study is the only study to show worsening first pass success in the ramped position. One mechanism for this is that the design of an ICU bed differs from an EMS gurney, or ED gurney making access to the elevated head of bed difficult. This was not seen in the Seattle study where patients were also intubated in hospital beds.
ICU / In-hospital Intubation Bottom Line:
In-hospital studies are split, with one showing a dramatic reduction in peri-intubation adverse events with HOB elevation, and another showing a reduction in first pass success that may be associated with ICU bed design.
Other patient-oriented benefits:
Other than during the peri-intubation period, another potential patient oriented outcome to pre-oxygenation / intubation with HOB elevation is improved compliance with a ventilator induced pneumonia bundle of care. PMID: 29225790
Head of bed elevation in intubated patients has been identified as one of the factors that can reduce the incidence of ventilator associated pneumonia.
If patients are intubated with HOB elevation, they may be more likely to have their chest x-ray in HOB elevated position, and to remain in HOB elevated position for the duration of their ED stay and ICU transfer.
- Pre-oxygenation and intubation in HOB elevated position makes physiologic sense.
- Pre-oxygenating obese and non obese patients undergoing elective surgery in HOB elevated position can prolong the non patient oriented outcome of safe apnea duration by over 1 minute. This supports the physiologic plausibility of HOB elevation improving respiratory dynamics.
- Intubating non trauma and non cardiac arrest patients in a pre-hospital setting in a HOB elevated position is associated with improved first pass success, improved glottic visualization, and a decrease in the presence of airway secretions during laryngoscopy.
- ED studies show mixed results with one study showing improved first pass success without a difference in peri-intubation hypoxia or rates of post intubation pneumonia. A larger registry-based study showed no difference in first pass success, but a higher incidence of peri-intubation hypoxia in the HOB elevated group that may have been a sicker population.
- In-hospital studies are split, with one showing a dramatic reduction in peri-intubation adverse events with HOB elevation, and another showing a reduction in first pass success that may be associated with ICU bed design.
- Equipment / position issues may be overcome with deliberate practice and increased experience.
- For ED patients requiring intubation HOB elevation makes physiologic sense and is supported by prehospital and ED studies. There is no evidence of harm in the ED setting.
- Lane S et al. A prospective, randomized controlled trial comparing the efficacy of pre-oxygenation in the 20 degree head-up vs supine position. Anesthesia 2005. PMID: 16229689
- Dixon BJ et al. Preoxygenation is More Effective in the 25 degree Head-up Position than in the Supine Position in Severely Obese Patients. Anesthesiology 2005; 102:1110-5 PMID:15915022
- Murphy DL et al. Inclined position is associated with improved first pass success and laryngoscopic view in prehospital endotracheal intubations. Am J Emerg Med. 2019. PMID: 30826211
- Turner JS et al. Feasibility of upright patient positioning and intubation success rates at two academic emergency departments. Am J Emerg Med 2017. PMID: 28202295
- Stoecklein HH et al. Multicenter Comparison of Nonsupine Versus Supine Positioning During Intubation in the Emergency Department: A National Emergency Airway Registry (NEAR) Study. PMID: 31116893
- Khandelwal N et al. Head-Elevated Patient Positioning Decreases Complications of Emergent Tracheal Intubation in the Ward and Intensive Care Unit. Anesth Analg 2016. PMID: 26866753
- Semler MW et al. A Multicenter, Randomized Trial of Ramped Position vs Sniffing Position During Endotracheal Intubation of Critically Ill Adults. Chest 2017. PMID: 28487139
- Timsit JF et al. Update on Ventilator Associated Pneumonia. F1000res. 2017. PMID: 29225790
Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)
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