#26 BREAKING NEWS: PREOXI Study Published
Extra Extra - Read All About It!! It is our pleasure to bring to you - hot off the presses - the results from the PREOXI Trial which looks at whether or not preoxygenation with non-invasive positive pressure ventilation results in better peri-intubation outcomes versus non-pressurized preoxygenation strategies. Joining us is the primary author on this paper, Dr. Kevin Gibbs, MD of Wake Forest University School of Medicine. Practice changing? Practice affirming? Does it even matter?! Check out our interview with Dr. Gibbs and see what you think!
Quick Take Home Points:
Hypoxemia occurs in 10-20% of ED/ICU intubations and is associated with adverse outcomes including cardiac arrest and death.
Preoxygenation is essential to reduce the incidence of hypoxemia with endotracheal intubation.
The PREOXI trial randomized critically ill patients undergoing endotracheal intubation to preoxygenation with either an oxygen mask .
Use of non-invasive ventilation (NIV) for 3-5 minutes of pre-oxygenation prior to endotracheal intubation substantially reduced the incidence of hypoxemia during intubation compared to oxygen mask.
Use of NIV preoxygenation CUT IN HALF the risk of hypoxemia: 9.1% in the noninvasive ventilation group and 18.5% in the oxygen mask group. This was a statistically and clinically very significant effect.
NNT 11 to prevent one desaturation below 85%.
The use of NIV also reduced the risk of cardiac arrest with endotracheal intubation likely due to preventing desaturation events. (0.2% vs 1.1%)
There was no apparent increased risk of aspiration with NIV.
The benefits of NIV were seen in all pre-specified subgroups (ED vs ICU, hypoxemic as baseline vs not, obese vs non-obese, etc)
Our conclusions: Use of NIV for preoxygenation should be standard of care in (most) critically ill patients undergoing endotracheal intubation.
The Paper:
Link to the article in NEJM is here.
Show Notes:
Why is pre-oxygenation so important?
Hypoxemia occurs during 10% to 20% of tracheal intubations in the emergency department or intensive care unit and is associated with cardiac arrest and death. 1-2% of intubations performed in the ED or ICU result in cardiac arrest!
Preoxygenation is important to reduce the risk of hypoxemia with intubation, but the optimal strategy for pre-oxygenation is unknown.
High flow oxygen via mask can achieve an FiO2 close to 100% but doesn’t provide any PEEP or ventilation during apnea.
Non-invasive positive pressure can also achieve an FiO2 of 100% and also provides PEEP and ventilation, but it takes longer to setup and theoretically has a greater risk of aspiration.
Determining the optimal approach to pre-oxygenation can improve safety in ED/ICU intubations by reducing the incidence of peri-procedural hypoxemia.
The PREOXI Trial
The PRagmatic trial Examining OXygenation prior to Intubation (PREOXI) was a prospective, multicenter, non-blinded randomized comparative effectiveness trial conducted in 7 emergency departments and 17 intensive care units across the United States.
Critically ill patients undergoing tracheal intubation were randomly assigned to receive preoxygenation using either noninvasive ventilation or an oxygen mask.
The primary outcome was the incidence of hypoxemia, defined as an oxygen saturation of less than 85% during the interval between induction of anesthesia and 2 minutes after tracheal intubation. The secondary outcome was the lowest oxygen saturation during the interval between induction of anesthesia and 2 minutes after tracheal intubation.
Supplemental Figure 1 - Design of the intervention in the PREOXI trial
This pragmatic trial enrolled a mixture of patients undergoing intubation for many different reasons.
1301 patients were randomized.
645 patients were assigned to the noninvasive ventilation group and 656 patients to oxygen mask.
The median age of patients was 61 yo.
The most common reasons for intubation were hypoxemic respiratory failure and encephalopathy. Some patients were intubated for GI bleed and other indications that would normally preclude using of NIPPV.
73% of patients were intubated in an ICU and in an emergency department for 27% in an ED>
Residents and fellows performed the majority of the intubations. The median number of prior intubations for each operator was 50.
Most intubations were performed using etomidate + rocuronium.
Preoxygenation with NIV substantially reduced the incidence of hypoxemia.
Hypoxemia - defined as a SpO2 less than 85% (primary outcome) - occurred in 9.1% in the noninvasive ventilation group and 18.5% in the oxygen mask group.
Another way to frame that is in terms of NNT. If you preoxygenate 11 people with NIV you will prevent 1 significant episode of hypoxemia!
This was also true for other definitions of hypoxemia:
An SpO2 <80% occurred in 39 patients (6.3%) in the noninvasive ventilation group and in 84 patients (13.2%) in the oxygen mask group.
An SpO2 <70% occurred in 15 patients (2.4%) in the noninvasive ventilation group and in 36 patients (5.7%) in the oxygen mask group.
Regardless of the definition of hypoxemia used, NIV HALVED the incidence of post intubation hypoxemia.
Supplemental Figure S4
Mortality was also significantly reduced when NIV was used for preoxygenation.
Cardiac arrest between induction of anesthesia and 2 minutes after tracheal intubation occurred in one patient (0.2%) in the noninvasive ventilation group and 7 patients (1.1%) in the oxygen mask group.
Hemodynamic collapse following induction occurred in 113/645 (17.5%) people in the NIV group versus 127/656 (19.4%) people in the oxygen mask group.
Use of vasopressors was similar in both groups. The dose is not reported.
The authors do not report the volume or number of of fluid boluses given.
While it is possible that the use of positive pressure ventilationchanged physician behavior (e.g. boluses of higher dose of vasopressors), it seems more likely that the difference in mortality is explained by higher rates of hypoxemia rather than differences in hemodynamics.
There was no increase in aspiration with non-invasive ventilation preoxygenation
There were 9 operator reported aspirations in the oxygen mask group compared to 6 in the NIV group.
There was no difference in the number of new infiltrates on chest imaging.
There were numerically more ventilator free days (21 vs 17) and ICU free days (16 vs 14) in the group who received NIV preoxygenation, hinting at potential lingering benefit throughout the ICU course, potentially from reduced aspirations.
Note: of the 3161 people who were excluded from the study, 389 were excluded because they had emesis, hematemsis, hemoptysis, or epistaxis. Thus it is likely that the highest risk patients for aspiration were not included in this trial.
Table 3 - Outcomes of tracheal intubation
The benefits of preoxygenation with NIV were seen in every pre-specified subgroup:
Both patients who were on ambient air (21% FiO2) and those on high flow oxygen (>70% FiO2) in the hour prior to intubation appeared to benefit.
Patients in the ICU and ED both benefited from use of NIV preoxygenation.The benefit of NIV may be greater in people with obesity (BMI > 30 kg/m2)
Figure 2 - Prespecified Subgroup analysis
Conclusions:
Pre-oxygenation with non-invasive ventilation (NIV) was safe and feasible in both emergency departments and ICUs.
In many cases the same equipment could be used for NIV and invasive ventilation. This is potentially simpler than using a separate piece of equipment such as heated high flow nasal cannula.
Use of NIV for 3-5 minutes of pre-oxygenation prior to endotracheal intubation substantially reduced the incidence of hypoxemia during intubation.
NIV reduced the risk of hypoxemia by approximately 50%
NNT 11 to prevent one desaturation below 85%.
This is a statistically and clinically very significant effect.
The use of NIV also reduced the risk of cardiac arrest with endotracheal intubation likely due to preventing significant desaturation events.
Cyrus & Nick’s conclusion: NIV should be standard of care for preoxygenating critically ill patients prior to endotracheal intubation in most circumstances!
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