The Pre-Oxi Study and Practical Application
Contributor: Jason Hine MD
In this episode of the SimKit podcast, we delve into the ‘Pre Oxi Study’ published in the New England Journal of Medicine in June 2024. The study investigates whether non-invasive ventilation (NIV) prior to intubation improves outcomes compared to conventional oxygen mask use.
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Understanding the Pre Oxy Study: Non-Invasive Ventilation in Emergency Intubation
The Study
Noninvasive Ventilation for Preoxygenation during Emergency Intubation
Authors: Kevin W. Gibbs, M.D., Matthew W. Semler, M.D., Brian E. Driver, M.D. https://orcid.org/0000-0002-7141-0256, Kevin P. Seitz, M.D., Susan B. Stempek, P.A., Caleb Taylor, M.D., M.P.H., Daniel Resnick-Ault, M.D., +51 , for the PREOXI Investigators and the Pragmatic Critical Care Research Group*
Ten Thousand Feet- The Clinical Question
The study investigated the clinical question: Does non-invasive ventilation (NIV) prior to intubation improve outcomes for critically ill adults compared to oxygen masks?
Article Type
Multi-center, randomized, unblinded parallel group trial involving 24 US-based Eds and ICUs. 7 Eds and 17 ICUs, in 15 institutions.
Criteria
Inclusion Criteria: critically ill adult individuals undergoing intubation with sedation and a laryngoscope.
Exclusion Criteria: pregnant, prisoner, or already on PPV, were apneic or hypopnea, or had immediate need for intubation precluding randomization. **Also excluded at physician discretion “determined that preoxygenation with noninvasive ventilation or an oxygen mask was either necessary or contraindicated.”
Intervention
NPPV group got PPV from start of preoxygenation until initiation of laryngoscopy, set on a conventional ventilator or dedicated noninvasive ventilator. Settings were 100% Fi02, at least 5 expiratory pressure, at least 10 inspiratory pressure and at least 10 breaths per minute.
Oxygen-mask group got supplemental oxygen with either a nonrebreather mask or bag-mask device without manual ventilation. Highest flow rate recommended. **Protocol did allow either group to assist ventilations after induction meds were given.
Preoxygenation was for at least 3 minutes if feasible. NC allowed under the intervention mask if chosen by the operator.
Outcome Measures
• PRIMARY: hypoxemia during intubation (O2 sat < 85%) during intubation and up to 2 minutes after
• SECONDARY: lowest 02 sat during intubation and 2 minutes after
• Exploratory: hypotension, new or increased vasopressor, cardiac arrest
Results
4500 met inclusion criteria, but 3200 were excluded (924 because intubation too emergent, 840 already on PPV, 398 vomiting or other reason for no PPV, 248 too agitated, etc). so 1300 patients. 73% intubated in the ICU 27% in the ED and 86% by resident or fellow
• PRIMARY OUTCOME: hypoxemia <85% in 9% of PPV group and 18.5% of oxygen mask group
• SECONDARY and exploratory OUTCOMES: sat <80% 6% PPV vs 13%, <70% 2.4% PPV vs 5.7%, and cardiac arrest 1 in 645 0.2% in PPV and 7 in 656 1.1% in oxygen mask group
• Safety outcomes: aspiration 0.9% in PPV and 1.4% in oxygen mask group, statistically significant.
• Interesting subgroup: Fig 2 highlights the BMI breakdown and primary outcomes. In patients with BMI > 30, 26% in the oxygen group vs 9% in the PPV group had a 02 sat <85%
Strengths
Multi-center study, large sample size with a variety of indications for intubation. Well conducted research with a good protocol but an allowance for individual practice making it mirror real world practice.
Limitations
An 02 sat <85% is not a clinically meaningful outcome. The lower saturations are meaningful and of course cardiac arrest is, but the primary outcome is not a patient centered one. Most intubations were in the ICU and done by learners.
Author's Conclusions
Among critically ill adults undergoing tracheal intubation, preoxygenation with noninvasive ventilation resulted in a lower incidence of hypoxemia during intubation than preoxygenation with an oxygen mask.
Clinical Application
To integrate these findings into practice, two types of intubation scenarios are considered: cases where there is time for preparation, and urgent situations requiring immediate intervention. For the former, using pressure support settings on the ventilator for preoxygenation is advised. Here we can stick to the 10 over 5 for inspiratory and expiratory pressures and base rate of 10 breaths per minute; for the latter, the more critically ill or more expeditious intubation, a combination of nasal cannula and bag-valve mask with a PEEP valve is recommended. Here the provider, RT, or a trained tech can do gentle breaths every 6 seconds timed up with the patient’s respirations would be ideal. This can also allow for proper apneic oxygenation while awaiting RSI/DSI meds to take effect.
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