Bag-Mask Ventilation Helps Prevent Hypoxemia

Marcia Frellick

February 21, 2019

SAN DIEGO — Critically ill adults who underwent tracheal intubation with bag-mask ventilation had higher oxygen saturations than those who received no ventilation, and were less likely to experience severe hypoxemia in the randomized PreVent trial (NCT03026322).

These results should change practice, said Jonathan Casey, MD, from the Vanderbilt University Medical Center in Nashville, Tennessee, noting that he expects "most ICU providers and anesthesia providers across the country who intubate patients out of the emergency room to start doing this."

"I hope people in the emergency room do, too, and if they don't, maybe we'll have to study it again in their population," he added.

The results were presented here at the Society of Critical Care Medicine 2019 Congress and simultaneously published online in the New England Journal of Medicine.

The use of bags is controversial; fears about a higher risk for aspiration have persisted for decades. But this trial provides some reassurance because the incidence of aspiration was numerically lower with the bag-mask than with no ventilation.

The PreVent trial enrolled 401 patients from seven academic intensive care units (ICUs) in the United States from March 2017 to May 2018.

The median lowest oxygen saturation level was significantly higher in the bag-mask group than in the unventilated group (96% vs 93%; = .01).

Overall, 21 of the 199 patients in the bag-mask group and 45 of the 202 patients in the unventilated group developed severe hypoxemia (10.9% vs 22.8%; relative risk, 0.48; 95% confidence interval [CI], 0.30 - 0.77). The condition — an oxygen saturation of less than 80% — is the most common complication when critically ill adults undergo tracheal intubation, Casey and his colleagues write, adding that it can increase the risk for cardiac arrest and death.

"These results suggest that for every nine critically ill adults undergoing tracheal intubation, providing bag-mask ventilation between induction and laryngoscopy would prevent severe hypoxemia in one patient," they report.

Less Aspiration in the Bag-Mask Group

Aspiration during intubation was less common in the bag-mask group than in the unventilated group (2.5% vs 4.0%; = .41), which suggests "that short-period bagging doesn't cause aspiration," Casey told Medscape Medical News.

However, the PreVent trial likely was not large enough to definitively determine the aspiration risk with the bags during rapid-sequence intubation, Patricia Kritek, MD, and Andrew Luks, MD, both from the University of Washington in Seattle, write in an editorial accompanying the published results.

Still, "the findings provide a strong suggestion that the practice is not harmful," the pair notes.

But they draw attention to the "failure to standardize the preoxygenation strategy," which led to more people in the bag-mask group than in the unventilated group receiving oxygen before induction (39.7% vs 10.9%; relative risk, 3.65; 95% CI, 2.37 - 5.60).

"On the basis of differences in preoxygenation strategies, it is conceivable the bag-mask group had a significantly higher arterial partial pressure of oxygen than the control group and greater reserve protecting against peri-intubation hypoxemia," Kritek and Luks write.

Casey said he agrees that it is never good to have differences in any baseline characteristics between groups, but he explained that in this case, "if anything, that probably made us underestimate how effective bag-mask ventilation is."

He and his colleagues acknowledge that the trial "did not examine the use of noninvasive ventilation during the interval between induction and laryngoscopy and does not inform the choice between noninvasive ventilation and bag-mask ventilation."

But, they add, more than 1.5 million patients in the United States undergo tracheal intubation each year, and up to 40% of the intubations in ICUs are complicated by hypoxemia.

The study was funded by the Vanderbilt Institute for Clinical and Translational Research. Casey reports grant support from the National Institutes of Health (NIH). His coauthors report grant support from the NIH and the National Heart, Lung, and Blood Institute, and financial relationships with Cempra Pharmaceuticals, Ferring Pharmaceuticals, Biotest, Merck, Gilead Pharmaceuticals, Pfizer, Cumberland Pharmaceuticals, Avisa Pharma, and Takeda Pharmaceuticals. Luks reports receiving personal fees from Merck, Springer, Wolters Kluwer, and Informa. Kritek has disclosed no relevant financial relationships.

Society of Critical Care Medicine (SCCM) 2019 Congress. Presented February 18, 2019.

Follow Medscape on Twitter @Medscape and Marcia Frellick @mfrellick

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