麻豆传媒

Compared with preoxygenation with an oxygen mask, preoxygenation with noninvasive ventilation led to a lower incidence of hypoxemia during emergency intubation among critically ill adults undergoing tracheal intubation, the randomized PREOXI trial showed.

In the 1,300-patient trial, hypoxemia during intubation -- defined by an oxygen saturation of less than 85% during the interval between induction of anesthesia and 2 minutes after tracheal intubation -- occurred in 9.1% of patients who received preoxygenation with noninvasive ventilation versus 18.5% of those who received preoxygenation with an oxygen mask (P<0.001), reported Kevin W. Gibbs, MD, of the Wake Forest School of Medicine in Winston-Salem, North Carolina, and co-authors.

The median lowest oxygen saturation during the interval between induction of anesthesia and 2 minutes after tracheal intubation -- the secondary outcome -- was 99% in the noninvasive-ventilation group and 97% in the oxygen-mask group, according to findings published in the and presented at the meeting in Belfast, Ireland.

Cardiac arrest occurred in one patient (0.2%) in the noninvasive-ventilation group and in seven patients (1.1%) in the oxygen-mask group (difference -0.9 percentage points, 95% CI -1.8 to -0.1). Aspiration occurred in six (0.9%) and nine patients (1.4%), respectively (-0.4 percentage points, 95% CI -1.6 to 0.7), a nonsignificant difference.

More than 1.5 million critically ill adults undergo tracheal intubation each year in the U.S., and hypoxemia occurs during 10% to 20% of procedures, and is associated with cardiac arrest and death.

"In current clinical care, most critically ill adults receive preoxygenation by means of an oxygen mask," Gibbs and team wrote. "Oxygen masks are simple to set up and can deliver a fraction of inspired oxygen (FIO₂ ) as high as 100% under ideal conditions. However, oxygen masks do not provide positive pressure or ventilatory support, and the actual FIO₂ received may be as low as 50% when ambient air is entrained around a loose-fitting mask."

"Noninvasive ventilation, also referred to as bilevel positive airway pressure, is an alternative to an oxygen mask for preoxygenation in critically ill adults," they continued. "Noninvasive ventilation, which involves the use of a tight-fitting mask and a high gas flow, can deliver an FIO₂ of 100%, provide positive pressure, and support ventilation. However, noninvasive ventilation requires more time to set up and could potentially increase the risk of aspiration of gastric contents during intubation."

Two small randomized trials have compared noninvasive ventilation versus oxygen masks for preoxygenation, but results were conflicting -- one suggested that the with noninvasive ventilation versus an oxygen mask, and the other trial did not show .

The was conducted at 24 emergency departments and intensive care units (ICUs) in 15 medical centers in the U.S. A total of 1,301 adults who were undergoing tracheal intubation that involved the use of sedation and a laryngoscope were randomized 1:1 to preoxygenation with noninvasive ventilation or an oxygen mask.

Patients were excluded from the trial if they were in urgent need of tracheal intubation, which precluded randomization; if they were pregnant; if they were already receiving positive pressure ventilation; or if they had apnea or hypopnea.

Median patient age was 61, about 40% were women, 60-61% were white, 19-23% were Black, and 10-12% were Hispanic.

Of the patients, 48.1% had hypoxemic respiratory failure. Tracheal intubation was performed in an ICU in 73.2% of the patients, and in an emergency department in 26.8%.

Common chronic conditions included cirrhosis (16-19%), chronic obstructive pulmonary disease (12-15%), congestive heart failure (12-14%), and obstructive sleep apnea (6-7%), while common acute conditions included altered mental status (60-62%), sepsis or septic shock (47-48%), pneumonia (16-17%), gastrointestinal bleeding (16-17%), and traumatic injury (6%).

Patients who underwent preoxygenation with noninvasive ventilation had a median of 21 ventilator-free days and 16 ICU-free days compared with 17 days and 14 days, respectively, for the oxygen-mask group. In-hospital death occurred in 32.4% of those in the noninvasive-ventilation group and 33.1% in the oxygen-mask group.

The incidence of new opacity on chest radiography and of pneumothorax were similar between the groups, as were oxygen saturation and FIO₂ at 24 hours after intubation.

Gibbs and colleagues highlighted several limitations to their study. Because the study dictated that patients were excluded if they were already receiving positive pressure ventilation at the time of eligibility assessment, the study findings do not inform decisions for preoxygenation in this patient population. This was also the case for patients who had vomiting, hematemesis, hemoptysis, or epistaxis. In addition, patients, clinicians, and trial personnel were aware of the trial-group assignments.

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