Background and Methods
- Published on June 24,2024, the PREOXI trial compared preoxygenation with noninvasive ventilation or an oxygen mask in patients undergoing endotracheal. The PICO Method was used. In total, 1301 patients were enrolled. The primary outcome was defined as an oxygen saturation less than 85% during the interval between induction of anesthesia and 2 minutes following tracheal intubation. A secondary outcome was defined as the lowest oxygen saturation during the interval between anesthesia and 2 minutes after tracheal intubation. There were 645 patients in the noninvasive arm and 656 patients in the oxygen mask arm.
- In the noninvasive group, operators used a tight-fitting mask connected to a conventional mechanical ventilator or a dedicated noninvasive ventilator prior to induction of anesthesia. The type of ventilator and mode were selected by the operator, and best practices regarding preoxygenation were provided to the operators. The operators were instructed to provide this non-invasive ventilation from the start of preoxygenation until initiation of laryngoscopy. FiO2 was set to 100%, expiratory pressure was set to 5cm H20, inspiratory pressure to at least 10cm H2O, and respiratory rate was set to at least 10 breaths per minute.
- Operators in the oxygen mask group were instructed to deliver supplemental oxygen via a nonrebreather mask or bag-mask device without manual ventilation prior to induction of anesthesia. Operators were allowed to choose between these two. As in the noninvasive group, best practice recommendations were provided. Operators were instructed to provide supplemental oxygen from the start of preoxygenation until initiation of laryngoscopy, and to administer the highest flow rate of oxygen available.
- In both groups, at least three minutes of oxygenation occurred prior to anesthesia. Ventilation with a bag-mask device was allowed at the discretion of the operators after induction of anesthesia. Supplemental oxygen was also allowed via nasal cannula or high-flow nasal cannula during the interval between induction of anesthesia and laryngoscopy.
Highlights
- Over 1100 of the intubations in this study were performed by a resident or fellow, and operators had performed a median of 50 prior intubations.
- The noninvasive group had hypoxemia of less than 85% in 9.1% of patients while those in the oxygen mask group had a hypoxemia of less than 85% in 18.5%. A saturation of less than 80% was observed in 6.2% of the noninvasive group and in 13.2% of the oxygen mask group
- The median lowest oxygenation saturation between induction of anesthesia and 2 minutes after intubation was 99% in the noninvasive group and 97% in the oxygen mask group.
- Of the 645 patients initially assigned to the noninvasive group, only 6 aspirated, compared to 9 of the 656 total patients in the oxygen-mask group.
- Cardiac arrest occurred in one patient in the noninvasive group and in 7 patients in the oxygen mask group.
- The incidence of hypoxemia in the noninvasive group was lower than that in the oxygen mask group. This noninvasive group did not have an increased risk of aspiration.
- More patients in the oxygen mask group were found to have a lower oxygen saturation than the noninvasive group during the interval between induction of anesthesia and intubation.
Strengths
- Large sample size allowed for detection of clinically significant differences in incidence of hypoxemia
- Multiple sites and enrollment of critically ill adulst with broad range of conditions allowed for increased generalizability
- Independent observers collected data, minimizing bias
Limitations
- Patient’s already receiving positive pressure ventilation were excluded. Patients that were vomiting, had hematemesis, hemoptysis, or epistaxis were also excluded. Base on clinician perception that patients were high risk for aspiration, this group of patients was excluded.
- This trial did not evaluate high flow nasal cannula either alone or in combination with an oxygen mask.
- Patients, clinician, and trial personnel were aware of the trial group assignments.
What Does This Trial Show Us?
- Preoxygenation with noninvasive ventilation reduced the incidence of hypoxemia when compared with oxygen masks. While concern for aspiration is commonly cited as a reason to not use positive pressure ventilation, this did not affect the incidence of aspiration during preoxygenation. In fact, the incidence of aspiration was lower in the noninvasive group than in the oxygen mask group.
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