Similar outcomes found between varying oxygenation targets in mechanical ventilation
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Different oxygen saturation targets ranging from 90% to 98% did not significantly impact days alive without a mechanical ventilator among adults in the ICU or ED, according to a study published in The New England Journal of Medicine.
These findings were published in NEJM in conjunction with the European Society of Intensive Care Medicine LIVES 2022 Annual Congress, held Oct. 22 to 26 in Paris.
“The findings of the PILOT trial mean that clinicians caring for critically ill adults receiving mechanical ventilation can feel reassured that outcomes will be broadly similar whether oxygen therapy is titrated to achieve oxygen saturation levels on the lower end (eg, 90%), the middle (94%) or the higher end (98%) of the range used in clinical care,” Matthew W. Semler, MD, MSc, assistant professor of medicine and biomedical informatics at Vanderbilt University Medical Center, told Healio. “For most patients, this means clinicians can select an oxygen target in this range and then shift focus to delivering other aspects of mechanical ventilation in ways proven to improve outcomes, such as using lower tidal volumes.”
In a pragmatic, cluster-randomized and cluster-crossover trial, Semler and colleagues evaluated 2,541 adults receiving invasive mechanical ventilation in an ICU or ED to observe what target of oxygen saturation had the best outcomes for the patient population.
Researchers divided patients into three target groups for oxygen saturation, all of which were determined by pulse oximetry (SpO2), with 808 patients (median age, 57 years; 44.7% women) in the lower-target group of 90% (goal range, 88%-92%); 859 (median age, 59 years; 44.8% women) in the intermediate-target group of 94% (goal range 92%-96%); and 874 (median age, 59 years; 46.8% female) in the higher-target group of 98% (goal range, 96%-100%).
Number of ventilator-free days, or days alive and without mechanical ventilation up until day 28, served as the study’s primary endpoint. Death in the hospital by day 28 was a secondary outcome.
According to researchers, the median number of ventilator-free days did not significantly differ between the three groups, at 21 days in both the intermediate- (interquartile range [IQR], 0-25) and higher-target groups (IQR, 0-26), and 20 days (IQR, 0-25) in the lower-target group.
Researchers noted that these findings persisted in analyses of key subgroups, including patients with cardiac arrest, acute myocardial infarction, acute respiratory distress syndrome and sepsis, and based on receipt of vasopressors.
Similarly, researchers observed that the number of in-hospital deaths recorded after 28 days did not vary greatly between groups, with 281 (34.8%) deaths in the lower-target group, 292 (34%) in the intermediate-target group and 290 (33.2%) in the higher-target group.
Additionally, researchers reported that the three target groups showed comparable incidence of adverse events including cardiac arrest, arrhythmia, myocardial infarction, stroke and pneumothorax.
Semler told Healio the fact that their trial’s findings were consistent with other recent trials, such as HOT-ICU, ICU-ROX and O2-ICU, was surprising.
“Initially, smaller trials had suggested the potential for better outcomes with either lower or higher oxygen saturation targets,” Semler said. “The recent trials, including PILOT, show remarkable consistency in outcomes across oxygen saturation targets from the lower end to the higher end of the range used in clinical care.”
Future studies that uncover small details about oxygen therapy are necessary, according to Semler.
“Because oxygen therapy is received by millions of patients each year, even small differences in outcomes matter,” Semler told Healio. “Therefore, future trials should be designed to enroll the tens-of-thousands of patients needed to detect small, but meaningful, differences in outcomes. Such trials should also apply modern statistical methods to understand the effect of treatment on outcomes, not on average for all patients, but for each individual patient based on his or her individual characteristics.”
For more information:
Matthew W. Semler, MD, MSc, can be reached at matthew.w.semler@vumc.org.
Perspective
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The PILOT study by Semler and colleagues is the latest study that attempts to identify the optimal oxygen-saturation targets in mechanically ventilated patients in the ICU. The results add to the evidence of three recent studiesdemonstrating no significant difference in outcomes between liberal vs. conservative oxygenation strategies. Specifically, limiting exposure to supplemental oxygen by targeting a lower saturation did not have any effect on mortality or liberation from mechanical ventilation at 28 days. The incidences of cardiac arrest, myocardial infarction and ischemic stroke were similar across the three different oxygen-saturation target groups.
The results of this study, however, are different from a trial by Barrot and colleagues that was published in The New England Journal of Medicine in 2020 showing that patients with acute respiratory distress syndrome had higher mortality with lower partial pressure of oxygen target of 55 mmHg to 70 mmHg. What is unique about the study by Semler and colleagues is the pragmatic, cluster randomization design. This allowed the recruitment of a relatively large sample size (2,541 patients) over a 3-year span from a single medical center.
This study has multiple limitations, such as the single-center design which affects generalizability, but in my opinion the most important issue is that the 80 patients who were in the lower target group had a median SpO2 of 94%, which was 4 points above the target of 90% of this group (range, 88%-92%).
Barrot L, et al. N Engl J Med. 2020;doi:10.1056/NEJMoa1916431.
Gelissen H, et al. JAMA. 2021;doi:10.1001/jama.2021.13011.
Schjørring OL, et al. N Engl J Med. 2021;doi:10.1056/NEJMoa2032510.
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