Oxygen-Saturation Targets for Critically Ill Adults Receiving Mechanical Ventilation

Abstract

Background: Invasive mechanical ventilation in critically ill adults involves adjusting the fraction of inspired oxygen to maintain arterial oxygen saturation. The oxygen-saturation target that will optimize clinical outcomes in this patient population remains unknown.

Methods: In a pragmatic, cluster-randomized, cluster-crossover trial conducted in the emergency department and medical intensive care unit at an academic center, we assigned adults who were receiving mechanical ventilation to a lower target for oxygen saturation as measured by pulse oximetry (Spo₂) (90%; goal range, 88 to 92%), an intermediate target (94%; goal range, 92 to 96%), or a higher target (98%; goal range, 96 to 100%). The primary outcome was the number of days alive and free of mechanical ventilation (ventilator-free days) through day 28. The secondary outcome was death by day 28, with data censored at hospital discharge.

Results: A total of 2541 patients were included in the primary analysis. The median number of ventilator-free days was 20 (interquartile range, 0 to 25) in the lower-target group, 21 (interquartile range, 0 to 25) in the intermediate-target group, and 21 (interquartile range, 0 to 26) in the higher-target group (P = 0.81). In-hospital death by day 28 occurred in 281 of the 808 patients (34.8%) in the lower-target group, 292 of the 859 patients (34.0%) in the intermediate-target group, and 290 of the 874 patients (33.2%) in the higher-target group. The incidences of cardiac arrest, arrhythmia, myocardial infarction, stroke, and pneumothorax were similar in the three groups.

Conclusions: Among critically ill adults receiving invasive mechanical ventilation, the number of ventilator-free days did not differ among groups in which a lower, intermediate, or higher Spo₂ target was used. (Supported by the National Heart, Lung, and Blood Institute and others; PILOT ClinicalTrials.gov number, NCT03537937.).

Figure 1.

Spo₂ and Fio₂ Values in Each Group. Shown are the mean values (colored lines) and 95% confidence intervals (gray shading) for the hourly mean oxygen saturation as measured by pulse oximetry (Spo₂) (Panel A) and the fraction of inspired oxygen (Fio₂) (Panel B) from enrollment to day 7; data were censored at the time that invasive mechanical ventilation was discontinued. Spo₂ and Fio₂ values were obtained approximately every 1 minute, and hourly means were calculated by averaging all measurements obtained during the hour. The number of patients who were alive and receiving invasive mechanical ventilation in each group on each day is shown.

Figure 2.

Proportion of Patients Alive and Not Receiving Invasive Mechanical Ventilation. The proportion of patients who were alive and breathing without invasive mechanical ventilation during the 28 days after enrollment in each Spo₂-target group is shown. In a proportional-odds model, the number of days that patients were alive and free of invasive mechanical ventilation through day 28 did not differ significantly among the groups (P = 0.81).

Figure 3.

Subgroup Analyses of the Primary Outcome. The median number of ventilator-free days is compared among the three Spo₂-target groups in subgroups of patients defined according to prespecified baseline characteristics. Odds ratios greater than 1.0 indicate a greater number of ventilator-free days (i.e., a better outcome). IQR denotes interquartile range.