Mackle D, Bellomo R, Bailey M, et al. - As patients who are undergoing mechanical ventilation in the intensive care unit (ICU) are frequently administered a high fraction of inspired oxygen (Fio₂) and have high arterial oxygen tension, researchers examined if using oxygen conservatively could decrease oxygen exposure, reduce lung and systemic oxidative injury, and thereby improve the number of ventilator-free days (days alive and free from mechanical ventilation). Thousand adult patients who were anticipated to require mechanical ventilation beyond the day after recruitment in the ICU were randomized to undergo conservative or usual oxygen therapy. The default lower limit for oxygen saturation as measured by pulse oximetry (Spo₂) was 90% in the two groups. In the conservative-oxygen group, they set the upper limit of the Spo₂ alarm to sound on reaching the level of 97%, and the decrease of the Fio₂ to 0.21 was done if the Spo₂ was above the acceptable lower limit. Outcomes revealed no significant effect of using conservative oxygen therapy vs usual oxygen therapy on the number of ventilator-free days among adults undergoing mechanical ventilation in the ICU.