TOPLINE:

In patients undergoing elective surgery, the administration of pure oxygen vs lower fractional inspired oxygen (FiO₂) levels during anesthetic washout and extubation led to a greater reduction in end-expiratory lung volume and a shift in ventilation toward a more ventral distribution, consistent with formation of atelectasis.

METHODOLOGY:

• Researchers conducted a randomized controlled trial at a medical center in Boston to investigate the impact of avoiding pure oxygen during anesthetic washout and extubation on atelectasis formation and periextubation oxygenation.
• A total of 48 adult participants undergoing elective surgery under general anesthesia with tracheal intubation and an anticipated duration of 1-5 hours were randomly assigned to receive either pure oxygen (100% FiO₂; n = 24) or lower FiO₂ levels (70% in 12 participants or 40% in 12 participants) from the start of anesthetic washout until tracheal extubation.
• The primary outcome was atelectasis formation, measured at 1 minute after extubation and assessed as the change in the center of ventilation index and end-expiratory lung volume from baseline using electrical impedance tomography.
• Secondary outcomes were oxygenation trajectories measured as peripheral oxygen saturation (SpO₂) within 10 minutes before and after extubation, lowest SpO₂ and the occurrence of hypoxemia (SpO₂ < 90%) within 10 minutes after extubation, and clinical outcomes in the postanesthesia care unit.

TAKEAWAY:

• Participants who received pure oxygen had a greater ventral shift in the center of ventilation, indicating atelectasis formation in dependent lung regions, than those who received lower FiO₂ levels (median change from baseline, -0.31% vs 1.25%; P = .041).
• Participants receiving pure oxygen experienced a greater reduction in the end-expiratory lung volume after extubation than those receiving lower FiO₂ levels (mean difference, 643 mL; P = .006).
• No difference was observed in the shift of the center of ventilation index or in the change in the end-expiratory lung volume between patients receiving 70% FiO₂ and those receiving 40% FiO₂.
• SpO₂ values within 10 minutes after extubation were higher in participants receiving 70% FiO₂ than in those receiving 100% or 40% FiO ₂ (P = .039), and postextubation SpO₂ trajectories differed significantly: the pure oxygen group showed a decrease in SpO₂, the 40% FiO₂ group showed an increase in SpO₂, and the 70% FiO₂ group showed stable SpO₂.

IN PRACTICE:

The findings “suggest that lower FiO₂ might be preferable” to maintain functional residual capacity compared with pure oxygen, the researchers reported. “Our findings further present a rationale for future trials investigating the impact of lower FiO ₂ before extubation on relevant clinical outcomes, including postoperative pulmonary complications,” they added.

SOURCE:

This study was led by Béla-Simon Paschold, MD, of the Department of Anesthesia, Critical Care and Pain Medicine at Harvard Medical School in Boston. It was published online on June 15, 2026, in the British Journal of Anaesthesia.

LIMITATIONS:

This was a single-center trial with a relatively small sample size. The administration of oxygen in the postanesthesia care unit and the initiation of opioid treatment were not done according to a set protocol.

DISCLOSURES:

This study received support from institutional and departmental sources. Some authors reported receiving funding or honoraria from various sources, and one of them disclosed receiving funding for investigator-initiated studies from Merck & Co related to this manuscript. Two of the authors reported serving as associate editors for BMC Anesthesiology.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.