Impact of high versus low fraction of inspired oxygen for anaesthetic washout and extubation on postoperative pulmonary atelectasis formation and oxygenation: a randomised controlled trial.

BACKGROUND

Clinicians often administer 100% inspired oxygen (fraction of inspired oxygen [Fio2] = 1) for washout of volatile anaesthetics before tracheal extubation, potentially aggravating atelectasis formation and compromising oxygenation. We evaluated whether lower Fio2 during emergence from anaesthesia reduces atelectasis and improves oxygenation.

METHODS

We conducted a single-centre, randomised controlled trial (NCT06538740) in 48 adult participants undergoing elective surgery under general anaesthesia. Participants were randomised to receive either pure oxygen (100%) or lower (70% or 40%) Fio2 for anaesthetic washout before extubation. The primary outcome was atelectasis, assessed as changes in centre of ventilation and end-expiratory lung volume using electrical impedance tomography.

RESULTS

Twenty-four participants (mean age 57 [range: 19-82] yr; 42% female) were randomly allocated to receive pure oxygen and 24 received 40% or 70% Fio2. Participants receiving pure oxygen had a more ventral shift in the centre of ventilation (median [IQR], -0.3% [-2.2 to 1.3]), compared with lower Fio2 (1.3% [0.0-2.8]; P=0.041). Participants receiving pure oxygen also had a greater reduction in end-expiratory lung volume after extubation (-1067 [-1839 to -589] ml) compared with participants receiving lower Fio2 (-423 ml [-873 to -53]; P=0.006). There was no difference in end-expiratory lung volume between patients receiving 70% or 40% Fio2 (P=0.39). Spo2 (oxygen saturation measured by pulse oximetry) 10 min after extubation was higher in participants receiving 70% Fio2 (interaction P=0.028).

CONCLUSIONS

Avoiding pure oxygen before extubation preserved end-expiratory lung volume with more dorsal distribution of ventilation. Postextubation oxygenation was optimal with 70% Fio2.