Atelectasis frequently occurs early on during anaesthesia in children. We hypothesised that positive expiratory pressure (PEP) generated via high-flow nasal cannula (HFNC) could prevent atelectasis in non-intubated children under general anaesthesia. The objective was to compare the volume of atelectasis present in patients treated via HFNC to that of patients treated via a face bag-mask without PEP. The outcome used for this comparison was the ratio of the atelectasis volume to the total pulmonary volume.

A prospective single-centre, single-blind, randomised trial was conducted in a tertiary hospital from November 2018 through May 2019. The trial subjects were infants and children between six months and six years of age who required anaesthesia for an MRI. The children were randomised to receive sevoflurane for maintenance of anaesthesia either via a classic face bag-mask or by HFNC. The atelectasis volume was measured from thoracic MRI images. The judgement criterion was the ratio of the atelectasis volume to the lung volume.

Of a trial group of 42 patients, 21 received anaesthesia via a face bag-mask and 21 via HFNC. After three patients were excluded for technical issues, the data for 39 patients were analysed. The atelectasis volume to the lung volume ratio in the HFNC group was significantly smaller than the ratio for the face bag-mask group (1.6% vs 6.8%, respectively; p=0.002).

HFNC was associated with a lower atelectasis lung ratio compared to using a face bag-mask during anaesthesia for children maintained with spontaneous ventilation. Registered on Clinicaltrials.gov: NCT 03592589