High inspired oxygen fraction impairs lung volume and ventilation heterogeneity in healthy children: a double-blind randomised controlled trial

Br J Anaesth. 2019 May;122(5):682-691. doi: 10.1016/j.bja.2019.01.036. Epub 2019 Mar 11.


Background: Although a high inspired oxygen fraction (FiO2) is commonly used in paediatric anaesthesia, the impact on postoperative lung function is unclear. We compared lung volume, ventilation heterogeneity, and respiratory mechanics in anaesthetised children randomised to receive low or high FiO2 intraoperatively.

Methods: In a double-blind randomised controlled trial, children scheduled for elective surgery were randomly assigned FiO2 100% (n=29) or FiO2 80% (n=29) during anaesthesia induction and emergence. During maintenance of anaesthesia, participants assigned FiO2=100% at induction/emergence received FiO2=80% (FiO2>0.8 group); those randomised to FiO2=80% at induction/emergence received FiO2=35% intraoperatively (FiO2 [0.8→0.35 group]). During spontaneous breathing, we measured the (i) functional residual capacity (FRC) and lung clearance index (ventilation inhomogeneity) by multiple-breath nitrogen washout; and (ii) airway resistance and respiratory tissue elastance by forced oscillations, before operation, after discharge from the recovery room, and 24 h after operation. Mean (95% confidence intervals) are reported.

Results: Fifty eight children (12.9 [12.3-13.5] yr) were randomised; 22/29 (high group) and 21/29 (low group) children completed serial multiple-breath nitrogen washout measurements. FRC decreased in the FiO2>0.8 group after discharge from recovery (-12.0 [-18.5 to -5.5]%; P=0.01), but normalised 24 h later. Ventilation inhomogeneity increased in both groups after discharge from recovery, but persisted in the FiO2>0.8 group 24 h after surgery (6.1 [2.5-9.8%]%; P=0.02). Airway resistance and respiratory elastance did not differ between the groups at any time point.

Conclusions: FiO2>0.8 decreases lung volume in the immediate postoperative period, accompanied by persistent ventilation inhomogeneity. These data suggest that FiO2>0.8 should be avoided in anaesthetised children with normal lungs.

Clinical trial registration: NCT02384616.

Keywords: functional residual capacity; hyperoxia; lung function; mechanical ventilation; paediatric anaesthesia; ventilation heterogeneity.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adolescent
  • Airway Resistance / drug effects
  • Anesthesia, General / methods
  • Child
  • Double-Blind Method
  • Female
  • Functional Residual Capacity / drug effects
  • Humans
  • Intraoperative Care / adverse effects*
  • Intraoperative Care / methods
  • Male
  • Oxygen / administration & dosage*
  • Oxygen / adverse effects
  • Oxygen / pharmacology
  • Oxygen Inhalation Therapy / adverse effects*
  • Oxygen Inhalation Therapy / methods
  • Postoperative Complications / etiology
  • Postoperative Period
  • Pulmonary Atelectasis / etiology*
  • Pulmonary Atelectasis / physiopathology
  • Respiratory Mechanics / drug effects


  • Oxygen

Associated data

  • ClinicalTrials.gov/NCT02384616