title: Ventilatory response to nitrogen multiple-breath washout in infants.
abstract: BACKGROUND
  Nitrogen multiple-breath washout (N2 MBW) using 100% oxygen (O2) has regained interest to assess efficiency of tracer gas clearance in, for example, children with Cystic Fibrosis (CF). However, the influence of hyperoxia on the infants' respiratory control is unclear. We assessed safety and impact on breathing pattern from hyperoxia, and if exposure to 40% O2 first induces tolerance to subsequent 100% O2 for N2 MBW.
  
  
  METHODS
  We prospectively enrolled 39 infants aged 3-57 weeks: 15 infants with CF (8 sedated for testing) and 24 healthy controls. Infants were consecutively allocated to the protocols comprising of 100% O2 or 40/100% O2 administered for 30 breaths. Lung function was measured using an ultrasonic flowmeter setup. Primary outcome was tidal volume (VT).
  
  
  RESULTS
  None of the infants experienced apnea, desaturation, or bradycardia. Both protocols initially induced hypoventilation. VT temporarily declined in 33/39 infants across 10-25 breaths. Hypoventilation occurred independent of age, disease, and sedation. In the new 40/100% O2 protocol, VT returned to baseline during 40% O2 and remained stable during 100% O2 exposure. End-tidal carbon dioxide monitored online did not change.
  
  
  CONCLUSIONS
  The classical N2 MBW protocol with 100% O2 may change breathing patterns of the infants. The new protocol with 40% O2 induces hyperoxia-tolerance and does not lead to changes in breathing patterns during later N2 washout using 100% O2. Both protocols are safe, the new protocol seems an attractive option for N2 MBW in infants.
authors.affiliation: Department of Paediatrics, University Hospital of Bern, Bern, Switzerland; University Children's Hospital of Zurich, Zurich, Switzerland.
authors.forename: Florian
authors.initials: F
authors.lastname: Singer
authors.forename: Sophie
authors.initials: S
authors.lastname: Yammine
authors.forename: Anne
authors.initials: A
authors.lastname: Schmidt
authors.forename: Elena
authors.initials: E
authors.lastname: Proietti
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kieninger
authors.forename: Juerg
authors.initials: J
authors.lastname: Barben
authors.forename: Carmen
authors.initials: C
authors.lastname: Casaulta
authors.forename: Nicolas
authors.initials: N
authors.lastname: Regamey
authors.forename: Per
authors.initials: P
authors.lastname: Gustafsson
authors.forename: Urs
authors.initials: U
authors.lastname: Frey
authors.forename: Philipp
authors.initials: P
authors.lastname: Latzin
mesh_terms: D003550:Cystic Fibrosis / Q000175:diagnosis* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009584:Nitrogen / Q000494:pharmacology; D010100:Oxygen / Q000008:administration & dosage / Q000494:pharmacology; D011446:Prospective Studies; D012129:Respiratory Function Tests / Q000379:methods; D013990:Tidal Volume / Q000187:drug effects
chemical_list: D009584:Nitrogen; D010100:Oxygen
keywords: cystic fibrosis; inert gases; lung function tests; respiratory physiology