title: An authentic animal model of the very preterm infant on nasal continuous positive airway pressure.
abstract: BACKGROUND
  The surge in uptake of nasal continuous positive airway pressure (CPAP) for respiratory support in preterm infants has occurred in the absence of an authentic animal model. Such a model would allow investigation of research questions of physiological and therapeutic importance. We therefore aimed to develop a preterm lamb model of the non-intubated very preterm infant on CPAP.
  
  
  METHODS
  After staged exteriorisation and instrumentation, preterm lambs were delivered from anaesthetised ewes at 131 to 133 days gestation. Via a single nasal prong (4-mm internal diameter, 6- to 7-cm depth), positive pressure was delivered from the outset, with nasal intermittent positive pressure ventilation (NIPPV) used until transition to nasal CPAP was attempted, and periodically thereafter for hypoventilation. Caffeine and doxapram were used as respiratory stimulants. Gastric distension was prevented with an oesophageal balloon. Cardiorespiratory parameters and results of arterial blood gas analyses were monitored throughout the study period, which continued for 150 min after first transition to CPAP.
  
  
  RESULTS
  Ten preterm lambs were studied, at gestation 132 ± 1 days (mean ± SD) and birth weight 3.6 ± 0.45 kg. After stabilisation on NIPPV, transition to nasal CPAP was first attempted at 28 ± 11 min. There was transient respiratory acidosis, with gradual resolution as spontaneous respiratory activity increased. In the final hour, 79% ± 33% of time was spent on CPAP alone, with typical respiratory rates around 60 breaths per minute. PaCO2 at end-experiment was 58 ± 36 mmHg.
  
  
  CONCLUSIONS
  Non-intubated preterm lambs can be effectively transitioned to nasal CPAP soon after birth. This animal model will be valuable for further research.
authors.affiliation: Department of Paediatrics, Royal Hobart Hospital, 48 Liverpool St, Hobart, Tasmania, 7000, Australia, peter.dargaville@dhhs.tas.gov.au.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Dargaville
authors.forename: Anna
authors.initials: A
authors.lastname: Lavizzari
authors.forename: Priscila
authors.initials: P
authors.lastname: Padoin
authors.forename: Don
authors.initials: D
authors.lastname: Black
authors.forename: Elroy
authors.initials: E
authors.lastname: Zonneveld
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Perkins
authors.forename: Magdy
authors.initials: M
authors.lastname: Sourial
authors.forename: Anushi E
authors.initials: AE
authors.lastname: Rajapaksa
authors.forename: Peter G
authors.initials: PG
authors.lastname: Davis
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Hooper
authors.forename: Timothy Jm
authors.initials: TJ
authors.lastname: Moss
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Polglase
authors.forename: David G
authors.initials: DG
authors.lastname: Tingay