title: Inspired gas humidity and temperature during mechanical ventilation with the Stephanie ventilator.
abstract: OBJECTIVE
  To measure inspired gas humidity and temperature delivered by a Stephanie neonatal ventilator with variations in (i) circuit length; (ii) circuit insulation; (iii) proximal airway temperature probe (pATP) position; (iv) inspiratory temperature (offset); and (v) incubator temperatures.
  
  
  METHODS
  Using the Stephanie neonatal ventilator, inspired gas humidity and temperature were measured during mechanical ventilation at the distal inspiratory limb and 3 cm down the endotracheal tube. Measurements were made with a long or short circuit; with or without insulation of the inspiratory limb; proximal ATP (pATP) either within or external to the incubator; at two different inspiratory temperature (offset) of 37(-0.5) and 39(-2.0)°C; and at three different incubator temperatures of 32, 34.5, and 37°C.
  
  
  RESULTS
  Long circuits produced significantly higher inspired humidity than short circuits at all incubator settings, while only at 32°C was the inspired temperature higher. In the long circuits, insulation further improved the inspired humidity especially at 39(-2.0)°C, while only at incubator temperatures of 32 and 37°C did insulation significantly improve inspired temperature. Positioning the pATP outside the incubator did not result in higher inspired humidity but did significantly improve inspired temperature. An inspiratory temperature (offset) of 39(-2.0)°C delivered significantly higher inspired humidity and temperature than the 37(-0.5)°C especially when insulated.
  
  
  CONCLUSIONS
  Long insulated Stephanie circuits should be used for neonatal ventilation when the infant is nursed in an incubator. The recommended inspiratory temperature (offset) of 37(-0.5)°C produced inspired humidity and temperature below international standards, and we suggest an increase to 39(-2.0)°C.
authors.affiliation: Australian National University Medical School, Canberra, ACT, Australia.
authors.forename: Bianca L
authors.initials: BL
authors.lastname: Preo
authors.forename: Bruce
authors.initials: B
authors.lastname: Shadbolt
authors.forename: David A
authors.initials: DA
authors.lastname: Todd
mesh_terms: D058109:Airway Management; D006801:Humans; D006813:Humidity; D007223:Infant; D007231:Infant, Newborn; D008953:Models, Anatomic; D012121:Respiration, Artificial / Q000379:methods*; D012143:Respiratory Physiological Phenomena; D013696:Temperature; D012122:Ventilators, Mechanical
keywords: Stephanie ventilator; children; infants; inspired humidity; inspired temperature; mechanical ventilation