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The effects of non-invasive respiratory support on oropharyngeal temperature and humidity: a neonatal manikin study
  1. Calum T Roberts1,2,
  2. Rebecca Kortekaas1,3,
  3. Jennifer A Dawson1,2,4,
  4. Brett J Manley1,2,
  5. Louise S Owen1,2,4,
  6. Peter G Davis1,2,4
  1. 1The Royal Women's Hospital, Melbourne, Victoria, Australia
  2. 2Department of Obstetrics and Gynaecology, The University of Melbourne, Melbourne, Victoria, Australia
  3. 3Leiden University, Leiden, The Netherlands
  4. 4Murdoch Childrens Research Institute, Melbourne, Victoria, Australia
  1. Correspondence to Dr Calum T Roberts, Newborn Research Centre, The Royal Women's Hospital, Level 7, 20 Flemington Road, Parkville, VIC 3052, Australia; calum.roberts{at}


Objective Heating and humidification of inspired gases is routine during neonatal non-invasive respiratory support. However, little is known about the temperature and humidity delivered to the upper airway. The International Standards Organization (ISO) specifies that for all patients with an artificial airway humidifiers should deliver ≥33 g/m3 absolute humidity (AH). We assessed the oropharyngeal temperature and humidity during different non-invasive support modes in a neonatal manikin study.

Methods Six different modes of non-invasive respiratory support were applied at clinically relevant settings to a neonatal manikin, placed in a warmed and humidified neonatal incubator. Oropharyngeal temperature and relative humidity (RH) were assessed using a thermohygrometer. AH was subsequently calculated.

Results Measured temperature and RH varied between devices. Bubble and ventilator continuous positive airway pressure (CPAP) produced temperatures >34°C and AH >38 g/m3. Variable flow CPAP resulted in lower levels of AH than bubble or ventilator CPAP, and AH decreased with higher gas flow. High-flow (HF) therapy delivered by Optiflow Junior produced higher AH with higher gas flow, whereas with Vapotherm HF the converse was true.

Conclusions Different non-invasive devices deliver inspiratory gases of variable temperature and humidity. Most AH levels were above the ISO recommendation; however, with some HF and variable flow CPAP devices at higher gas flow this was not achieved. Clinicians should be aware of differences in the efficacy of heating and humidification when choosing modes of non-invasive respiratory support.

  • non-invasive ventilation
  • continuous positive airway pressure
  • neonatal intensive care
  • humidity

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