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An evaluation of temperature stability and resistance in neonatal ventilator circuits

  • Ruppert, Jennifer A.1
  • McNinch, Neil L.2
  • Volsko, Teresa A.3
  • 1 Department of Respiratory Care, Akron Children’s Hospital, Akron, OH, USA
  • 2 Rebecca D. Considine Research Institute, Akron Children’s Hospital, Akron, OH, USA
  • 3 Department of Nursing Administration, Akron Children’s Hospital, Akron, OH, USA
Published Article
Canadian Journal of Respiratory Therapy: CJRT = Revue Canadienne de la Thérapie Respiratoire : RCTR
Canadian Society of Respiratory Therapists
Publication Date
Jan 29, 2021
DOI: 10.29390/cjrt-2020-042
PMID: 33532559
PMCID: PMC7845534
PubMed Central


Background Gas conditioning minimizes complications associated with invasive ventilation of neonates. Poorly conditioned gas contributes to humidity deficit, facilitates condensate pools, and contributes to safety events. The specific aim was to objectively quantify the temperature drop across the unheated portion of a neonatal circuit and the impact condensation has to resistance to flow in the ventilator circuit. Methods Ventilator circuits and filters were obtained, assembled according to manufacturer recommendations, and operational verification procedures were performed prior to data collection. A neonatal test lung was connected to each Servo-I ventilator with the following settings: pressure control IMV mode; inspiratory pressure: 14 cm H2O to achieve an exhaled tidal volume of 6.0 mL; PEEP: 5 cm H2O; pressure support: 5 cm H2O, FIO2: 0.21; set frequency 40/min; and inspiratory time: 0.4 s. The Fisher and Paykel MR850 and ChonchaTherm Neptune heaters were set at a temperature of 40°C. To evaluate both systems under similar conditions, the ChonchaTherm Neptune heater humidity control was set to midline. Heaters were turned on simultaneously and given 1 h to equilibrate. Readings for room temperature, airway temperature at the patient connection, airway resistance, exhaled tidal volume, and direct observation of circuit condensation and (or) pooling were recorded hourly for a 48-h period. Summary statistics were calculated for the variables of interest. Results Mean (±SD) air temperature was 26.3°C (±1.4) for the Fisher & Paykel MR850 system and 26.2°C (±1.5), for the ChonchaTherm Neptune system. Mean (±SD) airway resistance was 229.3 cm H2O/L/s (±81.0) for the Fisher & Paykel system and 196.2 cm H2O/L/s (±39.4) for the ChonchaTherm Neptune system. Mean (±SD) tidal volume for the Fisher & Paykel MR850 system was 6.5 mL (±0.4), and for the ChonchaTherm Neptune system was 7.2 mL (±0.6). Conclusion Circuit condensate increased tidal volume delivery and airway resistance. Temperature at the patient connection was lower than the temperature monitored by the system 12 inches distally, which can negatively impact gas conditioning.

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