Quantifying temperature and relative humidity of medical gases used for newborn resuscitation.

AIM: The gases used to stabilise infants during resuscitation are usually unconditioned air and oxygen, often described as 'cold and dry', in comparison with the heated, humidified gases used for ongoing ventilation in neonatal intensive care units. The aim of this study was to determine exactly how 'cold and dry' these unconditioned gases are. METHOD: Multiple measurements of temperature and relative humidity (RH) of piped gases were recorded at different sites, and at different times of day, across The Royal Women's Hospital, Melbourne. Ambient temperature and relative humidities were also recorded. RESULTS: Eighty paired air and oxygen measurements of temperature and RH were recorded. Mean temperatures of piped oxygen and air were 23.3 (0.9) and 23.4 (0.9) °C respectively. Mean RH of piped air was 5.4 (0.7) %; piped oxygen was significantly drier, mean RH 2.1 (1.1) %. CONCLUSION: Piped gases were delivered at room temperature and were extremely dry. This highlights the importance of research assessing the practicality of heating and humidifying resuscitation gases, and assessing the impact of their use on clinically important neonatal outcomes.

Feasibility and practical considerations for heating and humidifying gases during newborn stabilisation: an in vitro model.

BACKGROUND: Gases for respiratory support at birth are typically 'cold and dry', which may increase the risk of hypothermia and lung injury. OBJECTIVES: To determine the feasibility of using heated humidification from birth. METHOD: A humidifier targeting 37°C, a manual-fill chamber and a Neopuff Infant T-piece resuscitator and circuit were attached to a face mask and a manikin. Recordings using 20 ml H2O for humidification and a flow of 10 l/min were undertaken. Temperature and relative humidity (RH) were recorded. Additional recordings were made, each with one alteration to baseline (50 ml H2O for humidification, auto-fill chamber, a flow of 8 l/min, addition of circuit extension piece, warmed humidification H2O, increased ambient temperature and targeting 31°C). The duration of heated humidification and the response to disconnecting the power were investigated. RESULTS: The baseline circuit achieved 95% RH and 31°C in 3 min, >99% RH in 7 min and ≥35°C in 9 min. No circuit alterations resulted in faster gas conditioning. The extended length circuit and targeting 31°C reduced the maximum temperature achieved. A flow of 8 l/min resulted in slower heating and humidification. The baseline circuit delivered heated humidification for 39 min. Without power, the temperature and humidity fell below international standards in 3 min. CONCLUSION: Rapid gas conditioning for newborn stabilisation is feasible using the experimental set-up, ≥20 ml H2O and a flow of 10 l/min. The circuit could be used immediately once switched on. Without power, conditioning is quickly lost. Investigation of the clinical effects of gas conditioning is warranted.