Feasibility and Practical Considerations for Heating and Humidifying Gases during Newborn Stabilisation: An in vitro Model

Abstract

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.

Use of Heated Humidified Gases for Early Stabilization of Preterm Infants: A Meta-Analysis

“…CPAP was given with a T piece resuscitator (Neopuff, Fisher & Paykel, Auckland, New Zealand). The setup of gas supply, humidifier (if used) and T piece were as described in previous studies ( 9 , 10 ). Transport to the neonatal unit was carried out at one site using a radiant warmer with portable power supply and humidifier attached and abdominal temperature set to 37°C on servo control (which controls warmer output by feedback from the achieved temperature).…”

“…In one study, the mean temperature of piped wall air was 23.4°C and mean relative humidity 5.4% ( 8 ). In a bench study, gases could be heated and humidified to levels recommended for patients with an artificial airway by 3 min ( 9 ). Using 50 ml water in the humidifier chamber resulted in more rapid achievement of 95% relative humidity than using larger volumes of water.…”

“…Using 50 ml water in the humidifier chamber resulted in more rapid achievement of 95% relative humidity than using larger volumes of water. It was shown that temperature and humidity of the gases fell rapidly if the power supply was discontinued ( 9 ).…”

A humidifier in the invasive mode during noninvasive respiratory support could increase condensation and thereby impair airway patency

“…Since the total amount of moisture input that is required is 44 mg H 2 O/L, the portion that is supplied by the humidifier should be 0.75 × 44 mg H 2 O/L = 33 mg H 2 O. Although the manufacturer recommends using the invasive mode during noninvasive ventilation , the aforementioned adverse effects of over‐humidification should be seriously taken into consideration, especially because misinterpretation of the standard referenced above may be applied to current clinical practice.…”

“…The results of our study may have varied if we had used other settings or modes of noninvasive support. Two studies addressed this in a number of ways, including varying the flow and making slight adaptations to the humidifier and circuit set‐up . The second limitation was that we did not quantify condensation at the different settings and, therefore, we cannot substantiate clinically assumed differences between the invasive and noninvasive humidification modes.…”