Comparative Efficacy of Humidifiers for Noninvasive Infant Respiratory Support

Background: Delivery of cold, dry air to infants while supporting their breathing can irritate and damage their sensitive nares. In high resource settings, electric heated humidifiers are used to mitigate this problem. In many resource-constrained settings, passive non-electric bubbling humidifiers are instead used. We here compare the efficacy of conventional electric heated humidification, custom-built low cost heated humidification, passive non-electric bubbling humidification and a control (no humidification). Methods: In a hospital patient room (Temperature 22C, humidity 50%), the temperature and humidity delivered to a simulated patient lung via a BC161-10 Fisher Paykel bubble CPAP system were measured with conventional electric heated humidification, low cost custom-built heated humidification, passive bubbling humidification and no humidification. (Delivered CPAP: 5 cm H2O; flow rate varied from 4 to 8 LPM in 2 LPM increments.) Results: As flow rate was varied from 4 - 8 LPM, delivered relative humidity (standard deviation) with each humidifier was as follows: control 10% (3.6%), passive bubbler 44% (3.7%), custom-built humidifier 67% (1.7%), electric heated humidifier 91% (0.86%). Delivered temperature with the electric heated humidifier was 38C (0.21C) vs. 33C for all other setups. Conclusions: Conventional electric heating humidification is more effective than passive bubbling humidification, and the custom-built low cost humidifier provides an intermediate degree of humidification. Through further improvement of this concept with a heated inspiratory circuit and sensor based control of the heating element, an effective yet low cost solution heating humidification could be developed.