P3.083: Effect of Power Outages on Relative Humidity for Infants on Respiratory Support

Background: Infants on respiratory support that receive unconditioned air are susceptible to airway injury, decreased respiratory efficiency, and a heightened risk to infection. Heated humidifiers can be used to improve the quality of the delivered air. Healthcare facilities in low to middle-income countries (LMIC) are at greater risk of power disruptions. This study aims to determine the effect of power outages on delivered relative humidity (RH).

Methods: Heated and humidified oxygen was delivered to a simulated patient lung instrumented with temperature and RH sensors (DHT22) using a BC161-10 (Fisher Paykel) bubble continuous positive airway pressure (bCPAP) system. The test lung was maintained at a physiologic temperature in an infant Isolette 8000 incubator (Dräger). Circuit pressure was set to 5 cm H2O and flow rates used were 3, 6 and 9 LPM. Power outage lengths were 5, 30, and 60 minutes. An indefinite power outage was also investigated.

Results: A 5 minute power outage did not affect delivered RH. For a 30 minute outage, RH decreased to an average (SD) of 67% (0.5). Flow rate did not affect the minimum RH for both the 5 and 30 min power outages. During a 60 minute power outage, RH decreased to 68, 61, and 49% for 3, 6, and 9 LPM respectively. Indefinite power outages at 95% and 100% initial RH reached steady state at 700 and 500 min in that order. An average (SD) steady state RH of 39% (8) was reached. A passive bubbler humidifier has an average (SD) RH of 44% (4). (John et al., 2023)

Conclusion: A 5 min power outage is unlikely to affect the patient. Literature results suggest that repeated 30 and 60 min power disruptions may adversely affect the patient, although more investigation is required. To preserve the RH during 60 min power outages, low flow rates should be used. In power limited facilities, a bubble through humidifier will perform comparably to a passover humidifier.