Using heated humidified high-flow nasal cannulas for premature infants may result in an underestimated amount of water reaching the airways

Aim Condensation often occurs when providing humidified respiratory support. We examined conditions conducive to excess water formation in heated humified high-flow nasal cannula (HHHFNC). Methods An HHHFNC device, at 35 or 37 degrees C, was attached with a nasal cannula to a reservoir and tested in five ambient conditions and flows. For Group A, tubing and collection bottle remained at room temperature (23 degrees C). Group B, tubing and reservoir remained inside an incubator (31 degrees C). Group C, tubing and reservoir remained at 33 degrees C. In Group D, the HHHFNC was set to 35 degrees C, the reservoir remained at 33 degrees C, and the nasal cannula and tubing remained at 23 degrees C. Group E, same as D, with HHHFNC at 37 degrees C. Results The largest amounts of collected water were in groups A and E. Both had highest temperature differences. Median (range) was 4.9 degrees C (4.1-6.9) and 4.0 degrees C, collecting 38.4 (26.4-50.4) and 26.4 (19.2-50.4) ml/24 h, respectively. Smallest amounts of water were seen with lower temperature differences as in groups B, C, and D with 2.7 (1.9-4.7), 1.6 (1.2-2.1), and 2.0 degrees C with 8.4 (0.0-33.6), 2.4 (0.0-14.4), and 9.6 (4.8-16.8) ml/24 h, respectively. Conclusion HHHFNC devices may produce clinically significant amounts of water reaching the upper airways. This may be prevented with appropriate device set-up.