PT - JOURNAL ARTICLE AU - Yusuke Chikata AU - Kazuaki Unai AU - Masayo Izawa AU - Nao Okuda AU - Jun Oto AU - Masaji Nishimura TI - Inspiratory Tube Condensation During High-Flow Nasal Cannula Therapy: A Bench Study AID - 10.4187/respcare.04331 DP - 2015 Dec 08 TA - Respiratory Care PG - respcare.04331 4099 - http://rc.rcjournal.com/content/early/2015/12/08/respcare.04331.short 4100 - http://rc.rcjournal.com/content/early/2015/12/08/respcare.04331.full AB - BACKGROUND: High-flow nasal cannula (HFNC) therapy provides better humidification than conventional oxygen therapy. To allay loss of vapor as condensation, a servo-controlled heating wire is incorporated in the inspiratory tube, but condensation is not completely avoidable. We investigated factors that might affect condensation: thermal characteristics of the inspiratory tube, HFNC flow, and ambient temperature.METHODS: We evaluated 2 types of HFNC tubes, SLH Flex 22-mm single tube and RT202. Both tubes were connected to a heated humidifier with water reservoir. HFNC flow was set at 20, 40, and 60 L/min, and FIO2 was set at 0.21. Air conditioning was used maintain ambient temperature at close to either 20 or 25°C. We weighed the tubes on a digital scale before (0 h) and at 3, 6, and 24 h after, turning on the heated humidifier, and calculated the amount of condensation by simple subtraction. The amount of distilled water used during 24 h was also recorded.RESULTS: At 25°C, there was little condensation, but at 20°C and HFNC flow of 20, 40, and 60 L/min for 24 h, the amount of condensation with the SLH was 50.2 ± 10.7, 44.3 ± 17.7, and 56.6 ± 13.9 mg, and the amount with the RT202 was 96.0 ± 35.1, 72.8 ± 8.2, and 64.9 ± 0.8 mg. When ambient temperature was set to 20°C, condensation with the RT202 was statistically significantly greater than with the SLH at all flow settings (P < .001).CONCLUSIONS: Ambient temperature statistically significantly influenced the amount of condensation in the tubes.