Abstract
Background: Respiratory viruses such as influenza and human rhinoviruses are temperature sensitive. Rhinothermy delivers heated, humidified air to the upper airways via the nares, and by possibly inhibiting viral replication, it is proposed as a potential therapy to attenuate the severity and duration of common cold or influenza symptoms. The effect of rhinothermy on nasopharyngeal air space temperature is uncertain. The objective of this study was to investigate the effect of rhinothermy delivering 100% humidified air at 41°C on nasopharyngeal air space temperature. The hypothesis was that the mean nasopharyngeal air space temperature while nose breathing would be within 1.5°C of the device's set dew point temperature of 41°C. Methods: In this single-center nonblind nonrandomized parallel arm interventional study, nasopharyngeal air space temperature was continuously measured during delivery of 100% humidified air via a nasal high-flow device at 41°C and 30-35 L/min (rhinothermy [rNHF]) (n = 6), and at 31°C and 10 L/min ('sham' rhinothermy) (n = 6). The primary outcome measure was mean nasopharyngeal air space temperature during delivery of rNHF while nose breathing. Change in nasopharyngeal air space temperature during nose breathing and mouth breathing was compared for both interventions. Results: Twelve participants age 18-75 years were recruited. The mean (SD) nasopharyngeal air space temperature during rNHF at 41°C while nose breathing was 37.9°C (1.22) and with sham rhinothermy at 31°C was 36.8°C (0.18). There was no significant difference in nasopharyngeal air space temperature between nose and mouth breathing for both interventions combined (difference [95% CI] -0.1°C [-0.59 to 0.36], P = .60). Conclusions: The mean nasopharyngeal air space temperature during rNHF while nose breathing was not within 1.5°C of the device's set dew point temperature of 41°C. rNHF temperatures may need to be set considerably higher than the target nasopharyngeal air space temperature when investigating the effect of rhinothermy on symptom severity or duration of respiratory infections caused by viruses with temperature-dependent replication.