Purpose/Aim: To investigate the effect of rhinothermy delivering 100% humidified air at 41°C and 30 to 35L/min on nasopharyngeal airspace temperature.

Materials and Methods: In this single-centre, non-blind, non-randomized, parallel arm interventional study, nasopharyngeal airspace temperature was continuously measured during delivery of 100% humidified air via a rhinothermy device at 41°C and 30 to 35L/min (rNHF) (n=6), and at 31°C and 10L/min (‘sham’ rhinothermy) (n=6).  The primary objective was to determine whether the mean nasopharyngeal temperature during delivery of rNHF whilst nose breathing was within 1.5°C of the device’s set dew point temperature of 41°C. Change in nasopharyngeal temperature during nose breathing and mouth breathing was also compared for both interventions.

Results: 12 participants aged 18 to 75 years were recruited. The mean (SD) nasopharyngeal airspace temperature during delivery of rNHF at 41°C whilst 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 airspace temperature between nose and mouth breathing for both interventions combined (difference (95% CI) -0.1°C (-0.59 to 0.36), p=0.60).

Conclusions: The mean nasopharyngeal airspace temperature during delivery of rNHF whilst nose breathing was not within 1.5°C of the device’s set dew point temperature of 41°C. Dew point temperatures may need to be set considerably higher than the target nasopharyngeal airspace temperature when investigating the effect of rhinothermy on symptom severity or duration of respiratory tract infections caused by viruses with temperature-dependent replication.