Factors affecting pain intensity in a pain model based upon tonic intranasal stimulation in humans

Abstract.

Objective: The present publication describes an inflammatory pain model based on an air-stream introduced in the nasal cavity. The aim of the present study was to investigate the influence of flow, humidity and temperature of the air-stream on the intensity of the evoked pain sensations.¶Methods: Six healthy volunteers participated in the study. Pain was produced by a stream of air introduced to the nasal cavity at different flow rates (5, 6 and 8 l/min), humidity (20 and 80% relative humidity) and temperature (16, 24, and 32 °C). The evoked pain was quantified by means of visual analogue scales.¶Results: The air-stream induced a dull and burning painful sensation. The intensity of pain was found to be related to the air-stream's humidity and temperature. Specifically, a dry air-stream (20% relative humidity) evoked significantly stronger pain than a humidified air-stream (80% relative humidity). Pain was significantly greater at a temperature of 32 °C than at 24° and 16 °C, while the temperatures of 16 and 24 °C did not differ with respect to pain intensity. In contrast, a tendency towards stronger pain produced by a flow of 8 l compared to that with 5 l could not be statistically justified within the present study.¶Conclusions: The non-invasive pain stimulus was found to be easily applicable and the evoked pain sensation could be modified by variation of humidity and temperature of the air-stream.