A non-invasive method of demonstrating the nasal cycle using flexible liquid crystal thermography

The relationship between air flow at 38 degrees C and area colour change on a flexible liquid crystal film was found to be virtually linear between the values of 1 and 31 min-1 cm-2. This value of flow per unit area corresponded to values expected at the level of the nostril during quiet breathing. A series of 6 subjects were asked to breathe over a flexible liquid crystal film regularly during the day and the area of colour change produced by flow from each nostril was examined. Four subjects showed a regular change in relative flow through each nostril whilst 2 subjects showed a constant flow through each nostril. This simple and non-invasive technique provides a method of examining the nasal cycle in adults and children in health and disease.