What is optical rhinometry ?

In the course of a nasal congestion, for instance during an allergig reaction, the nasal mucosa around the conchea will be flooded with arterial blood. The Rhinolux is able to continuously measure that increase in blood volume during the swelling process. Therefore an optical sensor is used that is integrated in a spectacle frame, which can be conveniently weared by the patient. The optical sensor transilluminates the nasal tissue with infrared light. This light deeply penetrates the nasal tissue, in particular the structures of the lower and middle conchea. There, the light is absorbed by hemoglobine whereby the strength of absorption is proportional to the blood respectively tissue volume. Due to appropriate selection of the light wavelength the absorption signal is independent of blood oxygenation. Furthermore, the light is absolutely harmless to the patient.

Only a very small portion of the measurement light reaches the detector on the opposite side of the nose. This wanted signal is separated by application of a highly sensitive and patented optical sensor technology in the Rhinolux and displayed as a continuous swelling curve on the PC monitor.





Anatomy of the nasal cavities and location of the measurement field in optical rhinometry.



Swelling curve for a positive nasal reaction on stinging-nettle pollen.


Since the thickness of the nasal tissue strongly varies intra- and interindividually a differential measurement approach is used in optical rhinometry. First, a baseline of light intensity is recorded for a recommended inital time interval of 2 minutes. After that an accoustic signal from the Rhinolux indicated that the provocation substance can be applied. From then on the optical absorption value of the tissue is calculated relative to the baseline value and displayed.

The figure above shows a typical Rhinolux result of a positive nasal swelling reaction on stinging-nettle pollen. The swelling curve has a characteristic shape. After provocation the curve still moves about the baseline value (ΔE = 0). Then, after a patient and allergene specific latency time T1 the curve climbes continuously up due to increasing blood volume and thus infrared absorption in the nasal tissue. After the time T2 has passed the swelling process is finished. The overall increase in optical absorption is a quantitative measure for the swelling strength. In this case it is ΔE = 0.52 optical densities. Results of clinical studies showed that a value of at least 0.2 O.D. indicates a swelling reaction, whereas unspecific blood volume fluctuation are well below ±0.1 optical densities.

Publications:

E. G. Wüstenberg, K.-B. Hüttenbrink, B. Hauswald, U. Hampel, E. Schleicher, "Die optische Rhinometrie - Kontinuierliche, direkte Messung der Schwellung der Nasenschleimhaut bei Allergenprovokation", HNO, vol. 52, 798-806, 2004.

U. Hampel, E. Schleicher, E. G. Wüstenberg, K.-B. Hüttenbrink, "Optical Measurement of Nasal Swellings", IEEE Transactions on Biomedical Engineering, vol. 51, pp. 1673, 2004.