The application of laser Doppler flowmetry in non-invasive measurement of microcirculation perfusion in the human external auditory canal and tympanic membrane

Laser Doppler flowmetry (LDF) has been used extensively over the last twenty years for measuring perfusion of the microcirculation in many clinical fields. One area that had not been studied extensively is in otology. In this study LDF was used to measure perfusion of the microcirculation in four sites of the external auditory meatus. Site 1: skin of the tragus. Site 2: skin of the cartilaginous part of the EAC. Site 3: skin of the deep bony part of the EAC. Site 4: the outer external surface of the tympanic membrane. This study was carried out in three groups: Control subjects (n=43) otitis externa patients (n=20) Myringoplasty patients (n=18). Measurements were made in a controlled environment with standard technique using a Perimed 5000 LDF instrument. Data were presented as arbitrary perfusion units (PU) set by the manufacturer. In the control group, the results showed that there was significant variation in the difference between the four sites with a descending site order of 3:2:1:4. The statistical distribution of the perfusion data showed that there was considerable variation between sites in their distribution patterns. No differences were apparent due to sex, age or core body temperature. There was no difference between right and left ear. There was no correlation between PU at each site, and intrasubject variability was not significant over two measures in n=13 subjects. In the otitis externa patients very large increases in the median PU values for all sites were seen with up to seven fold increases in perfusion being measured. The site order changed to 3:2:4:1. In the myringoplasty group no significant changes were seen pre- and post-operatively although individual patients exhibited substantial variation in individual pre- and post-site measurements. These results provide the first detailed measures of perfusion in the external auditory meatus and tympanic membrane. Whilst these results and the LDF technique are of principally experimental interest, they provide a systematic basis for the use of LDF as a clinical tool in otology.