Blood flow in the external auditory canal and tympanic membrane as assess by laser doppler blood flowmetry

INTRODUCTION: Procedures within the external meatus and tympanum constitute a large part of otological surgery. Successful healing after procedures on the tympanic membrane will in large part be dependent on the integrity of local blood flow. However, there appear to have been relatively few studies investigating blood flow in the external auditory meatus and tympanum in normal subjects and those with conditions requiring surgery, e.g. tympanoplasty. The aim of this study is to obtain such data using Laser Doppler Blood Flowmetry. METHOD: Control volunteers (n = 30) and patients requiring tympanoplasty (n = 20) were recruited for the study. Laser Doppler Blood Flowmetry was performed in all patients using a commercially available system (Periflux 5000, Perimed AB, Sweden) at four sites: (1) preauricular skin; (2) cartilaginous ear canal; (3) bony ear canal; and (4) tympanic membrane. Mesotympanic temperature was also measured using a Braun Infrared thermometer. Blood flow (flux) was measured as RBC density 'speed following internal calibration. RESULTS: Analysis revealed that in both the control subjects and pretympanoplasty patients, the ranking of blood flow at the sites was 3, 2, 1 and 4 (highest to lowest). Comparing matched sites, there were no significant differences between the two groups. The amplitude of flow was not found to be correlated with mesotympanic temperature. CONCLUSION: Grafts applied to repair perforations of the tympanic membrane are likely to obtain the majority of their blood supply from the bony external auditory meatus rather than that tympanic membrane. Further studies are ongoing to define local blood flow patterns in order to optimize the results of tympanoplasty.