Laser doppler fluxmetry and the larynx

Abstract

Problem: The study has three aims: (1) to determine whether a laser Doppler flux meter is a reliable and reproducible measure of laryngeal blood flux. (2) to determine whether blood flux, as measured, correlates with microvessel density as a less invasive, reliable method of quantifying angiogenesis. (3) to measure the effect of sequential division of nerves and vessels on laryngeal blood flow using the aforementioned specially designed laser Doppler probe. Methods: Using a laser Doppler monitor we measured the response to a known vasoconstrictor in the animal experiments. Reproducibility was tested and LDF readings obtained were compared to conventionally obtained quantification of microvessel density. Patients undergoing laryngectomies had continuous LDF measurements and the effect of sequential division of nerves and vessels was assessed. Results: In an animal model we demonstrated that the laser Doppler flux meter was capable of detecting change when one was expected ( P = 0.01). We also demonstrated good reproducibility of laser Doppler measurements in laryngeal mucosa both in the human and animal models (correlation coefficients of 0.956 and 0.947, respectively; with P = 0.01). Division of the superior laryngeal nerve caused a marked drop in ipsilateral laryngeal blood flux. Laser Doppler fluxmetry did not correlate with micro-vessel density as measured conventionally using immuno-histochemistry. Conclusion: Laser Doppler fluxmetry is a reliable and reproducible method of estimating blood flux in the larynx. We were able to show that division of the superior laryngeal nerve causes a significant fall in mucosal blood flux and therefore should be preserved whenever possible. However, it would seem that blood flux and microvessel density were not directly comparable parameters. Significance: It would appear from our study that LDF cannot be directly used to quantify angiogenesis. An improved understanding of laryngeal innervation and blood supply will contribute to the complex knowledge base that underpins the future of laryngeal transplantation. Support: This study was made possible by funds kindly donated from the estate of the late Thomas Green Esquire, and managed by the Medway Head and Neck Cancer Research Fund.