Response to “Comments on ‘Vigilance monitoring – review and practical aspects’, by Sebastian Canisius and Thomas Penzel”; Biomed Tech 2008; 53: 160–161

Abstract

First we would like to thank Dr. B. Wilhelm for her valuable and insightful comments w4x on our paper w1x. We would like to explain why we reported on a selection of methods to monitor vigilance and why we placed little emphasis on the pupillography method, as correctly indicated by Dr. Wilhelm. We carefully reviewed previous publications, including the review by the Vigilance Task Group of the German Sleep Society (DGSM), and we have cited their paper accordingly w3x. The aim of our own review w1x was to give an overview of the technical aspects of vigilance monitoring and recording. Therefore, we did not include a detailed description of several underlying models of attention as referred to in the letter by Dr. Wilhelm. For the same reason, the definition of vigilance and daytime sleepiness was only briefly described in our paper. We only mentioned aspects of the definition that have a direct impact on the usefulness of the test systems presented. Our aim to present technical aspects was furthermore somewhat biased by the fact that we were originally looking for test systems to assess vigilance and sleepiness for research purposes and in industrial applications in a continuous manner rather than in a clinical setting. We agree that this is a limitation of our paper, but this approach was intended to focus more on the technology. We know that other research groups have addressed sleepiness in drivers with more interesting test systems w2x. We tried to assess the usefulness of test systems from the point of view of research-related and industrial applications, and therefore we present slightly different results than previous review papers. We recognise that the Vigilance Task Group of the DGSM has provided substantial data on assessment of the quality of different test systems. Despite this achievement, we believe that the authors’ own experience and knowledge influence the conclusions of any new review. We agree with the main statement made by Dr. Wilhelm that the pupillographic sleepiness test (PST) is a very important system for assessing sleepiness and vigilance, and that it is frequently used in selected sleep disorder centres to assess sleepiness and vigilance in different sleep-related disorders. It has been also used on German highways to assess sleepiness in car drivers when stopping to rest or refuel. The PST investigates the tone of the sympathetic system, which correlates with sleepiness. The PST is strongly influenced by stimulants such as caffeine or nicotine. The goal of our review was to reflect systems that could potentially act as an online signal of driver vigilance during driving. A test that prevents the driver from watching the road would not be feasible and therefore we did not describe the PST extensively in our review.