PDF hosted at the Radboud Repository of the Radboud University Nijmegen The following full text is a publisher's version. For additional information about this publication click this link. http://hdl.handle.net/2066/148026 Please be advised that this information was generated on 2021-10-08 and may be subject to change. Ié>63 Bij^iit.:.., * й :. • THE INNER EAR AND HYPERBARIC CONDITIONS an electrophysiological and morphological study P. С LEVENDAG THE INNER EAR AND HYPERBARIC CONDITIONS an electrophysiological and morphological study Promotores: Prof. Dr. P. van den Broek Prof. Dr. J. J. Eggermont Co-referent: Dr. W. Kuijpers THE INNER EAR AND HYPERBARIC CONDITIONS an electrophysiological and morphological study PROEFSCHRIFT TER VERKRIJGING VAN DE GRAAD VAN DOCTOR IN DE GENEESKUNDE AAN DE KATHOLIEKE UNIVERSITEIT 1 E NIJMEGEN, OP GEZAG VAN DE RECTOR MAGNIFICUS PROF DR Ρ G А В WIJDEVELD VOLGENS BESLUIT VAN HET COLLEGE VAN DECANEN IN HET OPENBAAR ГЕ VERDEDIGEN OP DONDERDAG 21 MEI 1981 DES NAMIDDAGS TE 2 00 UUR PRECIES door PETER CAREL LEVENDAG geboren te Bandoeng krips repro meppel 1981 ACKNOWLEDGEMENTS Although I am not allowed to acknowledge some of the closest co-workers who advised tirelessly throughout this experimental study in the prepa­ ration of the manuscript, I am greatly indebted to many others, of whom I would very much like to mention Ing. H. Huibers because of his skilful technical assistance and Dr. P.L.M. Huygen for the data analysis and statistical work up. Also I would like to express my gratitude to Mr. J. Konings for the many fine illustrations. Credit must go to Mr. P. Spaan and co-workers of the Central Animal Labora­ tory for taking care of the animals, to Mr. P. van Wichen and Miss E. Camps of the Biological Research Laboratory of the E.N.T. department for pre­ paring light microscopical sections, and to Mrs. E.C.T. Willart of the department of Cytology and Histology for the performance of the scanning electron microscopy. 1 am very much indebted to Ir. J.P. van Oeveren and Mr. H.P. Boeyen for the development of the high pressure equipment, and to Dr. Ir. H.P. Kimmich and Mr. J.G. Spaan of the department of Physiology for the help in monito­ ring the gascompositions. I am also greatly indebted to Dr. J. Lubbers of the department of Medical Physics of the University of Groningen for his interest and the valuable discussions throughout the course of this investigation, with regard to the section on ultrasonics. I am most grateful for the finishing touch of the manuscript that was given by Dr. L.M.G. Geeraedts and Drs. F.J.B. Collens and Miss Y. Hennink. My thanks are also due to many collegues of the E.N.T. department who participated in this research project by taking over some part of the obligatory clinical workload. Last but not least I am extremely grateful to Miss I. Pernot for typing patiently the many versions of this thesis throughout the past period. This study was performed in the research section of the E.N.T. department of the University Hospital Sint Radboud, Nijmegen, the Netherlands. IV гУгг~7ове€ No experiment is ever a complete failure - it can always serve as a negative example. Murphy's Futility Factor. VI CONTENTS GENERAL INTRODUCTION 1 CHAPTER I: PHYSIOLOGICAL AND PATHOPHYSIOLOGICAL ASPECTS OF DIVING 1. Introduction 3 2. Short history of diving techniques 4 3. Diving medicine 6 a. Direct effects of pressure 6 Squeeze 6 High PresBure Nervous Syndrome 7 b. Indirect effects of pressure 8 Carbondioxide retention 9 Oxygen intoxication 9 Nitrogen narcosis 10 Décompression sickness - introduction 10 Décompression sickness - bubble detection 14 CHAPTER II: HEARING AND VESTIBULAR FUNCTION IN HYPERBARIC ENVIRONMENTS 1. Introduction 19 2. Hearing under hyperbaric conditions 22 a. Underwater environment 22 b. Hyperbaric chamber environment 23 Air 23 Helium-oxygen 24 3. Pathology of the ear related to dysbarism 25 a. Introduction 25 b. Aural barotrauma 28 1. Middle ear 28 2. Inner ear 31 Explosive route 34 Implosive route 35 VII c. Inner ear pathology and decompression sickness 37 1. Hearing disorders 37 2. Vestibular disorders 40 d. Animal experiments 42 4. Purpose of this study 42 CHAPTER III: MATERIALS AND METHODS 1. Introduction 45 2. Hyperbaric chamber conditions 45 a. Monitoring equipment 45 b. Fixation frame 46 с Profiles 47 - compression phase 50 - decompression phase: 50 profile-A 51 profile-B 52 profile-C 53 3. Ultrasonic bubble detection 53 a. Theoretical considerations 53 b. Measuring device 56 4. Implantation of electrodes 57 5. Calibration 59 a. Introduction 59 b. Condenser microphone 60 c. Earphone 63 d. Characteristics of condenser microphone and earphones 64 under increased atmospheric pressures 1. Condenser microphone 64 - compressed air 64 - helium-oxygen gasmixtures 65 2. Earphones 66 - compressed air 66 В and К earphone 66 ΌΤ-48 earphone 68 VIII - helium-oxygen gasir.ixtures: 68 В and К earphone 68 DT-48 earphone 70 6. Stimulation and recording apparatus for Electrocochleo- 72 graphy and Brainstem Electric Responses a. Introduction 72 Eleatroooohleography (ECoG) 72 Brainstem Electric Responses (BER) 73 b. Stimulation equipment 74 с Recording equipment 75 7. Morphological techniques 76 a. Light Microscopy (LM) 76 b. Scanning Electron Microscopy (SEM) 77 CHAPTER IV: RESULTS 1. Introduction 79 2. Auditory evoked responses under normobaric conditions 79 Electroaochleography (ECoG) 79 Brainstem Electric Responses (BER) 81 3. Auditory evoked responses under hyperbaric conditions 82 a. Preliminary studies 82 b. Cochlear microphonics 88 c. Compound Action Potentials and Scattergrams 92 d. Brainstem Electric Responses 104 4. Morphology of the inner ear 107 a. Nonrobaric conditions 107 b. Hyperbaric conditions 108 5. Ultrasonic surveillance of decompression sickness 122 CHAPTER V: DISCUSSION 1. Calibration of sound stimulus device 125 2. Doppler controlled dive-profiles 126 3. Effects on the middle ear 127 4. Cochlear and Brainstem Electric Responses 130 5. Morphology 131 IX SUMMARY 135 SAMENVATTING I37 REFERENCES 139 CURRICULIM VITAE 149 X GENERAL INTRODUCTION During the last two decades there has been a tremendous increase in commercial and sport diving. In the same period new methods have been developed of safely exposing humans to greater depths. In spite of the progress made in the prevention of deleterious effects of diving, still a considerable number of divers suffer from some form of diving patho­ logy. Although not life-threatening, the most common illness affecting divers and pressure workers in general has been listed as middle ear barotrauma. Also inner ear disturbances, not only after diving at great depths but also at shallow depths after short periods of time, have been reported with increasing frequency. In order to prevent and to treat many of these problems, otolaryngologists and the diving community in general must gain a better understanding of inner ear physiology and pathology in compressed gas environments. Studies of inner ear physiology and pathology under diving conditions indicate that the causes and treatment of these problems differ depending on the phase and type of diving. In addition, experiments in animals showed that hearing loss could be induced at high pressure and after the introduction of a mild degree of decompression sickness. For the data as presented in literature on inner ear pathology in humans and experimen­ tal animals, the etiology and pathology is often unclear. Although oto­ logic decompression sickness is often called upon as a separate clinical entity, many of the studies on this subject do not meet the rigid criteria necessary for hyperbaric environments. Therefore this study was undertaken in an attempt to investigate the inner ear and auditory brainstem function under hyperbaric conditions. Using rats with chronically implanted electrodes, the electrocochleogram and the brainstem electric responses could be recorded during compression and decompression under clearly defined conditions. Furthermore the function of the inner ear and brainstem were tested in a similar way after the introduction of a mild or grave form of de­ compression sickness. Finally, possible morphological changes in the inner ear structures were studied with the use of light and scanning electron microscopical techniques. CHAPTER I PHYSIOLOGICAL ΑΛΤ) PATHOPHYSIOLOGICAL ASPECTS OF DIVING 1. Introduction One of the fascinating properties of marine mammals is their ability to remain submerged for extended periods of time and to dive to considerable depths. The maximum reported breath-holding dive, or free dive, achieved by man (100 m (11 ATA) by Jacques Mayol in 1977) ·' sharply contrasts with the record depth of 1134 m (114.4 ATA) reported for the sperm whale (Hempleman, 1978). Apparently, man, going underwater, breath-holding or with diving equipment, even when pressurized in a hyperbaric chamber, is confronted with forces and physiologic effects which impose certain limits on his well-being under these circumstances. Although the dangers of diving have been popularly associated with great depths, it is important to note that both shallow breath-hold and SCUBA (Self Contained Underwater Breathing Apparatus) diving present real risks to the diver. For a good understanding of the several medical problems in diving and their management the knowledge of the obligatory features of a hyperbaric environment is a prerequisite. In addition to a short history of diving techniques, the physiology and pathophysiology frequently en­ countered in hyperbaric conditions will be described in this chapter. Special attention will be paid to the pathophysiology of decompression sickness. 1) Since in literature on diving different pressure units and depth equiva­ lents are used, for the literature review the specific units given by the authors are presented. For clarity reasons these data were converted in atmospheres absolute (ATA) and presented between brackets, as the pressure unit used in our experiments, is also atmosphere. The used pressure-conversion relationships are presented below, although it should be stated that no account has been given for the variation of the specific gravity with temperature and locality in case of calculating the depth equivalents.