Table Of ContentThe
NeuroscieNces
aNd The
PracTice of aviaTioN MediciNe
Experience is never limited, and it is never complete;
it is an immense sensibility, a kind of huge spider web of the finest silken
threads suspended in the chamber of consciousness, and catching every
air-borne particle in its tissue.
The art of fiction
Henry James
(1843–1916)
dedication
Centre of Human and Aerospace Physiological Sciences
School of Biomedical Sciences
King’s College London
The
Neurosciences
and the
Practice of aviation Medicine
edited by
aNThoNy N. NicholsoN
Readers are advised to consult the most recent publications of Pharmaceutical Companies before prescribing any
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administration.
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Contents
v
List of Figures vii
List of Tables xiii
Foreword by The Rt Hon. the Lord Owen CH MA MB BChir FRCP xv
Preface xvii
Authors and Affiliations xix
1 Wakefulness, Awareness and Consciousness 1
Anthony N. Nicholson
2 Circadian System and Diurnal Activity 15
Russell G. Foster
3 Aircrew and Alertness 35
Anthony N. Nicholson and Michael B. Spencer
4 Spatial Orientation and Disorientation 55
J. R. Rollin Stott
5 Cerebral Circulation and Gravitational Stress 93
Anthony N. Nicholson
6 Oxygen Delivery and Acute Hypoxia: Physiological and Clinical
Considerations 103
Jane Ward
7 Hypobaric Hypoxia: Adaptation and Acclimatization 163
John H. Coote and James S. Milledge
8 Profound Hypoxia: Extreme Altitude and Space 201
Anthony N. Nicholson
9 The Neurological Examination: Aeromedical Considerations 215
Michael D. O’Brien
10 Investigation of Sleep and Wakefulness in Aircrew 219
Anthony N. Nicholson
vi The NeuroscieNces aNd The PracTice of aviaTioN MediciNe
11 Excessive Daytime Sleepiness: Clinical Considerations 231
Thomas C. Britton, Andrew R. C. Cummin and Anthony N. Nicholson
12 The Diagnosis of Epilepsy 255
Matthew C. Walker
13 Syncope: Physiology, Pathophysiology and Aeromedical
Implications 275
David A. Low and Christopher J. Mathias
14 Hypoglycaemia and Hypoglycaemia Awareness 291
Simon R. Heller
15 Headache 325
Thomas C. Britton
16 Traumatic Brain Injury and Aeromedical Licensing 347
Garth S. Cruickshank
17 Neuro-Ophthalmology 377
Gordon T. Plant
18 Vestibular and Related Oculomotor Disorders 395
Nicholas J. Cutfield and Adolfo M. Bronstein
19 Disorders of Hearing 421
Linda M. Luxon and Ronald Hinchcliffe
Appendix I A Bibliography of Case Reports of Neurological Disorders in Aircrew 475
Appendix II International Standards for Hearing Measurements, Aircraft Noise
and Vibration Control 479
Appendix III World Health Organization Descriptors of Hearing Impairment 483
Index 485
List of figures
v
1.1 Schematic depiction of the studies by Bremer (1935, 1938) and
Moruzzi and Magoun (1949) 3
1.2 Minnie 4
2.1 Generalized phase response curve of the circadian system 18
2.2 Schematic depiction of the key components of the mammalian
circadian system 19
2.3 Diagram illustrating the key components in the generation and
maintenance of sleep 22
2.4 Mammalian molecular clock 24
2.5 Cellular structure of the retina 27
3.1 Percentage of aircrew sleeping at different times during the day
after a 12-hour transition 36
3.2 Sleep patterns (hypnogram) after a westward flight with a time-
zone change of five hours 37
3.3 Sleep patterns (hypnogram) after an eastward flight with a time-
zone change of five hours 37
3.4 Duration of sleep in hours and wake-up time prior to the start of
duty 38
3.5 Duration of sleep in hours and wake-up time after the end of duty 39
3.6 Trends in sleep duration (hours) in a bunk related to the start of
the rest period 40
3.7 Circadian rhythms of aircrew on return from a polar flight 41
3.8 Alertness ratings during flights 43
3.9 Trends fitted to alertness levels as a function of time of day at
the start of duty 44
3.10 Alertness on outward and return flights after one- and two-day
layovers 44
3.11 Alertness levels on flights with double crews 45
3.12 Trends in alertness at top of descent related to time of day and
time on duty 45
3.13 Alertness related to time of day and time since sleep 46
3.14 Schematic representation of a model with application to aircrew 47
3.15 Duration of sleep (hours) related to the time of going to bed 48
4.1 Pattern of activity in a) a place cell in the hippocampus and b) a
grid cell in the entorhinal cortex 57
viii The NeuroscieNces aNd The PracTice of aviaTioN MediciNe
4.2 Firing rate of a typical head direction cell from the anterodorsal
thalamic nucleus plotted against head orientation relative to the
environment 58
4.3 Human inner ear 60
4.4 Diagram to illustrate the function of a semicircular canal 62
4.5 Response of the semicircular canal to sustained angular velocity 63
4.6 Structure of the otolith organ 65
4.7 Frequency response of the vestibular system to angular oscillation
about a vertical axis in the dark as measured by the induced
angular eye movements 66
4.8 The coordinated turn 74
4.9 Equivalent effect of tilt and linear acceleration on the otolith organ 77
4.10 Somatogravic effect during acceleration and deceleration in the
line of flight 77
4.11 The leans 79
4.12 The cross-coupled (Coriolis) stimulus: Response of an idealized
canal in the transverse plane of the head 82
5.1 Optic tract discharges (upper traces) and electroretinograms
(lower traces) of the cat induced by flashes of light during
hypotension 97
5.2 Cortical responses of the cat elicited by stimulation of the optic
tract during hypotension 98
5.3 Cortical responses of the cat evoked by stimulation of the optic
tract during a positive acceleration (+3 Gz) 99
6.1 Effect of altitude on barometric pressure 104
6.2 a) Time course of the rise in PO along the pulmonary capillary
2
in a healthy person at sea level (solid line) and b) Time course of
the rise in PO along the pulmonary capillary in a healthy person
2
at high altitude 107
6.3 Oxygen–haemoglobin dissociation curve 108
6.4 Oxygen–haemoglobin dissociation curve 114
6.5 Carbon dioxide dissociation curves for whole blood 120
6.6 Effect on PCO (top) and PO (lower) of changing ventilation
2 2
with metabolic rate constant 121
6.7 Carbon dioxide response curve 125
6.8 Ventilatory response to changing arterial PO 126
2
6.9 Effects of acute exposure to high altitude on alveolar PO and
2
PCO 129
2
7.1 Oxygen sensing in the carotid body 166
7.2 Hypoxia-inducible factor pathway 168
7.3 Key sites in ventilatory control 169
7.4 Transport of oxygen from inspired air to cells 170
7.5 Chemoreceptor drive with decreasing altitude 170
7.6 Changes in alveolar oxygen tension and carbon dioxide at
increasing altitude 171
7.7 Ventilatory acclimatization 171
7.8 Haemoglobin–oxygen association and oxygen delivery at altitude 172
7.9 Oxygen delivery in the brain 175
lisT of figures ix
7.10 Effect of oxygen partial pressure on rate of different oxygen-
consuming reactions 177
7.11 Hypnograms showing effect of altitude on sleep structure 182
8.1 Calculated profiles of the cabin altitude during a decompression
in a transport aircraft operating at 60,000 feet with an emergency
descent rate of 5,000 feet per minute 203
8.2 Distribution and intensity (as indicated by shading) of neuronal
loss in the baboon (Papio cynocephalus) that exhibited decorticate
behaviour 205
8.3 Performance in the monkey (Macaca mulatta) on various tasks after
a decompression to 37,500 feet that involved permanent brain
damage 206
8.4 Distribution and intensity (as indicated by shading) of neuronal
loss that was predominantly cortical 207
8.5 Distribution and intensity (as indicated by shading) of neuronal
loss that was predominantly subcortical 207
8.6 Calculated decompression profile (hatched) in a supersonic
transport aircraft with an emergency descent rate of 7,000 feet
per minute with a defect in the cabin wall of 6 inch diameter 211
8.7 Profiles of decompressions that relate to brain damage 211
10.1 Awake activity 222
10.2 Stage 2: The onset of sleep 222
10.3 Slow-wave sleep 223
10.4 Rapid eye movement sleep 223
10.5 Hypnogram 224
10.6 a) Stage 2 sleep immediately preceding the apnoea and b) The
apnoea with an arousal 225
10.7 Periodic leg movements during stage 2 sleep with an arousal 226
10.8 Daytime sleep latency 226
10.9 Mean daytime sleep latencies 227
12.1 Incidence and prevalence of epilepsy in the United Kingdom 256
12.2 Examples of benign EEG patterns a) 6 Hz spike-wave burst and
b) 14 and 6 Hz positive bursts 266
12.3 Probability of epilepsy given prior probability after epileptiform
abnormality on EEG 269
12.4 Probability of no epilepsy given prior probability and how
probability is modified by no epileptiform abnormality on EEG 270
13.1 Scheme outlining autonomic neural pathways that control arterial
blood pressure 276
13.2 Outline of the major transmitters at autonomic ganglia and post-
ganglionic sites supplied by the sympathetic and parasympathetic
efferent pathways 277
13.3 Average cardiovascular responses to standing in healthy aged
matched control subjects and in patients with significant
autonomic dysfunction during the first and the last 60 seconds of
five minutes of standing (black bar) 278
