RESEARCH REPORT 017 - Health and Safety Executive · RESEARCH REPORT 017. HSE Health & Safety...

Neuro-behavioural impairment afterneurological decompression illness

Prepared by Angus Hickish for the Health and Safety Executive 2002

RESEARCH REPORT 017

HSE Health & Safety

Executive

Neuro-behavioural impairment afterneurological decompression illness

AE Hickish, GW Hickish, J Harvey, TJR Francis and M Mullee

The New Medical Centre Ringwood Road

Bransgore Nr Christchurch

Dorset BH23 8AD

The neuropsychological performance of a group of 51 divers was evaluated using a computer administered psychometric test battery and the General Health Questionnaire. All had suffered a single episode of neurological decompression illness between six and thirty nine months earlier. Their results were compared with those from an individually matched group of divers who had never suffered decompression illness and a second similarly matched group who had never dived. No significant difference was found between the performances of the three groups. The findings of this study suggest that the outlook for recovery (or preservation) of cognitive function following neurological decompression illness is good..

This report and the work it describes were funded by the Health and Safety Executive (HSE) Its contents, including any opinions and / or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

HSE BOOKS

© Crown copyright 2002

First published 2002

ISBN 0 7176 2559 1

All rights reserved. No part of this publication may bereproduced, stored in a retrieval system, or transmitted inany form or by any means (electronic, mechanical,photocopying, recording or otherwise) without the priorwritten permission of the copyright owner.

Applications for reproduction should be made in writing to: Licensing Division, Her Majesty's Stationery Office, St Clements House, 2-16 Colegate, Norwich NR3 1BQ or by e-mail to [email protected]

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CONTENTS PAGE No.

1. INTRODUCTION 1

1.1 OBJECTIVE 1 1.2 BACKGROUND 1

2. MATERIALS AND METHODS 3

2.1 PILOT STUDY 3 2.2 SUBJECT GROUP 4 2.3 CONTROL GROUP (DIVERS) 4 2.4 CONTROL GROUP (NON-DIVERS) 5 2.5 EVALUATION 5 2.6 PROCEDURE 6

3. RESULTS 7 3.1 DESCRIPTIVE DATA (INCLUDING NART SCORES) 7 3.2 PSYCHOMETRIC TEST DATA (NES RESULTS) 10 3.3 GHQ RESULTS 17 3.4 ANALYSIS 17

4. DISCUSSION 19

5. CONCLUSIONS 21

6. REFERENCES 23

7. APPENDIX 25 ACKNOWLEDGEMENTS TABLE 1 (MEDICAL DETAILS OF SUBJECT GROUP) TABLE 2 (MEDICAL DETAILS OF DIVER CONTROL GROUP) TABLE 3 (MEDICAL DETAILS OF NON-DIVER CONTROL GROUP) TABLE 4 (DETAILS OF SUBJECTS’ DECOMPRESSION ILLNESS) TABLE 5 (SUBJECTS’ SELF-EVALUATION OF PSYCHOLOGICAL

SYMPTOMS) TABLE 6 (MISSING DATA) DESCRIPTION OF COGNITIVE FUNCTION TESTS

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1) INTRODUCTION

1.1 OBJECTIVE.

This report describes a study attempting to identify neuropsychological impairment in a group of recreational divers who have had an apparently satisfactory outcome from treatment for neurological Decompression Illness (DCI).

1.2 BACKGROUND

In 1959 Rozsahegyi (1,2) drew attention to long term neurological and psychological disabilities amongst a group of compressed air workers who had been treated for DCI acquired whilst building the Budapest Metro. Over a half the subjects were reported to display clinical features of “chronic encephalomyelopathy, vegetative neurosis, or psychosomatic symptoms”. In 1976, Peters, Levin and Kelly (3) undertook a detailed assessment of cognitive and neurological function in a group of 20 divers with a history of neurological DCI and described a high incidence of abnormality. Both these studies challenged the belief - widely held at the time - that neurological DCI was primarily a condition of the spinal cord. Other studies have revealed similar findings (4,5,6). These, together with studies of the radiological (7), electrophysiological (8,9) and histological findings (10) associated with DCI have led to the present day model of a multi-focal disease from which no part of the central nervous system is immune. Moreover it has become clear that the standard bed-side neurological examination is at best a rough guide to the site and extent of the disease process.

Although both Rozsahegyi and Peters et al reported an alarmingly high incidence of neurobehavioural abnormalities, the majority of their subjects had persisting deficits as judged by a standard clinical neurological examination (1,2,3,4), and thus could not be described as having made a complete recovery. Data concerning the incidence of neurobehavioural morbidity amongst individuals who appear to have made an apparently full recovery from neurological DCI are scanty. Nevertheless there is concern that significant morbidity goes unrecognised and there are many anecdotes (11) of divers suffering a variety of psychological problems, including suicide, despite appearing to have fully recovered.

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2) MATERIALS AND METHODS

The neurobehavioural performance of three groups was compared.

1. Subject group. Recreational divers who had a history of neurological DCI from which they had made an apparent full recovery.

2. Control group (divers). Individually matched recreational divers with no history of DCI.

3. Control group (non-divers). Individually matched patients from a General Practice age/sex register who had never dived.

Individuals from each group undertook a common evaluation consisting of: Enquiry into - Medical history.

- Educational history. - Occupational history.

-Alcohol and tobacco use. -Computer experience. -Diving history (subjects and diver controls).

National Adult Reading Test. Completion of General Health Questionnaire. Neurological examination. Computer administered psychometric test battery.

2.1 PILOT STUDY

The study was preceded by a pilot designed to test feasibility, method and procedures. Ten subjects and individually matched controls were studied. Analysis of their data was used to calculate the number of subjects that would be required to produce statistically valid results (between fifty and one hundred). Procedural changes were made as a result of experience acquired during the pilot but none were made to the methodology employed.

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2.2 SUBJECT GROUP (Tables 1 and 4)

Fifty-one subjects participated; all had suffered neurological DCI during recreational dives whilst breathing compressed air. All but one had been treated at either Poole Hyperbaric Centre (PHC) (situated on the south coast of England) or the hyperbaric chamber of the Diving Diseases Research Centre (DDRC) (situated at Plymouth in the south west of England). The exception had been referred for follow up to PHC after initial treatment at a facility abroad. Potential subjects were identified from the two Centres’ databases and invited by telephone to participate in the study. No attempt was made to select subjects on the basis of the severity of the illness they had suffered. Ease of travel, as perceived by the researchers, was the only factor that determined whether or not an invitation was made. Only three divers declined to participate in the study, citing logistical reasons for doing so. Two more agreed to participate but it proved not possible to arrange an appropriate time for the assessment. There did not appear to be any evidence that the subject group was selfselecting.

All subjects were believed to have made a full recovery. However, at assessment, when asked “ Have you got over your bend?” a number volunteered symptoms. Several had minor sensory disturbances (nine). One considered that he had become more emotional since his illness. One volunteered diplopia when fatigued, one impotence (also sensory disturbance of his legs), one impaired balance in the dark, and one declared concerns about his short-term memory. Further psychological symptoms in a number of other subjects were elicited from the questionnaire. (table 5)

Six subjects had subsequently been investigated for patent foramen ovale (investigations in two being positive and four negative).

Subjects were assessed between six and thirty nine months after the episode of DCI (mean interval being twelve months).

Two divers were recruited but subsequently excluded when it was discovered that they were taking psychotropic medication.

2.3 CONTROL GROUP (DIVERS) (Table 2)

For each subject a control was sought of the same sex and similar age who also matched, as closely as possible his or her: - Diving experience (in terms number, depth of dives and length of diving career). - Educational attainment. - Alcohol habit. - Smoking habit.

A database of the diving experience and personal details of two hundred and fifty eight recreational divers living in the Wessex region was compiled during the early stages of the study. This was achieved by circulating the membership of diving clubs in the area with information about the study and appeals for individuals to submit

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personal details. From this data base a control for each subject was selected. No control had suffered DCI of any form.

Suitable matches could not be found for two subjects who had both logged a very large number of dives during their recreational careers (subjects 156 and 159).

2.4 CONTROL GROUP (NON-DIVERS) (Table 3)

Using the computerised records of a general practice of eight thousand five hundred patients a second control was found for each subject who also matched in terms of sex, age, educational attainment, alcohol and smoking habit but who had never dived.

Suitable matches were found for all subjects.

2.5 EVALUATION

Subjects and individuals from both controls groups underwent a common evaluation consisting of:

- Questionnaire enquiries into: medical history, computer experience, level of education, diving experience (length of diving career. number of dives undertaken. frequency of dives to greater than thirty meters), tobacco use and alcohol use. All participants were asked to declare a history of alcohol or substance dependency and recreational drug use. Subjects were also asked to self evaluate and report increased forgetfulness, impaired concentration, irritability, anxiety, depression and clumsiness since the episode of DCI.

- General Health Questionnaire (GHQ). This questionnaire is a wellestablished screening device for psychiatric morbidity (12). The sixty-item version of the GHQ was used.

- The National Adult Reading Test (NART). This test is a wellestablished measure of pre-morbid ability and would appear to be resistant to central nervous system damage (13).

- A series of 6 computer administered psychological tests selected from the Neurobehavioural Evaluation System (NES).(14). Finger tapping (FT), Symbol digit substitution (SDS), Serial digit learning (SDL), Paired associate learning (PAL), Colour word (CW), Switch attention (SA). These tests were chosen to evaluate a range of cognitive function. A customised Toshiba Satellite Pro 400 CS lap top computer was used to administer the tests. (See appendix for description of tests).

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- Neurological examination (of the detail that might be expected at a hospital medical in-patient clerking examination).

2.6 PROCEDURE

Subjects were tested at either DDRC in Plymouth or Bransgore New Medical Centre (situated near PHC). Participants from both control groups were tested at Bransgore New Medical Centre. At both sites a quiet, comfortable and appropriately illuminated room was used. Participants attended one at a time and appointments were generally made at least a week in advance choosing a time when the individual could be as relaxed and rested as possible. Alcohol consumption during the forty-eight hours before testing was discouraged. After a period of relaxation and the opportunity for refreshment participants completed the questionnaires and then undertook the psychometric tests. They then underwent a neurological examination. The procedure was supervised by a single individual (JH), a State Registered Nurse who had been trained for the purpose of this study at the Department of Occupational Medicine of Birmingham University. The same individual was responsible for recruiting participants and for arranging appointments and re-imbursement of their expenses.

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3) RESULTS

Comparisons were made between the three groups of:

- Descriptive data: Age, diving experience, alcohol consumption, tobacco use, pre-morbid ability (NART score).

- Outcome data: NES test scores, GHQ results.

3.1 DESCRIPTIVE DATA

Comparison of the three groups: Subjects (S) Diver Controls (DC) Non-Diver Controls (NDC)

Valid N Mean Std Median Min- Maxi-Deviatn mum Mum

Age S 51 40.82 10.21 40.21 21.74 72.30 (years) DC 49 41.74 10.60 39.45 25.27 74.05

NDC 51 40.94 10.30 40.97 22.28 76.01

Units of S 51 11 10 9 1 50 alcohol DC 49 14 11 11 1 50 weekly NDC 51 11 13 8 1 85

No. of S 51 769 1324 350 8 8500 dives in DC 49 608 926 319 10 5000 Career NDC

No. of S 51 128 158 80 0 1000 dives DC 49 105 99 75 0 600 past NDC

3 years

No of S 51 12.04 9.94 9.0 1.0 38.0 years as DC 49 13.51 11.05 9.0 1.0 46.0

Diver NDC

7

Count Col. %

Proportion of dives to more

S Group total Less than one third

51 27

100% 52.9%

than 30M Between one and two thirds 19 37.3% More than two thirds 5 9.8%

DC Group total Less than one third

49 26

100% 53.1%

Between one and two thirds 20 40.8% More than two thirds 3 6.1%

Smoking Habit S Group total Current smoker

51 6

100% 11.8%

Ex-smoker 16 31.4% Never smoked 29 56.9%

DC Group total Current smoker

49 4

100% 8.2%


NDC Group total Current smoker

51 5

100% 9.8%


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NART SCORES

Valid N Mean Std Median Mini- Maxi-Deviat- mum mum

ion Predicted Performance IQ 49 115 7 116 95 127 Subjects

Predicted Performance IQ 46 114 6 114 99 126 Diver controls

Predicted Performance IQ 51 114 5 114 102 127 Non-diver controls

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3.2 OUTCOME DATA

RESULTS OF NES TEST SCORES

FINGER TAPPING

Number of finger taps (using preferred hand) 1 N Median Interquartile

range Median

difference Z p

Subjects 49 179.00 163.00 to 192.00 -14 -1.82 0.07

Diver controls

49 193.00 174.50 to 203.50

Subjects 51 179.00 164.00 to 194.00 -5 -0.77 0.44

Non diver controls

51 184.00 163.00 to 201.00

Number of finger taps (using preferred hand) 2 Subjects 49 179.00 171.00 to 195.00

-5 -1.35 0.18 Diver controls

49 184.00 173.00 to 199.00

Subjects 51 179.00 171.00 to 197.00 -6 -1.52 0.13

Non-diver controls

51 185.00 173.00 to 200.00

Number of finger taps (using non-preferred hand) Subjects 49 161.00 148.00 to 177.50


49 168.00 153.00 to 184.00

Subjects 51 165.00 148.00 to 177.00 -3 -0.78 0.43

Non-diver controls

51 168.00 156.00 to 177.00

Number of finger taps (using alternating hands) Subjects 49 158.00 133.50 to 195.00


49 159.00 121.00 to 192.50

Subjects 51 158.00 131.00 to 194.00 1 -0.34 0.73

Non-diver controls

51 157.00 128.00 to 188.00

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Finger tapping errors (preferred hand) 1 – frequency of people

No errors One or more errors Subjects 51 (100%) 0

Diver controls 49 (100%) 0

Non-diver controls 51 (100%) 0

Finger tapping errors (preferred hand) 2 – frequency of people Subjects 50 (98%) 1 (2%)



Finger tapping errors (non-preferred hand) – frequency of people Subjects 51 (100%) 0



Finger tapping errors (alternating hands) N Median Interquartile

range Median

difference Z p

Subjects 49 31.00 14.50 to 42.00 -2 -1.30 0.19

Diver controls

49 33.00 22.50 to 42.00

Subjects 51 31.00 15.00 to 42.00 2 -0.20 0.84

Non-diver controls

51 29.00 16.00 to 41.00

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PAIRED ASSOCIATE LEARNING

Trial 1 (number of correct responses) N Median Interquartile

range Median

difference Z P

Subjects 47 3.00 1.00 to 5.00 0 -0.36 0.72

Diver controls

47 3.00 2.00 to 5.00

Subjects 49 3.00 1.00 to 5.00 0 -0.52 0.60

Non-diver controls

49 3.00 2.00 to 5.00

Trial 2 (number of correct responses) Subjects 47 5.00 4.00 to 6.00

1 -0.26 0.80 Diver controls

47 4.00 3.00 to 6.00

Subjects 49 5.00 4.00 to 6.00 1 0.54 0.59

Non-diver controls

49 4.00 3.00 to 6.00

Trial 3 (number of correct responses) Subjects 47 5.00 4.00 to 7.00


47 6.00 5.00 to 7.00

Subjects 49 5.00 3.00 to 7.00 0 -0.64 0.52

Non-diver controls

49 5.00 3.50 to 6.00

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SERIAL DIGIT LEARNING

Score 1 (sum of errors) N Median Interquartile

range Median

difference Z P

Subjects 48 2.50 1.00 to 5.00 0.5 -1.58 0.11

Diver controls

48 2.00 0.00 to 3.75

Subjects 51 3.00 1.00 to 5.00 1 -1.80 0.07

Non-diver controls

51 2.00 0.00 to 3.00

Score 2 (sum of errors) Subjects 48 4.50 2.00 to 10.75

1.5 -1.12 0.26 Diver controls

48 3.00 0.00 to 7.75

Subjects 51 5.00 2.00 to 10.00 2 -1.20 0.23

Non-Diver controls

51 3.00 0.00 to 8.00

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COLOUR-WORD TEST

Colour-word – mean reaction time (msecs) N Median Interquartile

range Median

difference Z P

Subjects 45 656.00 633.50 to 688.00 7 -0.69 0.49

Diver controls

45 649.00 610.00 to 702.00

Subjects 46 669.00 634.75 to 694.00 26 -1.21 0.23

Non-diver controls

46 643.33 609.50 to 696.00

Colour-word – median reaction time (msecs) Subjects 45 640.00 616.00 to 671.00


45 643.00 600.00 to 681.00

Subjects 46 653.50 616.00 to 688.25 22.5 -0.81 0.42

Non-diver controls

46 631.00 601.50 to 685.00

Colour-word – number of stimuli Subjects 45 34.00 32.00 to 35.00


45 35.00 34.00 to 35.25

Subjects 46 34.00 32.00 to 35.00 -1 -2.08 0.04

Non-diver controls

46 35.00 34.00 to 35.25

Colour-word – false positives Subjects 45 1.00 1.00 to 2.00


45 2.00 0.00 to 2.00

Subjects 46 1.00 0.75 to 2.00 0 -2.09 0.04

Non-diver controls

46 1.00 0.00 to 2.00

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Colour-word – non response N Median Interquartile

range Median

difference Z p

Subjects 45 2.00 1.00 to 4.00 1 -1.39 0.16

Diver controls

45 1.00 0.00 to 3.00

Subjects 46 2.00 1.00 to 4.00 1 -2.05 0.04

Non-diver controls

46 1.00 0.75 to 2.00

SWITCHING ATTENTION

Switching attention – side – mean reaction time (msecs) N Median Interquartile

range Median

difference Z p

Subjects 46 337.50 314.00 to 377.50 10 -0.90 0.37

Diver controls

46 327.50 305.50 to 354.00

Subjects 48 339.50 316.25 to 379.00 7 -1.04 0.30

Non-diver controls

48 332.50 306.25 to 354.50

Switching attention – direction – mean reaction time (msecs) Subjects 46 480.00 436.25 to 509.50

14.5 -0.23 0.82 Diver controls

46 465.50 432.75 to 505.00

Subjects 48 485.50 437.25 to 510.00 -10 -1.28 0.20

Non diver controls

48 495.50 445.00 to 534.50

Switching attention – switch side – mean reaction time (msecs) Subjects 46 513.50 434.50 to 651.00

-11.5 -0.47 0.64 Diver controls

46 525.00 410.25 to 665.75

Subjects 48 513.50 436.25 to 644.75 3.5 -0.70 0.49

Non diver controls

48 510.00 429.50 to 602.50

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Switching attention - switch direction – mean reaction time (msecs) N Median Interquartile

range Median

difference Z p

Subjects 46 644.00 598.75 to 772.25 14 -0.51 0.61

Diver controls

46 630.00 549.00 to 785.25

Subjects 48 647.50 603.75 to 768.50 -22 -0.51 0.61

Non-diver controls

48 669.50 575.25 to 784.00

SYMBOL DIGIT TEST

Response time (latency) Valid

No. Mean Std

Deviation

Median Minimum

Maximum

Symbol digit. Average latency Subjects (msecs)

51 2.33 0.41 2.22 1.69 3.95

Symbol digit. Average latency Diver controls (msecs)

49 2.27 0.54 2.22 1.60 4.13

Symbol digit. Average latency Non-diver controls (msecs)

51 2.25 0.34 2.17 1.76 3.24

A Friedman test was used to compare the medians of the three groups, which suggested there was insufficient evidence to reject the null hypothesis (n = 49, Chi² = 2.23, degrees of freedom = 2, p = 0.329) A Wilcoxon signed rank test was therefore not performed.

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3.3 GHQ SCORES

N Median Interquartile range

Median difference

z P

Subjects 48 1.0 0.00 to 6.00 0.5 -1.67 0.09

Diver controls

48 0.5 0.00 to 3.00

Subjects 51 1.00 0.00 to 6.00 1 -1.43 0.15

Non-diver controls

51 0.00 0.00 to 3.00

3.4 ANALYSIS

Outcome data from the Subject group was compared with that from each Control group. ie: Subject vs Control group:divers (49 pairs). Subject vs Control group:non-divers (51 pairs).

Wilcoxon’s signed rank test was used to compare data from the performance of each NES test which both subject and matched control had successfully completed. (apart from Symbol digit substitution which was analysed with a Friedman test) and the GHQ.

No apparent significant difference was observed between the groups in performance of Paired Associate Learning, Symbol Digit Substitution, Serial Digit Learning or Switching Attention.

No significant difference was observed in response time for the Colour-word test between the three groups. Subjects registered fewer false positive responses than both control groups (i.e. made fewer mistakes). In the case of the non-diver control group the difference was notable (p = 0.04). Conversely, the subject group failed to respond to a greater number of stimuli than both control groups; again notably so compared with the non-diver controls (p = 0.04). Fewer responses to stimuli were recorded by the subjects compared with both control groups. This difference was probably a consequence of the differing rates of false positive and non-responses.(See Appendix for description of Colour-word test).

The subject group scored less than the control groups in all four elements of Finger Tapping test (preferred hand - first period, preferred hand - second period, nonpreferred hand, alternating hands). Composite test scores were derived for each individual from the sum of the four elements of the test. A Friedman test was used to compare the medians of the three groups. The test indicated there was insufficient

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evidence to reject the null hypothesis. (n = 49 Chi² = 0.78, degrees of freedom = 2, p = 0.679).

Valid N Mean Std Median Minim- Maxi-Deviation Mum mum

Derived total score 51 676.69 112.74 677.0 130.00 919.00 Subjects

Derived total score Diver controls 49 690.73 89.21 711.00 490.00 825.00

Derived total score Non-diver controls 51 689.10 93.91 687.00 524.00 924.00

The subject group scored more highly on the GHQ (high scores implying increased psychological morbidity), however the difference was small and not statistically significant (p=0.09 subject vs diver controls. p = 0.15 subject vs non-diver controls). The scores of all groups were in any case low compared to normative data.(15)

Some individuals from each group were unable to complete some tests - for a variety of reasons (see table 6 appendix). An additional small amount of data was lost by individuals failing to complete questionnaires clearly.

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4) DISCUSSION

The tests employed in this study failed to register convincing evidence of a degraded cognitive performance by the subject group. The differing rates of false positive responses and non-responses between the subject and non-diver control groups in the Colour-word test could possibly be construed as evidence of the subjects being more cautious. The observed differences, however, were of equivocal significance (p = 0.04) and the opposite to what one might expect from the result of neuronal damage. The differences observed in psychiatric morbidity between the groups (as measured by GHQ scores) were small and unlikely to be significant. All three groups had low scores (indicating reduced morbidity) compared to data from studies of “normal” populations. Hopefully these results suggest that the prospects for recovery (or preservation) of cognitive function following neurological DCI where a functional neurological recovery has occurred are good. However they should not be assumed to imply immunity from long term damage. The subject group included a wide variety of cases of neurological DCI in terms of severity and differing clinical syndromes but included very few cases presenting more than forty-eight hours after the relevant dive. Most had presented and commenced treatment within several hours of diving. It is possible that delayed presentation or treatment might be associated with an increased risk of persistent neurobehavioural problems even if a functional neurological recovery had occurred.

It is acknowledged that there is some controversy surrounding the validity of computer administered cognitive function tests. Nevertheless they are accepted as a meaningful research tool for epidemiological studies in a number of fields including Occupational Psychology (14:15). The test battery used for this study was chosen to provide a general screen of cognitive function rather than detailed examination of any particular aspect.

The lack of difference in performance between the divers and non-divers (ie subjects and diver controls compared with non-diver controls) should not be taken as evidence against diving per se being a risk factor for cognitive impairment. As can be seen from Table 4 a number of the subjects had very short diving careers and were unlucky enough (or perhaps physiologically predisposed) to get bent after a handful of dives. The non-diver control group did however offer a second yardstick with which the subjects could be compared.

It is not possible to draw valid conclusions from an individual’s failure to complete a test. A handful of individuals from each group failed to complete one of the tests (none was unable to complete more than one test.) It is to be noted that four of the subjects abandoned tests (for reasons other than colour blindness) compared with two individuals in the diver control group and two in the non-diver control group.

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5) CONCLUSION

This study identified no significant evidence of long term neurobehavioural impairment in a group of recreational divers who had made a full functional recovery from neurological DCI.

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6) REFERENCES

1 Rozsahegyi I. Brit. Journ. Ind. Med. 1959 16 331. 2 Rozsahegyi i. Roth B. Ind. Med. Surg. 1966 16 101-110 3 Peters B.H. Levin H.S. Kelly P.J. Neurology April 1979. 381 4 Levin H.S. International Symposium of Man in the Sea 1975 Vol 6 232-241 5 Todnem K. Nyland H. Kambestad B.K. Aarli J.A. Brit. Journal. Ind. Med. 1990

47 708-714 6 Curley M.D. Schwartz H.J.C. Zwingelberg K.M. Undersea Biomed RES. 1988 15

223-236 7 Warren L.P. et al. American Journal of Radiology 1988 151 1003-1008 8 Murrison A.W. Undersea and Hyperbaric Medicine Vol 20 No 4 1993 347-373 9 Murrison A.W. Glasspool E. Pethyridge R.J. Francis T.J.R. Sedgwick E.M.

Occupational and Environmental Medicine 1994 51 730-734 10 Palmer A.C. Calder I.M. Hughes J.T. Lancet Dec 12 1987 1365-1366 11 Cross M. Elliott D.H. Personal communication “Fitness to Dive Seminar”

Norwich Norfolk U.K. April 1988. 12 Goldberg D. (1978) “Manual of the Health Questionnaire” Windsor: NFER-

Nelson 13 Nelson H.E. (1982) “National Adult Reading Test” Windsor: NFER-Nelson 14 Baker E.L. Letz R. Fidler A. Journ. Occup. Med. 1985 27 206-212 15 Goldberg D. et al. Brit J. Prev. Soc. Med. 1970 24 18-23 16 Spurgeon A. et al American Journal Indust. Medicine 22: 235-335. (1992)

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7) APPENDIX

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ACKNOWLEDGMENT AND GRATITUDE TO:

Dr Phil Bryson and the Diving Diseases Research Centre Plymouth for advice and practical help recruiting subjects and allowing their facilities to be used to conduct interviews and tests. Dr Anne Spurgeon (Department of Occupational Medicine, University of Birmingham) for help and advice with the study design and for training in administration of the computerised psychometric tests. Stuart Munroe of Atlantic Enterprises for kindly providing NES software. Spencer Phillips, Manager of Poole Hyperbaric Centre for help with computing and recruiting subjects. Dr Desmond McCann and Dr Gerry Roberts of Madeira Medical Centre, Poole and Poole Hyperbaric Centre for advice, support and recruiting subjects. Dr Clare Lawson, Clinical Psychologist (formerly of Branksome Clinic, Poole) for help with data analysis. Bernard Brooks MBA. for patient and kind help with computing. Colleagues and staff at Bransgore and Burton Medical Centres for their support and

patience. Jack Hickish for data handling, computing and preparation of the manuscript. Tess and Tom Hickish for help with the computer. Joanne Turnbull (Department of Medical Statistics and Computing, University of Southampton) for analysing the data. Professor David Elliott for advice, support and encouragement. Mr David Tee and his predecessors at the HSE for patiently and supportively managing the project. The patients of Bransgore and Burton Medical Centre who kindly allowed themselves to be recruited into the non-diver control group. All the very many divers who helped with the study, either as participants, potential participants or advisers. May they always dive safely.

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TABLE 1 Medical details of Subject group

Code No. Medication Medical History

110 - 1991 Laceration Lt wrist (non-dominant). Tendon injury repaired. No apparent residual disability.

111 - -112 - -113 Diclofenac Fractured Rt (dominant) wrist 3yrs before assessment 115 - # Rt arm. #Rt thumb. Dislocated Lt little finger 4 years before assessment. 116 - -117 - Treated for depression 5 years before assessment. Medication for 4 months. 118 - -119 - -120 Cimetidine Reflux oesophhagitis. 121 - -122 - Treated for anxiety 18 years before assessment. 123 - -124 - -125 - Fractured metacarpal bones both hands 15 years before assessment. 126 - -127 - Injury Rt thumb. Persistently impaired function. 128 - Hayfever.

Fractured finger Rt hand years before assessment. 129 - Treated for chronic fatigue syndrome 11 years before assessment. 130 - Asthma diagnosed 2 years before assessment.

Dislocated finger years before assessment full recovery of function. 131 Oxytetracycline Rosacea 132 Amlodipine 5mg od.

Atorvastatin 10mg od Hypertension diagnosed 20 years before assessment.

133 - Fracture arm years before assessment. 134 - -135 - -136 Femodene -137 - -138 Paramax Migraine (inactive for more than 1 month before assessment).

Tendonitis Rt wrist. Full recovery. 139 - -140 - -141 Codeine Phosphate

30mg bd prn Mechanical back pain.

142 - Lumbar laminectomy 5 years before assessment. 143 Bisoprolol 2.5 mg od.

Co-codamol 4 tabs daily

Fractured Rt radius 20 years before assessment. Hypertension Recurrent mechanical back pain.

144 - -145 - Repair tendon injury Rt little finger years before assessment. 146 - Fracture Lt arm. Full recovery. 147 Amitriptylline 10mg

on. Codeine phosphate 30 mg od prn

Chronic recurrent mechanical back pain.

149 - -150 - -151 - Fractured wrist 13 years before assessment.

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153 Gaviscon Zantac

Oesophageal reflux. Diphtheria in 1947.

154 - -155 Brevinor -156 Ibuprofen -157 - -158 Prempac 1.25 -159 - Episode of sciatica several years before assessment. 160 - -161 - “Mild asthma”.

Fractured finger years before assessment. 162 - -163 - Minor head injury 5 years before assessment. Not hospitalised.

TABLE 2 Medical details of Diver control group

210 - -211 - -212 Diclofenac

Flixonase Bilateral carpal tunnel release 2 years before assessment.

213 - -214 - Tendon injury Rt thumb years before assessment. 216 - Minor head injury 1 year before assessment. Not hospitalised. 217 - -218 - Fracture Lt thumb 6 years before assessment.

Fracture Lt wrist 5 years before assessment. 219 Diclofenac -220 - Fractured bone Lt hand years before assessment. 221 - -222 - -223 - -224 - -225 - Fractured finger Lt hand years before assessment. 226 - -227 - -228 - -229 - Fractured Lt wrist years before assessment. 230 - Perthes disease.

Migraine. Inactive at time of assessment. 231 - “Mallet finger” – LT little finger. From injury years before assessment. 232 - Fracture Rt wrist years before assessment.

Hayfever – inactive at time of assessment. 233 - -234 - “Mild asthma”.

Fracture Rt thumb years before assessment. 235 - Fractured wrist years before assessment. 236 - -237 - -238 - -239 Becotide inhaler

Ventolin inhaler Asthma. Period of depression following divorce.

240 Salbutamol inhaler “Mild” asthma. Laceration with tendon damage to Rt middle finger years before assessment.

241 - -

29

242 - -243 - -244 - -245 - -246 - -247 Flixonase Seasonal rhinitis. 249 - -250 - -251 - -

253 Ibuprofen 254 - Pulmonary tuberculosis 1953. 255 Bisoprolol

Aspirin Hypertension.

257 - -258 - -260 - -261 - -262 - -263 - -

TABLE 3 Medical details of Non-diver control group

310 Lipantyl Hypercholesterolaemia. 311 - -312 - -313 Co-proxamol Cervical Spondylosis 315 - -316 - -317 Combined oral

contraceptive. -

318 - -319 - -320 Atenolol Hypertension. 321 Bricanyl Inhaler Asthma. 322 - -323 - -324 - -325 Beconase. Allergic rhinitis. 326 Allopurinol. Hyperuricaemia. 327 Cetirizine.

Beconase. Becotide

Asthma. Allergic rhinitis. Keratoconus.

328 - -329 - -330 Cetirizine. Hayfever. 331 Dislocated Rt thumb and Lt shoulder 8 years before assessment. 332 - -333 Ventolin.Becotide. Asthma. 334 Amlodipine.

Atorvastatin. Hypertension. Hyperlipidaemia.

335 - -

336 - -

30

337 - -338 - -339 Ventolin. Asthma. 340 - Episode of depression 5 years before assessment. 341 Mesalazine Ulcerative colitis in remission at time of assessment. 342 - -343 - -344 - Episode of depression 3 years before assessment. 345 - -346 - -347 - -349 - -350 - -351 - -353 Pulmicort. Polio.

Asthma. Ischaemic heart disease. Coronary artery bypass graft 8 years before assessment.

TABLE 4 Subjects: Diving history and features of decompression illness

Code no.

Age Sex Total number of dives

Interval between incident

Interval between

incident and

Main clinical features Presumed anatomical site of main

Primary treatment

Follow up Therapies

Residua Comments

and treatment lesion assessment

110 44 M 1500 8 months. Vertigo, vomiting, Vestibular Resumed diving. ataxia. ?Brain

stem. 111 43 M 1000 8 months 112 51 M 220 6 months 2 hrs. Fatigue + malaise

associated with ? 0 None Resumed diving.

omitted decompression.

113 56 M 2000 11 months Flank pain. Paraesthesiae both

Spinal. None Resumed diving.

legs. 115 53 M 1502 10 months Chest pain with ? None Resumed diving.

dyspnoea. 116 40 M 35 14 months None Resumed diving 117 27 F 12 13 months Disorientation. Cortical. None Gave up diving.

Discomfort Rt arm Rt leg.

118 23 M 17 17 months 24 hrs Weakness Rt leg + Spinal. 1 None Gave up diving. dizziness.

119 32 M 350 15 months None Resumed diving. 120 50 M 400 13 months 48 hrs. Pain weakness Lt arm. Spinal. None Resumed diving. 121 29 M 500 12 months 2 hrs. Shoulder girdle pain. Spinal None Resumed diving.

Pain Lt arm. Faintness. 122 48 M 220 17 months Cerebral Subjective

sensory Abandoned

diving. impairment Lt

foot. 123 36 M 450 6 months None Resumed diving.

124 40 M 250 13 months Numbness Lt Foot.

125 5 M 35 15 months Weakness Lt arm + Lt Cortical Emotional Leg. liability noted by

patient. 126 52 M 1000 Paraparesis with Spinal

urinary retention.

31

127 37 M 1000 15 months Impaired balance in dark.

Abandoned diving. Studies

for patent Foramen Ovale

negative. 128 26 M 600 6 months Vertigo quadriplegia Cerebral. None 129 40 M 120 19 months 14 hrs. Paraparesis Spinal Table 62 4 short

tables None Studies for patent

Foramen Ovale over 2 days.

positive.

130 41 M 600 7 months 3hrs Numbness Rt leg Spinal Table 62 1 short None

131 32 M 800 27 months 1 hr Paraparesis. Vomiting. Spinal Comex 30 2 short None Studies for patent Foramen Ovale

positive. 132 40 M 200 23 months 2 hrs Brief loss of

consciousness. Cerebral Table 62 None Resumed diving.

Exhaustion. Weakness Lt arm.

133 38 M 900 21 months 2 hrs Back pain. Paraplegia. Spinal Table 62 7 short tables

None Studies for patent Foramen Ovale

over 7 days.

negative.

134 44 M 750 19 months 2hrs General myalgia. ? Table 62 None Studies for patent Arthralgia. Lassitude. Foramen Ovale

negative. 135 56 M 3000 6 months 2 hrs Paraparesis Spinal Table 62 None Resumed diving. 136 25 F 50 11 months 48 hrs. Rash. Confusion.

Weakness Rt arm. Cerebral Table 62 9 short

tables None Studies for patent

Foramen Ovale over 9 days.

negative.

137 50 M 201 18 months None Resumed diving

138 29 F 170 18 months Girdle pain. Loss of balance. Fatigue.

Spinal Table 62 9 short tables over 9

None Resumed diving.

days 139 40 F 20 10 months None Resumed diving. 140 21 M 20 7 months Weakness numbness Cerebral Table 62 1 short Subject concerned Resumed diving.

Rt arm. Confusion. about short-term memory.

141 53 M 3000 8 months Tingling Rt foot. 142 40 M 45 10 months 2 hrs. Paraparesis. Urinary

retention. Spinal Table 62 Multiple

short Numbness both legs. Required

self-

Abandoned diving.

catheterisation for 6 moths.

143 37 M 200 9 months Paraparesis. Spinal Numbness both legs.

Abandoned diving.

144 36 F 400 10 months Table 62 1 short Resumed diving. table

145 39 M 270 11 months Paraparesis Spinal Table 62 3 short tables

None

146 34 M 250 13 months Paraparesis. Chest pain.

Spinal Table 62 5 short tables over 5

Numbness Lt foot.

days.

147 30 F 80 15 months Rash. Numbness both hands.

Spinal Table 62 None

149 30 F 250 16 months Rash. Numbness + pain Lt arm.

Spinal Table 62 Table 62 None Resumed diving.

150 47 M 350 39 months Quadriplegia. Spinal Tingling hands & feet. Impotence.

151 40 F 175 13 months Paraesthesiae fingers Spinal None both hands. Extreme

fatigue. 153 72 M 101 15 months Spinal Tingling fingers

Lt hand. 154 50 M 2400 9 months Pain Rt arm.

Paraparesis. Spinal Comex 30 9 short

tables. Numbness Rt arm.

Subjective sensory

disturbance both

32

legs both arms. 155 38 F 197 8 months Abdominal pain. Spinal Diplopia when Studies for patent

Paraparesis. tired. Foamen Ovale negative.

156 52 M 2000 9 months Pain and tingling Lt Spinal None arm.

157 40 F 8 9 months Los of consciousness (30 secs). Chest pain.

Cerebral. Table 62 None

158 47 F 360 10 months Vertigo. Vestibular. None 159 46 M 8000 12 months Pain Rt knee. Spinal None

Numbness Lt leg. 160 35 M 200 12 months Rash. Extreme fatigue. Table 62 None

161 29 M 360 14 months Pain and tingling both arms and legs.

Spinal None

162 29 M 70 10 months Numbness tingling Rt Spinal None Resumed diving. arm.

163 30 M 80 14 months Nausea. Numbness Spinal Table 62 1 short None and tingling both arms table.

and legs.

TABLE 5

SELF-EVALUATION OF PSYCHOLOGICAL SYMPTOMS (SUBJECTS)

Subject no. Forgetfulness Poor Concentration Irritability Depression Anxiety Clumsiness

110 + 111 + 113 + 115 + + 116 + + 117 + + 123 + 124 + + + + + + 125 + + + 127 + + + + 128 + + + 129 + 133 + + 134 + + + 137 + + + 140 + + + + + + 141 + + 143 + + + + + 146 + + 147 + + 150 + + + + + + 153 + 154 + + + 155 + + + + 158 + + 161 +

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TABLE 6

Subject/Control Code No.

Subject Group.

142 141 140 137 126 116

Control Group: divers;

253 235 235

MISSING DATA

Test

SA CW PAL SA PAL CW

CW CW SA

Reason

Abandoned at subject’s request. Subject colour blind. Abandoned at subject’s request. Abandoned at subject’s request. Abandoned at subject’s request. Subject colour blind.

Abandoned at control’s request. Control colour blind. Abandoned at control’s request.

Abandoned at control’s request. Control colour blind. Control colour blind. Abandoned at control’s request.

Control Group: non-divers;

356 SA 354 CW 328 CW 318 CW

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DESCRIPTION OF INDIVIDUAL COGNITIVE FUNCTION TESTS

FINGER TAPPING TEST

This is a perceptual-motor test of speed and accuracy. The individual is asked to press a button as many times as possible within a defined interval (one minute) The number of responses (finger taps) are counted and recorded. Four counts are made: 1) Using the index finger of the preferred hand (according to whether the individual is right or left handed). 2) A second count using the index finger of the preferred hand. 3) Using the index finger of the non-preferred hand. 4) Using the index fingers of the preferred and non-preferred hand alternating. Mistakes are also counted and recorded.

PAIRED ASSOCIATE LEARNING TEST

This is a test of learning and memory. A series of pairs such as “KEN is a PLUMBER” are presented on the screen for a short period, one pair at a time. After all the pairs have been presented the individual is given a prompt such as “KEN is a:..” along with all the alternative occupations. Upon answering the individual is given feedback: “Yes (or No) KEN is (is not) a PLUMBER”. Each of the items is presented in random order. Three different trials consisting of presentation of each of the names and occupations followed by prompting with each of the names are given. The order in which the pairs are presented and the name-prompt is given changes with each trial. The number of correct responses is recorded for each trial.

SERIAL DIGIT LEARNING

This is also a test of learning and memory. A long sequence of digits is presented on the screen, one digit at a time. The individual is then asked to recall and enter into the computer as many of the digits as he or she can in the correct sequence. The same sequence of digits is presented until either the individual recalls the complete sequence correctly for two trials in a row or the specified maximum number of trials is reached. An error score is calculated from the sum of the errors over all the trials attempted and recorded.

COLOUR-WORD TEST

In this test the words “RED”, “GREEN”, “YELLOW” and “BLUE” are flashed briefly on the screen, one at a time, presented in one of the four colours with the word and colour uncorrelated. On the occasions when the word and colour are congruent the individual is required to respond by pressing a marked key on the keyboard. The latency between response and stimulus is measured for each correct response together with false positive responses and non-responses.

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SWITCHING ATTENTION TEST

This test is designed to measure the individual’s ability to switch rapidly between responses to simple two-choice visual discriminations based on changing verbal clues. A series of three different testing conditions are used. In the first testing condition (“SIDE”) the subject must respond to each of a series of large rectangles presented in succession on the video screen. In each trial the rectangle appears on the right or left of the screen and the individual must respond by pressing a marked key on the corresponding right or left side of the keyboard. In the second testing condition (“DIRECTION”) the subject must respond to a succession large arrows appearing in the middle of the screen which point to the right or left by pressing the key on the corresponding side of the keyboard. In the third condition (“SWITCHING”) the command “SIDE” or “DIRECTION” appears on the screen immediately before each stimulus. The stimuli are arrows pointing to the left or the right, which appear on the left or right side of the screen. The subject must respond by pressing the button on the appropriate side of the keyboard according to the command. The stimulus remains on the screen until a correct response is made. The response time is measured and recorded for each stimulus and number of incorrect responses.

SYMBOL-DIGIT SUBSTITUTION TEST

This is a perceptual-motor test. Nine symbols and nine digits appear paired at the top of the screen as a “key”. The nine symbols then appear on a different part of the screen in a scrambled order and the individual is required to press digit-keys on the keyboard to assign the appropriate digit to each symbol according to the “key”. Six sets of nine symbol-digit “keys” are presented in succession (the first is a practice set). The latency of each response is measured.

Printed and published by the Health and Safety ExecutiveC1.25 10/02

ISBN 0-7176-2559-1

RR 017

780717625598£10.00 9

RESEARCH REPORT 017 - Health and Safety Executive · RESEARCH REPORT 017. HSE Health & Safety...

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