DAVID HANNAN and COMCARE
[2009] AATA 864
•10 November 2009
Administrative Appeals Tribunal
DECISION AND REASONS FOR DECISION [2009] AATA 864
ADMINISTRATIVE APPEALS TRIBUNAL )
) No 2008/4807
GENERAL ADMINISTRATIVE DIVISION ) Re DAVID HANNAN Applicant
And
COMCARE
Respondent
DECISION
Tribunal Mr S. Webb, Member
Dr P. Wilkins, Member MBEDate10 November 2009
PlaceCanberra
Decision The decision under review is affirmed.
....................[sgd]...................
Mr S. Webb, Presiding Member
CATCHWORDS
COMPENSATION - claimed injury - disease – deep vein thrombosis - bus driving - risk factors - evidence of risk does not equate to evidence of cause – need for probative evidence to support inference as to probability – common sense approach to attribution of legal responsibility - mere possibility not sufficient – contribution that is not to a significant degree not sufficient – decision affirmed
Safety, Rehabilitation and Compensation Act 1986 ss 5A, 5B, 14
Kennedy Cleaning Services Pty Ltd v Petkoska (2000) 200 CLR 286
Minister for Immigration and Ethnic Affairs v Pochi (1980) 4 ALD 139
Briginshaw v Briginshaw (1938) 60 CLR 336
Repatriation Commission v Smith (1987) 74 ALR 537
Jones v Dunkel (1959) 101 CLR 298
Bater v Bater [1950] 2 All ER 458
March v Stramare (E & MH) Pty Ltd (1991) 171 CLR 506
Chappel v Hart (1998) 156 ALR 517
Seltsam Pty Ltd v McGuiness; James Hardie & Coy Pty Ltd v McGuiness (2000) 49 NSWLR 262
REASONS FOR DECISION
10 November 2009 Mr S. Webb, Member
Dr P. Wilkins, Member1. David Hannan is a bus driver. He suffered from a venous thrombosis in his right leg that he attributes to inadequate seating and long periods of immobility while driving buses. He claimed compensation.[1] Comcare rejected his claim at first instance and on reconsideration.[2] Unhappy with that result Mr Hannan applied for review.
[1] T4b.
[2] T15 and T23.
2. The issue for determination is whether Mr Hannan suffered an injury in relation to which he is entitled to compensation.
3. The relevant facts are not in dispute. Mr Hannan worked as a baker for many years before commencing work as a bus driver. At the time of the alleged injury and, by his own account, for many years his weight was in excess of 112 kilograms, rendering him clinically obese. In 2004 he commenced part time employment with the Australian Capital Territory Department of Territory and Municipal Services driving ACTION buses while continuing to work part time as a baker employed by Woolworths Pty Ltd. In or about August 2007 he ceased work as a baker and commenced full time employment driving ACTION buses. When working as a full time bus driver, Mr Hannan drove P3 buses on the ‘night’ shift, from 3.00pm to 12.00am. In each shift, he would have a 1 hour meal break and short breaks of up to 10 minutes between runs; runs would be of varying durations of up to one hour. Sometimes, if the runs were behind schedule, Mr Hannan would be unable to take short breaks between runs. The P3 buses were fitted with an ‘air-ride’ seat that allowed for some adjustment. The adjustments, however, were not sufficient to permit Mr Hannan to rest his feet on the floor of the bus when driving – he could reach the accelerator and brake pedals with his right foot, but he could not rest his foot on the floor. The bus had an automatic transmission and he was not required to use his left leg when driving – this limb would rest over the left side of the driver’s seat with the foot dangling in space.
4. On 20 February 2008 Mr Hannan consulted Dr R. Bate, his treating general practitioner, with complaints of increasing pain behind his right knee which he had been suffering for a number of days.[3] The Doctor found no evidence of thrombosis and suspected that Mr Hannan may have ruptured a cyst behind his right knee. On 21 February 2008, however, Mr Hannan experienced breathlessness and chest pain and was admitted to the Canberra Hospital. A diagnosis of venous thrombosis below or behind the right knee was made, with suspected pulmonary embolism. He was initially treated with Heparin and Celaxane. No pulmonary embolism was found in a subsequent scan on 22 February 2008. He was treated by Dr I. Prosser, clinical haematologist, who prescribed decoagulant treatment with Warfarin. Mr Hannan had some time off work, but made a full recovery and returned to full time work, driving different buses on a split shift basis. He has had no apparent recurrence of thrombosis.
[3] T4a and T11.
5. At the outset of the hearing we were informed that the parties are in agreement that the injury claimed is a deep vein thrombosis of gradual onset in Mr Hannan’s right lower limb, at or below the knee. This, we were informed, is an ailment for the purposes of the Safety, Rehabilitation and Compensation Act 1986 (the Act). On the present evidence, that assessment appears to be correct and we will proceed on that basis. Thus, it follows that Mr Hannan will only be entitled to compensation if his employment has contributed in a significant degree to that ailment.[4]
[4] Section 5B Safety, Rehabilitation and Compensation Act 1986.
6. We note in passing that Mr Hannan did not press a case based on pulmonary embolism – this, we understand, was left to be dealt with as a sequellae of the venous thrombosis if liability was found to lie against Comcare for that ailment. Nevertheless, it is appropriate to deal briefly with this aspect of his case. Embolism, and in this case purported pulmonary embolism, involves the sudden blockage of an artery by a clot or other material carried by the blood flow. Thus, embolism is more consistent with an injury, being a sudden physiological change in a body system, rather than a disease for the purposes of the Act.[5] Even though it can be accepted that Mr Hannan’s symptoms on presentation to the Canberra Hospital on 21 February 2008 included chest pain and shortness of breath, being indicators of a possible pulmonary embolism, no such embolism in his lung was found on further investigation. The evidence of Dr Prosser takes that matter no further. On balance, it appears possible that a pulmonary embolism may have caused Mr Hannan’s chest and breathing symptoms, but the present evidence does not establish the presence of any such pulmonary embolisation as a matter of probability, to the reasonable satisfaction standard.[6] Thus, if pressed, we would be compelled to conclude that the evidence is not sufficient to establish the presence of a pulmonary embolism injury in Mr Hannan on or about 21 February 2008.
[5] Kennedy Cleaning Services Pty Ltd v Petkoska (2000) 200 CLR 286 at 300.
[6] Exhibit A2, 29 August 2008, p1.
7. As we have said, Mr Hannan’s case was pressed on the basis of venous thrombosis in his right leg and not embolism in his lung. Mr Hannan asserts that two factors in his employment significantly contributed to the thrombosis in his right leg: specifically, the architecture of the driver’s seat in the P3 buses he was required to drive, as a result of which his legs were suspended without being able to rest on the floor of the bus, with the seat pressing against the back of his lower right thigh while driving; and the extended periods of immobility while driving the buses during eight-hour shifts. In his submission, as we understand it, the pressure of the seat on his lower right thigh and the long periods of immobility significantly contributed to venous stasis or pooling in his right lower limb and reduced venous blood flow return. This, he says, was a significant factor in the onset of coagulative processes in his right lower leg that resulted in clotting and thrombosis at or below his right knee. Mr Hannan relies on the expert evidence of Dr Prosser, his treating haematologist, and Dr Bate, his treating general practitioner, in relation to the issue of causation and work contribution. Furthermore, Mr Hannan relies on the evidence of Associate Professor J. Koutts, a consultant haematologist, and Dr P. Stevenson, a consultant occupational physician, concerning the aetiology of venous thrombosis and associated risk factors.
8. Mr Hannan says that he had no previous or family history of thrombosis, and he has no genetic or other predisposition. Although he accepts that his weight increased his risk of thrombosis, Mr Hannan says that his weight had been stable for many years and had caused no previous difficulty. The only factor that changed in the period prior to February 2008 was the change in his employment, driving P3 buses on a full time bases from in or about August 2007, when he ceased working part time as a baker. On this basis, Mr Hannan asserts that it is a matter of common sense that the change in his employment to driving the P3 buses in eight hour shifts significantly contributed to the thrombosis he suffered.
9. It follows, in Mr Hannan’s submission, that the venous thrombosis in his right lower leg is within the meaning of ‘disease’ set out at section 5B of the Act and, thus, it is an injury for the purposes of sections 5A and 14 of the Act in relation to which he is entitled to compensation.
10. We do not agree.
11. For Mr Hannan to succeed it must be established to the reasonable satisfaction standard, on the balance of probability, that his right leg thrombosis was contributed to in a ‘significant degree’ by his employment. Under subsection 5B(3) ‘significant degree’ means ‘a degree that is substantially more than material’. Even if the evidence before us points to the possibility that Mr Hannan’s employment contributed to his thrombosis in the manner alleged, for his case to be made out an employment contribution that is substantially more than material must be established by probative evidence as a probability rather than merely a possibility[7]. This is a difficulty for Mr Hannan.
[7] Minister for Immigration and Ethnic Affairs v Pochi (1980) 4 ALD 139 at 155-156.
12. On the evidence of Dr Prosser and Professor Koutts the aetiology of venous thrombosis, generally, is not uncontrovertibly accepted – it is described by a number of predisposing and risk factors, some of which are controversial. The actual process by which thrombosis occurs may be scientifically described, and we have heard some evidence on this point, but there are processes concerning the onset and progress of coagulation that may vary in each case.
13. In Mr Hannan’s case, there is no direct evidence concerning the onset of his thrombosis. Even though Dr Bate and Dr Prosser describe the possibility of a causal connection with Mr Hannan’s employment in positive terms, even, in Dr Prosser’s case, using the language of probability, as it appears to us such conclusions are speculative. In truth, Dr Prosser’s evidence that the particular circumstances in Mr Hannan’s employment ‘probably’ made a ‘significant contribution’ to his thrombosis is based on his clinical assessment of Mr Hannan after the initial event and an analysis of risk factors;[8] it was not based on direct evidence of any reduction in venous return or any observed venous stasis or oedema in Mr Hannan’s right leg on or before 20 February 2008, although the possibility of reduced venous return is noted.[9] No such direct evidence was adduced before us. Dr Bate examined Mr Hannan on 20 February 2008 and reported “no signs of a deep vein thrombosis”, although he noted “a tender swelling behind his right knee”.[10]
[8] Exhibit A2, 17 December 2008, pp1-2.
[9] Exhibit A2, 17 December 2008, p1.
[10] T11 folio 49.
14. Dr Prosser accepted that his conclusion concerning the causal factors of Mr Hannan’s right leg thrombosis was partly based on his opinion that the association between long haul flights and increased risk of venous thrombosis “appears also to be associated with other forms of travel”, where immobilisation “may be” a common factor, even though “the mechanism of this increased risk is as yet insufficiently characterised”.[11] Dr Prosser’s evidence is that the primary risk factor in Mr Hannan’s case is his long-standing obesity, with his sedentary lifestyle and work being secondary factors, although the Doctor observed that these risk factors are not simply concomitant, but are cumulative.
[11] Exhibit A2, 17 December 2008, p1-2.
15. Professor Koutts agreed that the mechanism of increased risk associated with long haul air travel is not yet fully understood and suggested that this may relate to immobility, pressure or dehydration, for example, in air travel of more than four hours duration. The Professor agreed with Dr Prosser that obesity and immobilisation in a variety of settings, post-surgical immobilisation in hospital for example, are risk factors for venous thromboembolism. He also agreed that such risk factors may be cumulative. Nevertheless, in his opinion there is simply no evidence relating the increased risk of venous thrombosis in long haul air travel to other forms of surface travel, in long haul bus travel for example, or to particular seat architecture. We note the contents of the meta-analysis and systematic review in Exhibits A3 and R4 are broadly consistent with that conclusion. Furthermore, the Professor explained that the rate at which the risk of thrombosis in long haul air travel eventuates in individual cases is very low. He noted that Mr Hannan’s thrombosis was in his right lower leg, being the limb used to manipulate the accelerator and brake pedals while driving the P3 bus. This movement, in his opinion, would involve the use of muscles in the right lower limb in a manner that would be sufficient to minimise venous stasis and to provide adequate venous return, operating in the manner of a ‘pump’. The Professor was not willing to speculate about whether Mr Hannan’s particular seating arrangement while driving the P3 buses may have been a material factor contributing to the thrombosis in his right leg.
16. When assessing the evidence and making findings we must apply the reasonable satisfaction civil standard. Reasonable satisfaction should not result from indefinite evidence or indirect inferences.[12] Mere possibility or conjecture alone is not sufficient. That is so even if the possibility is real rather than fanciful. Beaumont J discussed the meaning of the term “reasonable satisfaction” in Repatriation Commission v Smith[13] and said:
There is, in this connection, a distinction of substance to be drawn between probabilities on the one hand and mere possibilities, even if they are real as distinct from fanciful, on the other.[14]
[12] Briginshaw v Briginshaw (1938) 60 CLR 336 at 362-363.
[13] (1987) 74 ALR 537.
[14] Ibid, at 547.
The balance of probabilities test does not authorise us to choose between guesses, on the ground that one guess seems more likely than another.[15] Nevertheless, as Lord Denning observed “in civil cases, the case may be proved by a preponderance of probability, but there may be degrees of probability within that standard”.[16] Even though Mr Hannan asserts that his case is simply one of common sense, much has been said about elements of risk and epidemiological studies concerning venous thrombosis by counsel and the experts alike. Thus, setting philosophical or scientific theories of causation to one side and addressing the question of legal liability raised by section 14 of the Act,[17] we must decide whether the epidemiological studies in evidence and the expert evidence based on such studies form sufficiently robust ‘strands in a cable’ to justify an inference as to the probabilities in the manner contended for by Mr Hannan. As Spigelman CJ said in Seltsam Pty Ltd v McGuiness “an inference as to the probabilities may be drawn from a number of pieces of particular evidence, each piece of which does not itself rise above the level of possibility”.[18]
[15] Jones v Dunkel (1959) 101 CLR 298 at 305.
[16] Bater v Bater [1950] 2 All ER 458 at 459.
[17] March v Stramare (E & MH) Pty Ltd (1991) 171 CLR 506 at 509 per Mason CJ (with whom Toohey and Gaudron JJ agreed); Chappel v Hart (1998) 156 ALR 517 at 519, 523, 533-534.
[18] (2000) 49 NSWLR 262 at 278.
17. As it appears to us, however, to draw such an inference would be a step too far from the established facts. Evidence of risk does not equate to evidence of cause in the particular circumstances. Even if we were to accept the possibility that Mr Hannan was exposed to an increased risk of venous thrombosis in the circumstances of his employment driving buses, and that is not established, mere exposure alone is not a sound basis on which to draw an inference that the increased risk eventuated in the thrombosis in his right lower leg. Exposure to risk is not sufficient to establish a causal nexus between circumstances in employment and injury; risk of harm remains in the realm of possibility unless and until the actual risk is realised.[19] To that end it is necessary to establish that “The possibility that X might cause Y had in fact eventuated, not in the sense that X happened and Y had also happened, but that it was undisputed that Y had happened because of X”.[20]
[19] Chappel v Hart (1998) 156 ALR 517 at 525 per McHugh J.
[20] Seltsam Pty Ltd v McGuiness; James Hardie & Coy Pty Ltd v McGuiness (2000) 49 NSWLR 262 at 280.
18. All that can be said on the present evidence is that it is possible that Mr Hannan may have been exposed to an increased risk of thrombosis in his employment as a bus driver, and he suffered a thrombosis several months after taking on full time bus driving duties. Despite Dr Prosser’s opinion on this point, which we have found to be speculative, there is no compelling probative evidence that the risk of thrombosis was realised because of the particular circumstances in his employment. As we have said, mere possibility is not sufficient to establish a material or significant contribution by employment to the claimed injury.
19. On balance, evaluating the evidence of Dr Prosser and Professor Koutts, and having regard to the reports of Dr Stevenson[21] and Dr Bate,[22] we do not accept Dr Prosser’s opinion concerning the ‘probability’ that Mr Hannan’s employment contributed ‘to a significant degree’ to the thrombosis; we prefer the opinion of Professor Koutts. We accept that it is possible that the particular seating arrangement and the periods of immobility Mr Hannan experienced while driving P3 buses prior to 20 February 2008 may have contributed in some way to the venous thrombosis in his right lower leg. We are not persuaded, however, that any such contribution is established as a matter of probability and we are unable to conclude that the circumstances of Mr Hannan’s employment to which attention has been directed contributed in a significant degree to the thrombosis in his right lower leg - if there was any material contribution, and that is not made out on the present evidence, it was not a ‘significant contribution’ – being substantially more than material – as required by section 5B of the Act.
[21] T22.
[22] T11.
20. That conclusion is made having due regard to the matters set out at subsection 5B(2) of the Act to which we may have regard. Mr Hannan urges us to accept that the thrombosis followed soon after his commencement of full time bus driving duties in or about August 2007. Plainly that is correct. He also presses us to find that the particular seat architecture and the extended periods of immobility increased his risk of thrombosis above that previously pertaining to his obesity, especially in light of the cumulative nature of such risks. We can make no such finding as a matter of probability, although the possibility remains open and the cumulative nature of concomitant risk factors, generally, can be accepted.
21. Mr Hannan says that his obesity caused him no problems in the past and it defies common sense, in all of the circumstances, to attribute his thrombosis to that risk factor. Our task is not to establish a precise cause of Mr Hannan’s thrombosis, but rather it is to determine whether his employment contributed to that condition to a significant degree. We have adopted a commonsense approach. But we are not able to attribute legal responsibility for the thrombosis to Mr Hannan’s employment in the absence of evidence that permits such a finding or inference to be drawn as a matter of probability. We have found Dr Prosser’s evidence concerning the issue of employment contribution to be speculative and not sufficient to establish a sound basis for legal attribution of responsibility or causation. We note Professor Koutts’ evidence that the risk of thrombosis as a result of obesity cannot simply be ruled out because that particular risk did not materialise for many years; he likened that risk to the health risk associated with smoking – the risk does not diminish with the passage of time and cannot simply be ruled out because it has not materialised after a number of years.
22. Finally, Mr Hannan asserts that he was active in employment as a baker, working on his feet during each shift, but that ceased when he commenced full time sedentary duties as a bus driver. This change, he says, further supports his case. We do not agree and note that Mr Hannan has been obese, by his own account, over many years. This suggests that he was not especially active during the period he worked as a baker. Furthermore, we note that he used his right foot and leg to manipulate the accelerator and brake pedals in the P3 buses he drove; he had breaks of up to 10 minutes between most runs he drove, each run lasting up to one hour; and he had a one hour meal break half way through each eight-hour shift. Even though Mr Hannan’s evidence is that he did not exercise during these breaks, we are satisfied that he was using muscles in his right leg in a manner and degree that was sufficient to facilitate venous return. We find that he was not immobilised in a manner that can be likened to a passenger in an aircraft on a long haul flight – on the contrary, as it appears to us on the basis of Professor Koutts’ evidence, Mr Hannan used his right foot and leg in a manner that is remarkably similar to exercises that are recommended for passengers on long haul flights in order to reduce the risk of venous thrombosis.
23. It follows, in conclusion, that we are not able to find in Mr Hannan’s favour. There is not sufficient evidence to establish, to the reasonable satisfaction standard, that Mr Hannan’s employment contributed to the thrombosis in his right lower leg to a significant degree. Thus, we are compelled to find that Mr Hannan’s right leg thrombosis is not a disease or, therefore, an injury for the purposes of the Act. That being so, the decision under review must be affirmed.
I certify that the 23 preceding paragraphs are a true copy of the reasons for the decision herein of Member S. Webb.
Signed: ....................[sgd]...................................
J. Lakin, AssociateDate of Hearing 14 October 2009
Date of Decision 10 November 2009
Solicitor for Applicant Maurice Blackburn Lawyers, Canberra
Counsel for Applicant Mr W. Sharwood
Solicitor for Respondent Dibbs Barker, Canberra
Counsel for Respondent Ms L. Walker
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