Statement of Principles concerning decompression illness (Balance of Probabilities) (No. 24 of 2023)

The instrument establishes a tight conceptual framework for how decompression illness is treated for the purposes of veterans’ and service members’ claims. Key concepts are defined expressly in the text and in Schedule 1.

Decompression illness is defined as an injury caused by bubbles of nitrogen and other inert gases forming in tissues and blood vessels after a reduction in ambient pressure (s7(2)(a)). The definition explicitly includes arterial gas embolism not due to pulmonary barotrauma, and decompression sickness (s7(2)(b)(i)-(ii)), and explicitly excludes a list of other pressure and hypobaric conditions such as altitude illness, arterial gas embolism due to pulmonary barotrauma, barotrauma, ebullism, osteonecrosis, high pressure neurological syndrome/inert gas narcosis, and cerebrovascular accident not due to an arterial gas embolism (s7(2)(c)). The instrument notes typical clinical manifestations (musculoskeletal, cutaneous, lymphatic, cardiopulmonary, inner ear or neurological signs) and lists inert gases (nitrogen, argon, helium, xenon, krypton) (Notes 1-2 to s7).

The notion of a “substantial episode of decompression” is given descriptive contours in Note 1 to s9(1): it is a rapid, substantial reduction in ambient pressure where the person had been at higher pressure for a substantial period. The instrument gives an enumerated list of substantive exposure scenarios that qualify as factors, including surfacing from dives that required decompression stops, flying at greater than 5,486 metres altitude in unpressurised craft, flying within a no‑fly interval after diving when such an interval was recommended by decompression tables, ascent from submerged submarines at specified depths or pressures, loss of cabin pressure at specified altitudes or in spacecraft above the von Karman line, returning to surface air pressure after working in hyperbaric compressed air environments (tunnels, caissons, tunnel boring machines), transferring from higher to lower pressure in space including extravehicular suit activities, exposure in hypobaric chambers, and returning to surface air pressure after hyperbaric chamber exposure or pressure testing of vessels (s9(1)(a)-(j)). The temporal window for these exposure factors is seven days before the clinical onset of decompression illness (s9(1) and Note 1).

The SoP also recognises a non‑exposure factor: inability to obtain appropriate clinical management for decompression illness (s9(2)). Section 10(2) clarifies that this inability factor applies only to material contribution to, or aggravation of, decompression illness where the decompression illness was suffered or contracted before or during (but did not arise out of) the person's relevant service.

Other conceptual features: the instrument treats death as including terminal events or conditions contributed to by decompression illness (s7(3) and Schedule 1 definition of “terminal event”), and it binds into other Statements of Principles where overlap exists (s11). The instrument is framed as a probabilistic causation device , the RMA’s stated basis is that, on the “balance of probabilities”, decompression illness can be related to relevant service (s8).

This Statement of Principles operates within the statutory architecture of the VEA and the MRCA, so its immediate legal effect is on claimants and decision‑makers in those schemes. The instrument applies to a claim to which s120B of the VEA or s339 of the MRCA applies (s5). Those references specify the classes of claims for which the SoP is the relevant medical causation instrument; the SoP itself does not re‑define the statutory eligibility categories (the statutory provisions are not reproduced in the instrument).

Who pays or benefits is not specified in the instrument; rather, the instrument supplies the causal link required in claims that are being considered under the named statutory provisions. Practically, this means:

• Persons who are veterans, members of the Forces, or members whose service falls within the definitions of “relevant service” in Schedule 1 will be the class seeking to rely on the SoP. The instrument defines “relevant service” to include eligible war service (other than operational service) and defence service (other than hazardous service and British nuclear test defence service) under the VEA, and peacetime service under the MRCA (Schedule 1). That textual definition delimits which categories of personnel the SoP is meant to assist in connecting decompression illness to service.
• Administrative decision‑makers who assess claims under s120B VEA or s339 MRCA will apply the SoP’s factors (s5). The instrument itself names the Repatriation Medical Authority as the maker (s3), and it prescribes how its factors are to be applied, including cross‑reference rules to other SoPs (s11).
• Medical practitioners, hospitals, hyperbaric facilities, dive contractors, aircraft operators and other providers of services implicated in the listed exposure scenarios will be indirectly affected because evidence of the enumerated factors (for example, dive logs, flight records, hyperbaric treatment records) will be material to establishing that a factor existed within the temporal window set by the instrument. The instrument does not mandate specific records, but the necessity of proving a factor implies documentary or clinical evidence will be required in practice.

The instrument also affects the legal relationship between pre‑existing decompression illness and subsequent service. Section 10(2) limits the operation of the inability‑to‑obtain‑appropriate‑management factor so it only applies where the decompression illness was suffered or contracted before or during (but did not arise out of) the person’s relevant service, and where the inability materially contributed to, or aggravated, the condition. This narrows the class of situations in which s9(2) will assist a claimant.

Finally, the instrument excludes several related conditions from the SoP’s scope (s7(2)(c)). Individuals whose medical issues fall within those exclusions will not succeed under this SoP and may need to rely on other SoPs or statutory provisions.

The Statement of Principles sets out criteria rather than prescriptive duties in the penal or administrative sense; however, it creates binding causation conditions that must be met for a finding that decompression illness or death from decompression illness is connected with relevant service in a claim to which the instrument applies (s5, s9). The operative requirement is that at least one of the factors listed in s9 must exist for a positive connection to be found on the balance of probabilities (s9, opening words).

Rights and burdens of proof

• The instrument is explicit that the causation test it supplies is the balance of probabilities. The Repatriation Medical Authority records that, on the sound medical‑scientific evidence available, it is of the view that it is more probable than not that decompression illness can be related to relevant service (s8). The SoP therefore sets the evidential standard for causation as the civil standard for the purposes of these claims.
• The “must exist” formulation in s9 places the evidential burden on the claimant to demonstrate, on balance, that at least one enumerated factor is present and that it is related to the person’s relevant service (s10(1)). The SoP does not itself allocate the legal burden for discharging other elements of entitlement under the VEA or MRCA.

Specific requirements and limits

• Temporal proximity is mandated: for the enumerated exposure factors in s9(1)(a)-(j), the exposure must have occurred within seven days before the clinical onset of decompression illness (s9(1)). This is a strict temporal condition embedded in the SoP.
• The inability to obtain appropriate clinical management is an alternative factor (s9(2)), but s10(2) narrows its application so it only operates as material contribution or aggravation where the decompression illness was suffered or contracted before or during relevant service but did not arise out of it.
• Section 11 makes the SoP subject to interaction with other SoPs: where a factor in s9 refers to an injury or disease covered by another Statement of Principles, the factors in that other SoP apply in accordance with its terms as in force from time to time (s11). This establishes a hierarchical or cross‑reference duty for decision‑makers to consult and apply other relevant SoPs where overlap exists.

Duties of decision‑makers

• The instrument itself does not recite administrative decision‑maker duties in procedural detail. It does, however, prescribe the substantive causal factors and cross‑reference rules that decision‑makers must apply when assessing whether decompression illness is connected with relevant service in claims falling under the statutory provisions named in s5. The SoP therefore operates as a substantive normative input into adjudication of those claims.

No penalties established

• The instrument does not create offences or civil penalties. Its legal effect is to inform entitlement decisions under the named statutory frameworks; it does not purport to impose direct sanctions for non‑compliance with the SoP itself.

The Statement of Principles does not create criminal offences, civil penalties, or explicit enforcement mechanisms. Its legal role is evidentiary and determinative within claims processing rather than punitive. The instrument is made under subsection 196B(3) of the VEA (s3) and applies to claims under s120B of the VEA or s339 of the MRCA (s5). Accordingly, enforcement , to the extent the term is applicable , occurs through the administration and adjudication of entitlement claims under those Acts, not by direct sanction in the SoP.

Mechanism of effect in decision‑making

• The SoP supplies the medical causation criteria that must be considered and satisfied when a claim to which s120B VEA or s339 MRCA applies is assessed (s5, s9). If the relevant factor(s) in s9 are established on the balance of probabilities, and are related to the claimant’s relevant service (s10(1)), the SoP supports a finding that decompression illness is connected with service for the purposes of entitlement decision‑making under the statutory provisions named in s5.
• If a factor in s9 refers to an injury or disease covered by another SoP, decision‑makers must apply the factors in that other SoP “in accordance with the terms of that Statement of Principles as in force from time to time” (s11). This cross‑application is an internal enforcement mechanism ensuring consistency across SoPs.

Practical enforcement implications

• Although no fines or offences are created, the SoP’s fixed factors and temporal windows will constrain the outcomes of claims , claimants who cannot show a qualifying factor (for example the enumerated exposures within seven days before clinical onset) cannot rely on this SoP to establish a connection to relevant service.
• The instrument does not set procedural timelines for administrative decision‑makers, nor does it prescribe investigatory powers. It does not specify who must supply evidence or how that evidence is to be weighed; those procedural and evidentiary functions remain in the institutions that administer the VEA and MRCA claims (s5). The SoP imposes a substantive test that those institutions must apply.

No penalties for non‑adherence to the SoP

• As an evidentiary instrument, the SoP cannot be enforced by penal measures against an applicant, practitioner, or third party for failing to produce records. Its effect is remedial: it sets out what must be shown for a causal connection to be found. Any consequences of failure to show a factor are confined to claim outcomes (acceptance or rejection) and any administrative or judicial review processes available under the VEA or MRCA framework.

The instrument is made under the VEA (s3) and expressly applies to claims to which s120B of the VEA or s339 of the MRCA applies (s5). Those statutory references embed the SoP within the statutory claims regime: decision‑makers use the SoP when assessing whether decompression illness is connected with relevant service for the purposes of entitlements governed by the specified provisions.

Cross‑reference to other Statements of Principles

• Section 11 creates a rule for interaction with other SoPs: if a factor in s9 refers to an injury or disease covered by another Statement of Principles determined under subsection 196B(3) of the VEA, then the factors in that other SoP apply according to its terms as in force from time to time. This provision requires administrative decision‑makers to consult and apply the content of other applicable SoPs where there is overlap between conditions or where a listed factor involves an injury/disease already covered by another SoP. The instrument therefore sits within a network of SoPs and can trigger their application.

Relationship to the statutory concepts of “relevant service”

• The instrument defines “relevant service” in Schedule 1 to mean eligible war service (other than operational service) under the VEA, defence service (other than hazardous service and British nuclear test defence service) under the VEA, or peacetime service under the MRCA (Schedule 1). This definition interacts with statutory eligibility rules in the VEA and MRCA to determine whether the SoP can be invoked in a particular claim. The SoP does not alter those statutory eligibility concepts; it functions only where the claim is already one to which s120B VEA or s339 MRCA applies (s5).

Exclusions and competing legal pathways

• The instrument expressly excludes a number of conditions from the definition of decompression illness (s7(2)(c)). Where a claimant’s condition falls within one of those exclusions (for example osteonecrosis, barotrauma, high pressure neurological syndrome/inert gas narcosis), the SoP will not assist; claimants and decision‑makers will need to consider whether those conditions are covered by other SoPs or by other statutory provisions.
• The instrument’s cross‑application rule (s11) means that where an exposure factor references an injury or disease covered by another SoP, the other SoP’s criteria may govern entitlement for that part of the claim. This can create interaction effects in multi‑morbid claims.

No express override of other statutes

• The instrument does not purport to override, amend or modify the substantive provisions of the VEA or MRCA. It is an instrument made under the VEA for the purpose of informing claims under the VEA and MRCA. The SoP’s legal force is therefore limited to its role in causation enquiries binding decision‑makers under the statutory framework.

The instrument contains a limited amendment history recorded within its own text. It repeals the previous Statement of Principles concerning decompression sickness No. 14 of 2015 (Federal Register of Legislation No. F2014L01832) that had been made under subsection 196B(3) of the VEA (s4). The instrument itself is dated 24 April 2023 and commenced on 23 May 2023 (s2 and the introductory material). No other amendments are recorded within the instrument.

What the instrument records about its provenance

• The instrument was made by the Repatriation Medical Authority under subsection 196B(3) of the VEA (s3). The introductory pages show the instrument was sealed at the direction of the Chairperson (professor named in the seal page). The instrument’s recitals state that it is a Statement of Principles “(Balance of Probabilities)” and that it is No. 24 of 2023.
• Section 8 records the basis for the RMA’s determination: on the sound medical‑scientific evidence available, the RMA is of the view that it is more probable than not that decompression illness and death from decompression illness can be related to relevant service under the VEA or MRCA. That statement functions as an internal evidentiary justification for the RMA’s decision to make this SoP.

Implications for future amendments

• The instrument does not set out a process for amendment beyond normal constitutional and legislative mechanisms for the RMA and the VEA. It does, however, by its cross‑reference language (s11), make its operation contingent on the content of other SoPs “as in force from time to time”. That language implicitly allows for the SoP to interact automatically with later changes to other SoPs.
• Any subsequent repeal, modification or replacement of this SoP would need to be recorded in like manner; the instrument’s own repeal of the 2015 SoP demonstrates that the RMA operates through successor SoPs to update the medical causation framework.

What is not in the amendment history

• The instrument contains no record of prior amendments to itself (other than the repeal it effects of the 2015 instrument), no transitional provisions, and no staged implementation changes. The commencement clause (s2) gives a single start date for operation.

The instrument itself does not record any litigation history. It contains no references to judicial decisions, tribunal determinations, or litigation outcomes that have tested or interpreted its content. The instrument is purely the RMA’s Statement of Principles and does not include administrative or judicial review records.

What the absence of litigation history in the instrument implies for users

• Because the instrument does not record litigation or review, users (claimants, advisors, decision‑makers) should not infer settled case law from the instrument alone. The SoP is a statutory instrument setting causation criteria; whether and how those criteria will be interpreted in administrative decision‑making and judicial review will depend on the practices of the decision‑making bodies and any subsequent legal challenges outside the text of the SoP.
• The SoP’s text provides firm substantive content , the list of factors in s9, the temporal window of seven days, the exclusions in s7(2)(c), the cross‑application rule in s11, and the limits on s9(2) in s10(2). These textual features will be the primary reference points in any later dispute about whether a claimant has established the required causal connection.

Practical note for practitioners

• Because the instrument does not supply litigation history, legal advisers, advocates and claimants will need to consult administrative decisions and case law outside the instrument to understand how decision‑makers and courts/tribunals have applied comparable SoPs in practice. The SoP itself should be used as the governing substantive yardstick when preparing or defending claims that fall within s120B VEA or s339 MRCA.
• The cross‑reference to other SoPs (s11) and the exclusions list (s7(2)(c)) are likely to be focal points in any litigation about overlapping or borderline conditions; however, this instrument does not provide guidance on how tribunals or courts should resolve competing medical opinions or evidentiary disputes.

The instrument contains several technical features and narrow conditions that can catch claimants and advisers if not observed carefully. These practical “gotchas” are textual and procedural in nature.

1. Narrow temporal window for exposure factors. For all the enumerated exposure scenarios in s9(1)(a)-(j), the exposure must occur within seven days before the clinical onset of decompression illness (s9(1)). If a claimant cannot show an exposure within that seven‑day window, that enumerated exposure will not satisfy s9(1), and the SoP will not, by itself, establish a connection to relevant service for that exposure.

2. The requirement that “at least one” factor must exist. The instrument requires a claimant to establish at least one of the listed factors in s9. If a claimant has multiple possible contributors but none fits the enumerated factors or the “inability to obtain appropriate clinical management” factor (s9(2)), the SoP will not assist. This is a binary threshold: at least one qualifying factor must be shown.

3. Exclusions from decompression illness. The SoP excludes certain conditions (s7(2)(c)), including altitude illness, arterial gas embolism due to pulmonary barotrauma, barotrauma, ebullism, osteonecrosis, high pressure neurological syndrome/inert gas narcosis, and cerebrovascular accident not due to an arterial gas embolism. If a claimant’s presentation is captured by one of these exclusions, that injury is outside the scope of this SoP.

4. Distinction between types of arterial gas embolism. The SoP includes arterial gas embolism not due to pulmonary barotrauma (s7(2)(b)(i)), but excludes arterial gas embolism due to pulmonary barotrauma (s7(2)(c)(ii)). Medical and factual proof on causation will need to address this distinction; a diagnosis labelled “arterial gas embolism” is not automatically within the SoP’s scope without clarification on the causal mechanism.

5. The “inability to obtain appropriate clinical management” factor is constrained. Section 10(2) specifies that the inability factor in s9(2) applies only where the decompression illness was suffered or contracted before or during (but did not arise out of) the person’s relevant service, and only to material contribution or aggravation. This means that inability to obtain appropriate care cannot be used broadly to establish causation in cases where the condition first arose out of relevant service.

6. Overlap with other SoPs. Section 11 requires that where a factor in s9 refers to an injury or disease covered by another SoP, the factors in that other SoP apply in accordance with its terms. This means that a claimant who relies on a factor that is governed elsewhere must comply with that other SoP’s requirements; failure to do so can undermine the claim.

7. Definitions and excluded diving modes. Note 2 to s9(1) lists modes of underwater diving included in the definition, and expressly states that “this underwater diving does not include diving within normobaric diving bells or armoured suits.” If a claimant’s exposure involved those excluded diving contexts, the SoP’s diving‑related factors may not be satisfied.

8. Death and terminal events. The instrument treats death as including terminal events or conditions contributed to by decompression illness (s7(3) and Schedule 1 definition of “terminal event”), and then lists examples (pneumonia, respiratory failure, cardiac arrest, circulatory failure, cessation of brain function). Practitioners must be careful to link the terminal event causally to decompression illness on the balance of probabilities; death alone does not dispense with the causation requirement.

9. “Substantial episode of decompression” is descriptively defined, not quantitatively. Note 1 to s9(1) describes the term but does not provide numerical thresholds for what constitutes “substantial” or “rapid”. This descriptive standard may generate disputes over medical interpretation and will place emphasis on clinical and operational records.

10. The SoP does not dictate evidentiary forms. The instrument does not prescribe the nature of evidence (for example, documentary records, witness statements, dive logs, flight manifests, hyperbaric treatment records) that will be decisive, only that the factor must exist. Practitioners must therefore anticipate evidentiary challenges and prepare appropriate records.

This SoP is a substantive instrument used when assessing claims under s120B VEA or s339 MRCA (s5). Compliance, in practical terms, requires establishing on the balance of probabilities that at least one of the factors in s9 existed and that it was related to relevant service (s10(1)). The following steps are focused on pragmatic compliance measures directly tied to the instrument’s text.

1. Identify the relevant statutory basis for the claim. Confirm that the claim being advanced falls within the ambit of s120B of the VEA or s339 of the MRCA so that this SoP applies (s5). Also confirm that the claimant’s service meets the SoP’s definition of “relevant service” in Schedule 1.

2. Map clinical onset to exposures. Establish the clinical onset date of the decompression illness. For any enumerated exposure in s9(1)(a)-(j), ensure the exposure occurred within seven days prior to that clinical onset date (s9(1)). This temporal link is mandatory for those exposure factors.

3. Assemble exposure documentation. For each potential s9(1) factor, collate contemporaneous records that demonstrate the exposure occurred and its nature. Relevant items include, where applicable:

   • Dive logs, decompression tables used, whether decompression stops were required, and any dive computer or operator records for surfacing events (s9(1)(a); Note 3).
   • Aircraft manifest, flight altitude and cabin pressurisation records, parachute/balloon records showing altitude, or evidence of loss of cabin pressure for exposures at >5,486 metres (s9(1)(b), (e)).
   • Records of hyperbaric work environments (tunnel, caisson, tunnel boring machine entries) and the timing of return to surface air pressure (s9(1)(f)).
   • Submarine or vessel internal pressure and depth records where ascent from >90 metres seawater or ascent from increased internal pressure is alleged (s9(1)(d)).
   • Records of hyperbaric chamber exposures, hyperbaric oxygen therapy sessions, or pressure testing events (s9(1)(i)-(j)).
   • Logs or mission records for extravehicular activities in space or hypobaric chamber use (s9(1)(g), (h)). The SoP does not require particular forms of documentary proof, but these are the sorts of records that will demonstrate the existence of the enumerated factors.

4. Address excluded conditions. Check that the claimant’s diagnosis falls within the SoP’s definition of decompression illness and is not in the list of exclusions (s7(2)(c)). If the diagnosis is one of the exclusions, the SoP will not assist.

5. Where arterial gas embolism is alleged, clarify the mechanism. If a diagnosis of arterial gas embolism is present, obtain clinical evidence clarifying whether it was due to pulmonary barotrauma. The SoP includes arterial gas embolism not due to pulmonary barotrauma (s7(2)(b)(i)) and excludes arterial gas embolism due to pulmonary barotrauma (s7(2)(c)(ii)). Medical records should address the mechanism.

6. If relying on inability to obtain appropriate clinical management (s9(2)), document the circumstances. For that factor to operate in material contribution or aggravation, the condition must have been suffered or contracted before or during relevant service and not have arisen out of relevant service (s10(2)). Compile contemporaneous clinical records, referrals, correspondence about access to treatment, and expert medical opinions on whether delay or lack of appropriate management materially contributed to or aggravated the condition.

7. When a factor refers to another SoP, comply with that SoP. If a s9 factor refers to an injury or disease covered by another Statement of Principles, identify the other SoP and ensure the claim meets its factors “as in force from time to time” (s11). This may impose different temporal or diagnostic criteria that must be satisfied.

8. Prepare medical causation evidence. Because the SoP operates on the balance of probabilities and refers to “sound medical‑scientific evidence” as the RMA’s basis (s8), include medical expert reports that address the causal link between the established exposure factor and the clinical presentation. Experts should address the SoP’s definitional distinctions and the seven‑day temporal condition.

9. Anticipate challenges on descriptive terms. Terms like “substantial episode of decompression” (Note 1 to s9) are descriptive rather than quantitative. Where these terms are disputed, obtain expert opinion that addresses whether the episode in question meets the SoP’s described standard.

10. Document the relation to relevant service. Section 10(1) requires that any factor in s9 be related to the relevant service rendered by the person. Evidence should therefore link the documented exposure or inability to obtain care concretely to the individual’s service record , for example, showing that the dive, flight, hyperbaric work, or other exposure took place while the person was on relevant service duty as defined in Schedule 1.

11. Record death‑related causal links carefully. Where a claim concerns death from decompression illness, ensure that the terminal event or condition (as defined in Schedule 1) is shown to have been contributed to by decompression illness (s7(3) and Schedule 1 definition of “terminal event”). Provide expert mortality causation evidence tying decompression illness to the terminal event.

12. Keep cross‑referenced SoPs under review. Because s11 brings other Statements of Principles into play where relevant, maintain awareness of current SoPs that may affect the claim and update evidence accordingly.

13. Prepare for administrative application of the SoP. The SoP sets substantive criteria. Administrative staff or decision‑makers will apply it alongside statutory rules in the VEA and MRCA. Ensure that case files clearly map the SoP’s factors to the claimant’s medical and service records to facilitate transparent application.

Following these steps focuses compliance on the textually mandated requirements of the SoP: establishing on the balance of probabilities that at least one enumerated factor exists within the set temporal limits and is related to relevant service, or that the narrow inability‑to‑obtain‑management factor applies as limited by s10(2).