Statement of Principles concerning decompression illness (Reasonable Hypothesis) (No. 23 of 2023)

The instrument’s core legal concept is the “reasonable hypothesis” for linking decompression illness or death from decompression illness to relevant service. The SoP sets out the minimum factual circumstances that must exist before a decision‑maker may conclude that such a reasonable hypothesis has been raised (s 9). This is not a definition of causal proof; rather it establishes the minimal factual predicates the Repatriation Medical Authority considers necessary to move a claim to the next stage of compensable assessment under the VEA/MRCA regime (s 9).

Decompression illness is defined as injury caused by formation of bubbles of nitrogen and other inert gases within tissues and blood vessels as a result of a reduction in ambient pressure (s 7(2)(a)). The definition explicitly includes arterial gas embolism not due to pulmonary barotrauma and decompression sickness (s 7(2)(b)(i)-(ii)). The definition also lists exclusions: 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 (s 7(2)(c)). The instrument adds clarifying notes that clinical manifestations may include musculoskeletal, cutaneous, lymphatic, cardiopulmonary, inner ear or neurological signs or symptoms, and that inert gases include nitrogen, argon, helium, xenon and krypton (s 7 Notes).

The “factors that must exist” are concrete exposure events or circumstances listed in s 9(1)(a)-(j). These include surfacing from dives requiring decompression stops, flying above 5,486 metres in unpressurised aircraft, flying within the recommended no‑fly interval after diving, ascending from submerged vessels under particular depth/pressure conditions, cabin pressure loss at >5,486 metres or in spacecraft above the von Karman line, returning to surface pressure after working in hyperbaric compressed air environments, transferring between pressure environments in space (including donning extravehicular suits), being in a hypobaric chamber, returning to surface pressure after hyperbaric chamber exposures, and returning to surface pressure after pressure testing of pressure vessels (s 9(1)(a)-(j)). Each listed factor must have occurred within seven days before clinical onset of decompression illness (s 9(1)).

The SoP treats inability to obtain appropriate clinical management for decompression illness as an alternative factor that can raise a reasonable hypothesis (s 9(2)). However, s 10(2) limits that factor’s application to material contribution or aggravation where the decompression illness was suffered or contracted before or during, but did not arise out of, relevant service. The instrument’s Schedule defines “relevant service” to include various categories under the VEA and MRCA such as operational service, peacekeeping service, hazardous service, British nuclear test defence service, and warlike or non‑warlike service under the MRCA (Schedule 1).

Finally, the SoP addresses overlapping instruments: where a factor in s 9 refers to an injury or disease already covered by a distinct SoP, that other SoP applies according to its terms in force (s 11).

The instrument explicitly affects persons making claims under the VEA or the MRCA where the relevant claim provisions are section 120A of the VEA or section 338 of the MRCA (s 5). By the instrument’s own formulation and authority, it is directed at veterans, members of Peacekeeping Forces, and members of the Forces under the VEA or MRCA whose service is classified as relevant service in Schedule 1. The Schedule defines “relevant service” to include operational service, peacekeeping service, hazardous service, British nuclear test defence service under the VEA, and warlike and non‑warlike service under the MRCA (Schedule 1).

Who must produce evidence: claimants who assert decompression illness or death from decompression illness in the course of a claim must rely on the factual predicates the SoP sets out. Section 9 establishes that at least one of the listed factors must exist before a decision‑maker can say a reasonable hypothesis has been raised. Those factors are largely event‑based and temporal: exposures such as particular types of diving or flight at specified altitudes, or return to surface pressure after hyperbaric exposures (s 9(1)). The alternative factor of inability to obtain appropriate clinical management is also available (s 9(2)), but s 10(2) constrains its application to circumstances where the decompression illness pre‑existed or occurred during service but did not arise out of service.

Who decides whether the SoP’s thresholds are met: the instrument is made by the Repatriation Medical Authority (s 3) and is to be applied to claims specified in s 5. That places the SoP into the administrative decision‑making process for claims under the VEA and MRCA. The instrument does not itself identify the particular decision‑maker role that applies the SoP, but its application clause (s 5) and the statutory authority (s 3) make plain that it is to be used within the statutory claims framework governed by the VEA and MRCA.

Family members and estates are affected where death is claimed to be from decompression illness. The SoP includes death from decompression illness where a terminal event or condition was contributed to by decompression illness (s 7(3)), and the Schedule defines “terminal event,” including examples such as pneumonia, respiratory failure, cardiac arrest, circulatory failure and cessation of brain function (Schedule 1). This affects claims that rely on post‑service mortality linked to decompression illness.

Medical practitioners and record keepers are implicated because the SoP anchors the assessment to medical sequencing (clinical onset within seven days of exposures, clinical manifestations listed in notes) and to records of exposures such as dive logs, aircraft flight records, hyperbaric chamber records, and documentation of attempts to obtain clinical management when that factor is invoked (s 9; s 7 Notes; s 9 Notes). The SoP’s exclusions (s 7(2)(c)) also require clinicians and assessors to distinguish decompression illness from other pressure‑related conditions.

This instrument does not create new statutory monetary entitlements or alter existing statutory duties in the sense of imposing criminal sanctions. Instead it prescribes evidentiary thresholds and definitions for use when assessing whether a reasonable hypothesis links decompression illness or death from decompression illness to relevant service. The core duty it imposes on claim processors and decision‑makers within the VEA/MRCA framework is to apply the SoP’s factors when considering whether the reasonable hypothesis threshold is met (s 9; s 5). The SoP sets the minimum factual circumstances that must exist before a decision‑maker may say the reasonable hypothesis is raised (s 9).

For claimants, the SoP creates a practical obligation to marshal evidence addressing the specified factors where they wish to have a claim considered under the relevant statutory provisions. That evidence will need to show the occurrence of at least one of the s 9(1) exposures within seven days of clinical onset, or document an inability to obtain appropriate clinical management (s 9(1)-(2)). The Schedule’s definition of relevant service requires documentary proof of the nature of the service if the link to service is to be established (Schedule 1; s 10(1)). Section 10(1) requires that any factor in s 9 be related to the relevant service rendered by the person. This introduces a procedural link between the existence of a factor and the person’s service record.

Medical professionals who provide evidence have the right and duty to identify clinical manifestations consistent with decompression illness and to record timing of clinical onset relative to potential exposures (s 7 Notes; s 9(1)). The SoP expressly lists possible clinical manifestations (s 7 Note 1), which frames the type of medical evidence decision‑makers will consider relevant.

Where a factor refers to an injury or disease covered by another SoP, s 11 delegates the application to that other SoP as in force from time to time. This creates a procedural duty on assessors to cross‑refer and apply the terms of other SoPs when relevant, rather than applying a single instrument in isolation.

Rights to challenge administrative decisions lie in the underlying statutory framework of the VEA/MRCA and are not created or described by this instrument. The SoP itself contains no enforcement mechanism, penalty regime, or appeal pathway; it is an administrative instrument intended for use in claim assessment (see s 3-5).

The instrument contains no penalty provisions, enforcement fines, or criminal sanctions. It is a determinative Statement of Principles made under subsection 196B(2) of the VEA, intended for application to claim assessment under the VEA and MRCA (s 3; s 5). The text does not create compliance offences, civil penalties, licensing duties, or statutory obligations enforceable by pecuniary penalties. Its mechanism is administrative and evidentiary: it frames when a reasonable hypothesis may be said to have been raised concerning causation between service and the listed condition (s 9).

Enforcement, in the sense of ensuring the SoP is used, is implicit in its statutory provenance. The Repatriation Medical Authority made the instrument and affixed its Common Seal at the direction of the Chairperson (document header and signatory). The instrument’s legal force comes from the RMA’s statutory power and the operation of the VEA/MRCA claim frameworks to which it applies (s 3; s 5). The text does not assign powers to inspectors, authorise searches, or mandate compliance audits.

If a decision‑maker within the VEA/MRCA framework fails to apply the SoP when it is applicable, the remedy and consequences would arise from the procedures and review rights set out in the VEA and MRCA and the administrative law framework. This SoP does not itself identify or alter appeal rights, merits review, judicial review avenues, or administrative sanctions. It also does not specify any reporting obligations, time limits for decision‑makers to use the SoP, or record‑keeping mandates beyond the factual composition of the factors and definitions it contains.

Practically, parties will meet the SoP’s effect through the claim assessment process: decision‑makers will determine whether the factors are present in the evidence supplied and thus whether a reasonable hypothesis is raised. The instrument supplies the substantive criteria a decision‑maker is to apply; it does not set out separate enforcement modalities for ensuring decision‑makers apply those criteria.

The instrument sits within the VEA/MRCA statutory architecture. It is made under subsection 196B(2) of the VEA (s 3). It applies to claims to which section 120A of the VEA or section 338 of the MRCA applies (s 5). Those cross‑references indicate that the SoP is designed to operate as a medical premise used in adjudicating entitlements and rehabilitation/compensation claims under those Acts. The Schedule also defines “relevant service” by reference to the categories used in the VEA and MRCA such as operational service, peacekeeping service, hazardous service, British nuclear test defence service, and warlike/non‑warlike service (Schedule 1).

The instrument expressly addresses overlap with other Statements of Principles. Section 11 provides that if a factor in this SoP refers to an injury or disease already covered by another SoP made under subsection 196B(2) of the VEA, then the factors in that other SoP apply in accordance with its own terms as in force from time to time. This creates an inter‑instrument cross‑application rule: where exposures or conditions fall into the scope of a different SoP, assessors must apply that other SoP’s factors rather than attempt to subsume them here (s 11). The wording requires assessors to be attentive to multi‑instrument interactions and to the current text of any cross‑referenced SoP.

The instrument also repeals the earlier SoP No. 13 of 2015 (s 4), which means claim assessments after commencement will use this instrument rather than the 2015 instrument for the matters it covers. The repeal is a direct interaction with prior administrative instruments; it does not purport to amend primary legislation.

The Schedule’s definitions and the SoP’s exclusions may require decision‑makers to engage with other statutory or regulatory frameworks when distinguishing decompression illness from excluded conditions. For example, the exclusion for arterial gas embolism due to pulmonary barotrauma (s 7(2)(c)(ii)) and the exclusion of barotrauma and ebullism (s 7(2)(c)(iii)-(iv)) mean that where a medical record points to those excluded mechanisms, assessors will need to consider whether the claim is more properly assessed under another applicable SoP or legal pathway.

The instrument does not purport to displace other laws outside the VEA/MRCA claims context, such as workplace health and safety legislation, aviation regulation, or maritime safety law. It is narrowly crafted as a medical/evidentiary instrument for the statutory claims system and its scope is defined accordingly (s 5; s 3).

This Statement of Principles is identified as No. 23 of 2023 and dated 24 April 2023 (document header). It commences on 23 May 2023 (s 2). The instrument expressly repeals the Statement of Principles concerning decompression sickness No. 13 of 2015 (Federal Register of Legislation No. F2014L01830) (s 4). The RMA affixed its Common Seal to the instrument at the direction of its Chairperson, Professor Terence Campbell AM (instrument signatory and seal statement).

The instrument records the statutory basis for its making as subsection 196B(2) of the Veterans’ Entitlements Act 1986 (s 3). Section 8 contains the RMA’s statement that it is of the view there is sound medical‑scientific evidence indicating that decompression illness and death from decompression illness can be related to relevant service. That statement is the RMA’s recorded evidentiary predicate for determining the SoP.

There is no further amendment history recorded within the instrument itself. There are no schedules or notes indicating earlier amendments beyond the explicit repeal of the 2015 instrument. Any subsequent amendments, replacements, or further repeals will not appear within this instrument; they would be reflected in the Federal Register of Legislation or in a later SoP.

For practical purposes, assessors and practitioners should note that the 2015 SoP has been replaced from the commencement date and that the current legal criteria for raising the reasonable hypothesis for decompression illness are those set out in this 2023 instrument (s 2; s 4). The instrument’s cross‑reference provision (s 11) also contemplates the continued force of other SoPs where factors intersect; changes to those other SoPs after this instrument’s commencement will alter how cross‑referenced factors are applied.

The instrument itself contains no record of litigation, judicial consideration, or case law. It names no cases and does not report any disputes or judicial review outcomes in its text. The administrative provenance and use of SoPs sit within the broader VEA/MRCA review mechanisms and administrative law regime; those avenues govern any potential challenges to decisions that rely on this SoP. However, this instrument does not record or provide a litigation history or a catalogue of appellate decisions.

Practitioners needing to understand how decision‑makers have applied a Statement of Principles in contested determinations should therefore look to the decisions and published reasons of the statutory decision‑makers, merits review tribunals, and courts under the VEA/MRCA framework. The instrument itself supplies the substantive thresholds (s 9) and definitions (s 7; Schedule 1) that a tribunal or court would consider when reviewing whether a reasonable hypothesis was properly found to be raised; it does not include procedural directions for litigation or review.

If a decision relying on this SoP is subject to administrative or judicial review, the grounds and outcomes will be derived from the VEA/MRCA review mechanisms and general administrative law principles. The SoP contains no discussion of precedential application or any list of prior decisions; it is an administrative statement of medical‑fact criteria and definitional material to be used in claims assessment.

1. Minimum threshold language. Section 9 uses the phrase “At least one of the following factors must as a minimum exist before it can be said that a reasonable hypothesis has been raised.” That wording establishes a minimal evidentiary threshold rather than a conclusive nexus. Practitioners should not treat presence of a factor as automatic entitlement; it only moves a claim past the “reasonable hypothesis” step as framed by the RMA (s 9). The instrument itself provides no direction as to the subsequent steps in claim adjudication.

2. Seven‑day window and “clinical onset.” The listed exposure events must have occurred within seven days before the clinical onset of decompression illness (s 9(1)). The instrument does not define “clinical onset” beyond referencing the timing, so precise identification of onset in medical records will be consequential. Clinicians and advocates must ensure the medical file contains dated clinical findings or symptom onset notes that align to the seven‑day period.

3. Exclusions create tight distinctions. The SoP includes arterial gas embolism not due to pulmonary barotrauma (s 7(2)(b)(i)) while excluding arterial gas embolism due to pulmonary barotrauma and barotrauma more generally (s 7(2)(c)(ii)-(iii)). Assessors will need to distinguish mechanisms in clinical records,whether embolism is attributable to pulmonary barotrauma or to decompression bubble formation,because that mechanistic attribution determines inclusion or exclusion under the instrument.

4. Scope of “underwater diving.” The Note to s 9 clarifies that “underwater diving” includes breath hold diving, bounce diving, umbilical/hookah/hard hat diving, SCUBA, rebreather diving, and saturation diving, but excludes diving within normobaric diving bells or armoured suits (s 9 Note 2). Where records show use of diving bells or specialised suits, assessors may need to resolve whether the exposure falls within the SoP.

5. “Substantial episode of decompression” is a qualifying phrase. The Note to s 9 defines substantial episodes as rapid substantial reductions in ambient pressure when the person had been at higher pressure for a substantial period. The instrument leaves room for medical interpretation of “substantial” for both rate and duration. That interpretative elasticity may be a point of contention in assessing whether particular exposures meet the requirement.

6. Inability to obtain appropriate clinical management is narrowly constrained. Section 9(2) is an alternative factor but s 10(2) restricts its use to material contribution or aggravation where decompression illness was suffered or contracted before or during, but did not arise out of, service. Practitioners invoking this factor will need contemporaneous evidence of attempts to access care and the timing relation between illness and service.

7. Interaction with other SoPs. Section 11 mandates that if a factor refers to an injury or disease covered by another SoP, the other SoP applies as in force. This can create procedural complexity where multiple SoPs intersect; practitioners must check the current text of cross‑referenced SoPs, not assume this SoP alone governs.

8. Death claims require demonstration of contribution. The SoP includes death from decompression illness where a terminal event or condition was contributed to by the decompression illness (s 7(3)). The Schedule defines examples of terminal events (Schedule 1), but the instrument does not quantify degrees of contribution. Practitioners must produce medical evidence linking decompression illness to the terminal event identified.

9. No penalties, no procedural timelines. The instrument does not set time limits for filing or for decision‑maker use, nor does it provide enforcement provisions. Practitioners should not rely on the SoP for procedural relief; instead procedural questions remain governed by the VEA/MRCA and their rules.

10. Repeal of 2015 SoP. The 2015 instrument is expressly repealed (s 4). For cases where evidence spans the repeal date, practitioners should ensure they are using the current 2023 criteria for claims arising after 23 May 2023, and consider how earlier decisions using the 2015 SoP may affect existing administrative records.

For claimants and advisers:

• Anchor the claim to the appropriate statutory provision. This SoP applies only to claims to which VEA s 120A or MRCA s 338 applies (s 5). Confirm the claim’s statutory pathway before relying on this SoP.

• Show at least one s 9 factor within seven days of clinical onset. The principal route to establishing that a reasonable hypothesis has been raised is proving an exposure listed in s 9(1)(a)-(j) occurred within seven days prior to symptom onset. Gather dated, contemporaneous evidence such as dive logs, dive computer downloads, decompression stop records, flight manifests or flight logs (showing altitude and pressurisation), records of no‑fly interval guidance following dives, submarine or vessel ascent logs, hyperbaric chamber session dates, workplace records of hyperbaric compressed air work (tunnel, caisson, tunnel boring machine), and pressure testing or maintenance records (s 9(1)).

• Document clinical onset precisely. Because the seven‑day window is measured to clinical onset (s 9(1)), ensure medical records contain the earliest documented date of symptoms or clinical findings consistent with decompression illness. Where onset is gradual, obtain clinician statements that identify the onset date and describe clinical manifestations (s 7 Note 1).

• If relying on inability to obtain appropriate clinical management, prepare contemporaneous records. Section 9(2) provides an alternative factor, but s 10(2) limits its application to cases where the decompression illness was suffered or contracted before or during service but did not arise out of service. To rely on this factor, document attempts to obtain care, dates, referrals, refusals, delays, and how the lack of appropriate management materially contributed to or aggravated the condition.

• Address mechanistic distinctions and exclusions. Be prepared to show that the pathology is decompression illness as defined in s 7(2)(a) and included items in s 7(2)(b), and is not one of the named exclusions in s 7(2)(c). Where clinical notes suggest pulmonary barotrauma, barotrauma, ebullism, osteonecrosis or high pressure neurological syndrome, obtain specific medical opinions that differentiate these mechanisms from decompression bubble formation.

• For death claims, obtain medical evidence of contribution. Where death is asserted to be from decompression illness, produce clinician opinions stating that the terminal event or condition was contributed to by decompression illness (s 7(3)). Use the Schedule’s examples of terminal events to frame causation opinions and ensure opinions address proximate and ultimate cause as required by the Schedule’s definition of “terminal event” (Schedule 1).

• Check for cross‑referenced SoPs. If any s 9 factor refers to an injury or disease covered by another SoP, ensure evidence and submissions align with that other SoP’s factors and current text (s 11). Practitioners should verify whether any relevant SoP has been amended since this instrument’s commencement.

• Confirm relevant service. Section 10(1) requires the existence of any factor in s 9 to be related to the person’s relevant service. Compile service records that demonstrate the nature of the person’s service as defined in Schedule 1, including operational, peacekeeping, hazardous, British nuclear test defence, warlike, or non‑warlike service categories where relevant.

• Use targeted medical statements. Obtain medical reports that use the terminology and mechanism set out in the SoP: identification of decompression bubble pathology, arterial gas embolism not due to pulmonary barotrauma where applicable, and the clinical manifestations listed in the Note to s 7 (musculoskeletal, cutaneous, lymphatic, cardiopulmonary, inner ear or neurological signs or symptoms).

• Be attentive to timing and version. The current SoP commenced 23 May 2023 and replaces the 2015 instrument (s 2; s 4). Where a claim spans the repeal date or prior decisions relied on the 2015 instrument, ensure submissions adopt the current SoP criteria where applicable.

For decision‑makers and medical advisers:

• Apply the SoP as the minimum factual test for a reasonable hypothesis. Use s 9 to determine whether a reasonable hypothesis has been raised. If one of the listed factors exists and is related to relevant service (s 10(1)), then the SoP’s threshold is met for that stage of assessment.

• Cross‑check other SoPs when factors overlap. Where a listed factor refers to a condition already governed by another SoP, apply that other SoP in accordance with s 11.

• Distinguish mechanism with care. The SoP delineates included and excluded mechanisms (s 7(2)). Medical assessors must explain mechanistic reasoning in terms compatible with the SoP’s definitions when advising on causation.

• Record findings against the SoP language. When giving reasons, identify which s 9 factor(s) were considered, whether they occurred within seven days of clinical onset, whether the factor was related to the person’s relevant service (s 10(1)), and whether the alternative factor in s 9(2) is applicable subject to s 10(2).

• For inability to obtain appropriate clinical management claims, focus on evidence of attempts to obtain care and the temporal relationship between service, onset, and care limitations (s 9(2); s 10(2)).

This compliance guidance is procedural and evidential; it does not create or alter entitlements beyond the role the SoP plays within the VEA/MRCA claim assessment framework (s 5).