0.5.12 - ci-build
SpaceflightHealthSimulationsReferenceDocumentation - Local Development build (v0.5.12) built by the FHIR (HL7® FHIR® Standard) Build Tools. See the Directory of published versions
Underwater training facilities serve as realistic Earth-based analogs for space missions. For example, NASA's Neutral Buoyancy Laboratory (NBL) – one of the world's largest indoor training pools – is used for mission planning, procedure development, hardware verification, and astronaut training in preparation for spacewalks¹. In parallel, NASA's NEEMO missions immerse crews in the Aquarius undersea habitat (62 feet deep off Key Largo) for 1–3 week "saturation" dives, effectively simulating long-duration spacecraft habitation and hyperbaric exposures²'³. These environments allow multinational teams (NASA, ESA, CSA, UAE and others) to practice complex tasks like assembling habitat mockups, cargo handling, and emergency drills in an isolated, high-pressure setting⁴'³. By training underwater, astronauts and support personnel confront stressors analogous to those in space – from life-support dependency to confined isolation – making these dual-use operations invaluable for both diving medicine and space medicine.
This implementation guide provides comprehensive FHIR profiles for underwater training environments that serve as space analogs. The data model supports:
NeutralBuoyancySession profileDiveMedicalClearance profileDiveProfile and AdvancedDiveProfile profilesRegulatoryComplianceAssessment profileThe implementation includes several key profile categories:
| Profile Category | Primary Profiles | Purpose |
|---|---|---|
| Training Procedures | NeutralBuoyancySession, UnderwaterEVASimulation |
Document training activities and performance |
| Medical Assessments | DiveMedicalClearance, BarotraumaAssessment |
Track medical fitness and injuries |
| Dive Operations | DiveProfile, DecompressionProtocol |
Capture operational data and safety protocols |
| Emergency Response | DecompressionSickness, HyperbaricTreatment, UnderwaterEmergencyResponse |
Manage incidents and treatments |
| Equipment & Facilities | DivingEquipment, HyperbaricChamber, UnderwaterCommunicationSystem |
Track devices and locations |
The physiological and operational challenges of underwater environments closely parallel those encountered in space:
Confined, hostile environments: Underwater habitats and spacecraft are closed systems where even minor equipment failures can become critical. Life support (breathing gas, pressure regulation, thermal control) is mandatory in both settings¹. Crew members work in limited spaces, isolated from immediate external aid, which demands strict life-support and evacuation protocols.
Complex task performance: Astronauts must perform intricate tasks (tool handling, assembly, repair) while burdened by bulky gear or buoyancy effects. Underwater neutrality is often adjusted to simulate weightlessness, so that manipulating large masses feels akin to microgravity operations⁵. These simulations test fine motor skills and decision-making under physical strain and altered proprioception.
Emergency response protocols: Whether under water or in orbit, emergency scenarios (e.g. rapid depressurization, equipment failures, diver "out-of-air" events) require rigorously practiced procedures. In both domains, crews train for remote rescues and on-site first response – for example, using onboard oxygen supplies, communicating with support teams, and executing contingency escapes.
Equipment dependency: Survival depends on sophisticated life-support and mobility systems in both domains. Submersible breathing apparatus (SCUBA or mixed-gas regulators) and space suits provide breathable gas, pressure control, and thermal regulation. Facilities like the NBL maintain SCUBA and surface-supplied dive systems (air and nitrox) and even house an on-site hyperbaric chamber⁶. Similarly, spacecraft suits and vehicles carry redundant systems for gas supply, carbon dioxide scrubbing, and overheating prevention. Both require stringent pre-dive/airlock checks and backup contingencies.
Pressure-related medical considerations: Changes in ambient pressure affect the human body in comparable ways. Increased ambient pressure (immersion) increases tissue nitrogen load, while transitioning to lower pressures (surfacing or suit depressurization) risks inert gas bubbles and decompression sickness (DCS). For instance, NASA must prevent DCS during EVA by using 100% oxygen prebreathe to purge nitrogen before the suit's lower-pressure environment⁷. Similarly, divers follow staged decompression schedules and gas-switch protocols to avoid DCS.
This dual-use approach enables NASA and other agencies to apply spaceflight medical standards to dive training and vice versa. Underwater training leverages precise monitoring and safety practices so that lessons learned about human physiology, equipment, and procedures can directly improve space mission readiness and diving program safety.
The Neutral Buoyancy Laboratory (NBL) and similar facilities provide the highest-fidelity analog for EVA tasks on Earth. Astronauts wear full pressure suits and conduct simulated spacewalks beneath the pool surface, with expert divers providing safety and technical support⁶'⁵. In these sessions, every aspect of the dive is meticulously managed and recorded:
Each neutral buoyancy session is documented using the NeutralBuoyancySession profile, which captures:
Example Training Session:
{
"resourceType": "Procedure",
"meta": {
"profile": ["http://hl7.org/fhir/uv/aerospace/StructureDefinition/neutral-buoyancy-session"]
},
"status": "completed",
"code": {
"coding": [{
"system": "http://hl7.org/fhir/uv/aerospace/CodeSystem/neutral-buoyancy-training-cs",
"code": "eva-simulation",
"display": "EVA Simulation Training"
}]
},
"subject": {"reference": "Patient/CaptainJaneway"},
"performedDateTime": "2025-06-01T09:00:00Z",
"location": {"reference": "Location/NASANeutralBuoyancyLaboratory"}
}
For EVA-specific simulations, the UnderwaterEVASimulation profile extends the base training session with:
See the example training session for a complete implementation.
The standardized NeutralBuoyancyTrainingCS code system defines:
Underwater training allows detailed emulation of spacewalk conditions. Trainers measure how effectively crew members manipulate tools while weightless and wearing pressurized suits. They evaluate team coordination during multi-astronaut operations (e.g. mock ISS assembly or habitat construction) and monitor cognitive load and fatigue accumulation over hours of work. Communications systems (including specialized underwater full-face masks with hardwired links) are tested for clarity and reliability in the noisy environment⁸. Emergency drills (such as rapid ascent protocols or suit breach scenarios) are practiced with realism. All these factors—task performance, teamwork, fatigue, comms integrity, emergency responsiveness—are documented so that training effectiveness can be quantified and EVA procedures refined.
Diving for space analog training requires extending standard astronaut health screening to include dive-specific evaluations. The DiveMedicalClearance profile documents comprehensive medical assessments including:
Core Medical Evaluations:
PulmonaryFunction extensionCardiovascularFitness extensionVestibularAssessment extensionDivingContraindications extensionIn addition to routine aerospace medical exams, candidates undergo protocols similar to the NOAA Diving Medical Program. For example, all potential divers must demonstrate adequate respiratory function via spirometry and lung imaging⁹, ensuring no obstructive or restrictive disease impairs breathing under pressure. Cardiovascular fitness is also assessed (e.g. treadmill tests, ECG, lipid profile) to certify that the diver can handle the exertion and stress of diving¹⁰. A thorough neurological and vestibular exam is critical; inner-ear disorders (such as Meniere's disease, chronic otitis, or prior ear surgery) can prevent proper pressure equalization and are disqualifying¹¹.
Medical Contraindications:
The DivingContraindicatedConditions value set includes conditions such as:
Medical history reviews emphasize any previous dive-related incidents (decompression illness, arterial gas embolism, barotrauma) as potential contraindications or criteria for individualized assessment. Clearance to dive is granted only after all these factors meet conservative standards (e.g. absence of disqualifying conditions)⁹'¹¹. This multi-domain screening helps prevent medical emergencies during training dives.
Modern dive operations generate extensive digital logs that feed directly into training records using the DiveProfile and AdvancedDiveProfile profiles. These capture:
Core Dive Parameters:
Advanced Analytics (via AdvancedDiveProfile):
Commercial dive computers continuously record depth and time profiles for each dive, calculate decompression requirements, and monitor nitrogen saturation in tissues. After each dive, these logs (often in standard formats) can be uploaded to training databases. Key data such as maximum depth, bottom time, ascent rate, and required decompression stops are captured. Decompression obligations are computed using established dive tables or algorithms, and actual ascent profiles are compared to planned schedules. Environmental conditions (water temperature, visibility, currents) and the breathing gas mix used (air, nitrox, trimix) are annotated. Importantly, repetitive dives over days or weeks are tracked to quantify cumulative nitrogen loading; for example, NOAA requires dive computers for multi-day operations and mandates recording of residual nitrogen¹². This rich dive-exposure record integrates with the diver's health monitoring, enabling evaluation of cumulative decompression risk and informing safe scheduling of future dives.
This implementation guide defines comprehensive code systems for underwater training medicine:
NeutralBuoyancyTrainingCS: Training activities, performance metrics, environmentsDivingMedicineCS: Medical examinations, dive profiles, hyperbaric treatmentsDecompressionProtocolCS: Decompression algorithms, safety procedures, ascent protocolsUnderwaterCommunicationCS: Communication systems, protocols, equipment statusRegulatoryComplianceCS: NOAA, OSHA, NASA, and international standardsNeutralBuoyancyTrainingActivities: Training procedures and assessmentsUnderwaterTrainingProcedures: Underwater training and emergency proceduresDivingContraindicatedConditions: Medical conditions that preclude divingUnderwater training centers often include on-site hyperbaric chambers that serve both as safety assets and research platforms. The HyperbaricChamber location profile and HyperbaricTreatment procedure profile document:
Chamber Specifications:
Treatment Protocols:
The EnhancedHyperbaricTreatment profile captures:
These chambers can be multi-place (housing multiple people) or monoplace. Treatment protocols for any decompression sickness or other dive injuries follow established hyperbaric tables (e.g. U.S. Navy or NOAA recompression tables), which are documented and tracked in the training records. Physicians and chamber operators use standardized logbooks to record chamber pressure, gas mixtures, and schedule steps. Physiological monitoring under pressure is maintained for anyone undergoing compression: vital signs (heart rate, SpO₂) are tracked, and oxygen exposures are carefully controlled. Protocols for oxygen toxicity surveillance are strictly enforced: personnel are trained to watch for early CNS oxygen toxicity symptoms using mnemonics (e.g. VENTID‑C) and to apply air-breaks as needed¹³. Chamber operations include redundancies in breathing systems and emergency air sources, analogous to spacecraft life support. Thus, hyperbaric facilities not only treat DCS but also allow controlled exposure studies, validating equipment and procedures for high-pressure environments.
Decompression sickness (DCS) risk is a key concern shared by divers and astronauts. The DecompressionSickness profile extends the space medicine condition profile to capture:
DCS Documentation:
Associated Procedures:
DecompressionProtocol: Standardized decompression proceduresBarotraumaAssessment: Assessment of pressure-related injuriesComprehensive DCS management begins with rapid symptom identification (joint pain, neurological signs) and classification of severity. If DCS is suspected, the affected individual is promptly transferred to hyperbaric treatment. Treatment response is closely monitored: symptoms are recorded before, during, and after recompression therapy, ensuring that the protocol (e.g. USN Table 6) is followed and adjusted as needed. After treatment, outcome assessment documents resolution or any residual deficits. Detailed medical notes and follow-up evaluations inform the astronaut's return-to-training timeline. Training programs also analyze DCS incidents to improve prevention: for example, gas switch schedules, depth/time limits, and pre-dive oxygen prebreathe are reviewed in light of any "near miss" or decompression case. This iterative profiling of DCS events and responses supports evidence-based refinements to both dive practices and spaceflight pre-breathing protocols.
Rapid pressure changes are hazardous in both diving and spaceflight. Training programs continuously monitor pressure change rates during descent/ascent and ensure strict adherence to equalization protocols (e.g. ear clearing, mask balancing). The breathing gas composition is managed closely: divers often use nitrox (oxygen-enriched air) or mixed gases to optimize decompression, while spacecraft might adjust cabin O₂ levels for missions. Biophysically, models of nitrogen uptake and elimination are applied to predict tissue loading; these models are analogous to NASA's microgravity denitrogenation protocols. In an emergency (e.g. rapid ascent from a disabled submersible), divers and crews are trained in emergency decompress procedures, including rapid oxygen breathing and immediate chamber therapy. Sensors in the facility and suits track ambient pressure and gas partial pressures in real-time, alerting the team if thresholds are approached. All these measures ensure safe atmospheric transitions during analog missions.
Diving and spacecraft life-support equipment share many design principles. The DivingEquipment and UnderwaterCommunicationSystem profiles track:
Life Support Equipment:
Communication Systems:
Breathing gas quality is closely monitored: filter cartridges and compressors are inspected to prevent contamination (nitrogen dioxide, carbon monoxide, etc.). Life-support gear is built with redundancies – for instance, space suits have backup oxygen tanks, and divers carry independent bailout bottles. Training emphasizes failure response drills: if a regulator or suit fan fails, the diver/astronaut must switch to secondary systems immediately. Diving teams follow maintenance schedules (e.g. calibrating pressure gauges, servicing valves) that mirror aerospace maintenance protocols. Emergency life support durations are computed into mission plans: divers train to know exactly how long their bailout supply lasts at working depths, similar to how EVAs are planned around consumables. Communication systems are also stress-tested underwater: full-face masks with wired communication (used during SEATEST-7 and NEEMO) show how to maintain clear audio/video links even when handling cables⁸. By treating diving gear and spacecraft systems under a unified safety doctrine, programs ensure that astronauts can seamlessly apply space-proven life-support strategies in the water, and vice versa.
Studying crewmembers in underwater analogs yields valuable insights into human physiology that overlap with space medicine. For example, immersion-induced fluid shifts (centralization of blood volume due to buoyancy) share features with microgravity fluid redistribution. Research has shown that immersion reduces peripheral fluid extravasation and increases central blood volume, much like fluid moves cephalad in space¹⁴. Thermal regulation is another common challenge: wearing pressurized suits or wetsuits in water can lead to heat stress similar to extravehicular activity overheating. Cognitive performance and crew psychology under stress are monitored (mission planners track workload, team dynamics, and stress markers during long dives). Because these analog studies occur in controlled environments, physiologic measurements (heart rate variability, oxygen consumption, sleep patterns) from underwater missions can be directly compared with spaceflight data. Patterns of deconditioning (muscle fatigue, bone stress) during repeated long dives can inform countermeasures for microgravity effects. In essence, the underwater analog acts as a surrogate laboratory where hypotheses about space physiology can be tested and refined.
Quantitative evaluation is built into every dive program using the performance metrics captured in our FHIR profiles. The "skills transfer" from underwater training to space missions is assessed by comparing performance in neutral-buoyancy or saturation dives with performance in microgravity or simulator trials. Benchmark tasks (e.g. timed assembly of mock satellite components) are repeated across simulation modes to verify that underwater proficiency correlates with expected EVA performance. Medical monitoring is continuous: divers who train for weeks may undergo serial health checks to ensure continuity of medical data (e.g. tracking any signs of cumulative nitrogen exposure or stress). All mission logs, dive profiles, and medical observations feed into risk models. For instance, data on crew fatigue and decompression exposures can be used to predict DCS risk for upcoming training schedules. Likewise, psychological measures (mood questionnaires, decision-making tasks) are used to quantify cognitive effects of the extreme environment. This integrated monitoring allows for dynamic risk assessments – if certain profiles (e.g. repeated deep dives without adequate surface interval) are correlated with higher bubble scores, the program will adjust training protocols. The end goal is an evidence-based curriculum where individual response (fitness, stress tolerance, learning curves) informs personalized dive schedules and training loads.
The ExampleNeutralBuoyancySession demonstrates a typical 3-hour EVA simulation session with:
The ExampleDiveProfile shows comprehensive dive data collection including:
The ExampleDiveMedicalClearance illustrates the medical clearance process with:
Successfully managing underwater training requires fusing diverse data streams into a cohesive record. Dive computers export standardized log files (often in Garmin/CSV formats) that can be parsed into electronic health records. Physiological monitors (biotelemetry for heart rate, temperature, oximetry) feed into mission databases in real-time. Performance metrics (task timing, error counts) and environmental sensors (pool temperature, gas composition) are linked to each training session. These data should be codified with consistent units and time stamps. Medical evaluations (pre- and post-dive physical exams, imaging results, lab tests) are tracked alongside dive history. In an HL7 FHIR context (R4), this could involve using Observation resources for dive vitals, Procedure resources for dive events, Condition for any decompression illness, and Device for equipment logs. Notably, future FHIR versions introduce even more relevant features: for example, FHIR v6 (ballot) has a dedicated provider taxonomy entry for "Undersea and Hyperbaric Medicine" specialists¹⁵, and R5 is expected to add environmental exposure profiling. Leveraging these standards, the analog dive program can ensure interoperability of its health and training data with broader aerospace medical records.
Robust QA is essential for safe diving operations. All hardware (suits, breathing regulators, chamber valves) is calibrated and maintained on strict schedules parallel to aerospace quality protocols. Personnel are certified to diving standards: e.g. NASA divers often hold NOAA/AAUS certifications and attend requalification courses annually. Safety procedures are audited: checklists for dive briefings, emergency drills, and chamber operations are standardized and training sessions are observed for compliance. Incident reporting systems capture near-misses to continually refine safety plans. Medical surveillance includes routine follow-ups for divers, monitoring for late-onset dive-related effects (like ear trauma or subtle neurological symptoms). To ensure consistency across facilities, standardized training curricula and protocols are adopted (for instance, using common dive tables or preload protocols). By applying rigorous QA — analogous to spacecraft safety reviews — the underwater analog program maintains a "mission-ready" culture where both diving and spaceflight best practices reinforce each other.
Underwater analog training continues to evolve with advancing technology and medical knowledge:
Advanced simulation technologies: Virtual reality and haptic feedback may be integrated into underwater training (as in NASA's AMADEE/MOONDIVE projects) to superimpose mission visuals on divers, enhancing realism without additional physical hazard.
Enhanced physiological monitoring: Wearable sensors (e.g. NIRS, ECG patches) and AI-based analytics can provide richer real-time insight into diver health, allowing finer correlations between analog and spaceflight data.
Predictive risk modeling: Sophisticated models (possibly based on machine learning) could predict individual DCS or fatigue risk from prior dive history, customizing training regimens.
Personalized training protocols: Based on individual medical responses (heart rate trends, cognitive scores), dive exposures and prebreathe procedures could be tailored to optimize safety and learning for each astronaut candidate.
Dual-use equipment development: New life-support hardware (e.g. closed-loop rebreathers or hybrid buoyancy-suit systems) may be designed for both deep diving and planetary EVA, streamlining research for both fields.
In summary, leveraging underwater training and decompression medicine in a unified framework creates an evidence-based foundation for astronaut preparation. This approach not only enhances the safety and effectiveness of spacewalk and mission training, but also drives advances in diving and hyperbaric medicine that benefit the broader medical community.
¹ Neutral Buoyancy Laboratory - NASA
² Human Adaptations to Multiday Saturation on NASA NEEMO - PubMed
³ Astronauts Test Retro Spacesuit Tech for Mock Mars Missions Under the Sea & Space
⁴ From Sea to Space - Divers Alert Network
⁵ EVA and Environmental Physiology - NASA
⁹ NOAA Diving Medical Standards and Procedures Manual
¹³ RECOMPRESSION CHAMBER OPERATIONS
¹⁴ The Circulatory Effects of Increased Hydrostatic Pressure Due to Immersion and Submersion - PMC