Decompression sickness
Also: DCS risk
Hostile/Closed EnvironmentPulmonaryMusculoskeletalEVA & Surface OpsLEO long-durationLunar surfaceMars transit & surfacePublicClinicianResearcher
- No in-flight DCS has been reported, thanks to pre-breathe protocols validated for weightlessness. ◆◆◆◇ Moderate · F
- For lunar surface missions, NASA rates the risk 5×3, requiring mitigation, because partial gravity and frequent spacewalks are untested. ◆◆◆◆ High · E
Proposed certainty (◆ High → ◇ Very low) and evidence-type tags: F flight · A analog · M model/animal · C computational · E expert/operational/standards. AI-proposed, pending reviewer confirmation. How to read the grades.
NASA risk title (verbatim)
Risk of Mission Impacts and Long-Term Health Issues due to Decompression Sickness
NASA short title: DCS · HRP element: Human Health Countermeasures (HHC) · Status: Active [current research ongoing] [1]
What it is
Decompression sickness (DCS) happens when gas bubbles form in the body after a drop in pressure, as when moving from the cabin into a low-pressure spacesuit [1].
Current evidence
- No DCS cases have been reported in flight, but ground studies with similar decompression stress do produce DCS [1].
- Ground studies stop at the first symptom, so little is known about how symptoms progress [1].
- Partial gravity’s effect is unknown but is expected to raise risk compared with weightlessness [1].
- Current pre-breathe protocols are validated only for weightlessness and take hours [1].
NASA’s risk posture
NASA scores each risk for each design reference mission (DRM) as likelihood × consequence (LxC). Both run from 1 (lowest) to 5 (highest) on the HSRB’s 5×5 matrix [1][3]. Each score comes with a disposition, such as “Accepted”, “Requires Characterization” or “Requires Mitigation”. These ratings were last approved by NASA’s Human System Risk Board (HSRB) in 7/2023 [1].
| Mission | Duration | In-mission (operations) | Long-term health |
|---|---|---|---|
| LEO | Short (under 30 d) | 2x2 · Accepted | 2x1 · Accepted |
| LEO | Long (30 d–1 yr) | 2x2 · Accepted | 2x1 · Accepted |
| Lunar orbit | Short | 2x2 · Accepted | 2x1 · Accepted |
| Lunar orbit | Long | 2x2 · Accepted | 2x1 · Accepted |
| Lunar orbit + surface | Short | 5x3 · Requires Mitigation | 2x1 · Accepted |
| Lunar orbit + surface | Long | 5x3 · Requires Mitigation | 2x1 · Accepted |
| Mars preparatory | Under 1 yr | 2x2 · Accepted | 2x1 · Accepted |
| Mars planetary | 730–1,224 d | 5x3 · Requires Mitigation | 2x1 · Accepted |
This risk has no gaps of its own. Its research is carried under the EVA risk [1].
Copied from the Human Research Roadmap on 2026-10-14. Ratings change. Check the live record before citing.
Open knowledge gaps
NASA lists no gaps under this risk. Its research questions are tracked under the EVA risk [1].
See also Open questions.
Active countermeasure research
- Exploration atmosphere and suit. NASA recommends the 8.2 psia / 34% O₂ atmosphere with a variable-pressure suit and is validating it. Uncertainty in DCS risk-estimation tools limits major design decisions [1].
Project-level detail, including status, investigators and results, is in the NASA Task Book and on each HRR gap page.
Clinical articles
For practical, clinic-facing guidance, see:
Evidence profile
- Overall certainty
- ◆◆◆◇ Moderate (proposed)
- Evidence types
- F · Flight dataA · Terrestrial analogE · Expert / operational / standards
- Literature through
- 2026-10-14
- NASA source
- Human Research Roadmap risk page (last published 05/13/25; read 2026-10-14)
Requirements referenced 4
| Requirement | Title | Plain-language meaning |
|---|---|---|
| [V2 6008] | DCS Risk Identification | Mission-specific mitigation achieving less than 4% DCS probability at 95% confidence in ground tests; no serious DCS; VGE assessed. |
| [V2 6009] | DCS Treatment Capability | The system must provide DCS treatment capability. |
| [V2 6007] | Rate of Pressure Change | Limits how fast pressure may change (no more than 13.5 psi/min). |
| [V1 6006] | EVA Medical Clearance | Every crewmember medically cleared by ground medical support before each EVA. |
IDs as published in NASA-STD-3001 Vol. 1 Rev C (2023-09-15) and NASA-STD-3001 Vol. 2 Rev F (2026-07-14). NASA-STD-3001 binds NASA programs; it is not a regulation for commercial flights. Paraphrased. Standards quick reference.
References 3
- NASA Human Research Roadmap. Risk record: “Risk of Mission Impacts and Long-Term Health Issues due to Decompression Sickness”. Accessed 2026-10-14. humanresearchroadmap.nasa.gov/Risks/?i=168 NASA E
- NASA Human Research Program. Evidence report for the Hypoxia and DCS risks (approved October 31, 2023). humanresearchroadmap.nasa.gov/evidence/reports/Evidence%20Re… NASA E
- Antonsen EL, et al. Updates to the NASA human system risk management process for space exploration. NPJ Microgravity. 2023;9:72. doi:10.1038/s41526-023-00305-z PMID:37679359 Peer-reviewed E
Machine-checked on 2026-10-14: each URL resolved, each DOI's title/journal/year matched via Crossref, and claims were checked against the source text (abstract or full NASA page). Human verification against full text is still required before review. NASA documents are U.S. Government works (public domain) and are summarized with attribution; journal articles are summarized, not reproduced.
Article info
- Authors
- Pending (AI-assisted draft)
- Reviewer
- Pending review
- Last reviewed
- Pending review
- Literature through
- 2026-10-14
- AI-assisted
- Yes (disclosed)
- COI
- Pending
- License
- CC BY-SA 4.0
- Use
- Educational only · Disclaimer
- Cite this version
- Pending first edition