Fictional composite case
This case is invented for teaching. It combines typical features from the cited sources and describes no real astronaut, spaceflight participant or patient. No real patient data were used.
Case File: Shoulder Pain After a Spacewalk
Hostile/Closed EnvironmentMusculoskeletalNeurological & CognitivePulmonaryEVA & Surface OpsIn-flightLEO long-durationLunar surfaceMars transit & surfaceClinicianOperator / SFP
- Low suit pressure can release nitrogen bubbles; prebreathe protocols must show under 4% DCS probability in ground tests [1][3]. ◆◆◆◆ High · E A
- Most DCS presents 60–240 minutes after decompression; diagnosis is clinical [1]. ◆◆◆◇ Moderate · E
- Treatment in orbit is 100% oxygen and recompression with suit plus cabin pressure; NASA reports no Type II DCS in spaceflight [1]. ◆◆◆◇ Moderate · E F
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.
Presentation
A 39-year-old crewmember completes a 6.5-hour spacewalk (extravehicular activity, EVA) after the standard oxygen prebreathe protocol. About 2 hours after the airlock is repressurized, she reports a deep, dull ache in her right shoulder that is worse when she moves it.
- No numbness, weakness, confusion, visual change, ringing in the ears, rash, cough, chest pain or shortness of breath.
- The shoulder is not swollen or tender to touch. She did a lot of overhead work with tools during the spacewalk.
Questions
- What is the most likely diagnosis, and how would NASA classify it?
- Why do spacewalks cause decompression sickness?
- How is it treated in orbit?
- What would change your level of concern?
Think through your answers before opening the reveals below.
Reveal
Question 1: answer and discussion
What is the most likely diagnosis, and how would NASA classify it?
Possible Type I decompression sickness (DCS), the musculoskeletal form. NASA classifies Type I DCS as itching, joint or muscle pain and mild rash. Type II involves neurological, inner-ear or cardiopulmonary symptoms, or mottled skin. Most cases appear 60–240 minutes after decompression [1].
A strain from overhead suit work is the main alternative. Musculoskeletal injuries, especially minor hand injuries from glove use and repeated tasks, are known spacewalk hazards [2]. DCS is a clinical diagnosis. Bubbles on ultrasound are common without symptoms, and symptoms can occur without detectable bubbles [1]. When in doubt, treat as DCS.
Question 2: answer and discussion
Why do spacewalks cause decompression sickness?
Spacesuits run at a much lower pressure than the cabin (historically 4.3 psia in the U.S. suit, versus 14.7 psia). Nitrogen dissolved in tissues can come out of solution as bubbles, as in divers who surface too fast [1]. Breathing pure oxygen beforehand (prebreathe) washes nitrogen out. NASA requires prebreathe protocols to show a DCS probability below 4% with 95% confidence in ground chamber tests [1][3].
Question 3: answer and discussion
How is it treated in orbit?
There is no hyperbaric chamber in orbit. NASA’s approach [1]:
- 100% oxygen.
- Recompression using the suit plus cabin pressure. A minimum of about 16.4 psia may relieve symptoms, but the protocol depends on the scenario. The principle is the same as the U.S. Navy treatment tables.
- Oral or intravenous fluids, except in pulmonary DCS.
On Earth, call a hyperbaric or dive-medicine service. The pathophysiology and recompression principles are the same as in diving DCS [4].
Question 4: answer and discussion
What would change your level of concern?
Any Type II feature is an emergency: numbness or weakness, confusion, vertigo or hearing loss, chest pain, cough or shortness of breath (“the chokes”), or mottled skin [1]. NASA reports it has never had a Type II DCS event in spaceflight [1].
About one in four people has a patent foramen ovale (PFO), which can let venous bubbles reach the arteries. NASA does not currently screen crew out for a PFO [1].
Teaching points
- DCS after a spacewalk is the same disease as diving and altitude DCS [1][4].
- Type I is joint or muscle pain, itching or rash; Type II is neurological, inner-ear or cardiopulmonary, and is an emergency [1].
- Diagnosis is clinical; bubbles neither confirm nor exclude it [1].
- In orbit, treatment is oxygen plus recompression with suit and cabin pressure [1].
- Every spacewalk requires medical clearance [5].
Read more
Evidence profile
- Overall certainty
- ◆◆◆◇ Moderate (proposed)
- Evidence types
- E · Expert / operational / standardsA · Terrestrial analogF · Flight data
- Literature through
- 2026-10-14
- Case data
- Fictional composite; no real patient data
- Credit
- Educational only; no CME or other credit
Requirements referenced 3
| Requirement | Title | Plain-language meaning |
|---|---|---|
| [V1 6006] | EVA Medical Clearance | Every crewmember medically cleared by ground medical support before each EVA. |
| [V2 6008] | DCS Risk Identification | Mitigation achieving less than 4% DCS probability at 95% confidence in ground tests; no serious DCS. |
| [V2 6009] | DCS Treatment Capability | The system must provide DCS treatment capability. |
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 5
- NASA OCHMO. Decompression Sickness (DCS) Risk Mitigation. Technical Brief OCHMO-TB-037. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-037-decompr… NASA E
- NASA OCHMO. EVA Mishaps. Technical Brief OCHMO-TB-040. www.nasa.gov/wp-content/uploads/2023/12/ochmo-tb-040-eva-mis… NASA E
- NASA OCHMO. NASA-STD-3001, Volume 2: Human Factors, Habitability, and Environmental Health, Revision F (2026). standards.nasa.gov/standard/NASA/NASA-STD-3001_VOL_2 Standard E
- Vann RD, Butler FK, Mitchell SJ, Moon RE. Decompression illness. Lancet. 2011;377(9760):153–164. doi:10.1016/S0140-6736(10)61085-9 Peer-reviewed E
- NASA OCHMO. NASA-STD-3001, Volume 1: Crew Health, Revision C (2023). www.nasa.gov/wp-content/uploads/2023/11/nasa-std-3001-vol-1-… Standard E
Machine-checked on 2026-10-14: each URL was fetched, each DOI's title/journal/year matched via Crossref, PubMed IDs matched to DOIs, and claims were checked against the source text (abstract, NASA document or official web 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 · no CME credit · Disclaimer
- Cite this version
- Pending first edition
Educational use only · not medical advice · Disclaimer · CC BY-SA 4.0