Undersea Medicine Decision Tool
Comprehensive reference: U Factors, PHA Management, Issue Guidance, and Decision Support. References: UMG 100-01, 100-02, 200-01 through 200-07, CFHS 4000-04, CFHS 4030-71.
Disclaimer: Always reference the most current published guidelines. This tool is a decision aid only. If you identify any discrepancies, please contact Braedon Hendy on DWAN.
Undersea Factor (U) Definitions (UMG 100-01)
The Undersea Factor (U) designates medical fitness for employment in an undersea or hyperbaric environment, including as a diver, submariner, or diving support trade. U1-U4/U6 are "fit" factors for specific undersea roles; U5 indicates not assessed; U7 indicates medically unfit.
| U Factor | Definition | Applies To |
|---|---|---|
| U1 | Deep Water Diver – medically fit for unrestricted duties | Clearance Diver (00342), Clearance Diving Officer (00207), Port Inspection Diver (00226) |
| U2 | Submariner – medically fit for unrestricted duties | Submariner (various MOSIDs) |
| U3 | Undersea operator with an undersea environment restriction Specific restrictions must be defined as MELs (e.g., "Fit diving to max XX msw", "Unfit decompression diving") |
Any diver/submariner with medical restrictions |
| U4 | Shallow Water Diver – medically fit for unrestricted duties | Ship Diver (various MOSIDs), SAR Technician (00101), Combat Diver (00339), SOF Diver (various MOSIDs) |
| U5 | CAF member not medically assessed for CAF training or employment in an undersea environment | Non-divers, non-submariners, non-diving support trades |
| U6 | Diving support trade – medically fit for unrestricted duties | DMO (00393), DMS (00390), DPA (00374), DNP (00195), DMT (00334), DBO (00197), other inside attendant MOSIDs |
| U7 | Undersea operator medically unfit for employment in an undersea environment | Any diver/submariner deemed permanently unfit (unfit diving, unfit dive supervision, unfit RCC) |
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Output
Medical Issue Quick Reference (UMG 200 Series)
Issue-specific guidance for common conditions affecting diving fitness. Click each category to expand.
Respiratory illness increases risk of pulmonary barotrauma/AGE and may reduce exercise tolerance. Return-to-dive depends on symptom resolution and functional capacity.
| Scenario | Minimum Unfit Period | Return Criteria |
|---|---|---|
| Asymptomatic COVID-19 (positive test) | 5 days from positive test | No symptoms developed; complete 30 min high-intensity PT without performance change |
| Mild non-COVID illness | 48 hours after symptoms resolve | Fever/congestion/rhinorrhea/fatigue resolved WITHOUT medication; 30 min high-intensity PT at baseline |
| Mild COVID-19 | 7 days from symptom onset | Same as above + 48h symptom-free without meds; CDSM notified for tracking |
| Moderate-severe illness | Variable – ADMO review | Requires CDSM review; may need CXR, PFTs, exercise oximetry, ECG |
U Factor: Short illness = temporary unfit (no U change). Prolonged restrictions → consider U3. Permanently incompatible → U7.
Post-surgical cornea/lens integrity is critical for pressure tolerance. Minimum waiting periods required before return to diving.
| Procedure | Minimum Unfit Period |
|---|---|
| LASIK/SBK (myopic) | 4 weeks |
| LASIK/SBK (hyperopic) | 4 months |
| PRK/SMILE (myopic) | 3 months |
| PRK/SMILE (hyperopic) | 4 months |
| ICL / Refractive Lensectomy | 3 months |
| Retinal hole/tear laser | 2 weeks |
| Retinal detachment / vitrectomy | 2 months |
| Cataract / small corneal incision | 3 months |
| Pterygium surgery | 4 weeks |
| Laser iridotomy | 1 week |
| Corneal abrasion | Until healed (24-72h typical) |
Return requires ophthalmology clearance confirming stable healing/vision. Vision standards: near N8, distance 6/30 binocular correctable to V1.
CVD can present as sudden incapacitation during exertion/immersion. Screening aims for primary prevention and identification of high-risk individuals.
CV Risk Screening
| Risk Level (FHP/CDRC) | Action Required |
|---|---|
| Low (<10%/10yr) | Document risk %; risk factor counseling; routine screening interval |
| Intermediate (10-19%/10yr) | Group A SWD/Gp B: CDSM review if high risk. DWD (CD/PID): CT CACS + Astro-CHARM |
| High (≥20%/10yr or established disease) | CDSM review. If CACS ≥100 or Astro-CHARM ≥10%: beach diver, refer to CDSM |
Required tests: BP, lipid panel (fasting at initial), HbA1c, hsCRP, Lp(a) (once), ApoB, ECG. Screening interval: every 4 years to age 40, then every 2 years.
Hernias can worsen with Valsalva/heavy lifting and carry theoretical expansion/incarceration risk during decompression.
| Type | Disposition |
|---|---|
| Epigastric <2cm, asymptomatic | No MELs; reassess at Type I PHA |
| Epigastric ≥2cm or symptomatic | Requires repair; unfit CAF diving until repaired |
| Umbilical <2cm, congenital, asymptomatic | No MELs; reassess at Type I PHA |
| Umbilical ≥2cm, acquired, or symptomatic | Requires repair; unfit CAF diving until repaired |
| Inguinal, asymptomatic | Case-by-case; reassess at Type I PHA |
| Inguinal, ever symptomatic | Requires repair; unfit CAF diving until repaired |
| Femoral (any) | Requires repair; unfit CAF diving until repaired |
| Hiatal ≥50% stomach in chest | Likely requires repair; surgical SME determines |
| Incisional | Requires repair; unfit CAF diving until repaired |
| Post-operative (any type) | Unfit diving × 6 weeks minimum; surgeon review required |
Unrepaired MELs: No lifting >4.5kg; annual follow-up; remain within 6 hours of Role 3.
Hearing loss affects operational communication and safety. STS indicates progressive loss requiring monitoring.
| Scenario | Action |
|---|---|
| First STS (≥10dB avg at 2-4kHz OR ≥15dB at any 500-6000Hz) | Rule out reversible causes; repeat audiogram in 30 days (not <48h post-noise); if confirmed → new reference |
| Second STS (same ear) | Formal audiology referral; consider ENT if sudden loss |
| H2 Category | Specialized hearing protection (consult PMed); no PCAT required |
| H3 + Very Good SD, no aid | Annual hearing + audiology q2yr; PCAT required; file to CDSM |
| H3 + hearing aid recommended | As above + unfit diving if critical verbal underwater comms required |
| H3 + Good/Poor/Very Poor SD | CDSM / US-AUMB determination |
| H4 Category | CDSM / US-AUMB determination |
| Scenario | Unfit Period | Notes |
|---|---|---|
| Starting SSRI/SNRI | Minimum 3 months | At 3 months: if stable, single agent, no dive-relevant side effects → may be considered for restricted diving with CDSM |
| SSRI/SNRI dose increase | Minimum 2 weeks | Reassessment with dive clinician required |
| SSRI/SNRI dose decrease | Minimum 2 weeks | Monitor for return of symptoms |
| Stable on SSRI/SNRI | Restricted diving | Usually unfit decompression diving, unfit mixed gas; requires CDSM oversight |
| Other psychotropics | Contraindicated | Benzodiazepines, antipsychotics, mood stabilizers, stimulants → stop diving |
| ADHD with stimulants | Contraindicated | Stimulant medications not compatible with diving |
| Current suicidal ideation/NSSI | Absolute contraindication | Past attempt: usually disqualifying |
Required: ECG (QT prolongation check), MSE (especially insight/judgment), DMO follow-up minimum q6 weeks × 3 months.
Dysbaric Osteonecrosis (DON) screening is required for DWD at baseline and after certain exposures.
| Scenario | Imaging Required |
|---|---|
| Post-DCS | MRI at 3-4 months; then LBS at 5yr and 10yr |
| Post-submarine escape | MRI at 3-4 months |
| DON shaft lesion | May continue diving; monitor |
| DON juxta-articular lesion | PCAT unfit |
| Routine screening (DND 6122+) | LBS or MRI per UMG 100-02 pathway |
DWD (CD/PID): Baseline LBS required at initial PHA.
Quick Reference – Minimum Temporary Restrictions
| Exposure/Procedure | Minimum Unfit Diving Period |
|---|---|
| General anesthetic | 72 hours |
| Local/regional anesthetic (minor) | 12 hours |
| Blood donation | 72 hours |
| Platelet/Plasma donation (<450 cc) | 24 hours |
| Routine immunization | 12 hours |
| COVID-19 vaccination | 48 hours |
| Diving after flying (cabin altitude ≥2000m) | 12-24 hours (rule of thumb) |
| Flying after diving (general rule) | 24 hours post-last dive |
| WPET | 24 hours post-exposure |
| Hyperbaric O₂ treatment | Variable – per treating physician |
Common Medical Issue Grounding Periods
| Condition | Unfit Period | Reference |
|---|---|---|
| Asymptomatic COVID-19 positive | 5 days | UMG 200-01 |
| Mild non-COVID respiratory illness | 48h symptom-free | UMG 200-01 |
| Mild COVID-19 | 7 days from onset | UMG 200-01 |
| LASIK/SBK (myopic) | 4 weeks | UMG 200-02 |
| PRK/SMILE (myopic) | 3 months | UMG 200-02 |
| Cataract surgery | 3 months | UMG 200-02 |
| Hernia repair (any type) | 6 weeks | UMG 200-05 |
| Starting SSRI/SNRI | 3 months minimum | UMG 200-07 |
| SSRI/SNRI dose change | 2 weeks | UMG 200-07 |
| Post-DCS | Variable + MRI at 3-4mo | UMG 100-02 |