Decompression Sickness (DCS) Below 18,000 Feet:

A Large Case Series

William P. Butler, MD, MTM&H, FACS

James T. Webb, PhD

Disclosure Information84nd Annual Scientific Meeting

Col William P. Butler

I have no financial relationships to disclose.

I will not discuss off-label use and/or investigational use in my presentation.

The opinions expressed are mine only and do not represent DoD or Air Force positions.

Methods

• Source Material– Literature 84 cases– Unpublished 20 cases

• Davis Hyperbaric Laboratory– AFRL Altitude Research Database 7 cases– TOTAL 111 cases

• Descriptive Analysis

Results

• Source of Exposure– Aircraft = 39– Chamber = 69– Parachute = 3

• Mean Age = 26 (aircraft = 30 & chamber = 24)• Gender

– Male = 80– Female = 13– Unknown = 18

Results

Results

• DCS– Type I = 74 (joint*, skin)– Type II = 20 (eye, chokes, neurologic)– Unknown = 17

• Therapy– GLO = 8– TT5 = 5– TT6 = 24– TT8 = 2 (USAF experimental table 33 ft)– None = 50 (1940s = 41; 1960s-1980s = 9)– Unknown = 21

Results

• Residual – Joint pain = 3 (knee, shoulder)– Neurologic = 2 (tingling, numbness)

• Recurrence– Joint pain = 1 (knee)– Neurologic = 1 (ulnar nerve)

• Tailing Treatments (6)• Treatment Complications (2)

Results

• Risk Factors– No prebreathe (n = 101, 95%)– Exercise (n = 103, 76%)

• AFRL Altitude Research Database, p < 0.05– Prior exposures (n = 91, 74%)– Duration at altitude (n = 88)

• Range = 5 - 414 minutes• Mean time to symptoms = 83 minutes

Implications of Case Series-1

• Low Altitude DCS may not be uncommon

• Anecdotal cases routinely discussed• Bubble Data

– Webb & Pilmanis– Olson & Krutz

• Case Series

ADRAC Model of DCS Risk18,000 Ft --- No Prebreathe

Pilmanis et al; ASEM; 2004;75:749-759

Incidence of Low Altitude DCS

• Houston (1947) 2/387 = 0.5% (6/387 = 1.6%)• Smedal (1948)

– 5,000 ft 6/240 = 2.5%– 6,000 ft 4/22 = 18.2%– 10,000 ft 23/71 = 32.4%

• Smead (1986) 1/31 = 3.2% (15,000 ft)• Dixon (1986) 1/88 = 1.1% (16,500 ft)• AFRL database 7/424 = 1.7% (16,500 ft)*

Implications of Case Series-1

• Bubbles form below 18,000 feet– Bubbles evolve and grow below 18,000 feet– VGE and DCS may not be rare

• Issue– Cannot discount symptoms and DCS– Definitive treatment indicated (may need HBO)

Implications of Case Series-2• Operational Air Force

– U-2 operates up to 29,500 ft (soon to 15,000 ft)– AC-130 operates unpressurized to 18,000 ft– CV-22 operates unpressurized to 20,000 ft– Training chambers operate up to 25,000 ft

• Issue– Cannot discount VGE effects and DCS– Altered/aborted missions & long term health impacts– New Research

• Microparticles (MPs) --- encapsulated membrane fragments (Thom et al)• White Matter Hyperintensities (WMHs) --- rMRI (Jersey et al; McGuire et al)

– Future: pre/post-flight HBO for high decompression stress missions• Denucleates, denitrogenates, counters MPs & WBCs (Arieli et al; Thom et al)

Implications of Case Series-3

• Aeromedical Evacuation flies < 8,000 ft– VGE in normals = 28% (AFRL Database > 10,250 ft)– Patients are not normals

• Altered perfusion• Turbulent flow• Anesthetic gases• Transfusions infuse bubbles (macro)

– Warming releases dissolved gas (85% inert)• Transfusions introduce MPs (Pritts et al*, Thom et al)

– Proinflammatory (WBC activation with vascular/lung injury)– Abated with recompression (may have a gas component)

Implications of Case Series-3

• Aeromedical Evacuation flies < 8,000 ft– VGE, warmed blood gas evolution, and MPs

• Issue– Cannot discount “second hit” during AE– Cabin altitude restriction a cogent countermeasure– Future: pre/post-flight HBO (?? USAF TT8 ??)

• Compresses bubbles, oxygenates, counters MPs & WBCs (Thom et al; Arieli et al)

Conclusion

• Low Altitude DCS exists– May be more frequent than thought

• Treat like any altitude DCS– May be operationally relevant

• VGE, MPs, WMHs– May be very relevant to AE

• VGE, transfusion bubbles, MPs• “Second hits” and post-flight complications and CARs

– FUTURE: pre/post-flight HBO

Questions --- Thank you very much

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Decompression Sickness (DCS) Below 18,000 Feet: A Large Case SeriesDisclosure Information 84nd Annual Scientific Meeting Col William P. ButlerMethodsResultsSlide 5Slide 6Slide 7Slide 8Implications of Case Series-1ADRAC Model of DCS Risk 18,000 Ft --- No PrebreatheIncidence of Low Altitude DCSSlide 12Implications of Case Series-2Implications of Case Series-3Slide 15ConclusionPowerPoint PresentationReferences