Decompression Sickness (DCS) Below 18,000 Feet: A Large Case Series William P. Butler, MD, MTM&H, FACS James T. Webb, PhD
Disclosure Information 84nd 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Methods Source Material Literature Unpublished 84 cases 20 cases Davis Hyperbaric Laboratory AFRL Altitude Research Database TOTAL Descriptive Analysis 7 cases 111 cases
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 = Type II = Unknown = 74 (joint*, skin) 20 (eye, chokes, neurologic) 17 8 5 24 2 (USAF experimental table 33 ft) 50 (1940s = 41; 1960s-1980s = 9) 21 Therapy GLO = TT5 = TT6 = TT8 = None = Unknown =
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 Risk 18,000 Ft --- No Prebreathe Pilmanis et al; ASEM; 2004;75:749-759
Incidence of Low Altitude DCS Houston (1947) 2/387 = 0.5% Smedal (1948) (6/387 = 1.6%) 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
References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. Allan JH. Traumatic calcifications: a precipitating factor in bends pain. Aviation Medicine. 1945; 16:235-241. Butler WP. Epidemic decompression sickness: case report, literature review, and clinical commentary. Aviation, Space and Environmental Medicine. 2002; 73(8):798-804. Conkin J, Edwards BF, Waligora JM, Horrigan Jr DJ. Empirical models for use in designing decompression procedures for space operations. NASA Technical Memorandum 100456; June 1987. Houston CS. Occurrence of bends, scotomata and hemianopsia at altitudes below 20,000 feet. Aviation Medicine. 1947; 18:165-168. Kumar KV. Decompression sickness and the role of exercise during decompression. Aviation, Space and Environmental Medicine. 1988; 59(11):1080-1082. LeMessurier DH & Baxter R. Evidence of decompression sickness during flights at 20,000 to 24,000 feet above base. Medical Journal of Australia. 1964; 1:188-191. Lewis ST. Decompression sickness in USAF operational flying, 1968-1971. Aerospace Medicine. 1972; 43(11):1261-1264. Manton A. Three incidents of decompression illness at the RAF Centre of Aviation Medicine. Aerospace Medical Association Annual Scientific Meeting; Atlanta, GA; 13-17 May 2012. Moore J & Petersen C. Relapse of decompression sickness associated with exertion: case reports. Undersea & Hyperbaric Medicine Society Annual Scientific Meeting; La Jolla, CA; 28-30 June 2002. Rayman RB & McNaughton GB. Decompression sickness: USAF experience 1970-1980. Aviation, Space and Environmental Medicine. 1983; 54(3):258-260. Rudge FW. A case of decompression sickness at 2,437 meters (8,000 feet). Aviation, Space and Environmental Medicine. 1990; 61(11):1026-1027. Rush WL & Wirjosemito SA. The risk of developing decompression sickness during air travel following altitude chamber flight. Aviation, Space and Environmental Medicine. 1990; 61(11):1028-1031. Smart TL & Cable GG. Australian Defence Force hypobaric chamber training, 1984-2001. Australian Defence Force Health. 2004; 5:3-10. Smead KW, Krutz RW, Dixon GA, Webb JT. Decompression sickness and venous gas emboli at 8.3 psia. 24 th Annual SAFE Symposium; 1986; 196199. Smedal HA & Graybiel A. Effects of decompression: seventy subjects repeatedly exposed to a simulated altitude of 20,000 feet during approximately one month. Aviation Medicine. 1948; 19:253-269. Voge VM. Probable bends at 14,000 feet: a case report. Aviation, Space and Environmental Medicine. 1989; 60(11):1102-1103. AFRL Altitude Research Database