Decompression Sickness Incidence in the IAF Hypobaric Chamber between 1991-2003

1. Decompression Sickness Incidence in the IAF Hypobaric Chamber between 1991-2003 Chapnik L, Grossman A ,Barnboim E, Eliyahu U , Azaria B, Goldstein L.* The IAF aeromedical center ,Tel Hashomer,Israel. *The IAF surgeon general ,Tel Hashomer,Israel

2. Objective Evaluation of all the decompression sickness (DCS) incidence that occurred in the Israeli Air Force (IAF) hypobaric chamber between the years 1991-2003.

3. DECOMPRESSION SICKNESS(DCS) DCS is the result of inert nitrogen gas bubbles forming in all parts of the body (blood and body tissues).

4. Pathogenesis of DCS : 1. Mechanical - Direct effect of bubbles that disrupts tissue, resulting in pain and blocked circulation, and causing ischemia and possible infraction. 2. Biochemical - Platelet aggregation occurs, releasing vasoactive substances, which leads to vasoconstriction of blood vessels, increased blood viscosity and fluid shift from the intravascular to the extra vascular space.

5. DCS Risk Factors • Exercise ,during & after the flight . • Age , the incidence increases with age . (Heimbach RD. et al ,1996 Aerospace Medicine. 2nd edition). • Individual susceptibility. • Altitude above 18,000 feet & a substantial increase above 25,000 ft. (Ernsting K. ,1988 Aviation Medicine 2nd edition).

6. DCS-TYPES Ι:Limb Bends, Skin Manifestations and PNS symptoms. ІІ:CNS and Chokes.

7. Incidence Rate (Dehart 2nd edition) Limb Bends:65-70% Skin Manifestations:10-15% PNS symptoms:10.8% CNS:5-7% Chokes:2%

8. DCS incidence rate for altitude chamber training: 1. 0.029%-0.58% for trainees (Bason R. et al ,1976 Aviat Space Environ Med, Piwinski S. et al,1986 Aviat Space Environ Med). 2. 0.06%-0.616% for inside observers (IOs)(Bason R. et al ,1991 Aviat Space Environ Med, Rayman R. et al,1983 Aviat Space Environ Med ). • During recent years there has been a significant reduction in the incidence of DCS among IOs due to the adoption of recommended guidelines.

9. Recommended guidelines for flight safety (Rice GM ,2003 Aviat. Space Environ. Med) : • Prebreathing of 100% oxygen 30 min prior to the flight (trainees ,IOs). • Breathing of 100% oxygen the entire flight (IOs). • No more than 3 chamber flights above 18,000 feet in 7 days should be made, with a minimum of 48 hours between exposures. • avoid: 1. diving for at least 24h prior to the hypobaric chamber exposure. 2. to refrain from strenuous exercise and exposure to aircraft flight 24h post exposure.

10. Methods-Data collection(January 1991 and December 2003). The information Included: altitude, number of trainees and IOs, symptoms and onset of DCS symptoms.

11. Combat Protocol 40 Rapid Decompresion 35 Hypoxia Training High Pressure Oxygen Breathing 30 25 20 15 10 5 Denitrogenation 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Altitude Thousand feet Ears&Sinus CHECK Time (min)

12. 40 35 30 25 20 15 10 5 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Transport Protocol Altitude Thousand feet Hypoxia Training Night Vision Training Ears&Sinus CHECK Denitrogenation Time (min)

13. Results Table 1: Incidence of Decompression Sickness during 1 Jan. 1991 – 31 Dec. 2003.

14. Table 2.Symptoms of Decompression Sickness • Some of the subjects experienced multi-organ manifestation

15. Table 3: Altitude associated with DCS cases.

16. 12 cases (70.5%) were reported during the first 12 hours after the chamber flight. • Five (29.5%) were reported during the exposure in the chamber.

17. Discussion • The majority of DCS cases in our study, were type I, as reported in the literature (Robert W. et al 1990 ,Aviat Space Environ Med ). • Our incidence of DCS is at the range published in the literature. • The timing of symptoms in our study was also similar.

18. Altitude: The incidence of DCS below 25,000 , in our study was higher (47%) than published. (13%,Dehart 2nd edition). • A possible explanation to this difference is over diagnosis of borderline cases.

19. Questions ? Thank you!