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

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

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Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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


Objective

Objective

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


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

DECOMPRESSION SICKNESS(DCS)

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


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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.


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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).


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

DCS-TYPES

Ι:Limb Bends, Skin Manifestations and PNS symptoms.

ІІ:CNS and Chokes.


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

Incidence Rate (Dehart 2nd edition)

Limb Bends:65-70%

Skin Manifestations:10-15%

PNS symptoms:10.8%

CNS:5-7%

Chokes:2%


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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.


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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.


Methods data collection january 1991 and december 2003

Methods-Data collection(January 1991 and December 2003).

The information Included: altitude, number of trainees and IOs, symptoms and onset of DCS symptoms.


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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)


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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)


Results

Results

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


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

Table 2.Symptoms of Decompression Sickness

  • Some of the subjects experienced multi-organ manifestation


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

Table 3: Altitude associated with DCS cases.


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

  • 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.


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

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.


Decompression sickness incidence in the iaf hypobaric chamber between 1991 2003

  • 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.


Questions

Questions ?

Thank you!


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