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

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

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(DCS)

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


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.


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).


DCS-TYPES

Ι:Limb Bends, Skin Manifestations and PNS symptoms.

ІІ:CNS and Chokes.


Incidence Rate (Dehart 2nd edition)

Limb Bends:65-70%

Skin Manifestations:10-15%

PNS symptoms:10.8%

CNS:5-7%

Chokes:2%


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.


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).

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


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)


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

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


Table 2.Symptoms of Decompression Sickness

  • Some of the subjects experienced multi-organ manifestation


Table 3: Altitude associated with DCS cases.


  • 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.


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.


  • 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 ?

Thank you!


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