Decompression Sickness in Extravehicular Activities

Transcription

1 XX Convegno Nazionale A.I.M.A.S. - Firenze I.S.M.A. Decompression Sickness in Extravehicular Activities Cap Angelo Landolfi Reparto Medicina Aeronautica e Spaziale - Pratica di Mare (RM)-

2 Leonov,, 1965

3 EVAs, or spacewalks involve exposures of individuals to the environmental conditions of space: - Microgravity - Thermal extremes - Ionizing radiation - Objects traveling - Extremely low atmospheric pressures

4 Space-suites: life-support system One-gas Environment O 2 : 3 lt/min 30 lt/min Pressure: 300 mmhg o 0,4 ATA -Orlan- 222 mmhg o 0,3 ATA -Emu- Equivalent decompression to an altitude of 9144 m

5 Bubble Formation Pressure 760 mmhg ISS Tissues Saturation Gradient = 538 mmhg R = PN 2 /Pamb ½ gradient 222 mmhg EMU Time Tissues Oversaturation

6 Bubble Theory PRE-EXISTING GAS NUCLEI DE NOVO BUBBLE FORMATION -Nucleation -Tribonucleation - Cavitation SITES of BUBBLE FORMATION Intravascular Extravascular Arterial Intracellular Venous Interstizial

7 Manifestation of Altitude DCS TYPE I (mild DCS) - Joints, pain only BENDS - CUTANEOS and LYMPHATIC manifestations (skin Bends) TYPE II (serious DCS) - NEUROLOGIC: cerebrum, spinal cord,cranial nerves - VESTIBULAR - CARDIOVASCULAR and CHOKES

8 Incidence of Altitude DCS DATA: USAF; DAN Alert, 1994

9 Prevention of Decompression Sickness Staged Decompression: Shuttle cabin pressure to 527 mmhg 26.5 % Oxygen for 12 hours Oxygen Pre-breathing: P t = P 0 + [P i -P 0 ] [1-e t/t 1/2] P t inert gas partial pressure in tissue after t minutes P 0 initial inert gas partial pressure P i inert gas partial pressure in inspired gas time 240 min; FiO 2 90%; T 1/2 360 min

10 Inert Gas Elimination (1) TR = PN 2 /P amb 2 No Oxygen Prebreathing PN 2 /Pamb =573/222 = 2.58 J.S. Haldane, 1900 Oxygen Prebreathing PN 2 /Pamb = /222 = TR: Tissue Ratio

11 Inert Gas Elimination (2) No Oxygen Prebreathing TR = PN 2 /P amb 2 J.S. Haldane, 1900 PN 2 /Pamb =573/222 = 2.58 Oxygen Prebreathing TR: Tissue Ratio PN 2 /Pamb = 364/222 = 1.6

12 In Immersion Facilities: physiological implications NBL (Neutral( Buoyancy Laboratory): 12.2 mt In-water EMU overinflation: 222 mmhg Physiological depth: 0.29 bar

13 In Immersion Facilities: physiological implications USN No deco limits: 100 min 6 h activity 46% oxygen/54% nitrogen PpO 2 : 1.1 ATA Equivalent air depth: 7.3 m

14 Could the microgravity environment be protective for Decompression Sickness? Microgravity-induced cardiovascular changes - central fluid shifts - Microgravity-induced Ventilation/ Perfusion V/Q changes in the lung Reduction in gas-phase formation (venous gas emboli) - abaroferic hypothesis -

15 Microgravity-induced cardiovascular changes Cardiovascular changes (Central Fluid Shifts) and changes in tissue perfusion might affect both the N2 elimination profile and the formation of microbubbles.

16 Ventilation/Perfusion changes in Microgravity (1) Pulmonary perfusion became much more uniform in Microgravity with the abolition of the zone 1, 2, 3 pattern Prisk, G. Kim, Ann R. Elliott, Harold J. B. Guy, Janelle M. Kosonen, and John B. West. Pulmonary gas exchange and its determinants during sustained microgravity on Spacelabs. J. Appl. Physiol. 79(4): , 1995

17 Ventilation/Perfusion changes in Microgravity (2) Single-breath nitrogen washout test: The slope of phase III is reduced in microgravity Prisk, G. Kim, Ann R. Elliott, Harold J. B. Guy, Janelle M. Kosonen, and John B. West. Pulmonary gas exchange and its determinants during sustained microgravity on Spacelabs. J. Appl. Physiol. 79(4): , 1995

18 Oxygen Pre-breathe is more effective in µg Fluid shifts and V/Q changes in the lung may lead to enhanced Nitrogen elimination Michael R. Powell, James M. Waligora, William T. Norfleet, K. Vasantha Kumar. Gas Phase Formation in Simulated Microgravity. NASA Technical Memorandum , July 1993

19 Reduction in gas-phase formation (VGE) in µg: abaroferic hypothesis Abaroferia = non-weight bearing James T. Webb, Devin P. Beckstrand, Andrew A. Pilmanis, and Ulf I. Balldin Decompression Sickness During Simulated Extravehicular Activity: Ambulation vs. Non-Ambulation. Aviation Space Environment Medicine 2005; 76:

20 Treatment in Space Flight: return to Ground Level Ground Level Oxygen Ground Level Oxygen Post-breathe (2-h period) In-suit over pressure (1.65 bar) Krause KM, Pilmanis AA: The effectiveness of ground level oxygen treatment for altitude decompression sickness in human research subjects. Aviat Space Environ Med 2000; 71:115-8

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