Polk

Space Medicine: Past, Present and Future

J.D. Polk, DO, MS, MMM, CPE, FACOEP Deputy Chief Medical Officer

Chief, Space Medicine NASA Johnson Space Center

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Don’t stand here during launch

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Space Motion Sickness (SMS) or Space Adaptation Syndrome

Pho

to N

AS

A

• What is the problem? – Optic Disc Edema, Globe Flattening, Choroidal Folds, Hyperopic Shifts and Raised

Intracranial Pressure has occurred in Astronauts During and After Long Duration Space Flight

Choroidal Folds

Visual-Intracranial Pressure

Optic Disc Edema Globe Flattening

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Panoptic Fundoscopy

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Increased Optic Nerve Sheath Diameter seen on-orbit

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Flattening of Posterior Wall – most likely location of Choroidal Folds if any exist

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Elevation of Optic Disc

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Cardiovascular Effects

• Increase in ventricular size initially – Major increase in preload – Inhibition of erythropoietin – Fluid shift into the upper

thorax and head

• Increased GFR prompts a diuresis – Eventual decrease in

preload – Down regulation of

erythropoietin causes a spaceflight anemia.

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Fluid Shift a. On Earth, gravity exerts a downward force to keep fluids

flowing to the lower body (A) b. In space, the fluids tend to redistribute toward the chest and

upper body (B). This is responsible for the face congestion. At this point, the body detects a “flood” in and around the heart

c. The body rids itself of this perceived “excess” fluid. The body functions with less fluid and the heart becomes smaller (C)

d. Upon return to Earth, gravity again pulls the fluid downward, but there is not enough fluid to function normally on Earth (D)

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Neurovestibular

Vestibular Organs Vision

Proprioception

Muscles

Tendons and Joints Skin

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Vertical Pursuit Tracking with Head and Eye

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Musculoskeletal • Acute –

• Postural change with stretching of tendons and ligaments. Increase in on-orbit height by 2-6 cm

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Effects of Spaceflight on Muscle • Decrease in body mass • Decrease in leg volume • Atrophy of the antigravity muscles (thigh, calf)

– decrease in leg strength – extensor muscles more affected than flexor muscles

• Data showed an increase in number of Type II, “fast twitch” muscle fibers (those which are useful for quick body movements but more prone to fatigue)

Ground control Flight

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Musculoskeletal

• Chronic – – Decrease in weight bearing causes muscle

atrophy and bone demineralization, 1% - 2.4% per month in lower extremities and spine, with increased urine and fecal calcium

• A direct effect of microgravity is the loss of mechanical stress on the skeletal system

Konieczynski, D. D., Truty, M. J., and Biewener, A. A. Evaluation of a bone's in vivo 24-hour loading history for physical exercise compared with background loading. J Orthop Res 16; 1998, 29-37

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Loss of Bone Mineral Density

Bone Density Loss of 1-2.4% per month in the weight bearing areas, with the hips and lumbar spine being the highest areas. But density is only ½ of the story…matrix architecture changes

are also a concern, ie- Quality as well as quantity of bone.

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Immune System

• Depression of lymphocyte function affects at least 50% of space crew members – Decreased lymphocyte response to mitogens

in cosmonauts after space flight was reported for the first time in the early 1970s by Soviet immunologists

Cogoli A. Space flight and the immune system.Vaccine.1993;11(5):496-503.

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Hematopoietic system

• Reduction in Circulating Red Blood Cell mass – “Space Flight Anemia” Udden MM, Driscoll TB, Leach-Huntoon CS, Alfrey CP.

Decreased production of red blood cells in man exposed to microgravity. New England Journal of Medicine, 1994.

Lawrence Rice, Clarence P. Alfrey. Modulation of red cell mass by neocytolysis in space and on Earth. Pflugers Arch- Eur. J. Physiol., 441 (Suppl):R91-R94, 2000.

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Behavioral/Psycho-Social • Symptoms - Fatigue and

irritability • Causes

– Work load – Sleep habits and facilities – Crew personalities, “crew

space”, and cultural differences

– Temperature – Noise – Odors – Atmosphere – Diet – Lack of family contact

Changes in crew mood, morale, and circadian rhythm

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Radiation

• Exposure based on orbital altitude/inclination, duration, and solar activity

• Crewmembers are radiation workers • Limits for mission and career exposure are set by the

National Council on Radiation Protection

• As Low As Reasonably Achievable (ALARA) principle for mission planning

• Exposure monitored by active and passive dosimeters

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Countermeasures

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Countermeasures • Cardiovascular

– Fluid loading – Lower Body Negative

Pressure – G-suits and Liquid

Cooling Garment – Exercise – Medication

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Communications

Behavioral Health and Performance

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Levels of Care • Sure you can do major

surgery. It is feasible. But should you?

• Will there be prophylactic surgery on long duration Moon and Mars explorers (ie: appendectomy)?

• Will your consumables limit your ability to provide critical care?

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Pragmatic Tenets

• Mass • Power • Volume • Time • Money • Risk

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Application of the Pragmatic Tenets

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Futuristic?

Actually, It has already been done

NASA Houghton Mars Project

CPOD, NASA AMES

Pat Rawlings

EKG in Heads Up Display

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Polk-Aug 2009

Questions?

Slide courtesy of USAF 40

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References • Brooks AJ, et al. Fast on operational military deployment. Emerg Med J. 2005 Apr;22(4):263-5. • Bacal K, Beck G, McSwain NE Jr. A concept of operations for contingency medical care on the

International Space Station. Mil Med. 2004 Aug;169(8):631-41. • Wilde RC et al. One hundred US EVA’s: A perspective on spacewalks. Acta Astronaut. 2002 Jul-

Nov;51(1-9):579-90. • Skelton PA, Droege L, Carlisle MT. EMEDs and SPEARR teams: United States Air Force ready

responders. Crit Care Nurs Clin North Am. 2003 Jun;15(2):201-12.

• Peoples GE, Gerlinger T, Budinich C, Burlingame B. The most frequently requested precombat refresher training by the Special Forces medics during Operation Enduring Freedom. Mil Med. 2005 Jan;170(1):31-7.

• Chambers LW et al. Initial experience of US Marine Corps forward resuscitative surgical system during Operation Iraqi Freedom. Arch Surg. 2005 Jan;140(1):26-32.

• Billica RD et al. Perception of the medical risk of spaceflight. Aviat Space Environ Med. 1996 May;67(5):467-73.

• Busby DE. Space clinical medicine. A prospective look at medical problems from hazards of space operations. Space Life Sci. 1968 Aug;1(2):157-427. Review.

• McGregor A. Fitness standards in airline staff. Occup Med (Lond). 2003 Feb;53(1):5-9. Review. • Ridker P et al. C-Reactive Protein Levels and Outcomes after Statin Therapy. NEJM 2005.

Volume 352:20-28. • Peoples GE et al. From the war zone to the United States: Caring for the wounded in Iraq- A

photo essay. NEJM. 2004. Volume 351:2476-2480 .