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Space Medicine Biological Hazards and Medical Care in Space H.G. Stratmann, M.D.

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Presentation on theme: "Space Medicine Biological Hazards and Medical Care in Space H.G. Stratmann, M.D."— Presentation transcript:

1 Space Medicine Biological Hazards and Medical Care in Space H.G. Stratmann, M.D.

2 Vostok Launch

3 Mercury-Atlas 3 Liftoff

4 Gemini 12 Liftoff

5 Apollo 11 Launch

6 Astronaut on Moon

7 Skylab

8 Apollo-Soyuz Apollo capsule

9 Apollo-Soyuz Soyuz capsule


11 Mir

12 Earth from Moon

13 Terrestrial versus Extraterrestrial Environment EarthLEOMoonMars Atmosphere 78% Nitrogen 21% Oxygen ~ NoneNone95% CO 2 3% nitrogen 2% argon Pressure 760 mmHg ~ NoneNone ~ 5 mmHg Temperature (Celsius) 21 o -178 o to o ~ same as LEO -120 o to +25 o Gravity (g) 1.0 ~ None Radiation (rems/year) 0.1 to 0.2~ ~ 20.0~ 15.0

14 Major Biological Risks of Space Travel Loss of atmosphere Exposure to toxins Mechanical trauma Acceleration and deceleration Extreme temperatures Meteoroids and space debris Circadian rhythms and sleep Psychological Adverse biological effects of microgravity Radiation

15 Loss of Atmosphere Barotrauma –Expansion of gas temporarily trapped in a body cavity (e.g. ear or sinus) –Pressure differences causing pain or injury Decompression sickness –Ambient atmosphere pressure < partial pressure of inert gases (e.g. nitrogen) –Nitrogen forms bubbles in bloodstream Bends (pains in joints and muscles) Chokes (gas emboli) Neurological symptoms (weakness, convulsions, syncope)

16 Loss of Atmosphere Explosive decompression –Rate of decompression is so great that transient overpressure occurs in lungs and other air-filled cavities –Pressure difference in the lungs 80 mm Hg causes rupture and possible air embolism –Ebullism - boiling of body fluids (e.g. blood) At body core temperature of 37 o C, ebullism occurs at an ambient pressure of 47 mm Hg (Armstrong limit, roughly an altitude of 19 kilometers)

17 Loss of Atmosphere Ambient pressure/atmosphere in Space Shuttle is similar to sea level on Earth (14.7 psi, 78% nitrogen, 21% oxygen) Extravehicular activity (EVA) requires space suit pressure of 4.3 psi To prepare for EVA, cabin pressure is slowly lowered (maximum 0.1 psi/sec) to 10.2 psi for 24 hours Astronauts don space suits and prebreathe 100% oxygen to purge nitrogen from the blood, then undergo final decompression to 4.3 psi

18 Toxins Ammonia –Used in Shuttle environmental control and life- support systems –Causes irritation of eyes and mucous membranes –More severe exposure causes dyspnea, vomiting, and pulmonary edema Freon –Used in the heat exchange system –Can produce lightheadedness, dyspnea, liver damage, and arrhythmias

19 Toxins Hydrazine and monomethyl hydrazine –Use in Shuttle auxillary power unit –Cause severe burns, liver and kidney damage, and seizures in liquid and gaseous forms Nitrogen tetroxide –Used as oxidant in Orbital Maneuvering System –Causes burns and blindness in liquid form and pneumonitis and pulmonary edema when inhaled (Apollo-Soyuz, 1975)

20 Trauma and Mechanical Failure Astronauts are vulnerable to conventional injuries –Burns –Abrasions –Lacerations –Electrical shock –Fractures –Deliberately inflicted injuries

21 Space Fatalities Soyuz 1 (1967) 1 fatality when parachute system failed during reentry Soyuz 11 (1971) 3 fatalities due to sudden depressurization during reentry STS-51L (1986) 7 fatalities due to failure in booster rockets STS-107 (2003) 7 fatalities during reentry due to damage to left wing

22 Challenger Explosion

23 Columbia Launch

24 Acceleration and Deceleration Excessive g (an acceleration of 9.8 m/s 2 ) can cause lightheadedness or syncope Upper limit of 4 g for sustained long-term acceleration and (briefly) 18 g for control of movement Mercury program up to 8 g briefly during launch and up to 11 g during reentry –The Right Stuff Shuttle 3 g during launch, 1.2 to 1.4 g during reentry

25 Temperature Control Heat exchange in space is based solely on radiation, either from the Sun or to space itselfnot by conduction or convection Effective temperature-control systems are available for both space suits and spacecraft

26 Meteoroids and Space Debris Represent a risk of collision with spacecraft or astronauts during EVA Meteoroids consist of stone and iron, with a total of 200 kg within 200 km of Earths surface at any given time Average velocity of meteoroids is about 16 km/sec Most are 0.1 mm in diameter, but can be 1 cm

27 Meteoroids and Space Debris Over 3 million kg of man-made debris (old rocket boosters, destroyed satellites, flecks of pain or particles of rocket fuel) are within 2000 km of Earths surface Over 7000 objects > 20 cm in size are tracked by NORAD Collision velocity with an orbiting spacecraft would be about 10 to 13 km/sec Range in size from < 0.1 mm to meters

28 Circadian Rhythms and Sleep Body rhythms that occur over a period of about 24 hours Sleep/activity cycle, body temperature, heart rate and blood pressure, secretion of growth hormone, cortisol, melatonin, etc. Entrained on cyclical environmental stimuli, especially the light-dark cycle based on Earths 24-hour rotation

29 Circadian Rhythms and Sleep Rapid travel through different time zones on the Earths surface disrupts the synchronization between endogenous biological clocks and external cues like light/darkness The resulting desynchronosis (jet lag) is associated with insomnia, loss of appetite, and fatigue Light-dark cycles in space vary widely Light-dark cycle in low Earth orbit is between 80 to 140 minutes, 30-40% of which is darkness

30 Circadian Rhythms and Sleep Sleep disturbances are common in astronauts –Insomnia –Intermittent, poor quality, or even prolonged (up to 12 hours) sleep –Sleep disturbances can degrade work performance and alertness during routine or emergency situations –Half of Shuttle astronauts use sleeping medications

31 Psychosocial Stressors of Space Flight Isolation, loss of social contacts, reduced sensory stimulation, anxiety, boredom, loss of privacy, dealing with emergencies, overly busy work schedules Decreasing motivation, emotional hypersensitivity and lability, and irritability or hostility toward Earth-bound control personnel and crewmates occur during extended missions (e.g. Skylab, Mir, ISS)

32 Radiation Serious hazard for acute and long-term injury during prolonged space missions Sun produces electromagnetic (gamma rays and X-rays) and particulate (electrons and protons) radiation

33 Radiation Solar radiation is produced continuously (solar wind) and increases dramatically during solar particle events (high energy protons of 10 to 500 MeV) Cosmic radiation is a constant source of radiation, consisting of very high energy protons (up to 2 GeV), alpha particles, and heavier ions originating outside the Solar System (possibly from old supernovas)

34 Radiation Surface of Earth is protected by: –Atmosphere (e.g. ultraviolet light, X-rays, and gamma rays) –Van Allen Belts Two ring-shaped regions at average altitudes of 1000 to 10,000 km and 13,000 to 20,000 km where extraterrestrial electrons and protons are trapped by Earths magnetic field Lower belt descends to about 500 km at the South Atlantic anomaly, where the most radiation exposure in low Earth orbit occurs

35 Radiation Average annual radiation exposure at sea level is 0.1 to 0.2 rem Average annual radiation exposure in low Earth orbit (366-day Mir mission) was up to 14 to 21 rem EVA and solar events (particularly solar particle events associated with coronal mass ejections) increase radiation exposure –Could expose an astronaut to potential level dose of hundreds of rem Proper shielding of spacecraft and use of underground habitats on lunar and Martian missions would dramatically decrease radiation exposure

36 Risks of Radiation Exposure Acute effects of whole-body exposure –Prodromal syndrome (50 to 150 rem) –Hematopoietic syndrome (150 to 400 rem) –Hematopoietic-gastrointestinal syndrome (400 to 800 rem) –Gastrointestinal syndrome (800 to 2000 rem) –CNS syndrome (>2000 rem) LD 50 is about 400 rem

37 Risks of Radiation Exposure Long-term effects –Cataracts –Infertility –Defects in offspring –Malignancy Breast Thyroid Leukemia Lung

38 Biological Effects of Micro and Low gravity Neurovestibular Cardiovascular Hematological Musculoskeletal

39 Microgravity Neurovestibular Space Adaptation Syndrome –Occurs in 2/3 of astronauts (males > females) –Headache, nausea, vomiting, dizziness, malaise –Made worse by head and body movements –Develops shortly after entering orbit, peaks after 1 to 2 days, and usually resolves after 4 to 7 days –Responds fairly well to dimenhydrinate, promethazine, and other motion sickness medications

40 Microgravity Neurovestibular Sensory illusions (e.g. inversion illusion) Postflight problems –Feeling levitated over bed when trying to sleep at night –Ataxic gait and walking straight when trying to turn a corner –Feeling extraordinarily heavy or that one is being pushed to one side while only standing –May take weeks or months to resolve

41 Microgravity Cardiovascular Shift of 1.5 to 2.0 L of fluid from lower to upper body within minutes of entry into microgravity from loss of gravity-induced hydrostatic pressure –Jugular venous distention –Facial puffiness, nasal congestion, headaches, nasal voice –Reduction of calf diameters by 30% (bird legs) –Enlargement of liver and other visceral organs

42 Microgravity Cardiovascular Decreased sympathetic tone –Can cause orthostatic hypotension and syncope on return to Earth, particularly when coupled with redistribution of at least 1 L of reduced total body fluid volume to lower extremities –Heart size and mass decrease slightly –Variable, relatively mild changes in heart rate, blood pressure, and left ventricular systolic function –Minor arrhythmias

43 Microgravity Hematological Red blood cell counts decrease by 10 to 20% of preflight values within 2 to 3 weeks in space, then slowly recover after about 60 days –May represent increased destruction and decreased production of RBCs Spherocytes and echinocytes increase

44 Microgravity Hematological Neutrophil counts increase an average of 32% –May be due to stress-induced release of epinephrine and glucocorticoids Killer T-lymphocytes show diminished number and activity Little change in helper T-lymphocytes or B- lymphocytes Eosinophils decrease by an average of 62% of pre-flight values

45 Microgravity Musculoskeletal Relaxed astronauts in microgravity assume a fetal position, with loss of normal curve of the thoracolumbar spine Increase in height of 3 to 6 cm from decompression of intervertebral disks, with possible associated pressure on nerve roots and back pain

46 Microgravity Musculoskeletal Decrease in muscle mass (primarily in weight-bearing muscles of legs and back) –Vigorous exercise programs (up to 3 hours per day) using isotonic and isometric exercises help stabilize muscle mass at 80 to 85% of preflight value –Muscle weakness and soreness postflight, with gradual return of preflight muscle mass after weeks to months of exercise

47 Microgravity Musculoskeletal Microgravity causes demineralization of bone, decreased total bone mass, and increased urinary and fecal calcium loss (greater risk of urolithiasis) Mechanism for bone loss is not established –Activity of osteoclasts unchanged –Activity of osteoblasts decreased

48 Microgravity Musculoskeletal With exercise programs, total bone mass loss is similar to muscle loss (about 15 to 20% of preflight values) –Percentage of bone loss is greater in weight-bearing bones (e.g. calcaneus) –Bone mass may not return to preflight value even years later

49 Microgravity Countermeasures to microgravity Vigorous exercise programs –Treadmill –Rowing machine –Ergometer –Isometric exercise is more effective than isotonic (aerobic) exercise for reducing bone and (probably) muscle loss –Effectiveness of supplemental calcium or medications (calcitonin or clodronate) for controlling calcium loss hasnt been established –Penguin suit

50 Microgravity Countermeasures to microgravity Postflight orthostatic hypotension –Ingestion of salt tablets and 1 L of water shortly before reentry –Lower-body negative-pressure devices Chibas suit –G-suit

51 Microgravity Countermeasures to microgravity Artificial gravity –Rotation of spacecraft or habitat –Tethered system –Centrifuge for intermittent use Adverse effects of reduced gravity should be milder on Mars (0.38g) and the Moon (0.16g)

52 Medical Care of Astronauts Preflight screening Medical requirements for Shuttle crews vary –Pilot (Class I) –Mission Specialist (Class II) –Payload Specialist (Class III) –Space Flight Participant (Class IV)

53 Medical Care of Astronauts Requirements are most stringent for Class I (pilot) –Near vision better than 20/20 in each eye (uncorrected) and either far vision 20/100 or better uncorrected, or correctable to 20/20 each eye –BP no greater than 140/90 mmHg –Height between 64 inches and 76 inches

54 Medical Care of Astronauts Requirements for Class II (mission specialist) –Distance visual acuity: 20/200 or better uncorrected, correctable to 20/20 each eye –Blood pressure no greater than 140/90 mmHg measured in a sitting position –Height between 58.5 and 76 inches.

55 Medical Care of Astronauts Class III and IV have no limit on near vision and BP must be no greater than 150/90 mmHg

56 Medical Evaluation of Astronaut Candidates Medical history and physical examination Cardiopulmonary tests –Pulmonary function tests –Exercise treadmill test –Echocardiogram –EKG and 24-hour Holter monitor Eye and ear examination –Audiometry, visual acuity, color perception, tonometry

57 Medical Evaluation of Astronaut Candidates Dental examination Neurological examination (including EEG) Psychiatric interview and psychological tests Tests –X-rays of chest, sinuses, and teeth –Abdominal ultrasound –Mammogram in women

58 Medical Evaluation of Astronaut Candidates Laboratory tests –Chemistries, blood counts, screens for STDs –Urinalysis –24-hour excretion of calcium –Stool for ova and parasites –Drug screen –PPD –Pregnancy test (premenopausal women)

59 Medical Care of Astronauts Medical examinations are done 10 days, 2 days, and immediately before a Shuttle launch Crew members live in restricted quarters for a week prior to launch to minimize exposure to infectious diseases

60 Medical Care of Astronauts Two members of every Shuttle crew are assigned as medical officers –Non-physicians receive paramedic-level training –Advice during flight is available from ground-based Crew Surgeon and Deputy Crew Surgeon All crew members receive 16 hours of lectures on the physiological effects of space flight and are trained in CPR and first aid

61 Injuries and illnesses during space flight Space Adaptation Syndrome Nasal/sinus congestion Headache Backache Skin irritation/dryness/dermatitis Boils Urinary tract infection Renal colic Prostatitis

62 Injuries and illnesses during space flight Upper respiratory infection (cold) Pneumonitis Minor abrasions/lacerations Constipation Arrhythmias Decompression sickness Corneal abrasion/foreign body Musculoskeletal strain/sprain Minor trauma/contusions

63 Medical Supplies on Shuttle Missions and the ISS Medications –Analgesic and NSAIDs –Antiemetics –Antihistamines and H 1 blockers –CNS stimulants –Cardiovascular agents

64 Medical Supplies on Shuttle Missions and the ISS Medications –Antibiotics –Sedative-hypnotics –Antidepressants –Gastrointestinal agents –Dermatological agents –Ophthalmic and otic agents

65 Medical Supplies on Shuttle Missions Diagnostic equipment and supplies –Blood pressure cuff and sphygmomanometer –Stethoscope –Disposable thermometers –Otoscope –Ophthalmoscope –Fluorescein strips

66 Medical Supplies on Shuttle Missions Therapeutic items and other supplies –Needles –Syringes and tourniquet –IV tubing and normal saline –Suture equipment and supplies –Scalpels and scissors –Alcohol and betadine wipes, bandaids, gauze, bandages, sponges –Surgical masks and gloves –Oral airway and cricothyroidotomy set

67 Medical Supplies on Shuttle Missions A defibrillator is not carried on most Shuttle flights A ventilator and X-ray equipment are not carried on Shuttle flights A defibrillator and an ultrasound system are carried on the International Space Station

68 Nutritional Factors Food intake of at least 2500 to 3000 calories/day –Negative nitrogen balance Fluid intake up to 4200 ml/day (e.g. from fuel cells) Changes in sensitivity to taste and odors Food on Shuttle includes thermostabilized, rehydratable, intermediate-moisture, and natural-form items –Prepackaged for each crew member and stored in dry form when possible –Forced-air convection oven for heating foods

69 Infection Control Personal hygiene is difficult in microgravity Contamination by microorganisms from food, water (especially if recycled), wastes, experimental animals, and payload items Microorganisms continuously shed from skin, mucous membranes, and GI and respiratory tracts –Released as aerosols by sneezing, coughing, and talking –Droplets do not settle but remain suspended until striking a surface or coming into contact with a crewmember (e.g. inhalation) –Increased bacterial resistance to antibiotics and reduced immune function

70 Problems with Medical Care in Space Limited equipment and supplies Limited expertise and medications Adverse effects of microgravity

71 Problems with Medical Care in Microgravity Direct effects on the body –Relative anemia –Increased susceptibility to and delayed healing of fractures Difficulties with diagnostic and therapeutic procedures –No rising of air or layering of fluid on X-rays –No air-fluid levels in bowel obstruction –Placing patient in Trendelenburg position (e.g. hypovolemia) or reverse Trendelenburg (e.g. congestive heart failure) are ineffective

72 Problems with Medical and Surgical Care in Microgravity Space pharmacology –Timing of dosing and changes in absorption and metabolism of medications are not established –Limited types and supplies of medications

73 Problems with Medical and Surgical Care in Microgravity Surgery –All individuals involved (physician, nurse, patient) must be restrained –Difficulty maintaining a sterile field Drapes must be secured Special techniques for putting on surgical gowns and gloves Airborne particles dont settle Special equipment required for washing and disinfecting surgical equipment

74 Problems with Medical and Surgical Care in Microgravity Surgery –Use of inhaled agents for general anesthesia is dangerous in confined area of a spacecraft –Effectiveness of spinal anesthesia is at least partly gravity-dependent –Spurting arteries produce blood droplets suspended in air, and venous blood forms hemispheric domes –Abdominal viscera float out of the abdomen –IV fluids require a pressure pump –Collected urine and blood dont settle to bottom of a measuring container

75 ISS

76 Mars

77 Spirit Rover

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