I always figured one of the major health problems for astronauts would be lack of access to health care if anything happened. For instance, if an astronaut developed dangerous kidney stones, or appendicitis, who will do the surgery? If they have some sort of accident or major trauma, who would be qualified to fix that? And even if you have someone qualified, do you have the equipment, or the sterile environment, to perform whatever procedure needs to be done?

Dr. Gupta’s report on the space station was interesting but inaccurate. The astronauts are not living under zero gravity. They are only far enough away from the earth to experience approximately a 10-15% decrease in gravitational forces. The station is falling towards the earth and the floating is like going over the top of a hill in a car. Even that small reduction in gravity has significant effects on the astronauts. For instance, red blood cell production shuts down causing anemia – and that is just the tip of the ice berg of space medical problems. This is why we have not been back to the moon for decades.

Wherever we are, we need to do exercise. Our body is meant for that!

Since an astronaut’s cardiovascular system becomes lazy in space and highly fine tuned receptors in neck artery and other arteries(opposes gravity to maintain blood flow to the brain) that sense change in blood pressure and flow are no longer necessary in microgravity as the blood pools around the heart and thorax(fluid shift in other words, quantity and distribution of body fluids alter as it is free of gravitational effect). One develops puffy nose,head ache and the sinuses swell. The fluid shift also shrinks the size of your legs.

They need to do some exercise for legs(for the lower waist to maintain fluids in the lower part of the body). It’s b’coz of gravity blood flows to the toes. Venous pressures(related to the gravity) is more in the feet than in the brain.

The most abundant minerals in the blood are first calcium,second phosphorus in the ratio of 2:1. On earth, our bones support the weight of our body. The size and mass of our bones are balanced by the rate at which certain bone cells(osteoblasts) lay down new mineral layers and other cells (osteoclasts) which chew up those mineral layers. In space, our bones don’t need to support the body and most weight bearing bones(hip,back,thigh) are not used much. As a result of this, osteoblasts reduce even though osteoclasts remain constant. This results in the reduction of size and mass of bones as an astronaut remains in space, leading to bone loss & finally to osteoporosis. As the bones chewed up by osteoclasts, the blood calcium concentration level increases and the kidney has to get rid of thsi excess calcium which makes them susceptible to form kidney stones.

Our human red blood cells is biconcave discoid shape(like doughnut without a hole!). In space they transform to spherical shape but they return to their normal shape once the astronauts are back on earth. Very interesting. Another problem for astronauts is space radiation. Here on earth, the atmosphere and magnetic field provide shield for us from radiations(from outer space).

Who wants to go to space anyway? It’s so boring and unattractive. Earth and gravity are awesome.

You want to go to space Sanjay? As a Doctor, may be you can experiment with it and come up with some remedies.

On the gravity point, both Dr. Gupta and Mr. Wood are a little inaccurate. Yes, at low earth orbit where the space station hangs out the force of gravity is at about 90% of the strength it is at at the earth’s surface. However, as the space station and astronauts are in a constant state of free-fall which effectively counteracts that force, from their frame of reference they are experience zero gravity (or micro gravity to be precise). The effects on their bodies are the same as if they they were isolated in interstellar space.

Anyway, I thing by far the biggest risk to astronauts is radiation. While chronic bone loss and medical emergencies are not good, all it takes is one moderate solar flare (a common event) to fry all the astronauts in minutes. The space station is lucky in this regard because it is in the earth’s magnetosphere, but other trips to mars and the moon must deal with this. The best solutions are massive amounts of shielding by lead or heavy water (but this is very expensive to launch). I saw an article on a radiation damage pill that helped mice survive lethal doses if they took it an hour before exposure, this is also promising. Chronic radiation is also an obvious concern for future cancer.