of the body, meaning that if the g-force is elevated, all the blood pressure in veins will increase. This means less blood reaches the heart, affecting its ability to function, with decreased circulation. The effects for negative g-force can be more dangerous producing hyperemia and also psychotic episodes. In space, G forces are almost zero, which is called microgravity, meaning that the person is floating in the interior of the vessel. This happens because the gravity acts on the spaceship and in the body equally, both are pulled with the same forces of acceleration and also in the same direction. Hypoxia (medical) General effects Hypoxia occurs when the bloodstream lacks oxygen. In an aerospace environment, this occurs because there is little or no oxygen. The work capacity of the body is reduced, decreasing the movement of all muscles (skeletal and cardiac muscles). The decrease in work capacity is related to the decrease of the oxygen of transportation velocity. Some acute effects from hypoxia include: dizziness, laxity, mental fatigue, muscle fatigue and euphoria. These effects will affect a non-acclimated person starting in an altitude of 3650 meters above sea level. These effects will increase and can result in cramps or convulsions at an altitude of 5500 meters and will end in an altitude at 7000 meters with a coma. Mountaineering disease One type of hypoxia related syndrome is mountaineering disease. A non-acclimated person that stays for a significant amount of time at a high altitude can develop high erythrocytes and hematocrit. Pulmonary arterial pressure will increase even if the person is acclimated, presenting dilatation of the right side of the heart. Peripheral arterial pressure is decreased, leading to congestive cardiac insufficiency, and death if exposure is long enough. These effects are produced by a decrease of erythrocytes, which causes a significant increase of viscosity in blood. This causes diminished blood flow in tissues, so oxygen distribution decreases. The vasoconstriction of the pulmonary arterioles is caused by hypoxia in the right portion of the heart. Arteriole spasms include the major part of the blood flow through the pulmonary vessels, producing a short circuit in the blood flow giving less oxygen in blood. The person will recover if there is an administration of oxygen or if s/he is taken to low altitudes. Mountaineering disease and pulmonary edema are most common in those who climb rapidly to a high altitude. This illness starts from