Yet humans are rarely attacked by a shark, while millions of sharks are killed by humans. Some populations of shark species, such as the shortspine spurdog, may have dropped by 95 percent. The sharksâ population decline has a ripple effect â throwing entire marine ecosystems out of balance.
Quick Answer. A normal blood oxygen level during sleep is approximately 94 to 98 percent, according to Sleep Apnea Guide. Levels below 90 percent oxygen saturation are dangerous to the human body. The human brain can only survive four minutes without oxygen before cell death occurs.
An SaO 2 (arterial oxygen saturation) value below 90% causes hypoxemia (which can also be caused by anemia). Hypoxemia due to low SaO is indicated by cyanosis. Oxygen saturation can be measured in different tissues: 1  Venous oxygen saturation (SvO 2) is measured to see how much oxygen the body consumes.2  Under clinical treatment, a SvO 2 below 60% indicates that the body is in lack of oxygen, and ischemic diseases occur.n medicine, oxygen saturation (SO 2), commonly referred to as sats, measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen. At low partial pressures of oxygen, most hemoglobin is deoxygenated.