Causes of low blood oxygen levels include blocked airways, high altitudes, anemia, pneumonia, interstitial lung disease, acute respiratory distress syndrome and sleep apnea, according to Mayo Clinic. Other pulmonary conditions such as pulmonary edema, pulmonary embolism and pulmonary fibrosis also can cause low oxygen levels.
For effective functioning, the body needs circulation of a certain level of oxygen in the cells and tissues. A lower-than-normal blood oxygen level is referred to as hypoxemia, and it causes shortness of breath. Insufficient blood oxygen levels may also be caused by certain medications, including narcotics and anesthetics, which can lower breathing rates. Similarly, heart conditions at birth such as congenital heart disease can cause low blood oxygen levels, reports Mayo Clinic.
Any cause that affects the amount of air entering the lungs may lead to hypoxemia, according to Wikipedia. Similarly, any cause that influences the transfer of air from the lungs to the blood may also result in insufficient blood oxygen levels. A mismatch between ventilation and perfusion, shunts, and hypoventilation may cause low blood oxygen levels.
Acute respiratory distress syndrome occurs when fluids build up in the lung sacs. The greater the fluid accumulation, the lesser the amount of oxygen that is reaching the blood. This condition develops soon after the patient has suffered some serious trauma or injury. Shortness of breath is among the earliest symptoms.
Other causes of hypoxemia include chronic obstructive pulmonary disease, emphysema and pneumothorax, according to Mayo Clinic. Pneumothorax refers to a collapsed lung, and it occurs due to air leaking between the lungs and the chest wall. Emphysema gradually destroys the air sacs, causing a person to experience shortness of breath. Emphysema is one of a number of conditions that are grouped under chronic obstructive pulmonary disease, according to Mayo Clinic Other causes of low oxygen content in the blood are cyanide poisoning and strong pain medications.