What happens when blood oxygen levels drop below 90%?

　　Blood oxygen refers to blood oxygen saturation. In general, blood oxygen saturation below 90% can lead to decreased immune function, increased cardiac workload, nervous system damage, reduced lung function, and impaired cardiovascular system function. If necessary, timely medical attention is recommended. Detailed analysis is as follows:

　　1. Decreased immune function

　　The immune system requires adequate oxygen to maintain its normal function and activity. Hypoxia can impair immune system function, making the body more susceptible to infections. Low blood oxygen saturation may also delay wound healing and recovery processes.

　　2. Increased cardiac workload

　　The heart must work harder to compensate for the lack of oxygen in the blood. Long-term hypoxia can increase the cardiac workload, potentially leading to symptoms such as palpitations and arrhythmias.

　　3. Nervous system damage

　　The brain has a high demand for oxygen. Persistent low blood oxygen saturation can adversely affect brain function, causing symptoms of nervous system impairment such as difficulty concentrating, memory loss, and diminished cognitive function.

　　4. Reduced lung function

　　Low blood oxygen saturation may be caused by lung diseases, which can further lower blood oxygen levels. Pulmonary hypoxia can cause rapid and labored breathing, further increasing the burden on the lungs and leading to decreased lung function.

　　5. Cardiovascular system impairment

　　Hypoxia can cause vasoconstriction, increasing the cardiac workload. It can also affect myocardial cell metabolism and function, potentially triggering cardiovascular issues such as myocardial ischemia, angina pectoris, and acute myocardial infarction.

　　If low blood oxygen saturation is detected, immediate medical attention should be sought and appropriate treatment measures taken to improve the hypoxic condition and protect overall health.