What are the risks of blood oxygen saturation below 90%?

　　Blood oxygen saturation typically needs to be differentiated between arterial oxygen saturation and venous oxygen saturation. Venous oxygen saturation below 90% but greater than 64% is generally considered normal. If venous saturation falls below 64%, or arterial oxygen saturation drops below 90%, it may lead to tissue hypoxia and cell damage, shortness of breath and chest tightness, decreased lung function, increased cardiac workload, nervous system impairment, and other adverse effects. If abnormalities occur, timely medical attention is recommended. Detailed explanations are as follows:

　　1. Tissue Hypoxia and Cell Damage: Venous saturation below 64%, or arterial oxygen saturation below 90%, indicates reduced oxygen delivery to tissues and organs via the bloodstream, resulting in insufficient oxygen supply to cells and tissues. Prolonged tissue hypoxia can impair organ function and cause pathological changes such as cellular edema and necrosis, which may be life-threatening in severe cases.

　　2. Shortness of Breath and Chest Tightness: Venous saturation below 64%, or arterial oxygen saturation below 90%, may cause difficulty breathing and a sensation of breathlessness. The body attempts to increase blood oxygen levels by increasing respiratory rate and depth, but this often fails to effectively compensate for the oxygen deficiency, leading to symptoms such as chest tightness and dyspnea.

　　3. Decreased Lung Function: Low blood oxygen saturation may be caused by pulmonary diseases, which can further reduce oxygen saturation, creating a vicious cycle. Pulmonary hypoxia may lead to rapid breathing and worsening respiratory difficulty, further increasing the burden on the lungs and causing impaired lung function.

　　4. Increased Cardiac Workload: To compensate for oxygen deficiency in the blood, the heart must work harder. Prolonged increased workload can significantly burden the heart, potentially leading to cardiac problems such as palpitations and arrhythmias, and severe cases may even result in heart failure.

　　5. Nervous System Impairment: The brain has a high demand for oxygen, and persistent venous saturation below 64% or arterial oxygen saturation below 90% can adversely affect brain function, leading to symptoms of nervous system impairment such as difficulty concentrating, memory loss, and diminished cognitive function. Severe cases may even cause headaches and emotional agitation.

　　If related symptoms occur, immediate oxygen therapy via face mask or nasal cannula should be administered to rapidly increase blood oxygen levels. The patient should remain quietly at rest, environmental conditions should be adjusted, and excessive physical exertion should be avoided. Prompt medical consultation is necessary to identify the underlying cause and initiate appropriate treatment. If symptoms persist or are severe, mechanical ventilation support should be considered.