Generally there are two indicators of blood oxygen content: the first indicator, arterial partial pressure of oxygen, is the pressure generated by the oxygen physically dissolved in the blood, under normal circumstances the partial pressure of arterial blood oxygen is 95-100mmHg, when lower than 95mmHg is the partial pressure of arterial blood oxygen is reduced, when the partial pressure of arterial blood oxygen is lower than 60mmHg, the human body will appear obvious symptoms of hypoxia, manifested as The second indicator, arterial oxygen saturation, is 95%-98% under normal circumstances. Arterial oxygen saturation is the percentage of hemoglobin combined with oxygen to all hemoglobin, and when the arterial oxygen saturation is lower than 95%, it is reduced. When the arterial oxygen saturation is 90%, the patient will normally feel chest tightness, manifesting as difficulty in breathing, shortness of breath, etc. The lower the arterial oxygen saturation, the more serious the symptoms of hypoxia.