美國醫院裏的正常值一般是95%以上。儀器好壞重要的，200元人民幣的大概和醫院用的不一樣吧：）

https://www.healthline.com/health/pulse-oximetry

Pulse oximetry is typically a fairly accurate test. This is especially true when using high-quality equipment found in most medical offices or hospital settings. It consistently provides results within a 2-percent difference either way of what it truly is. If your reading was 82 percent, for example, your true oxygen saturation level may be anywhere from 80 to 84 percent. However, the quality of the waveform and assessment of the individual must be considered. Factors such as movement, temperature, or nail polish can impact the accuracy.

Typically, more than 89 percent of your blood should be carrying oxygen. This is the oxygen saturation level needed to keep your cells — and your body — healthy. While having an oxygen saturation below this temporarily is not believed to cause damage, repeat or consistent instances of lowered oxygen saturation levels may be damaging.

An oxygen saturation level of 95 percent is considered normal for most healthy individuals. A level of 92 percent indicates potential hypoxemia, or deficiency in oxygen reaching tissues in the body.