什么是最佳血氧飽和度
解讀時要關注血氧飽和度變化趨勢和潛在的疾病過程：
（1）如果患者先前的靜息氧飽和度為 99%，那么靜息氧飽和度變?yōu)?96% 則可能不正常。
（2）存在 COPD 患者急性加重時，88% ～ 92% 的目標水平可能就足夠。相比之下，對于急性呼吸窘迫綜合征孕婦，目標飽和度 > 95% 可能才理想。
然而脈搏血氧儀準確度的臨界值為 80%，即 pH 值為 7.4 時、動脈氧分壓 PaO2 約為 50 mmHg 時的狀態(tài)，當患者血氧飽和度在 80% 以下時，血氧儀的監(jiān)測結果會存在一定誤差。
異常數(shù)值分析
1. 讀數(shù)偏高（假性正常讀數(shù)）
一氧化碳中毒及慢性重度吸煙者
一氧化碳中毒及慢性重度吸煙者體內會存在高濃度的碳氧血紅蛋白，其脈搏血氧儀的讀數(shù)會偏高，這可能會掩蓋危及生命的動脈血氧飽和度下降。
在血糖控制不佳的 2 型糖尿病患者中，當糖化血紅蛋白 A1c 水平超過 7% 時，會導致脈搏血氧儀的測定值高于實際值。這可能與血紅蛋白與氧的親和力增加有關。
2. 讀數(shù)偏低（假性異常讀數(shù)）
灌注不足
血流動力學不穩(wěn)定時，或者肢體抬高、血管收縮及周圍血管病導致肢體灌注不良時，脈搏血氧儀讀數(shù)可能偏低。當收縮壓低于 80 mmHg 時，標準脈搏血氧儀的準確性急劇下降。
另外需強調的是，應避免將傳感器置于有血壓袖帶或動脈置管的同側肢體，因為這可能會導致錯誤讀數(shù)。如果對讀數(shù)有疑問，可將探頭夾在自己的手指上 (盡可能選取與患者相同的部位)，進行一次快速的質量保證測試。這可排除設備誤差引起的讀數(shù)異常。
脈搏血氧儀因為無創(chuàng)、可連續(xù)監(jiān)測，臨床應用相當廣泛，我們需要掌握如何正確判讀，并結合實際情況加以分析。同時我們也要知道，任何情況下血氣分析都是相對的金標準，不要只局限在血氧飽和度上。
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