氧是维系人类生命的基础,心脏的收缩和舒张使得人体的血液脉动地流过肺部,一定量的还原血红蛋白(HbR)与肺部中摄取的氧气结合成氧和血红蛋白 (HbO2),另有约2%的氧溶解在血浆里。这些血液通过动脉一直输送到毛细血管,然后在毛细血管中将氧释放,以维持组织细胞的新陈代谢。血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" 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title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度" title="血氧饱和度">血氧饱和度 (SO2)是血液中被氧结合的氧合血红蛋白(HbO2)的容量占全部可结合的血红蛋白(Hb)容量的百分比,即血液中血氧的浓度,它是呼吸循环的重要生理参数。而功能性氧饱和度为HbO2浓度与HbO2 Hb浓度之比,有别于氧合血红蛋白所占百分数。因此,监测动脉血氧饱和度(SaO2)可以对肺的氧合和血红蛋白携氧能力进行估计。
2.1 血氧饱和度检测分类
血氧浓度的测量通常分为电化学法和光学法两类。
传统的电化学法血氧饱和度测量要先进行人体采血(最常采用的是取动脉血),再利用血气分析仪进行电化学分析,在数分钟内测得动脉氧分压 (PaO2),并计算出动脉血氧饱和度(SaO2)。由于这种方法需要动脉穿刺或者插管,给病人造成痛苦,且不能连续监测,因此当处于危险状况时,就不易使病人得到及时的治疗。电化学法的优点是测量结果精确可靠,缺点是比较麻烦,且不能进行连续的监测,是一种有损伤的血氧测定法。
光学法是一种克服了电化学法的缺点的新型光学测量方法,它是一种连续无损伤血氧测量方法,可用于急救病房、手术室、恢复室和睡眠研究中。目前采用最多的是脉搏血氧测定法(Pulse Oximetry),其原理是检测血液对光吸收量的变化,测量氧合血红蛋白(Hb02)占全部血红蛋白(Hb)的百分比,从而直接求得SO2。该方法的优点是可以做到对人体连续无损伤测量,且仪器使用简单方便,所以它已得到越来越普遍的重视。缺点是测量精度比电化学法低,非凡是在血氧值较低时产生的误差较大。先后出现了耳式血氧计,多波长血氧计及新近问世的脉搏式血氧计。最新的脉搏式血氧计的测量误差已经可以控制在1%以内,达到临床使用的要求。尽管它们在某些方面还不尽如人意,但其所产生的临床效益已被广泛认同。
2.2 无损伤血氧饱和度检测原理
临床上多用功能氧饱和度来反映血液中氧含量的变化。无损伤血氧饱和度测量是基于动脉血液对光的吸收量随动脉搏动而变化的原理来进行测量的。基础研究表明,氧合血红蛋白和非氧合血红蛋白对不同波长入射光有着不同的吸收率。当单色光垂直照射人体,动脉血液对光的吸收量将随透光区域动脉血管搏动而变化,而皮肤、肌肉、骨骼和静脉血等其他组织对光的吸收是恒定不变的。当用两种特定波长的恒定光λ1、λ2照射手指时,假如适当选择入射光波长 λ1(Hb02、Hb在此处具有等吸收特性,即约805nm),运用Lambert-Bear定律并根据氧饱和度的定义可推出动脉血氧饱和度的近似公式为:Sa02=a bQ
式中:Q为两种波长(Hb02、Hb)的吸光度变化之比a、b为常数,与仪器传感器结构、测量条件有关。
注重到生物组织是一个各向异性、强散射、弱吸收的复杂光学介质,因此在实际测量中无法用一个严格的公式来描述,所以一般是通过测量双光束吸光度变化之比,然后通过经验定标曲线最终获取氧饱和度。而在选择双光束波长时,一般选择入射光波长为660nm和940nm。
2.3 无损伤血氧饱和度检测用光电传感器[2,3]
血氧传感器是检测血氧饱和度的重要部件,它的损坏会直接导致检测不准或整机瘫痪无法工作。血氧传感器按外形主要可以分为指套型、耳垂型、包裹型和粘附型,按用途又可分为成人型和儿童型、婴儿型几种。不论外形和类型如何,血氧传感器的原理构成是一样的,它们均由发光器件和接收器件组成。发光器件是由波长为660nm(650nm)的红光和波长为940nm(910nm)的红外光发射管组成。光敏接收器件大都采用接收面积大,灵敏度高,暗电流小,噪声低的PIN型光敏二极管,由它将接收到的入射光信号转换成电信号。
最新开发的脉搏血氧计大多采用的是指套式传感器探头。使用时探头套在指尖上。指套上壁固定了两个并列放置的发光二极管,发光波长分别为 660nm红光和940nm红外光。下壁是一个光敏接收器件,它将透射过手指的红光和红外光转换成电信号。血氧计运行时,分时驱动电路让两个发光二极管按一定的时间间隔并以较低的占空比分别发光,根据光二极管发光强度与光电管接收到的透射光的强弱比值可分别计算出全血吸收率a660和a940,然后结合实验标定的系数A和B,代入前述公式中,就可以算得血氧饱和度的数值了。
2.4 血氧仪系统框图
脉搏血氧仪一般由血氧饱和度检测模块、工控机或PC机、血氧检测探头(一般为指套式)等部分组成。也有些是直接研制成一体的或便携式的。假如采用的是已经研制好的血氧饱和度检测模块来搭建的系统,由于模块与工控机或PC机之间的电平电压不同,它们之间还要通过电平转换模块连接起来,这样才能够进行正确的通讯。
3 脉搏血氧计的操作使用
是否能够正确操作使用血氧计,关系到检测结果的准确性。透射式脉搏血氧计多以手指、耳垂、脚趾等作为检测部位,因为这些部位是光线最轻易透射过的部位。而对于采用指套式传感探头的脉搏血氧计,检测前最好应将手指非凡是指甲部位清洗干净,否则假如脏物过多,会阻碍光线的透射,从而对测量结果造成一定的影响。测量时将中指夹在指套里,注重指甲应正对上壁的发光管,夹好后还应注重指套四面是否密闭严实,以避免环境光的干扰。指套夹好并开机后,等待测量数据稳定后就可以读出血氧饱和度了,现在的血氧计一般还可以读出脉率值和脉搏波形。