血气分析临床基础.ppt

* * 临床举例1： 在甲型H1N1(甲流)的诊断过程中,血气分析是临床常用的检查项目。通过血气分析了解病情,决定治疗和观察的方向,对甲型流感患者的早期治疗有重要的指导作用。此外，在甲流患者的抢救过程中需要了解和评估患者的氧供和通气状况，以指导呼吸机的设置和药物的使用。 * 机械通气、或人工呼吸机，从开始仅作为肺脏通气功能支持的一种治疗手段，目前已发展到涉及气体交换、呼吸做功、肺损伤、胸腔内器官压力及容积环境、循环功能等多方面的重要干预措施，并主要通过提供氧输送（DO2）、保护肺脏、改善内环境等途径，成为治疗多器官功能障碍综合症（MODS）的重要手段。 进行机械通气治疗时必须进行血气监测，根据血气分析的结果及时调整呼吸机的参数，使病人的氧合指数达到理想水平。 * 血气分析已经从最初单纯检测血液pH值和气体含量，发展到多参数的诊断监测，包括： 血气参数：pH, PO2, PCO2 电解质参数：K+，Na+, Cl-, Ca2+ 代谢物参数：葡萄糖，乳酸，尿素氮 血氧参数: 氧饱和度，红细胞压积，总血红蛋白，氧合血红蛋白，还原血红蛋白，高铁血红蛋白，碳氧血红蛋白等 * External respiration or oxygen loading Oxygen is transferred from the atmosphere to the blood in the lungs Oxygen transport Oxygen is transported in the blood to the tissue Internal respiration or oxygen unloading Oxygen diffuses from the blood into the tissues pH and Hydrogen Ion Concentration pH is a measure of the [H+] concentration in the body. pH is the negative logarithm to the base 10 of the [H+]. As [H+] rises, pH falls. A low pH indicates that the blood is more acid than normal. A high pH indicates that the blood is less acid than normal. Acids and Bases An acid is any molecule able to donate a H+ ion. In aqueous solution it dissociates into H+ ions and anions. A base is any molecule able to accept an H+. The product formed by acceptance of a H+ is dependent upon the nature of the base. If the base is an acid anion (bicarbonate), an undissociated acid (carbonic acid) will be produced. Addition of acids and alkalis (bases) to a solution will result in changes in [H+] in the solution. Normal pH The body maintains [H+] between 35-45 nmol/l which corresponds to a pH of 7.35 - 7.45. Body function such as heart contraction and nerve conduction are adversely affected by [H+] outside of this range. pH values of less than 7.00 or greater than 7.80 are usually incompatible with life. Three primary systems exist to maintain and restore pH within the range compatible with life: 1. Extracellular buffers 2. The lungs 3. The kidneys Bicarbonate Buffer System The bica