所谓危重型呼吸衰竭指的是患者吸入氧浓度达80％以上,而动脉血氧张力(PaO_2)仍低于50毫米汞柱的严重情况。低氧血症与氧中毒治疗低氧血症常需吸入高浓度氧气,但氧浓度过高对肺有毒性,反而会加重低氧血症。表1列出与各种临床状况有关的动脉血氧张力和氧饱和度。动脉血氧张力的正常下限各家报告颇有差异,约为90～70毫米汞柱。当正常人呼吸海平面空气时,如氧合浓度低于正常值 The so-called critical respiratory failure refers to the patients inhaled oxygen concentration of more than 80%, while the arterial oxygen tension (PaO_2) is still below 50 mmHg serious situation. Hypoxemia and oxygen toxicity Hypoxemia often need to inhale high concentrations of oxygen, but the oxygen concentration is too toxic to the lungs, but will increase hypoxemia. Table 1 lists the arterial oxygen tension and oxygen saturation associated with various clinical conditions. The normal lower limit of arterial oxygen tension reported quite different from home, about 90 to 70 mm Hg. When normal breathing sea level air, such as oxygen concentration lower than normal