Wang Cecily F., Yandrapalli Srikanth
Straub Benioff Medical Center, University of Hawaii John A. Burns School of Medicine, OptimumAir Hawaii
New York Medical College/Westchester Medical Center
Refractory hypoxemia may develop in a small subset of patients with acute respiratory failure despite optimal mechanical ventilation. Acute respiratory distress syndrome is the most common underlying cause and poses a significant challenge to intensivists. Various ventilatory strategies can improve oxygenation but often lack a proven survival benefit. No universally accepted definition exists for refractory hypoxemia. However, the term generally refers to inadequate arterial oxygenation despite high inspired oxygen concentrations. A recent survey underscores the variability in how intensivists define this condition. Proposed definitions in the literature include a partial pressure of oxygen (PaO2) of 60 mm Hg or lower, or a ratio of PaO2 to the fraction of inspired oxygen (FiO2) of 100 or lower on an FiO2 of 0.8 to 1.0, with positive end-expiratory pressure greater than 15 cm H2O or plateau pressures exceeding 30 cm H2O, sustained for more than 12 hours despite low tidal volumes (4–6 mL/kg). The oxygenation index—calculated as mean airway pressure × FiO2 × 100/PaO2—is also used; values greater than 40 indicate refractory hypoxemia that may warrant rescue therapy, such as extracorporeal membrane oxygenation (ECMO), particularly after failure of standard interventions, including prone positioning, neuromuscular blockade, and pulmonary vasodilators.
尽管进行了最佳机械通气，一小部分急性呼吸衰竭患者仍可能出现难治性低氧血症。急性呼吸窘迫综合征是最常见的潜在病因，给重症监护医生带来了重大挑战。各种通气策略可改善氧合，但往往缺乏已证实的生存获益。目前尚无关于难治性低氧血症的普遍接受的定义。然而，该术语通常指尽管吸入氧浓度高但动脉氧合仍不足。最近的一项调查强调了重症监护医生对这种情况定义的差异。文献中提出的定义包括：在吸入氧分数（FiO2）为0.8至1.0、呼气末正压大于15 cmH2O或平台压超过30 cmH2O、低潮气量（4 - 6 mL/kg）持续超过12小时的情况下，氧分压（PaO2）为60 mmHg或更低，或PaO2与FiO2之比为100或更低。氧合指数（计算方法为平均气道压×FiO2×100/PaO2）也被使用；大于40的值表明难治性低氧血症，可能需要进行挽救治疗，如体外膜肺氧合（ECMO），特别是在包括俯卧位、神经肌肉阻滞和肺血管扩张剂等标准干预措施失败后。
