背景:呼吸暂停测试(AT)是根据神经系统标准(BD/DNC)确定脑死亡/死亡的重要组成部分,并且通常需要断开患者与呼吸机的连接,然后进行气管氧吹入以确保足够的氧合。为了将测试评为阳性,大多数国际指南指出,当二氧化碳的动脉分压(PaCO2)≥60mmHg时,必须证明缺乏自主呼吸。然而,与呼吸机断开相关的呼气末正压丧失可能导致快速减饱和.这个,反过来,可导致心肺不稳定(尤其是在患有肺损伤和急性呼吸窘迫综合征等疾病的患者中),增加患者的风险。因此,这项前瞻性研究旨在调查AT(MAT)的修改版患者保持与呼吸机的连接,是一种更安全但仍然有效的替代方案。
方法:在2019年1月至2022年12月之间注册的所有140名BD/DNC候选人中进行了mAT:预充氧10分钟后,(1)呼气末正压增加2mbar(1.5mmHg),(2)通气模式切换为持续气道正压通气,和(3)关闭呼吸暂停备用模式(流量触发10L/min)。当PaCO2增加至≥60mmHg(基线35-45mmHg)时,未发生自主呼吸时,认为mAT为阳性。记录MAT期间/之后的临床并发症。
结果:mAT在139/140患者中是可能的,中位持续时间为15分钟(四分位距13-19分钟)。严重并发症不明显。在51名患者中,MAT后动脉氧分压(PaO2)低于mAT前PaO2,而88例相同或更高。在肺损伤患者中,在MAT期间呼吸暂停氧合改善了PaO2。在123个案例中,在mAT结束时或之后,血压短暂下降,而在12个案例中,平均动脉压低于60mmHg。
结论:MAT是一种安全的保护性手段,可用于识别不再具有完整中枢呼吸驱动的患者,这是BD/DNC诊断的关键因素。临床试验注册DRKS,DRKS00017803,追溯注册23.11.2020,https://drks。去/搜索/去/试用/DRKS00017803。
BACKGROUND: The apnea test (AT) is an important component in the determination of brain death/death by neurologic criteria (BD/DNC) and often entails disconnecting the patient from the ventilator followed by tracheal oxygen insufflation to ensure adequate oxygenation. To rate the test as positive, most international guidelines state that a lack of spontaneous breathing must be demonstrated when the arterial partial pressure of carbon dioxide (PaCO2) ≥ 60 mm Hg. However, the loss of positive end-expiratory pressure that is associated with disconnection from the ventilator may cause rapid desaturation. This, in turn, can lead to cardiopulmonary instability (especially in patients with pulmonary impairment and diseases such as acute respiratory distress syndrome), putting patients at increased risk. Therefore, this prospective study aimed to investigate whether a modified version of the AT (mAT), in which the patient remains connected to the ventilator, is a safer yet still valid alternative.
METHODS: The mAT was performed in all 140 BD/DNC candidates registered between January 2019 and December 2022: after 10 min of preoxygenation, (1) positive end-expiratory pressure was increased by 2 mbar (1.5 mm Hg), (2) ventilation mode was switched to continuous positive airway pressure, and (3) apnea back-up mode was turned off (flow trigger 10 L/min). The mAT was considered positive when spontaneous breathing did not occur upon PaCO2 increase to ≥ 60 mm Hg (baseline 35-45 mm Hg). Clinical complications during/after mAT were documented.
RESULTS: The mAT was possible in 139/140 patients and had a median duration of 15 min (interquartile range 13-19 min). Severe complications were not evident. In 51 patients, the post-mAT arterial partial pressure of oxygen (PaO2) was lower than the pre-mAT PaO2, whereas it was the same or higher in 88 cases. In patients with pulmonary impairment, apneic oxygenation during the mAT improved PaO2. In 123 cases, there was a transient drop in blood pressure at the end of or after the mAT, whereas in 12 cases, the mean arterial pressure dropped below 60 mm Hg.
CONCLUSIONS: The mAT is a safe and protective means of identifying patients who no longer have an intact central respiratory drive, which is a critical factor in the diagnosis of BD/DNC. Clinical trial registration DRKS, DRKS00017803, retrospectively registered 23.11.2020, https://drks.de/search/de/trial/DRKS00017803.