Abstract：
Intracranial hypertension (IH) is a life-threating condition especially for the brain injured patient. In such cases, an external ventricular drain (EVD) or an intraparenchymal bolt are the conventional gold standard for intracranial pressure (ICPi) monitoring. However, these techniques have several limitations. Therefore, identifying an ideal screening method for IH is important to avoid the unnecessary placement of ICPi and expedite its introduction in patients who require it. A potential screening tool is the ICP wave morphology (ICPW) which changes according to the intracranial volume-pressure curve. Specifically, the P2/P1 ratio of the ICPW has shown promise as a triage test to indicate normal ICP. In this study, we propose evaluating the noninvasive ICPW (nICPW-B4C sensor) as a screening method for ICPi monitoring in patients with moderate to high probability of IH. This is a retrospective analysis of a prospective, multicenter study that recruited adult patients requiring ICPi monitoring from both Federal University of São Paulo and University of São Paulo Medical School Hospitals. ICPi values and the nICPW parameters were obtained from both the invasive and the noninvasive methods simultaneously 5 min after the closure of the EVD drainage. ICP assessment was performed using a catheter inserted into the ventricle and connected to a pressure transducer and a drainage system. The B4C sensor was positioned on the patient\'s scalp without the need for trichotomy, surgical incision or trepanation, and the morphology of the ICP waves acquired through a strain sensor that can detect and monitor skull bone deformations caused by changes in ICP. All patients were monitored using this noninvasive system for at least 10 min per session. The area under the curve (AUC) was used to describe discriminatory power of the P2/P1 ratio for IH, with emphasis in the Negative Predictive value (NPV), based on the Youden index, and the negative likelihood ratio [LR-]. Recruitment occurred from August 2017 to March 2020. A total of 69 patients fulfilled inclusion and exclusion criteria in the two centers and a total of 111 monitorizations were performed. The mean P2/P1 ratio value in the sample was 1.12. The mean P2/P1 value in the no IH population was 1.01 meanwhile in the IH population was 1.32 (p < 0.01). The best Youden index for the mean P2/P1 ratio was with a cut-off value of 1.13 showing a sensitivity of 93%, specificity of 60%, and a NPV of 97%, as well as an AUC of 0.83 to predict IH. With the 1.13 cut-off value for P2/P1 ratio, the LR- for IH was 0.11, corresponding to a strong performance in ruling out the condition (IH), with an approximate 45% reduction in condition probability after a negative test (ICPW). To conclude, the P2/P1 ratio of the noninvasive ICP waveform showed in this study a high Negative Predictive Value and Likelihood Ratio in different acute neurological conditions to rule out IH. As a result, this parameter may be beneficial in situations where invasive methods are not feasible or unavailable and to screen high-risk patients for potential invasive ICP monitoring.Trial registration: At clinicaltrials.gov under numbers NCT05121155 (Registered 16 November 2021-retrospectively registered) and NCT03144219 (Registered 30 September 2022-retrospectively registered).
摘要：
颅内高压（IH）是一种威胁生命的疾病，尤其是对于脑损伤的患者。在这种情况下,心室外引流(EVD)或脑实质内引流是颅内压(ICPi)监测的常规金标准.然而,这些技术有几个局限性。因此,确定理想的IH筛查方法对于避免ICPi的不必要放置和加快ICPi在需要的患者中的引入非常重要.潜在的筛查工具是ICP波形态（ICPW），其根据颅内容量-压力曲线而变化。具体来说,ICPW的P2/P1比率已显示出有望作为指示正常ICP的分诊测试。在这项研究中,我们建议评估非侵入性ICPW(nICPW-B4C传感器)作为ICPi监测中、高IH概率患者的筛查方法.这是一个前瞻性的回顾性分析，从圣保罗联邦大学和圣保罗大学医学院医院招募需要ICPi监测的成年患者的多中心研究。在EVD引流关闭后5分钟，从侵入性和非侵入性方法同时获得ICPi值和nICPW参数。使用插入心室并连接到压力传感器和引流系统的导管进行ICP评估。B4C传感器放置在患者的头皮上，不需要三分法，手术切口或钻孔，以及通过应变传感器获取的ICP波的形态，该传感器可以检测和监测由ICP变化引起的颅骨变形。所有患者均使用该非侵入性系统进行监测，每次至少10分钟。曲线下面积（AUC）用于描述P2/P1比率对IH的判别力，重点是负预测值(NPV)，基于Youden指数,和负似然比[LR-]。招聘发生在2017年8月至2020年3月。两个中心共有69例患者符合纳入和排除标准，共进行了111次监测。样品中的平均P2/P1比值为1.12。无IH人群的平均P2/P1值为1.01，而IH人群的平均P2/P1值为1.32（p<0.01）。平均P2/P1比率的最佳Youden指数的截止值为1.13，灵敏度为93％，特异性为60%，NPV为97%，以及0.83的AUC来预测IH。在P2/P1比率的1.13截止值的情况下，IH的LR-为0.11，对应于排除条件(IH)的强劲表现，阴性测试（ICPW）后病情概率降低约45％。最后，在这项研究中，无创ICP波形的P2/P1比值显示在不同急性神经系统疾病中具有较高的阴性预测值和似然比，以排除IH。因此,该参数在侵入性方法不可行或不可用的情况下可能是有益的,并且可以筛选高危患者进行潜在侵入性ICP监测.试用注册：在clinicaltrials.gov上，编号为NCT05121155（2021年11月16日注册-回顾性注册）和NCT03144219（2022年9月30日注册-回顾性注册）。
