文献导读&诊断性试验

Oxygen Reserve Index Predicts Hypoxemia During One-Lung Ventilation:

An Observational Diagnostic Study

氧储备指数预测单肺通气期间的低氧血症:

一项观察性诊断研究

By 喵&苗&丹妮

01

summary

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Objective: To determine the accuracy of the Oxygen Reserve Index (ORi) to predict hypoxemia during one-lung ventilation (OLV)．

Design: An observational diagnostic test study．

Setting: A tertiary care teaching hospital．

Participants: Forty consecutive patients scheduled for thoracic surgery with OLV．

Measurements and Main Results: Patients were ventilated with tidal volumes of 8 mL/kg ideal body weight during two-sided ventilation and 6 mL/kg during OLV, and with fraction of inspired oxygen (FIO2) of 60%． ORi was measured continuously．Sensitivity,

specifificity, positive and negative predictive values, likelihood ratios, and accuracy were calculated for ORi = 0 in different phases of anesthesia． Hypoxemia during OLV was defifined as SpO2 < 90%． Hypoxemia owing to malpositioning of the double lumen tube was an exclusion criterion． ORi = 0 fifive minutes after tracheal intubation in the supine position showed a sensitivity of 63．6% (confifidence interval [CI] 95% 31．6-87．6), specifificity of 93．1% (95% CI 75．8-98．8), and an accuracy of 85．0% (95% CI 69．5-93．8)． The rate of hypoxemia was 27．5% (95% CI 15．14- 44．14)．

Conclusions: An ORi value equal to zero, 5 minutes after the onset of mechanical ventilation in the supine position, predicts the development of hypoxemia during OLV． These fifindings may be helpful to adjust FIO2 individually in patients undergoing OLV and to avoid unnecessary high concentrations of oxygen

目的:确定氧储备指数(ORi)预测单肺通气(OLV)期间低氧血症的准确性

设计:一个观察性诊断试验研究

背景:一家三级保健教学医院

对象:40例计划接受OLV胸外科手术的患者

方法与主要结果:患者在双侧通气时潮气量为8mL/kg,在OLV时潮气量为6mL/kg,吸入氧气(FiO2)的比例为60%。连续测量ORi。计算ORi=0在不同麻醉阶段的敏感性、特异性、阳性和阴性预测值、似然比和准确性。OLV期间的低氧血症定义为spo2<90%。由于双腔管定位不当而引起的低氧血症是一个排除标准。仰卧位气管插管5分钟后显示敏感性为63．6%(95%CI:31．6-87．6),特异性为93．1%(95%CI:75．8-98．8),准确性为85．0%(95%CI:69．5-93．8)。低氧血症的发生率为27．5%(95%CI:15．14-44．14)。

结论:在仰卧位机械通气开始5分钟后,ORi值为0,可预测OLV期间低氧血症的发展。这些发现可能有助于对OLV患者个体化调整FiO2,并避免不必要的高浓度氧。

02

Table&Figure

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患者特征

ORi=0预测OLV期间低氧血症的准确性指标

NLHR:阴性似然比

NPV:阴性预测值

OLV:单肺通气

ORiORIb:基础ORi

ORI35:FiO2=35%硬膜外置管下ORi

ORI100:FiO2=100%预氧合后ORi

ORIDS5:仰卧位机械通气5min后ORi

ORIDL5:机械通气侧卧位5min后ORi

OROLV60．OROLV120:OLV后60s、120sORi

OROLV5．OROLV10:OLV后5min、10minORi

麻醉前诱导和OLV过程中ORi的演变．箱图

ORiORIb:基础ORi

ORI35:FiO2=35%硬膜外置管下ORi

ORI100:FiO2=100%预氧合后ORi

ORIDS5:仰卧位机械通气5min后ORi

ORIDL5:机械通气侧卧位5min后ORi

OROLV60．OROLV120:OLV后60s、120sORi

OROLV5．OROLV10:OLV后5min、10minORi

03

知识卡片

HAVE A NICE DAY

诊断性实验

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1．本质:诊断性试验与金标准结果作比较

2．基本概念

①敏感度(sensitivity,SEN):诊断性试验检测为阳性的病例在用金标准确定为“有病” 的病例中所占的比例。敏感度越高,漏诊率(1—SEN)越少 ,易误诊,有助于排除相应的疾病。

②特异度(specificity,SPE) :诊断性试验检测为阴性的受试者在用金标准确定为“无病”的受 试者中所占的比例。特异度越高,误诊率(1-SPE)越低 ,易漏诊,有助于确定诊断

③患病率(prevalence,PREV) 经诊断性试验检测的全部病例中,真正“有病”患者所占的比例。

④阳性预测值:诊断性试验“阳性”的所有病例中,金标准“有病”的病例所占比例

⑤阳性似然比:真阳性在“有病”中的比例与假阳性在“无病”中的比例的比值。比值越大,患病概率越大。

⑥ROC曲线(受试者工作特征曲线):距Y轴顶点直线距离最近的一点,即为正常值的最佳临界值

⑦似然比:真阳性率与假阳性率之比,综合了敏感度和特异度。有病患者呈现真阳性是无病患者呈现阳性的多少倍。

诊断性实验tips

①当试验方法和阳性标准固定时,每个诊断试验的灵敏度和特异度是恒定的。

②区分诊断试验正常和异常的临界点会影响灵敏度和特异度

③灵敏度越高的试验,阴性预测值越高;特异度越高的试验,阳性预测值越高;患病率的高低对预测值的影响更大