探讨阻抗心动描记图(ICG)在快速诊断ICU重症患者呼吸困难原因中的应用价值。

选择2014年6月至2016年3月急诊入ICU的80例呼吸困难患者纳入研究，采用盲法诊断试验。每例患者都行血常规、肝肾功、电解质、心电图、胸片、动脉血气分析等常规检查，ICU医师根据检查结果采用诊断标准对患者进行诊治；所有患者均采用ICG监测血流动力学，专人负责ICG监测和记录心指数(CI)、每搏指数(SI)、外周血管阻力指数(SVRI)、收缩时间比率(STR)、速度指数(VI)及胸腔液体水平(TFC)，而ICU医师并不知晓监测数据结果；患者出院后，由没有参与治疗且不知道ICG结果的专家团队综合所有的医疗数据，作出每个患者最终医院诊断：心源性或非心源性呼吸困难。比较ICG诊断以及ICU医师诊断呼吸困难原因的时间和结果；根据专家团队最终诊断，分别计算ICG诊断以及ICU医师诊断的敏感性、特异性、阳性预测值和阴性预测值，分析两者对心源性及非心源性呼吸困难的判断价值。

80例患者中因无法获得ICG数据排除4例，24例患者最终诊断为心源性呼吸困难，52例为非心源性呼吸困难。与最后诊断相比，心源性呼吸困难患者ICU医师组诊断正确20例，ICG诊断22例；非心源性呼吸困难患者，ICU医师组诊断40例，ICG诊断46例；诊断准确性ICU医师是79%(60/76) 、ICG为89%(68/76)，有统计学差异(P<0.05)。ICG血流动力学参数显示心源性呼吸困难患者存在低CI、SI和VI，高STR、SVRI和TFC，与非心源性呼吸困难患者参数比较存在显著差异，其中CI(2.00±0.95 vs. 3.00±0.72，P<0.001) STR(0.56±0.28 vs. 0.40±0.11，P<0.001)、VI(31.8±14.7 vs. 42.2±15.8，P＝0.008)、TFC(40.6±14.4 vs. 32.4±14.0，P＝0.021)；SI(27.8±11.4 vs. 34.6±10.8，P＝0.014)、SVRI(2 952±1 191 vs. 2 124±801，P<0.001)。诊断时间从入ICU开始计算，ICU医师在(1.57±1.14)h内完成诊断；ICG在(0.47±0.34)h内完成诊断，有显著差异(P<0.001)。ICG诊断与ICU医师诊断比较，其有更高的敏感性(91.7% vs. 83.3%)、特异性(88.5% vs. 76.9%)、阳性预测值(78.6% vs. 62.5%)和阴性预测值(95.8% vs. 90.9%)，对心源性及非心源性呼吸困难的诊断具有更好的判断能力。

ICG在诊断重症患者的呼吸困难原因中具有更高的敏感性、特异性、阳性预测值和阴性预测值，能帮助ICU医师有效、快速、准确诊断呼吸困难原因为心源性或非心源性，有利于指导临床治疗。

To investigate the effect of impedance cardiography on rapid diagnosis of severe patients with dyspnea.

A blinded trial was conducted. All 80 cases of dyspnea in ICU were enrolled in the study from June 2014 to March 2016. Each patient will be routinely checked, such as routine blood test, liver and kidney function, electrolytes, electrocardiogram, chest X-ray, arterial blood gas analysis. According to the results of the examination, ICU physician diagnosed and treated the patients. All patients were treated with ICG hemodynamic monitoring, the person responsible for the ICG monitoring and recording the cardiac index (CI), stroke index (SI), systemic vascular resistance index (SVRI), systolic time ratio (STR), velocity index (VI) and thoracic fluid content (TFC), but ICU physicians blinded to the ICG data. After discharge from the hospital, the team of experts who did not participate in the treatment and did not know the results of the ICG integrated all the medical data, the final hospital diagnosis of each patient: cardiac or non cardiac dyspnea. To compare the time and results of ICG diagnosis and ICU physician diagnosis of dyspnea; According to the team′s final diagnosis, the sensitivity, specificity, positive predictive value and negative predictive value of ICG diagnosis and ICU physician diagnosis were calculated respectively, and the judgment ability of both cardiac and non cardiac dyspnea was analyzed.

All 4 patients were excluded from the study because of unacquirable ICG data, and the final diagnosis of cardiac dyspnea was in 24 patients, and 52 were noncardiac dyspnea. The ICU physician diagnosed 20/24 patients correctly with final diagnosis of cardiac cause, and 40/52 with noncardiac cause. ICG correctly diagnosed 22/24 patients with cardiac cause, and 46/52 with noncardiac cause. Compared with the final diagnosis, the overall diagnostic accuracy by ICG was 89%(68/76) compared with 79% (60/76) for ICU physicians, with a statistically significant difference (P<0.05). ICG hemodynamic parameters showed low CI, SI and VI, high STR, SVRI and TFC in patients with cardiac dyspnea.There were significant differences in values of CI(2.00±0.95 vs. 3.00±0.72, P<0.001) STR(0.56±0.28 vs. 0.40±0.11, P<0.001), VI(31.8±14.7 vs. 42.2±15.8, P=0.008), TFC(40.6±14.4 vs. 32.4±14.0, P=0.021); SI(27.8±11.4 vs. 34.6±10.8, P=0.014), SVRI(2 952±1 191 vs. 2 124±801, P<0.001). between the cardiac and noncardiac groups, respectively. And there were significant differences in diagnosis time(0.47±0.34 vs. 1.57±1.14 h, P<0.00). ICG measurements demonstrated superior sensitivity (91.7% vs. 83.3%), specificity (88.5% vs. 76.9%), and positive and negative predictive values (78.6% vs. 62.5% and 95.8% vs. 90.9%, respectively) when compared with the ICU physician in the final diagnosis of cardiac vs. noncardiac cause of dyspnea.

ICG diagnosis of patients with severe dyspnea with superior sensitivity, specificity, positive predictive value and negative predictive value. ICU can help doctors quickly, effectively, accurately diagnose the cause of dyspnea as cardiac or noncardiac, to guide clinical treatment.