Clinical study of impedance cardiography in rapid diagnosis of severe patients with dyspnea

Abstract

Objective To investigate the effect of impedance cardiography on rapid diagnosis of severe patients with dyspnea. Methods 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. Results 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. Conclusions 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. Key words: Impedance cardiography; Severe patients; Dyspnea, cardiogenic; Noncardiac