姿態性低血壓患者心輸出量之量測與分析

Abstract

近年來隨著醫療儀器的發展快速進步，臨床量測心搏量與心輸出量之方法，大部份利用外科手術以侵入式方法量測得之。本研究主要探討受測樣本於傾斜床起臥過程產生的姿態性低血壓現象，其血壓、心率、心搏量及心輸出量之變化情形，利用阻抗式心動描記法(Impedance cardiography method, ICG)利用非侵入式方法量測心搏量與心輸出量，並且以Kubicek及Sramek所提之心搏量公式計算出心搏量及心輸出量。 本研究將受測者分為三組，正常組(M group)包含五名正常人(平均年齡 24.6 ± 2.41)，脊髓損傷組(S group)包含五名脊髓損傷患者(平均年齡51.4 ± 11.2)，帕金森式組(P group)包含兩名帕金森式症患者(平均年齡67.5 ± 8.5)。實驗過程為十五分鐘，傾斜床於第六分鐘，向上傾斜至60度，其傾斜速度以每秒2.5度向上傾斜，於實驗過程每分鐘取得收縮壓、舒張壓、心率及胸腔體表阻抗心電訊號等參數數據。利用巴特沃斯濾波器(Butterworth filter)，進行訊號之前處理，並以滑動視窗(Sliding window)偵測法，偵測心電訊號之波峰及阻抗心電訊號之波峰，可成功順利偵測出波峰達97%。 研究結果顯示正常組於起臥過程，其收縮壓或舒張壓約增加10∼20 mmHg，心跳明顯增加約10∼20心跳數，其心搏量則有明顯下降之趨勢。脊隨損傷患者有40%於起臥過程收縮壓或舒張壓約下降20 mmHg，具姿態性低血壓之現象。帕金森氏症患者於起臥過程血壓亦有下降之情形產生，亦具姿態性低血壓之現象。 本研究進一步分析具姿態性低血壓症狀之患者其實驗結果有何差異性，特再將樣本分為四組樣本，A組包含五名正常人，B 組包含兩名姿態性低血壓的脊髓損傷患者，C組包含三名脊髓損傷患者，但不具姿態性低血壓症狀，D組包含兩名具有姿態性低血壓症狀之帕金森式症患者，本研究以時間為內在因子，使用多變量方法(multivariate approach)進行重複測量變異數分析(Repeated measure ANOVA)。分析結果顯示正常組與具姿態性低血壓的脊髓損傷群組及帕金森氏症群組其血壓於傾斜床上升後前段時間具有統計上差異p < 0.05。同時，本研究以One-way ANOVA的Post Hoc Tests進行心率、心搏量以及心輸出量量測數據的統計分析，分析結果顯示具姿態性低血壓的脊髓損傷族群與非具姿態性低血壓的脊髓損傷群組及具姿態性低血壓病症帕金森症群組在傾斜床上升後的後半段時間，有統計上差異 p < 0.05。實驗分析結果亦發現，當收縮壓降低時，B與D受測群組之心率與心搏量的改變有顯著差異p < 0.05，CO_1與SV的改變有顯著差異p < 0.05，研究分析具有統計上之意義。另外利用三種不同公式所計算出心輸出量量測數值，在D受測群組中分析結果為p < 0.05，具有統計上之意義，亦即受測結果不因公式的不同而造成數據上之差異。

With the advanced medical instrument technology, invasive stroke volume (SV) and cardiac output (CO) assessment technique was widely applied in recent year. The primary research purpose of this study is to investigate the physiological responses of the recruited samples during head-upright tilt test. The impedance cardiography technique and the Kubicek and Sramek-Bernstein equations were used to model the SV and CO of the test subjects. This work studied 12 subjects, 5 subjects among them (5 males: 24.6 ± 2.41 years) have no previous history of either cardiovascular or hypertension diseases, 5 patients (5 males: 51.4 ± 11.2 years) with spinal cord injury (SCI) diseases, and 2 patients (2 males: 67.5 ± 8.5 years) with Parkinson’s disease (PD). The head-upright tilt test was conducted on all subjects for 15 minutes. All subjects lie down flat on a test bed in the first 5 minutes. Then, the tilt test bed increased its angle such that the head-up tilt of test subject reaches to 60° with a tilt speed of 2.5°/sec at the 6th minute, and no further angle changing on the head-up tilt in the following 10 minutes. All of test subjects’ blood pressure (BP), heart rate (HR), SV and CO were recorded and analyzed. This study used Butterworth filter to smooth the signals obtained from electrocardiogram and impedance cardiography. Also, a Sliding Window method was developed to detect the R peaks in electrocardiogram and the specified peaks in impedance cardiography. The successive rate of peak detection achieved is high up to 97%. The results of this study suggest that the systolic or diastolic pressures in the test group of normal subjects have a pressure gradient of more than 10 mmHg, heart rate increase of more 10 beats per minute, and stroke volume drops significantly. For the 40% of SCI patients and PD patients, their systolic or diastolic pressure decreases for more than 20mmHg during head-upright tilt test and this fact implies that these patients were with orthostatic hypotension (OH). Four groups (group A: normal subjects; group B: SCI with orthostatic hypotension; group C: SCI not with orthostatic hypotension; group D: PD with orthostatic hypotension) were included in the statistical test. The repeated measurement of ANOVA was used for inter-group comparisons of patient’s blood pressure. It was found that blood pressures in the test groups of A, B, and D have significant statistical difference (p < 0.05) at the first stage (i.e., during experimental course from 6 to 10 minutes) after head-up tilt to 60° already. Then, the differences of HR, SV, and CO between groups B or D and other groups are of interest. The Post Hoc test with one way repeated measures of ANOVA was used for inter-group comparisons. This study found that heart rate, stroke volume and cardiac output have significant changes (p < 0.05) between groups B and C, and groups B and D at the last stage (i.e., during experimental course from 11 to 15 minutes) after head-up tilt to 60° already, respectively. The statistical analysis also demonstrated that cardiac output in group D significantly changed when different stroke volume equations were used.