Physical principles of the Doppler echocardiography determination of heart minute volume

By means of Doppler echocardiography to measure blood flow velocity in the aorta and echocardiographic imaging to measure vessel diameter cardiac output can be assessed noninvasively in selected patients. This paper presents the underlying physical principles and discusses resulting aspects of measurement and limitations of the technique.     

胃镜检查对心率、血氧饱和度的影响

目的:探讨胃镜检查对各年龄段患者心率、血氧饱和度的影响。方法:对53名不同年龄的患者(被分为老年组、中年组、青年组)分别在胃镜检查的4个阶段(胃镜检查前1 min、经咽-贲门、进入胃腔、退镜后1 min)进行心率和血氧饱和度的监测,并进行比较。结果:心率各组检查前无显著差异,术中各阶段较术前显著增快(P<0.05~<0.01),以经咽-贲门时为最快(P<0.01);术中老年组心率上升幅度较低(P<0.05)。血氧饱和度术前后各组均无显著差异,但老年组的胃镜检查时有所降低。结论:对于老年人,心血管病人的胃镜检查最好是术时进行心电图和血氧饱和度的动态监测,以免不测。     

Spectrophotometric determination of oxygen saturation of blood independent of the presence of indocyanine green.

The strong absorbance of indocyanine green in a broad band around lambda = 800 nm invalidates the usual spectrophotometric two-wavelength methods for measuring oxygen saturation operating in the red and near infrared region. By proper wavelength selection, however, the effect of the dye can be eliminated. With the two-wavelength method utilising lambda = 660 and 860 nm oxygen saturation is measured virtually independent of the presence of indocyanine green.     

无痛胃镜检查对老年患者血压、心率和血氧饱和度的影响

目的:观察无痛胃镜检查对老年患者血压、心率和血氧饱和度的影响,了解老年患者行无痛胃镜检查的安全性.方法:无痛胃镜检查是在胃镜检查前先予以芬太尼及丙泊酚静脉麻醉.以多功能监护仪监测并记录无痛胃镜检查前、检查中、苏醒时和休息10min患者的收缩压、舒张压、心率和血氧饱和度,并记录不良反应(呛咳、呃逆、呼吸抑制等).结果:与...     

Demonstration of a non-invasive measurement of the heart minute volume]

With the help of a rapidly indicating oxygen gas analyser and the additional use of the rerespiration of a gas mixture, containing nitrogen and carbon dioxide, we succeed in analysing the partial oxygen pressure in the mixed venous blood and thus establishing non-operatively the minute output of the heart according to Fick's principle.     

Comparative evaluation of non-invasive methods of determining the minute blood volume

Comparative value of minute flow volume measurement by radiocardiography, echocardiography, tetrapolar chest rheography and ultrasonic impulse doppler flowmetry was assessed in 30 individuals. Radiocardiography was often associated with overstated values and could not be used for minute volume monitoring. Tetrapolar chest rheography was also associated with overstated values in cases of left-ventricular insufficiency, and inadequately overstated values in 6% of normal subjects and understated values in 1%. Ultrasonic impulse doppler flowmetry was not possible in 8% of the cases because of poor echo. Ultrasonic impulse doppler flowmetry and echocardiography were found to be the most promising and clinically suitable procedures.     

Oxygen saturation determination in frozen blood

A spectroscopic method for O₂ saturation determination in frozen blood has been developed. In the 500–575 nm range, frozen oxygenated and deoxygenated blood had essentially the same spectral absorption character as liquid blood, although apparent absorbance was much higher than liquid blood. The standard two-wavelength method for spectroscopic determination of O₂ saturation of blood was inadequate to correct for the nonspecific light loss through the ice crystals. A method for O₂ saturation determination using three wavelength (506, 523, and 560 nm) measurements is reported here. Compared with blood O₂ saturation determined by the Van Slyke technique, this three-wavelength method demonstrated an accuracy of 2–5% within 95% confidence limits. It also compared favorably with a previously reported four-wavelength geometric computational technique. The rate of freezing did not influence the absorption spectra nor the percentage saturation determination. Samples could be stored at −25° up to 49 days with no change in O₂ saturation. Our calculations reveal that the upper limit of blood O₂ saturation increase in a closed system due to freezing is 2.3%. The upper limits of variation in blood O₂ saturation due to freezing blood with various hemoglobin concentrations or at various initial pH was calculated to be about 1% or less. This method may be adapted for microspectrophotometric determination of regional arteriovenous blood O₂ saturation difference in quick frozen tissue.     

Stroke volume, central venous oxygen saturation and blood temperature as control parameters of frequency-adapted pacemaker stimulation

In order to compare various physiological parameters under identical conditions and to evaluate the "optimal" combination of parameters for triggering a pacing system, a multisensor-catheter of 7 F size was developed. By this catheter placed in the right ventricular cavity, sinus rate (SR), mixed venous oxygen saturation (SO2), temperature (T) and stroke volume (SV) were continuously recorded in 7 volunteers. SR, T, SO2 and SV were analysed for their steady state relationships to workload (P) and for their dynamic characteristics during standardized exercise tests. During exercise the delay times of SR, SO2 and SV were less than 10 sec., whereas that of T was markedly longer ranging from 70 sec. at low exercise levels to 30 sec. at high levels (200 Watts). During recovery delay times of SR, SO2 and SV ranged from 5 to 10 sec., that of T ranged from 20 to 30 sec. The relationship of SR to the workload (0-200 W) performed was linear (r = 0.98), that of T was linear above 50 Watts (r = 0.92), that of SO2 followed an exponential function (r = 0.89). Initial changes of SV were independent (r = 0.02) of the extent of workload. The sensitivity (S = dV/dP) was calculated from the relationship of the parameters (V) measured to the level of exercise performed. SO2 was highly sensitive at the lower range of exercise (less than 75 W), T became constantly sensitive above 50 W, below 50 W the sensitivity of T was continuously decreasing. SR was constantly sensitive over the whole range of exercise (0-200 W), the initial change of SV was not sensitive to the extent of workload.     

Afferent systems of the heart as the means of stabilizing stroke volume and the current value of the minute volume

A study of continuous electrocardiographic and sphygmographic records in patients with atrial fibrillation demonstrated a regulatory effect of the heart's afferent systems. Computerized mathematical treatment of stroke output variation in pairs of adjacent shortened or lengthened (as compared to the mean) cycles showed the afferent systems to stabilize current minute volume while the body's circulatory requirements remained constant.