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At least 289 records · Page 16Linked to original sources
PubMed1977

Measurement of rapid changes in cardiac stroke volume. An evaluation of the impedance cardiography method.

One hundred and twenty-nine simultaneous measurements were carried out on seven patients, 67 at rest and 62 during the Valsalva manoeuvre, in order to compare impedance cardiography with the thermodilution method, during rapid changes in cardiac stroke volume and pulmonary blood volume. A coefficient of correlation of 0.86 was found following linear regression analysis of the whole material. Analysis of the individual patient showed that the mean coefficient of correlation was 0.94 (range 0.91-0.97), and that the slope of the regression lines was 0.41 to 1.82, and further that the mean intercept was 0.2 ml. It is concluded that impedance cardiography can be employed for measuring the relative intraindividual changes in cardiac stroke volume during the Valsalva manoeuvre, and it is suggested that it may be of use in other situations, such as during haemorrhage or continuous positive pressure ventilation.

Adolescent↗
PubMed2000

Oscillations in stroke volume and cardiac output arising from oscillatory ventilation in humans.

Oscillations in the cardiovascular system have been observed in patients with periodic breathing. It is not clear whether these are driven by primary oscillations in the respiratory system or whether an intrinsic cardiovascular instability is required, as previous studies with subjects performing voluntary periodic breathing have failed to produce the cardiovascular oscillations. We investigated whether cardiovascular oscillations occurred in healthy controls performing voluntary periodic breathing. Six healthy subjects performed voluntary periodic breathing with guidance from a real-time computer display. We measured ventilation, end-tidal partial pressures of O2 (PO2) and CO2 (PCO2), heart rate, blood pressure (BP), arterial oxygen saturation and stroke volume and cardiac output by transthoracic impedance cardiography. Fourier analysis was used to quantify the size and phase of the periodic breathing-induced oscillations in these parameters. Periodic breathing (amplitude 30% of mean ventilation) induced oscillations in end-tidal PO2 (amplitude 0.8 kPa), end-tidal PCO2 (amplitude 0.3 kPa), R-R interval (amplitude 32.6 ms), systolic BP (amplitude 3 mmHg), diastolic BP (amplitude 3 mmHg), stroke volume (amplitude 8.0 ml, mean 79.5 ml) and cardiac output (amplitude 0.6 1, mean 5.9 l x min(-1)). The oscillations in stroke volume and cardiac output were nearly in phase with ventilation, with their peaks occurring 5.6 and 6.1 s, respectively, after the peak in ventilation. An oscillatory ventilatory pattern entrains the cardiovascular system in healthy controls into fluctuations, not only in heart rate and BP, but also in stroke volume and cardiac output.

Adult↗
PubMedDate not supplied

Hemodynamic consequences of heart-lung interactions.

The management of critically ill patients requires a fundamental understanding of cardiopulmonary interactions associated with mechanical ventilation. The hemodynamic changes due to ventilation are a result of changes in lung volume and intrathoracic pressure (ITP) and can occur during spontaneous or positive pressure ventilation despite constant tidal volumes. Pulmonary vascular resistance (PVR) and mechanical heart-lung interactions play prominent roles in determining the hemodynamic response to mechanical ventilation. Lung inflation alters PVR and right ventricular wall tension and, at high lung volume, mechanically limits cardiac volumes. The authors will consider the mechanisms of the effects of ITP on the pulmonary arterial and venous branches. These effects will aid in understanding the complex interactions between ventilation and right and left ventricular pressures and volumes, as well as the influence of lung inflation pressure on ventricular interdependence.

Cardiac Volume↗
PubMed1981

[Changes in circulatory parameters in dogs under general respiratory hypoxia].

The decrease in the oxygen content of the inspired air calls forth enhanced demands on the cardiocirculatory performance. In experiments on healthy dogs the haemodynamic shifts connected with short-term hypoxia were investigated, with particular attention to the possible presence of irreversible changes in the myocardium. With the aid of radiocardiography the following parameters were investigated before, during and after hypoxic test: blood volume, cardiac output, stroke volume, heart frequency, ejection fraction, mean right-to-left circulation time, and segmental lung volume. In dependence on the degree of hypoxia characteristic changes in the above parameters occurred. After the end of hypoxia most parameters returned to their initial levels. The presence of irreversible changes could not be proved. Under the given conditions, it was possible to test the individual level of cardiocirculatory performance with the aid of hypoxia similarly as by using the exercise test.

Animals↗
PubMed1987

Cardiac stroke volume during exercise measured by Doppler echocardiography: comparison with the thermodilution technique and evaluation of reproducibility.

Cardiac stroke volume was measured simultaneously by Doppler echocardiography and thermodilution in patients with severe coronary artery disease. One group (20 patients) was examined during supine exercise at 25 W and a second group (20 patients) during sitting exercise at 25 W and 50 W. In a third group (10 patients) the reproducibility of the non-invasive stroke volume estimate was determined during upright exercise. There was a considerable variation between results obtained with the invasive and non-invasive technique at rest and during exercise, but no systematic differences were found. Analysis of variance showed that no systematic differences between ultrasonic results were introduced by two observers or by measurements on different days. The coefficient of variation between any pairs of Doppler measurements in each patient was 6%. These findings demonstrate that the ultrasonic technique is suitable for detecting changes in stroke volume induced by low load exercise in patients with severe angina pectoris.

Adult↗
PubMed1994

Real-time ventricular volumes and cardiac function in the working rat heart.

The measurement of instantaneous left ventricular volumes throughout the cardiac cycle in a rat heart beating at rates of 300 to 600 min-1 with a chamber volume of only a few tenths of a milliliter is difficult. Combining an x-ray scatter detection system with a small x-ray source collimated to scatter low energy x-rays off a working rat heart, measurements of real-time changes in ventricular volumes can be determined. The x-ray scatter signal is proportional to the volume and can be calibrated to measure the actual volume. Using this system, changes in ventricular function can readily be detected. An example of data obtained from increasing preload with a fixed afterload is shown. This technique not only distinguishes an increasing stroke volume, but also more rapid early diastolic filling and systolic ejection rates with increasing preload. This new x-ray scatter technique appears to be a promising way to measure rapidly changing left ventricular volumes and function in the working rat heart. This could significantly enhance the scientific use of the rat model.

Animals↗
PubMed1995

Pilot prospective evaluation of counterpulsation with different intra-aortic balloon volumes on cardiac performance in humans.

UNLABELLED: Smaller intra-aortic balloons (IAB) may minimize peripheral vascular complications. To determine the influence of different IAB volumes on cardiac performance, we studied 20 hemodynamically stable patients on IAB counterpulsation. Variables were measured with either a 40cc or 32cc IAB displacement, at an assist ratio of 1:1 or 1:8: Heart rate, Ao and PA pressures, and Fick cardiac output. By echo-Doppler, the velocity time integral (VTI) across the LV outflow tract, a measure of stroke volume was also calculated. The mean age was 60 yr (range 18-77), height 5'6" (5'2"-5'11"), and body surface area 1.9M2 (1.5-2.3). Results presented as mean values were: [table: see text] *P < 0.005 1:1 vs 1:8 for both 40 and 32cc IAB. CONCLUSION: IAB pumping at 1:1 with either 40 cc or 32 cc volume displacement yields similar degrees of improvement in cardiac performance. A larger cohort is required to determine if smaller balloons may decrease complications without compromising efficacy.

Adolescent↗
PubMed1990

Alpha-adrenergic regulation of splanchnic volume and cardiac output in the dog.

The present study examined whether alpha-adrenergic stimulation causes a change in splanchnic intravascular volume in the anaesthetized animal with an intact circulation, which region(s) mediate the volume change, and whether the splanchnic volume change influences cardiac output. In order to ascertain that a radionuclide imaging technique could be used to assess total splanchnic volume changes, drugs known to increase or decrease splanchnic volume were infused on 21 occasions in eight dogs studied under conditions of selective perfusion and drainage of the splanchnic vasculature with erythrocytes labelled with 99Tcm and a gamma camera placed over the abdomen. For these 21 infusions, volume and radionuclide count changes were related: r greater than or equal to 0.90 (n = 20), r = 0.76 (n = 1). After ascertaining tissue attenuation and blood radioactivity in four of the animals, the standard error for a single estimate of the absolute volume change using the radionuclide technique was determined to be 75 ml. In six animals with intact circulations, phenylephrine (40-80 micrograms min-1) for 20 min was associated with an increase in cardiac output of 12 +/- 2% (P less than 0.001) and a decrease in total splanchnic volume estimated to be 431 +/- 95 ml (P less than 0.001). The splanchnic volume decrease was due entirely to decreases in splenic and intestinal volume. In eight eviscerated animals, cardiac output decreased by 30 +/- 2% (P less than 0.001) during phenylephrine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Influence of breathing frequency and tidal volume on cardiac output.

The aim of our experiment was to investigate the influence of increasing either breathing frequency or tidal volume on cardiac output (Q), in normocapnia. We measured Q with a CO2 rebreathing method in 6 men and 6 women in the sitting and the supine position, imposing different breathing patterns: in one set of experiments tidal volume was kept constant at 1 L while breathing frequency was randomly changed between 20, 30 and 40 breaths/min; in another breathing frequency was kept constant at 30 breaths/min while tidal volume was randomly altered between 1, 1.5 and 2 L. Switching from open circuit breathing to rebreathing (for measurement of Q) required no change in breathing pattern. From the beginning, CO2 was added to the inspired gas to maintain end-tidal FCO2 at 0.054, so as to obtain steady state conditions throughout the measurements. Q rose significantly when tidal volume was increased (938 ml/L rise in tidal volume when sitting, and 743 ml/L when supine). Breathing frequency had an insignificant effect (213 ml/10 breaths frequency increase when sitting and 142 ml/10 breaths when supine). The greater influence of ventilation on Q when sitting than when supine is best explained by the fact that in the latter position venous return is already high. There are no demonstrable differences in this effect between males and females.

Adult↗
PubMed1985

Hemodynamic measurements as aids to choosing drug treatment of essential hypertension.

A hemodynamic measurement system incorporating echocardiography with Doppler, the Evans-Blue method, and sphygmomanometry enables the clinician to estimate cardiac output, blood volume, cardiac contractile force, and total peripheral resistance. These determinations can be used by the clinician to choose appropriate antihypertensive therapy without resorting to the usual trial-and-error approach. With the aid of hemodynamic measurements, the treatment of hypertension can evolve from merely lowering blood pressure to correcting the whole hemodynamic derangement. In this study, the accuracies and normal ranges of the measurements were critically examined. Results of a comparative trial showed that use of hemodynamic measurements decreased the incidence of side effects and improved compliance of patients to the prescribed antihypertensive regimen.

Adult↗
PubMed2002

Genome-wide linkage scan for exercise stroke volume and cardiac output in the HERITAGE Family Study.

A genome-wide linkage scan was performed for genes affecting submaximal exercise cardiac output (Q) and stroke volume (SV) in the sedentary state and their responses to a standardized 20-wk endurance training program. A total of 509 polymorphic markers were used, and 328 pairs of siblings from 99 white nuclear families and 102 sibling pairs from 105 black family units were available. Q and SV were measured in relative steady state during exercise at 50 W (Q50 and SV50, respectively). Baseline phenotypes were adjusted for age, sex, and body surface area (BSA), and the training responses (post-training - baseline, Delta) were adjusted for age, sex, baseline BSA, and baseline value of the phenotype. Three analytical strategies were used: a multipoint variance components linkage analysis using all the family data, and regression-based single- and multipoint linkage analyses using pairs of siblings. In whites, baseline SV50 and DeltaSV50 showed promising linkages (P < 0.0023) with markers on chromosomes 14q31.1 and 10p11.2, respectively. Suggestive evidence of linkage (0.01 > P > 0.0023) for DeltaSV50 and Delta Q50 was detected on chromosome 2q31.1 and for baseline SV50 and Q50 on chromosome 9q32-q33. In blacks, markers on 18q11.2 showed promising linkages with baseline Q50. Suggestive evidence of linkage was found in three regions for baseline SV50 (1p21.3, 3q13.3, 12q13.2) and one for baseline SV50 and Q50 (10p14). All these chromosomal regions include several potential candidate genes and therefore warrant further studies in the HERITAGE cohort and other studies.

Adult↗
PubMed2000

Enhanced cardiac thermal dilution analysis for cardiac output, volumes, stroke volumes, and regurgitation rates--sensitivity analysis using digital simulation.

Cardiac output is measured by placing a double lumen catheter with a thermistor on the tip through the right ventricle into the pulmonary artery, injecting cold saline into the right atrium, and integrating the resulting pulmonary artery temperature profile. If a similar procedure is performed with thermistors located in the right atrium, right ventricle, and pulmonary artery, the resulting temperature curves are determined by the known or easily measured quantities: injectate temperature, injectate volume, heart rate, systolic time interval, body temperature, and time in the cardiac cycle at which injection begins and the unknown quantities: right atrial, right ventricular, pulmonary artery mean and stroke volumes, inflow and outflow valve regurgitation rates, and cardiac output. A digital computer program using a lumped parameter model has been developed to use these quantities to produce thermal dilution curves and optimize the fit of the model curves to the temperature curves from the thermal dilution measurement to determine the unknown quantities. The program is used to investigate the effects of measuring system time constant, heat transfer, and noise on the accuracy of these measurements. The results indicate that the method is practical.

Cardiac Output↗
PubMed1991

Comparison of the cardiovascular effects of nifedipine and nicardipine in the presence of atenolol.

A placebo controlled double blind crossover study was performed in 12 healthy volunteers to compare the cardiovascular effects of single oral doses of nifedipine (5, 10 and 15 mg) and nicardipine (20 and 30 mg) in the presence of atenolol 100 mg. Haemodynamic measurements were made by transthoracic electrical bioimpedance cardiography (TEBC) 2 h following drug administration during passive tilting, graded bicycle exercise (30-150 W) and recovery from exercise. In the absence of calcium channel blockade, atenolol reduced mean blood pressure, heart rate, and cardiac index, and increased stroke volume, peripheral resistance, pre-ejection period, and ventricular ejection time, particularly during and after exercise. In comparison with atenolol alone, addition of nifedipine or nicardipine reduced peripheral resistance but did not produce significant changes in stroke volume, cardiac output, dZ/dt [max], pre-ejection period (PEP). Ventricular ejection time (VET), PEP/VET, or Heather index at any point in the experiment. Similar reductions in peripheral resistance were produced by nifedipine 10 mg and nicardipine 20 and 30 mg. These apparently equivalent doses of nifedipine and nicardipine had similar effects on stroke volume, cardiac index, PEP/VET and Heather index. Thus the increases in ventricular performance previously demonstrated in association with nifedipine and nicardipine therapy were not observed in the presence of beta-adrenoceptor blockade. Under these conditions no important differences have been observed in the cardiovascular effects of these two calcium channel blockers.

Administration, Oral↗
PubMed1980

[Noninvasive method of determining the cerebral blood flow circulation rate and its correlations with cardiac minute volume].

A method is suggested for noninvasive determination of the cerebral circulation rate and its correlations with the cardiac output. It is based on the metrological possibilities of tetrapolar rheoencephalography in correlation with chest (transthoracic) rheography. The percentage of cerebral circulation rate in relation to the cardiac output measured by this method (Ic/o) characterizes the direction and value of compensatory blood redistribution in various hemodynamic situations, while the absolute values of cerebral circulation rate (Cm, in millilitres per minute) and their relation to the proper values (Cm. in % of proper values) make it possible to appraise the afficacy of the compensatory shifts in each individual case. The method may gain wide use in the clinic for indirect appraisal of the condition of the cerebral circulation.

Adult↗
PubMed1984

Comparison of noninvasive pulsed Doppler and Fick measurements of stroke volume in cardiac patients.

We compared simultaneous measurements of stroke volume by direct Fick (SVF) and noninvasive pulsed Doppler (SVD) techniques in 15 resting, supine cardiac patients. Doppler measurements of ascending aorta blood velocity were obtained from the suprasternal notch with a single crystal transducer. The systolic velocity integral of the spatial-average velocity waveform was multiplied by cross-sectional area from the systolic aortic diameter, obtained independently by M-mode echocardiography, to determine absolute values for SVD. The resulting linear regression equation was SVD = -1.14 + 0.95SVF, r = +0.91, p less than 0.0001. The mean SVD and SVF values were 68 and 73 cm3, respectively. These results in consecutive patients serve to validate empirically the pulsed Doppler method at rest. It is a convenient, safe, and painless procedure which appears appropriate for clinical diagnostic screening where serial measurements would be useful. However, this noninvasive technique does require technical experience and an understanding of anatomy and flow waveforms by the operator to obtain valid measurements.

Aged↗