The importance of blood resistivity in the measurement of cardiac output by the thoracic impedance method

1975 ◽  
Vol 13 (2) ◽  
pp. 187-191 ◽  
Author(s):  
D. W. Hill ◽  
F. D. Thompson
Keyword(s):  
Cardiac Output ◽  
Impedance Method ◽  
Thoracic Impedance ◽  
Blood Resistivity

Impedance cardiography for estimating cardiac output during submaximal and maximal work

1978 ◽  
Vol 45 (3) ◽  
pp. 459-462 ◽  
Author(s):  
Y. Kobayashi ◽  
Y. Andoh ◽  
T. Fujinami ◽  
K. Nakayama ◽  
K. Takada ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Cardiac Output ◽  
Impedance Cardiography ◽  
Venous Blood ◽  
Venous Catheter ◽  
Bicycle Ergometer ◽  
Impedance Method ◽  
Maximal Aerobic Capacity ◽  
Blood Resistivity ◽  
Work Up

Impedance cardiography was used to estimate cardiac output in 10 men during rest and within 5 s after exercise on a bicycle ergometer, including work up to and including maximal aerobic capacity. An indwelling venous catheter permitted simultaneous sampling of venous blood for observing changes in hematocrit associated with each exercise level. Cardiac output, calculated from a standard equation which assumes a constant value of 150 omega.cm for the electrical resistivity of blood, was compared with corresponding calculations in which blood resistivity was individually determined as a function of hematocrit. It is concluded that many of the discrepancies in the literature related to values for cardiac output obtained during exercise by the impedance method may be inherent in calculations that do not consider the changing electrical resistivity of the blood with a changing hematocrit.

USE OF NEW THORACIC IMPEDANCE METHOD TO ASSESS CARDIAC INDEX IN CHILDREN

1998 ◽  
Vol 89 (Supplement) ◽  
pp. 955A
Author(s):  
E Wodey ◽  
X Beneux ◽  
F Carre ◽  
O Azzis ◽  
C Ecoffey
Keyword(s):  
Cardiac Index ◽  
Impedance Method ◽  
Thoracic Impedance

Measurement of cardiac output by electrical impedance at rest and during exercise

1976 ◽  
Vol 40 (1) ◽  
pp. 91-95 ◽  
Author(s):  
J. C. Denniston ◽  
J. T. Maher ◽  
J. T. Reeves ◽  
J. C. Cruz ◽  
A. Cymerman ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Electrical Impedance ◽  
Bicycle Ergometer ◽  
Mean Value ◽  
Impedance Method ◽  
Wave Form ◽  
Graded Exercise ◽  
Movement Artifact ◽  
Maximum Work ◽  
Volume Equation

A comparison was made between cardiac output values determined by the dye dilution and electrical impedance methods in ten subjects at rest and during graded exercise on a bicycle ergometer. The cardiac output values determined by the two methods were linearly related and significantly (P less than 0.001) correlated (r = 0.90). Movement artifact associated with exercise at maximum or near-maximum work loads caused severe distortion of the dZ/dt wave form and prevented calculation of impedance cardiac output at these levels of work. Use of the lowest value of L (distance between mean value of L in the impedance stroke volume equation (SV = p(L2/ZO2) (dZ/dt)mt), resulted in nearly identical values for the least-squares line and equalvalue line of impedance and dye cardiac outputs. Although absolute values of cardiac output determined by the two methods were not identical in all subjects the changes in cardiac output were nearly identical during the different levels of exercise. The data support the validity of the impedance method as a noninvasive, atraumatic measure of cardiac output at rest and during graded exercise.

Optimization of Measuring Cardiac Output by Both Hands Electrode Impedance Method

2011 ◽  
Vol 60 (9) ◽  
pp. 1770-1776
Author(s):  
Sang-O Jung ◽  
Myeong-Heon Sim ◽  
Woon-Mo Jung ◽  
Min-Yong Kim ◽  
Chan-Sol Yoon ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Impedance Method ◽  
Electrode Impedance

Reduced stroke volume related to pleural pressure in obstructive sleep apnea

1983 ◽  
Vol 55 (6) ◽  
pp. 1718-1724 ◽  
Author(s):  
F. A. Tolle ◽  
W. V. Judy ◽  
P. L. Yu ◽  
O. N. Markand
Keyword(s):  
Obstructive Sleep Apnea ◽  
Cardiac Output ◽  
Sleep Apnea ◽  
Stroke Volume ◽  
Human Subjects ◽  
Left Ventricular ◽  
Pleural Pressure ◽  
Impedance Method ◽  
Similar Reduction ◽  
Obstructive Sleep

Left ventricular stroke volume (LVSV) falls during obstructed inspiration in animals and normal human subjects through mechanisms that may be closely related to pleural pressure. In this study we postulated that a similar reduction in LVSV should occur in patients with obstructive sleep apnea (OSA). Daytime polysomnograms were performed in 10 patients with OSA. A noninvasive electrical impedance method was used to determine LVSV. Pleural pressure was measured by esophageal balloon. In comparison with awake values, during OSA we found reductions in LVSV, cardiac output, and heart rate of 18, 27, and 11%, respectively (P less than 0.01). We observed that systolic pleural pressure did not have a significant effect on LVSV (P greater than 0.05). However, at pleural pressures lower than 10 cmH2O below resting expiratory level, there was a linear relationship between falls in LVSV and falls in middiastolic pleural pressure (P less than 0.0001). We concluded that reduced LVSV shown in patients with OSA was significantly related to diastolic pleural pressure level. Our findings suggested reduced preload as the most likely mechanism for decreased cardiac output in OSA.

Transthoracic admittance plethysmograph for measuring cardiac output

1976 ◽  
Vol 40 (3) ◽  
pp. 451-454 ◽  
Author(s):  
H. Ito ◽  
K. I. Yamakoshi ◽  
T. Togawa
Keyword(s):  
Cardiac Output ◽  
Stroke Volume ◽  
Correlation Coefficient ◽  
Healthy Subjects ◽  
Regression Line ◽  
Correlation Study ◽  
Impedance Method ◽  
Ventricular Stroke Volume ◽  
Transthoracic Impedance ◽  
Admittance Method

A plethysmograph for measuring ventricular stroke volume (SV) from the transthoracic admittance variation was developed. A correlation study between the SV values determined by this method (SVy) and those measured by Kubicek's transthoracic impedance method (SVz) was carried out on 24 healthy subjects; the correlation coefficient was r = 0.99 and the regression line of SVY on SVz was y = 1.03x - 0.47. Based on the results obtained through the study, it was concluded that the admittance method was more advantageous than the impedance method for measuring SV.

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