Biomedical subjects

P Sekelj

Publications and source records attributed to P Sekelj.

15 recordsLinked to original sources

PubMed1987

Preload-independent index of contractility for the assessment of left ventricular function.

We describe a method for the assessment of myocardial contractile force; it is based on the measurement of left ventricular pressure P and its first derivative dP/dt at two well-defined points on the isovolumic pressure curve. The slope Vs relating rise of dP/dt to rise of P is a measure of contractile element velocity. Vs values for normal children and adults, varying in body surface area from 0.18 to 2.14 m2 and in age from 1 day to 60 years, were in close agreement, indicating that this parameter is substantially independent of heart size. Ten children with myocardial disease all had lower Vs values than any of 24 children with normal left ventricular function. Within each of these two groups, the increase of dP/dt during isovolumic contraction was highly correlated with the increase of P, but the regression line for the normal group had a significantly steeper slope than that for the impaired group. The near zero intercepts of the two regression lines on both delta P and the delta dP/dt axes gave additional evidence that alterations of preload did not affect Vs.

Adolescent↗

PubMed1978

Fiberoptic ear densitometer for measurement of cardiac output.

This study presents theory, operation, and evaluation of a new earpiece method for measurement of cardiac output using the multichannel fiberoptic system recently described. The system includes an earpiece of simple design and small size suitable for applications in all subjects regardless of their age or size. The method requires no withdrawal and analysis of blood samples for calibration. Compared with earlier techniques the present method, based on measurements in three distinct absorption bands in the infrared, provides an increase in accuracy of the estimations. This accuracy was tested in children undergoing routine cardiac catheterization. Comparisons were made in 39 instances (25 subjects) between simultaneously carried out determinations by the earpiece and cuvette densitometer methods. The agreement was good (r = 0.97, p less than 0.001), with a standard deviation of the differences of 0.479 litre/min, or 10.2% of the mean values derived from the cuvette curves. The regression equation describing the values derived from ear curves in terms of values from the cuvette curves differed only slightly from unity (Y = 0.167 + 0.985X). The usefulness of the fiberoptic earpiece technique both in clinical investigations and cardiovascular diagnosis was demonstrated.

Cardiac Output↗

PubMed1977

Measurement of blood oxygen saturation using a multichannel fiberoptic oximeter-densitometer.

Design principles and performance of a new fiberoptic oximeter-densitometer for measurement of blood oxygen saturation are described. This instrument is capable of performing measurements using either an intravascular catheter, flow-through cuvette, or earpiece. The operations of the flow-through cuvette and earpiece are based on the principles of light transmission, that of the catheter on the principles of hemoreflection. The system incorporates five interference filters permitting the selection of a particular wavelength or combination of wavelengths to perform different modes of operation. Estimates using both catheter and cuvette appeared to be independent of variations over a wide range in hematocrit and flow rate. In the range from 20 to 100% saturation the standard deviation of the differences between the in vitro estimates by the catheter and (or) cuvette and the Van Slyke analyses were 1.62 and 1.73%, respectively. In 53 children with congenital heart disease (22 cyanotic) values calculated from readings by the earpiece were related to values of arterial oxygen saturation as measured by American Optical Company reflection oximeter at the time of cardiac catheterization. In the range from 50 to 100% saturation, the regression line between the two techniques was linear and the standard deviation of the differences was 2.89% (3.12% in cyanotic children alone). The method provides a high degree of compensation for variations in skin pigmentation.

Catheterization↗

PubMed1975

A simplified parameter of LV function in children with congenital heart disease.

Myocardial state in children with various congenital anomalies was assessed using pressured-derived parameters; Vmax and Vpm. A simple approach, based on the relationship between peak value of the first derivative of the left ventricular isovolumic pressure and its associated total pressure, for identifying patients with impaired myocardial function is described.

Adolescent↗

PubMed1974