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Biomedical subjects

T Pasch

Publications and source records attributed to T Pasch.

At least 127 records · Page 7Linked to original sources
PubMed1977

[Dependence of blood flow in human aorto-coronary bypass grafts on the extravascular resistance (author's transl)].

As has been shown in a large number of animal experiments, there is a marked difference between the systolic-to-diastolic flow ratios of the right coronary artery and the left. We examined these ratios in 107 patients who were undergoing aorto-coronary bypass surgery as treatment for coronary artery disease. After cessation of cardio-pulmonary bypass, the blood flow was recorded electromagnetically in a total of 126 venous grafts to the right or to the branches of the left coronary arteries. From these tracings, the following magnitudes were calculated: coronary stroke flow per heart beat, systolic and diastolic stroke flows, mean flow, systolic and diastolic flows. The ratio of the systolic to the diastolic stroke flow was 0.30 +/- 0.17 for the branches of the left coronary artery (n = 79) and 0.61 +/- 0.30 for the right coronary artery (n = 47). The ratio of systolic to diastolic flow was found to be 0.46 +/- 0.25 (branches of the left coronary artery) and 1.01 +/- 0.62 (right coronary artery), respectively. All these values differ statistically on a probability level of p less than 0.001. In principle, our results agree with those of canine experiments. The considerable variation of the individual values of the systolic-to-diastolic flow ratios can be explained by the following: 1. the variability of the pattern of coronary blood supply in man; 2. the actual right and left ventricular pressures; 3. the extent of stenoses present; 4. the degree of myocardial impairment due to ischemia. These factors combined determine the actual value of the extravascular (myocardial) component of the peripheral coronary resistance, which is most effective during systole.

Blood Flow Velocity↗
PubMed1975

The genesis of the pulse contours of the distal leg arteries in man.

In order to clarify the genesis of the human pressure and flow pulse contours of the distal leg arteries, in particular the posterior tibial artery, pulse recordings were performed with transcutaneous techniques under normal conditions and in the state of strong vasodilatation (reactive hyperaemia) in the distal parts of the lower legs. From the experimental results it is concluded that the contour of the incident pressure wave arriving in the leg arteries is very similar to the pressure pulse contour of the abdominal aorta, while the resulting contour in the leg arteries is determined by this incident wave and superimposed reflected waves. The latter arise from positive reflection in the periphery of the lower legs. The travel in retrograde direction, are reflected negatively in proximal regions, particularly in the abdominal aorta, and appear again, with opposite sign, in the leg arteries. In addition, retrograde waves reflected positively at the aortic valve and then traveling in antegrade direction also influence the pulse contours. By considering this wave travel, the genesis of the characteristic contours of the pressure and flow pulses of the lower leg arteries is explained in a satisfactory way. This is demonstrated by a simplified graphical pulse construction as well as by the calculation of pulse contours on the basis of a theoretical tube model of the arterial system with the aid of a digital computer. The results of these calculations are discussed with respect to the findings of previous investigators who used analog and digital models of the arterial system.

Adolescent↗
PubMed1975

The resolution of arterial pulses into forward and backward waves as an approach to the determination of the characteristic impedance.

Pressure and flow recordings from a given site in an artery can be used for the resolution of the pulse wave into its forward and backward components if the characteristic impedance (Z) is known. The principle of this method was reported by von Kries in 1892. In the present work, the procedure is first applied to a theoretical, non-uniform tube model. The characteristic impedance of the model are assumed to be real magnitudes. From the results it is seen that the calculated backward wave provides a criterion which indicates whether the true value of Z actually has been used for the resolving procedure. If, as in the case of natural pulses, Z is not known, its value can be obtained by repeatedly performing the resolving procedure using various values of Z, and choosing the value of Z employed to calculate the backward wave which best fits the criterion. The method is demonstrated on pulses of the abdominal aorta and carotid artery of the dog. The results are compared with the average values of the input impedance in the higher frequency range.

Analog-Digital Conversion↗