Biomedical subjects

K C Froehlich

Publications and source records attributed to K C Froehlich.

3 recordsLinked to original sources

PubMed1989

Computation of diagnostic data from coronary sinus pressure: a comparison between two possible models.

We have evaluated two mathematical models to describe the increase in coronary sinus pressure (CSP) following pressure controlled intermittent coronary sinus occlusion (PICSO). The models are evaluated and compared on the basis of human and canine data. Both models were fitted by non-linear least squares algorithms. Next, derived quantities, such as plateau, rise-time and mean integral of the coronary sinus pressure were calculated from the model parameters. Corresponding quantities for the two models were compared with regard to mean values, rate of successful calculation and specific features characterizing the human or canine case. One model was found to be superior for investigational purposes. The other model was found to be more stable in critical situations and is therefore suggested for usage in closed loop regulation of PICSO. Physiologically, the differences in mean values of the derived quantities between the two models were found to be negligible. The formal statistical significance of the differences is but a consequence of the large number of PICSO cycles analysed.

Algorithms↗

PubMed1988

Computation of derived diagnostic quantities during intermittent coronary sinus occlusion in dogs.

The haemodynamic responses to pressure controlled intermittent coronary sinus occlusion (PICSO) were recorded intraoperatively in dogs. After analogue-digital conversion the data for coronary sinus pressure were submitted to numerical analysis for detection of systolic and diastolic envelopes and their subsequent fitting by a non-linear model. From the model variables derived quantities, such as plateau and rise times, were constructed so as to resemble the most important features of coronary sinus pressure rise during each occlusion-release cycle. The derived quantities were then monitored during all consecutive cycles throughout the entire experiment. In each dog the measurements were taken during normal coronary artery perfusion, left anterior descending coronary artery infarction, and reperfusion. The analysis comprise time course, stability, and physiological correlates of the derived quantities, on some of which a closed loop regulation may be based. Predicted plateaus (systolic and diastolic) and mean integrals (systolic and diastolic) were found to be stable quantities which, on subaveraging of about five successive estimates, yielded a 10% accuracy on the mean. By contrast, the rise times required subaveraging of about 15 cycles to achieve the same relative stability. It is concluded that, on subaveraging, derived quantities lend themselves for closed loop regulation input. Thus this quantitative assessment of numerical coronary sinus pressure analysis, as obtained from animal data, may lay the basis for future human application.

Animals↗

PubMed1988

Intermittent coronary sinus occlusion in humans: pressure dynamics and calculation of diagnostic quantities.

Pressure controlled intermittent coronary sinus occlusion (PISCO) was applied in 30 patients undergoing coronary artery bypass surgery. The occlusion and release times were manually adjusted according to visual control of the intraoperatively monitored coronary sinus pressure. In six patients the coronary sinus measurements were additionally digitised with a personal computer before postoperative mathematical analysis, which comprised automatic detection of systolic peaks, diastolic troughs, and the calculation of derived quantities. The purpose of the analysis was (a) to assess quantitatively human coronary sinus pressure dynamics, (b) to determine whether visual control and interpretation of coronary sinus pressure rise could be replaced by a mathematical model, and (c) to ascertain whether the occlusion and release cycle lengths were adequate. Numerical estimates for intraindividual and interindividual spread of calculated quantities were produced, the mathematically obtained results were related to a possible physiological interpretation, and the most efficient method of statistical analysis was ascertained. These results form the numerical basis for a closed loop adjustment of pressure controlled intermittent coronary sinus occlusion cycling.

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