Thermodilution is widely used to measure cardiac output, ejection fraction and end diastolic volume. Even though the method is based on dynamic temperature measurements, little attention has been paid to the characterization of the dynamic behavior of the temperature sensor and to its influence on the accuracy of the method. This paper presents several theoretical and empirical results related to the thermodilution method. The results show that, at flow velocities above 0.2 m s(-1), the response of temperature sensors embedded in Swan-Ganz catheters can be accurately described by a convolution operation between the true temperature of the blood and the impulse response of the sensor. The model developed is used to assess the influence of the probe response on the measurement of cardiac output, and this study leads us to the conclusion that the probe response can cause errors in the cardiac output measurement, but this error is usually small (2% in cases with a high degree of arrhythmia). The results show that these small errors appear during arrhythmias that affect the R-R interval and when the real temperature distribution at the pulmonary artery does not possess a shape with perfect temperature plateaux.
This paper presents a deconvolution based method that allows the improvement of the time response of a Swan-Ganz catheter. The goal of the deconvolution method is to obtain the input signal of an LTI system from the knowledge of its output and its impulse response. The noise causes degradation of the recovered signal, and this phenomenon is also discussed. The deconvolved signal is enriched in function of the cutoff frequency of the filter. It is shown that as the cutoff frequency increases, the deconvolved signal becomes more nosier. A Butterworth digital filter of third order, multiplied by the reverse impulse response was used in the frequency domain, and the response in frequency for the 1/H(s) function, limited for the various cutoff frequency of the filter are shown. It can be clearly observed that for higher cutoff frequency magnitude, the signal becomes completely distorted. Experiments with animals were used to measure the impulse response and the obtained results were satisfactory, with average error of 8.9%. The results suggest that the method can be useful in applications of linear systems. Streszczenie. Opisano metodę poprawy odpowiedzi czasowej cewnika typu Swan_ganz bazująca na rozplocie. Umożlia to ocenę sygnału wejściowego na podstawie odpowiedzi układu I znajomosci odpowiedzi impulsowej. . W pracy analizowano wpływ filtru cyfrowego na parametry sygnału. Metode z dobrym rezultatem przetestowano na zwierzętach. Nowa metoda odzyskiwania sygnału w układach cyfrowych stosowanych w medycynie bazująca na rozplocie
O objetivo deste trabalho é apresentar a filosofia de Kant e o pensamento de Bohr como formas de conhecimento que se encontram, segundo alguns comentadores, a partir de conceitos da física clássica. Ademais, a epistemologia de Kant apresentou grande aproximação com a filosofia natural de Newton e, conceitualmente, alguns limites de fronteira com a filosofia da física quântica, se consideramos a fase inicial da mecânica clássica. Tais conceitos limítrofes adquiriram forma na física de Bohr e, por sua vez, se modificaram no pensamento do físico dinamarquês. Assim, aborda-se aqui a posição de Bohr sobre conceitos aproximados da filosofia kantiana, pelo viés clássico da preservação de conceitos como espaço, tempo, realismo e causalidade da física. Por outro lado, serão apresentados argumentos que indicam como não se sustentam todas as interpretações que construíram um “Bohr kantiano”.
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