Browsing by Author "Urzua Urzua, Jorge"

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    A fuzzy logic based model computes cardiac output from the radial arterial pressure waveform
    (IEEE, 1994) Urzua Urzua, Jorge; Guarini Hermann, Marcelo Walter; Cipriano, Aldo; Matus Acuña, Marcelo Enrique; Lee, J.; Salinas, C.; Olmedo Hidalgo, Juan Carlos; Lema F., Guillermo; Canessa, Roberto
    An interactive scheme for the development of a fuzzy logic based model has been implemented and applied to build a model that is able to determine cardiac output from radial arterial pressure. It was built using as input radial pressure waveforms from patients in whom cardiac output was simultaneously measured by thermodilution. The scheme was programmed in C language in an Apollo workstation under Unix. Input variables were area under the curve, ratio between systolic and diastolic pressure, and pulse frequency. To determine fuzzy sets and membership functions the authors used 149 pressure waveforms. To test the model, the authors used 6 waveforms not used in building the model. Correlation between predicted cardiac output with measured flow was 0.98.<>
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    A model of internal control may improve the response time of an automatic arterial pressure controller
    (IEEE, 2000) Urzua Urzua, Jorge; Sauma Santis, Enzo Enrique; Cipriano, Aldo; Guarini Hermann, Marcelo Walter
    A simplified model for the arterial pressure control system was implemented on a personal computer using Matlab Simulink(R). Model responses to variations of systemic vascular resistance were comparable to those predicted by physiology. Computer simulation suggested that including this model of the internal pressure control system within the design of an external controller would achieve better arterial pressure control and faster response than previous systems.
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    Results of the surgical management of abdominal aortic eurysms in 80 patients over 80 years of age
    (2003) Valdés E., Francisco; Bergoeing Reid, Michel Paul; Kramer, Albrecht; Mertens Martin, Renato; Canessa, Roberto; Lema F., Guillermo; Garayar Pulgar, Bernardita; Urzua Urzua, Jorge
    Background: Abdominal aortic aneurysms (AAA) may be lethal unless appropriately and timely treated. Since age is a surgical risk, octogenarians are usually not considered as candidates for surgical intervention. Aim: To asses surgical complications and mortality in octogenarians treated for AAA. Subjects and Methods: Patients aged 80 years older, treated consecutively between 1984-2001 were retrospectively analyzed. Results: Sixty one patients were male, and their age ranged from 80 to 95 years. All were treated with open surgery. The operation was elective in 58 and as an emergency in 22 patients (symptomatic or ruptured AAA). Aortic diameter was 6.8+/-1.4 cm in asymptomatic patients and 7.7+/-1.8 cm in emergency cases (p=0.024). Thirty days postoperative mortality was 5.1% in elective surgery compared to 40.6% in emergency operations (p < 0.01). Five years survival rate was 44.7% in asymptomatic patients compared to 10.4% in the emergency cases (p < 0.023). Conclusions: Elective surgery for asymptomatic AAA can be performed with low operative mortality in octogenarians. However, surgery in emergency cases has an 8 fold increase in risk. Accordingly, octogenarian patients should be considered for elective AAA repair in a selective basis.