The assessment of the mechanical properties of the respiratory system is typically done by oscillating flow into the lungs via the trachea, measuring the resulting pressure generated at the trachea, and relating the two signals to each other in terms of some suitable mathematical model. If the perturbing flow signal is broadband and not too large in amplitude, linear behavior is usually assumed and the input impedance calculated. Alternatively, some researchers have used flow signals that are narrow band but large in amplitude, and invoked nonlinear lumped-parameter models to account for the relationship between flow and pressure. There has been little attempt, however, to deal with respiratory data that are both broadband and reflective of system nonlinearities. In the present study, we collected such data from mice. To interpret these data, we first developed a time-domain approximation to a widely used model of respiratory input impedance. We then extended this model to include nonlinear resistive and elastic terms. We found that the nonlinear elastic term fit the data better than the linear model or the nonlinear resistance model when amplitudes were large. This model may be useful for detecting overinflation of the lung during mechanical ventilation.

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A QRS complex detection algorithm was developed using the available l e a b of the electrocardiogram (ECG). This detector is based on the combination of two improved versions of QRS detectors available in the literature. An important characteristic of this algorithm is the possibility of using two or more ECG channels for QRS detection. The first detection method is based on a cross number in a detection threshold defined by the authors. When a low reliability situation occurs in the first method, the output of the second detection method is used to confirm or reject the detection. The second method also uses an adaptive detection threshold dejked by the authors and a candidate QRS is tested against some criteria that use features as amplitude, width and RR interval to validate the candidate as a QRS. Testing the algorithm with MIT/BIH Arrhythmia Database resulted in 99.22% sensitivity and 99.73% positive predictivity.

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A new blood pressure measurement system was developed, based on the oscillometric method, using a controlled linear deflation technique. The system was structured in order to make several tasks independent and specialized, thus allowing for future punctual developments. An oscillometric signal data base was formed according to the standard A N S I / W S P I 0-1992, using the manual auscultatory method as a reference to determine measurement techniques to be used The correlation among several quantities, such as reference blood pressure measurements, characteristic ratios, age, weight, height and arm circumference size, was studied. A new strategy to obtain systolic, mean and diastolic pressures was oscillometric pulse envelope, depending on parameters such as actual cuf pressure, mean pressure, pulse amplitude and arm circumference size. Mean differences of about -I,49 and 0,6I and standard deviations of 5 , I I and 5,89 mmHg were obtained for systolic and diastolic pressure measurements, respectively. Moreover, a comparative study with a commercial equipment was performed, with a simulator. IntroductionThis research describes the development and the evaluation of a new system of blood pressure measurement by oscillometric method, with the use of a controlled linear deflation technique. Technological development has made the improvement of the performance of such equipment possible, arousing the need for a new blood pressure measurement system for systolic, mean and diastolic pressure based on the profile of oscillometric pressure pulse envelope. The system provides fast and more precise measurements, similar to those obtained with the conventional auscultatoxy method, and is also immune to mhythmia and motion. It was, therefore, necessaxy to change the process of deflating the cuff and to create a new algorithm which presented a significant performance improvement, mainly in measurement accuracy and precision. 0276-6547/99 $1 0.00 0 1999 IEEE Materials and methodsThe research was developed in three sequential phases: 1. Preparation of the acquisition and storing of oscillometric signals. Data base formation for oscillatory signals and data analysis to define the strategy for measuring systolic, diastolic and mean pressure of oscillometric pressure pulses resulting from a linear cuff deflation. 2. Development and interactive upgrading of the new blood pressure measurement system by oscillometric method, with the use of a controlled linear deflation technique. 3. Performance tests and comparative stuhes of the new measurement system.The oscillometric signal data base acquisition protocol was based on the American standard for electronic or automated esphygmomanometer ANSUAAMI SP 10-1992[1]. This data base was built with the pressure signals of 10 patients in the Kidney and Hypertension Hospital in UNIFESP and 75 employees of Dixtal Biomedical Co., all registered at least three times, thus totaling 255 measurements. All measurements were sampled and stored in files through the acquisition system. Each sampled signa...