Medical & biological engineering & computing
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Med Biol Eng Comput · May 2001
Error analysis of a natural breathing calibration method for respiratory inductive plethysmography.
Respiratory volumes are measured non-invasively by recording rib cage and abdominal motions using respiratory inductive plethysmography (RIP). Qualitative diagnostic calibration (QDC) of RIP is based on the natural variability in the relative rib-cage-to-abdomen contribution during tidal breathing. ODC does not require subject cooperation but it has previously been shown that accuracy may deteriorate when breathing pattern changes. ⋯ The PRA calibration factors were within 6% of those from REF, while the QDC rib-cage factor was underestimated by 15% and the abdominal factor was overestimated by 38%. Small natural variability in the relative rib-cage-to-abdomen contribution was related to poor accuracy. Each compartment's variability depended on its magnitude, which is a violation of the QDC assumptions.
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Med Biol Eng Comput · Jan 2001
A new approach to mechanical simulation of lung behaviour: pressure-controlled and time-related piston movement.
A mechanical lung simulator is described (an extension of a previous mechanical simulator) which simulates normal breathing and artificial ventilation in patients. The extended integration of hardware and software offers many new possibilities and advantages over the former simulator. The properties of components which simulate elastance and airway resistance of the lung are defined in software rather than by the mechanical properties of the components alone. ⋯ The different relations defined in the software can be changed from breath to breath. Three simulations are presented: (1) computer-controlled expiration in the artificially ventilated lung; (2) simulation of normal breathing; and (3) simulation of viscoelastance and cardiac influences during artificial ventilation. The mechanical simulator provides a reproducible and flexible environment for testing new software and equipment in the lung function laboratory and in intensive care, and can be used for instruction and training.
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A continuous cardiac output monitoring system has been developed in the laboratory to allow the real-time measurement of the cardiac output. This form of continuous cardiac output measurement allows the doctor to view the beat-to-beat cardiac output and can be employed to measure artery constrictions as well. ⋯ In laboratory tests, it was demonstrated on a heart-lung machine that the product of the two parameters measured is proportional to the actual flow volume of up to 6 lmin(-1) with a mean percentage error of 12.4% and a mean square error of 0.09 (using the lmin(-1) scale) were obtained. This is significantly more accurate than the measurement made using the thermodilution cathether.
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Med Biol Eng Comput · Sep 2000
Continuous estimation of systolic blood pressure using the pulse arrival time and intermittent calibration.
A continuous noninvasive method of systolic blood pressure estimation is described. Systolic blood pressure is estimated by combining two separately obtained components: a higher frequency component obtained by extracting a specific frequency band of pulse arrival time and a lower frequency component obtained from the intermittently acquired systolic blood pressure measurements with an auscultatory or oscillometric system. The pulse arrival time was determined by the time interval from QRS apex in electrocardiogram to the onset of photoplethysmogram in a fingertip beat-by-beat via an oximetric sensor. ⋯ The estimated values of systolic blood pressure were compared with those measured invasively using a radial arterial catheter. The results showed that the correlation coefficients between estimated values and invasively obtained systolic blood pressure reached 0.97 +/- 0.02 (mean +/- SD), and the error remained within +/- 10% in 97.8% of the monitoring period. By using a system with automatic cuff inflation and deflation to acquire intermittent systolic blood pressure values, this method can be applicable for the continuous noninvasive monitoring of systolic blood pressure.
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Med Biol Eng Comput · Mar 2000
Comparative StudyAdvantages of using a bank of allogenic keratinocytes for the rapid coverage of extensive and deep second-degree burns.
In 1975, serial subculture of human keratinocytes was first described. Clinical application of this discovery was made possible after the preparation of these cells into epithelial sheets. In 1981, the earliest application of cultured autologous epithelia was made for the treatment of extensive third-degree burns. ⋯ Moreover, autologous and allogenic cultured epithelia give good aesthetic results, without the mesh aspect obtained with a split-thickness autograft, and also without the discomfort for the patient of removing a sample of skin. Deep second-degree burns are an application of choice for the cultured epithelia, as the presence of the dermis avoids retractions responsible for functional complications usually observed in third-degree burns where dermis is absent. Because of the safety of the bank of allogenic keratinocytes, the treatment of extensive and deep second-degree burns has become safer and faster, with better functional and aesthetic results.