Journal of clinical monitoring and computing
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J Clin Monit Comput · Aug 1998
Influence of the reference gas of paramagnetic oxygen analyzers on nitrogen concentrations during closed-circuit anesthesia.
Nitrogen (N2) may accumulate to unacceptable levels during closed-circuit anesthesia (CCA) when the sampled gases are redirected to the anesthesia circuit, because many gas analyzers entrain air as a reference gas to calibrate for oxygen analysis. Using oxygen instead of air as the reference gas for paramagnetic oxygen analysis could attenuate N2 accumulation. Forty-three adult ASA physical status I-III patients undergoing a variety of peripheral and abdominal procedures were assigned to one of two groups, depending on the reference gas used by a paramagnetic oxygen analyzer, either air (group I, n = 23) or oxygen (group II, n = 20). ⋯ N2Et0min, N2Et5min, and N2Et55min were 0.87+/-0.93, 2.6+/-1.5, and 10.1+/-2.9%, respectively. The correlation (r2) between N2Et55min and N2Et0min was 0.04, and between N2Et55min and N2Et5min it was 0.40. We conclude that paramagnetic oxygen analyzers that use oxygen as the reference gas significantly attenuate N2 accumulation during CCA, which may reduce the need for frequent flushing of the anesthesia system, may provide more constant oxygen and nitrous oxide concentrations, and may simplify pharmacokinetic studies of potent inhaled anesthetics.
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J Clin Monit Comput · Aug 1998
Accuracy of volume measurements in mechanically ventilated newborns: a comparative study of commercial devices.
Ventilatory measurements in ventilated newborns are increasingly used to monitor and to optimize mechanical ventilation. The aim of this study was to compare the accuracy of volume measurements by different instruments using standardized laboratory conditions. ⋯ Most of the currently available neonatal spirometry devices allow sufficiently accurate volume measurements in the range of 10-60 ml and at frequencies between 30-60/min provided that an increased FIO2 is taken into account.
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J Clin Monit Comput · Aug 1998
In vivo evaluation of a closed loop monitoring strategy for induced paralysis.
Reliable closed loop infusion systems for regulating paralysis level can be a great convenience to the anesthesiologists in automating their task. This paper describes the in vivo performance evaluation of a self-tuning controller that is designed to accommodate large variations in patient drug sensitivity, drug action delays and environmental interfering noise. ⋯ The system adapted to a large variation in the sample subject drug sensitivity. It remained stable despite large amplitude disturbances and maintained the paralysis at the desired level following the removal of the disturbances.
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In the course of five years the development of an automated anesthesia record keeper has evolved through nearly a dozen stages, each marked by new features and sophistication. Commodity PC hardware and software minimized development costs. ⋯ In addition, we developed an evolutionary strategy that optimized motivation, risk management, and maximized return on investment. Besides providing record keeping services, the system supports educational and research activities and through a flexible plotting paradigm, supports each anesthesiologist's focus on physiological data during and after anesthesia.
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J Clin Monit Comput · Jul 1998
Normothermic cardiopulmonary bypass increases heparin requirements necessary to maintain anticoagulation.
With the practice of warm cardiopulmonary bypass (CPB) at our institution we have observed an apparent increase in heparin requirements. CPB temperature predictability affects pharmacokinetics and differences in drug metabolism can be expected. We hypothesized that heparin requirements would increase with increasing CPB temperature. ⋯ Maintenance of adequate heparin anticoagulation during CPB is clinically important. Warm CPB patients required more heparin per minute than those undergoing cold CPB. More frequent assessment of anticoagulation and administration of additional heparin should be considered in patients undergoing warm CPB.