Alteration of kafirin and kafirin film structure by heating with microwave energy and tannin complexation.

Heating with microwave energy and tannin complexation of kafirin both increase the tensile strength of cast kafirin bioplastic films. The effects of these treatments on the molecular structure of kafirin and of kafirin in the film were investigated. SDS-PAGE of heated wet kafirin showed an increase in kafirin oligomers. Disulfide groups increased in heated kafirin and in films made from the heated kafirin. Fourier transform infrared (FTIR) spectroscopy of heated kafirin and films made from the heated kafirin indicated an increase in beta-sheet conformation. In contrast, kafirin complexation with tannic acid (TA) and sorghum condensed tannin (SCT) resulted in a slight decrease in beta-sheet conformation in the kafirin and a larger decrease in the kafirin in the films. Raman spectroscopy showed that, with TA, there was a shift in peak from 1710 to 1728 cm(-1) for kafirin-tannic acid complexes, indicating kafirin and tannic acid interaction. The protein conformational changes presumably facilitated cross-linking between kafirin molecules and/or between kafirin and the tannins. Thus, although both heating with microwave energy and tannin complexation cause cross-linking of kafirin to increase film tensile strength, their effects on kafirin structure appear to be different.

A simulation-based evaluation of nine oscillometric blood pressure monitors for self-measurement.

OBJECTIVE: To evaluate the performance of nine self-measurement oscillometric blood pressure monitors using a simulator. METHODS: For each monitor, simulation data from 48 sets of simulated waveforms with four simulations for each set were used for analysis. The waveforms represent a wide range of blood pressure. The monitor-simulator blood pressure differences were analyzed according to the 1992 Association for the Advancement of Medical Instrumentation (AAMI) and 1993 British Hypertension Society (BHS) protocols, except that corrections were made to take into account simulation variability. One-way analysis of variance was used to compare the differences for various combinations of monitors. The monitors' heart rate readings were compared with the rated accuracy. RESULTS: First, the mean blood pressure differences in general vary from monitor to monitor, the absolute mean differences ranging from 1.2 to 18.2mmHg. This can be partly explained by the likely use of different blood pressure determination criteria. Second, the Omron HEM-711 and HEM-712C gave about the same mean difference for systolic pressure and for diastolic pressure, suggesting that the two monitors may be using the same or approximately the same set of determination criteria. Third, the quantitative assessments for some of the monitors, for systolic or diastolic pressure or both, satisfy the clinical-use accuracy criteria of the AAMI or BHS protocol or both. These assessments alone cannot, however, be used to conclude whether or not any of the monitors fulfils the accuracy requirements of either protocol. Fourth, the corrected standard deviations of the differences range from 1.5 to 16.6mmHg, most of them being substantially less than the 8mmHg limit stipulated in the AAMI protocol. The different standard deviations suggest a varying robustness of the signal-processing methods used by the monitors. Fifth, for 7 out of the 9 monitors, more than 94% of the heart rate readings fall within +/-5% of their reference readings. CONCLUSIONS: The nine monitors in general performed differently with respect to the simulator. The results cannot be used fully to reflect the monitors' performance on human subjects because they were not based on clinical evaluation. Studies that lead to a more realistic simulation of oscillometric blood pressure are needed. Protocols integrating both clinical and simulation-based evaluations need to be developed.

Automated noninvasive blood pressure measurement.

Noninvasive blood pressure (NIBP) is one of the most common vital signs monitored by today's bedside and transport monitors. A variety of NIBP measurement methods has been used in these monitors. Some of the methods provide intermittent measurements over a period of time, while others provide continuous measurement on a beat-to-beat basis. Most of the monitors provide for on-demand measurement as well as automatic measurement at user-selected intervals. The measurement accuracy of an NIBP monitor is typically established by clinical evaluation. Generally safe and easy to use, NIBP monitors play a very important role in patient care.

Survey of automated noninvasive blood pressure monitors.

Automated noninvasive blood pressure (NIBP) monitors, or automated sphygmomanometers, have been increasingly used both inside and outside clinical environments. An extensive survey of such monitors was carried out over the past five years. This survey covers a broad spectrum of monitors including ambulatory monitors, bedside and transport monitors, stress-test monitors, and monitors that are intended for self-measurement. It includes more than 400 models from suppliers in the United States and many other countries. A review of NIBP measurement methods that have been used in automated NIBP monitors is presented in this paper, along with statistical distributions of their use in the surveyed monitors and a list of the suppliers and monitors.

Update on methods & simulators for evaluation of noninvasive blood pressure monitors.

The development of methods and simulators for evaluating noninvasive blood pressure (NIBP) monitors has been dynamic during the past few years. As a complement to a previous review paper in this journal, several additional developments are reported in this paper. These include evaluation methods developed in Australia, the United States and Europe, as well as NIBP simulators developed in Germany and the United States.

Changes in oscillometric pulse amplitude envelope with cuff size: implications for blood pressure measurement criteria and cuff size selection.

Oscillometric blood pressures are derived from the amplitude envelope of oscillometric pulses generated in an occlusive cuff during cuff inflation or deflation; one factor which will affect the characteristics of these pulses is the size of the cuff bladder. Because limiting values are stipulated in recommendations and standards for bladder sizes, there is a wide variety of acceptable cuff sizes for any particular application. An experimental and theoretical study was undertaken to show the dependence of oscillometric blood pressures on bladder size. Actual cuff-arm compliance data were obtained from two subjects for two cuffs of different bladder size. Theoretical analysis was then applied to the data to predict the effects of different bladder sizes on the characteristics of the pulses. The results show that cuff-arm compliance and bladder size interact to affect the pulse amplitude and hence oscillometric blood pressure determination. These results suggest that blood pressures obtained using the oscillometric method may vary depending on cuff size, and in particular that replacement cuffs for oscillometric non-invasive blood pressure monitors should be chosen carefully.

Review of methods & simulators for evaluation of noninvasive blood pressure monitors.

Automated noninvasive blood pressure (NIBP) monitors have found widespread use both inside and outside clinical environments in recent years. Present methods for evaluating the measurement accuracy of this class of devices involve population studies that are meticulous, time-consuming and costly. These methods are also impractical for routine evaluation. NIBP simulators offer an alternative approach to evaluating automated NIBP monitors without directly using human subjects. They enable evaluation to be carried out on demand with little training, providing a safe and convenient way for manufacturers and hospitals to validate the performance of both new and existing monitors.