Applied potential tomography in liquid gastric emptying measurement: design, assembling, calibration, and clinical application.

The present study aimed to validate the accuracy of a homemade applied potential tomography (APT) apparatus for liquid gastric emptying (GE). Twelve electrodes were placed in a circular array around the subjects. Ten electrodes in a rotated order recorded electrical current delivered from a driving pair of electrodes. Based on tomography, averaged signals of changed resistivity were constructed to display area changes. Six beakers were respectively placed into a saline-filled Perspex tank to measure their cross-sections. True beaker cross-sections are 2.01, 15.9, 18.8, 30.19, 38.48, and 63.61 cm2, respectively, whereas APT generated cross-sections were 7.9 +/- 2.9, 16.7 +/- 3.3, 22.4 +/- 4.9, 28 +/- 4.8, 48.7 +/- 7.6, 67 +/- 6.1 cm2, respectively (r = 0.98, P < 0.001). Twenty-four healthy males ingested 500-ml test solution to assess GE using both APT and scintigraphy. Only 20 (83.3%) subjects had a successful measurement. The APT half emptying time was 15.6 +/- 4.8 min, whereas scintigraphy was 21.9 +/- 6.3 min (r = 0.67, P < 0.01). In conclusion, our APT apparatus is a simple, noninvasive, and inexpensive way to assess liquid GE. Its clinical usefulness is confirmed using both phantom and human models.

The pharmacological effect of omeprazole on water gastric emptying: A study based on an impedance measure.

The present study was performed to validate the accuracy of a self-designed applied-potential tomograph (APT) in measuring the cross area of a studied object and to assess the effect of omeprazole premedication on water gastric emptying (GE), based on APT. Twelve electrodes were evenly placed in a circular array around the studied subjects. Ten electrodes in a rotated order recorded the electrical current injected into paired electrodes. Based on tomography, averaged signals of changed resistivity were constructed to display the area of interest and GE curve. Six beakers of various diameters were respectively placed into a cylindrical perspex tank which was filled with saline to measure their cross areas via computer-generated diagrams of APT. One hour after either omeprazole (20 mg) or placebo premedication, 15 healthy males were ordered to consume 500 ml of test water to assess emptying for 40 min. Within 3 days, a similar procedure was repeated using the counterpart premedication. The true cross areas of the 6 beakers are 2.01, 15.9, 18.8, 30.19, 38.48 and 63.61 cm(2), whereas those obtained by APT were 7.9 +/- 2.9, 16.7 +/- 3.3, 22.4 +/- 4.9, 28 +/- 4.8, 48.7 +/- 7.6 and 67 +/- 6.1 cm(2), respectively (r = 0.98, p < 0.001). Valid emptying data were obtained in 73.3 and 86.6% of subjects, following placebo and omeprazole, respectively (not significant). The half emptying times were 12.7 +/- 5.1 min for the placebo-treated group and 10.5 +/- 3.6 min for the omeprazole-treated group, respectively (p < 0.05). The areas under the emptying curve were 1,611.5 +/- 357.6 and 1,317.3 +/- 316.7 arbitrary units, respectively (p < 0.01). In conclusion, our APT system is accurate for large-area measurements; acid inhibition before APT measurement does not increase the success rate but enhances water emptying. The interpretation of impedance-obtained GE should consider the acid-inhibitory effect.

Factors responsible for computed electrogastrographic parameters in humans.

OBJECTIVES: Clinical knowledge about myoelectrical frequency is well known, but the factors responsible for recorded myoelectrical amplitude remain less clear. METHODS: We assembled an electrogastrographic system that could automatically compute the dominant myoelectrical frequency and power and power ratio. We enrolled 50 healthy volunteers (25 men and 25 women) to study their myoelectrical characteristics. Three surface electrodes were placed in the fundic, stomach body, and antral positions for two 30-min recordings in the fasting and postprandial states. RESULTS: The three different electrodes recorded similar dominant frequencies of about 3 cpm before and after a meal. The fasting dominant powers from these electrodes were 52.9 +/- 14.7, 44.6 +/- 11.5, and 50.1 +/- 15.1 dB, respectively (p < 0.01), whereas the postprandial dominant powers were 61.6 +/- 28.8, 54.3 +/- 26.6, and 61.9 +/- 27.8 dB, respectively (p < 0.01). Meal ingestion did increase the power (p < 0.05). Women had a lower dominant power than men (p < 0.001). Moreover, the dominant powers of each electrode were significantly correlated with body mass index (r = 0.3-0.36, p < 0.05) regardless of meal ingestion. The postprandial power ratio was not influenced by electrode position, gender, or body mass index. CONCLUSIONS: Myoelectrical dominant frequencies and power ratios are similar throughout the whole stomach area, whereas a lower power area exists on the stomach body. Gender-related variation in dominant power seems to be an effect of body size. The power ratio is the only reliable parameter for expressing myoelectrical amplitude.

An assembled electrogastrographic device to examine the meal effect on gastric slow wave.

We have assembled an electrogastrographic device based on the main components of amplifiers, a band-pass filter, an analogue/digital converter, low band-pass digital filters and a personal computer. The analysis software uses autoregressive moving average modelling to compute the frequency of slow waves and uses fast Fourier transformation for power spectral computation. Twenty healthy young male volunteers were enrolled in the study to test meal-elicited responses of the slow wave. Subjects underwent a 15 min recording while fasting and then a standard breakfast, which included 250 mL milk and a cake with a total of 1.45 kj, was ingested within 5 min. The post-prandial 15 min recording was immediately resumed after the meal. A slight but significant increase in the frequency of slow waves was seen in post-prandial measurement (mean +/- s.d., 0.0506 +/- 0.0005 vs 0.0497 +/- 0.0005 Hz; P < 0.0001). Moreover, a significant enhancement of the power of slow waves was elicited following the meal (36.0 +/- 3.1 vs 27.6 +/- 3.1 dB; P < 0.0001). We conclude that this assembled electrogastrographic device is a reliable means of monitoring gastric myoelectrical activity because the phenomenon of post-prandial responses of slow waves in either frequency or power is well demonstrated.

A simple, noninvasive method to investigate vascular characteristics in children.

Palpation of pulses is an ancient clinical technique. In modern medical terms, arterial pulse analysis permits the evaluation of vascular characteristics, the important parameters for study of the properties of vessels. However, the various parameters used to describe the vascular characteristics have been conventionally deriving from expensive, invasive, and complicated methods and involving complex computations. The authors designed, therefore, a simple, noninvasive system to evaluate vascular characteristics. The system consisted of two units of pressure transducer for simultaneous recording of two peripheral arterial pulses, an analog signal processor, an A/D converter, and a personal computer. The vascular characteristics were analyzed by use of the Windkessel model and cross-correlation function. The analysis program was designed by members of this team. Through this system, systemic arterial compliance and pulse wave velocity can be obtained. Thirty-five children (11 normal children and 24 children with various stable, mild congenital heart diseases) were enrolled for data analysis. For these 35 children without hypertension or other clinically apparent arterial disease, the pulse wave velocity in the upper limb as between 3.7 and 16.8 m x sec-1, with a mean +/- standard deviation of 9.3 +/- 3.3 m x sec-1. The arterial compliance among the 11 normal children was between 0.72 and 1.72 mL x mmHg-1 x m-2 with a mean of 1.15 mL x mmHg-1 x m-2; both were consistent with the previously reported values obtained from complex methods. This system provides data comparable with those obtained from invasive methods. In the past, the arterial characteristics could not be extensively studied owing to the invasive nature of the conventional methods. This new, simple, convenient noninvasive system will thus provide a convenient method for clinical use in evaluating the vascular characteristics of patients, especially of children.

Vibration arthrometry of the knee with torn meniscus: a preliminary report.

Although projects using vibration signals generated by the joint to detect joint disorders are still experimental, vibration arthrometry has been shown to be useful in assessing meniscal pathology. A prospective study using vibration arthrometry to diagnose meniscal tears was carried out in 25 consecutive patients with knee injuries. They comprised 20 males and five females with an average age of 34 years. An arthroscopic examination of the injured knee was given to every patient. Six cases of medial meniscal tear, 12 lateral meniscal tear, and two torn discoid menisci were found. The remaining five cases had normal menisci. By correlating the vibration arthrography of the patients to their corresponding arthroscopic findings, 15 were found to be true-positive, five true-negative and five false-negative. There were no false-positive readings. The accuracy, sensitivity and specificity of the vibration arthrometry in diagnosing meniscal tear was 80%, 75% and 100%, respectively. Vibration arthrometry was shown to be a reliable, non-invasive diagnostic tool in diagnosing meniscal tear of the knee.

Surface temperature change, cortical evoked potential and pain behavior elicited by CO2 lasers.

The performance of a self-designed CO2 laser stimulator, TL#2, was evaluated against a commercial product, model DE20XL of the Direct Energy Inc. (Irvine). The major items evaluated were the temperature change of the irradiated surface and the electrophysiological and behavior changes in the rat elicited by single laser pulse irradiation. Single shots of TL#2 produced a profile of surface temperature change similar to those of the DE20XL, as quantified by their maximal temperature change, rate of rise (half time to maximum) and rate of temperature drop. TL#2 and DE20XL elicited the same pain behaviors and the same pattern of cortical evoked potential in awake, behaving rats. TL#2 differed from the DE20XL in its laser beam shape and focal depth. The cross sectional energy profile of the TL#2 was a Gaussian shape, i.e., most intense at its center point, whereas that of the DE20XL with the FL20XL attachment had a shape of an inverted Gaussian, i.e., most intense in the periphery. Consequently, the peak energy of the center of the TL#2 laser beam grows rapidly with an increase in the pulse intensity. Caution must be taken not to use this machine at high intensity or for long duration less permanent damage should be produced on tested animal or human subject. In summary, TL#2 when used properly, should be a useful tool in the study of pain mechanism.

The influence of body size to the parameters of gastric slow wave: studied with an assembled electrogastrography.

An electrogastrographic (EGG) device has been assembled, it consisted of the following main components: amplifiers, band-pass filter, analog/digital converter, low band-pass digital filters which could pick up signals between 0.02 Hz (1.2 cpm) and 0.1 Hz (6 cpm), and a personal computer. The analysis softwares employed autoregressive moving average modelling to compute frequency of slow wave, and overlapping Welch periodogram of fast Fourier transform for power computation. In order to study the influence of body size to the EGG parameters, 28 healthy males (age: 18-45 years) without any gastric dysmotor disorders were enrolled to record fasting EGG. Another 28 age-matched females were enrolled to record and to compare the EGG parameters. Of the EGG frequencies, both males and females were approximate to 0.05 Hz (NS). However, the EGG power values were markedly different between the male and female measurements (Mean +/- SD: 57.3 +/- 16.6 dB vs. 46.8 +/- 14.7 dB, p < 0.01). Correction with body mass index eliminated this difference. Of all measured EGG power values, a positive correlation with body mass index was seen (r = 0.39, p < 0.005). We conclude that a different EGG power value exists between the male and female subjects, body size is probable an important factor to elicit this difference.