Capacitive sensing of electrocardiographic potential through cloth from the dorsal surface of the body in a supine position: a preliminary study.

A method for obtaining electrocardiographic potential through thin cloth inserted between the measuring electrodes and the skin of a subject's dorsal surface when lying supine has been proposed. The method is based on capacitive coupling involving the electrode, the cloth, and the skin. Examination of a pilot device which employed the method revealed the following: (1) In spite of the gain attenuation in the high frequency region, the proposed method was considered useful for monitoring electrogardiogram (ECG) for nondiagnostic purpose. (2) The method was able to yield a stable ECG from a subject at rest for at least 7 h, and there was no significant adverse effect of long-term measurement on the quality of the signal obtained. (3) Electrode area was the factor that had most influence on the signal, compared with other factors such as cloth thickness and coupling pressure, but could be reduced to 10 cm2 for heart rate detection. (4) Input capacitance of the device was assumed to be the dominant factor for the gain attenuation in the high frequency region, and should be reduced with a view to diagnostic use. Although there is still room for improvement in terms of practical use, the proposed method appears promising for application to bedding as a noninvasive and awareness-free method for ECG monitoring.

An application of capacitive electrode for detecting electrocardiogram of neonates and infants.

A new system has been developed for obtaining electrographic potential through thin underwear inserted between the measuring electrodes and the skin of a neonate or an infant when lying supine. The system is based on capacitive coupling involving the electrode, the underwear, and the skin. Validation of the system revealed the following: (1) the signal detected using the system displayed a periodic waveform synchronized with the simultaneously recorded ECG, even when thin underwear was inserted between the electrode and the skin, (2) the gain of the system when the cloth was inserted decreased as the frequency increased. The present system appears promising for application to bedding as a non-invasive and awareness-free method for ECG monitoring of neonates or infants. However, there is still room for improvement in terms of its practical use, because the high-frequency component of the signal was depressed in comparison with the reference ECG.

[Study on the derivation of P300 with reference electrode in the oral cavity].

The event related potential P300 is useful as an index of the fall of the cognitive function attends by aging and the diagnosis of dementia. If the generator of P300 is assumed to be equivalent current dipole (ECD), the negative wave should be recorded at other sites which polarity differs from the positive wave on the scalp. This study is to determine the most suitable reference electrode site for P300 recording and to improve S/N of P300. In order to record the P300 or N300 potential which spread on the scalp, earlobe (A1), oral (X1) and under site of the nose(X2) was used as a reference electrode. Auditory oddball paradigm which consists of the acoustic sound of 2000 Hz (targets) and 1000 Hz (standards) was used for the measurement of P300. In this results, P300 or N300 was measured by using earlobe(A1) site as a reference electrode. P300 wave was detected by Cz-A1 derivation and also the negative wave of N300 was detected by X1-A1 and X2-A1 derivation. These results demonstrate that there is an ECD which goes to the parietal region from internal focal area as a source of P300, and also suggest that P300 amplitude with Cz-X1 or Cz-X2 derivation is higher than that with Cz-A1 derivation. Therefore, it was speculated that the most suitable reference electrode sites for the improvement of the S/N in the P300 are oral (X1) or under the nose (X2) that show the negative potentials (N300).

[Novel apnomonitor for use at home].

The monitoring technique for assessing suspected sleep apnea syndrome is a polysomnogram (PSG) performed in hospital. The typical PSG includes EEG, EOG, EMG, air flow at the nose and mouth, SO2, thoracicoabdominal motion and snoring sound. But the PSG test is expensive, and also is a stress load for the patient because this test requires recording throughout the night. Recently, a home-type apnomonitor that is used at home has been developed for the screening of apnea, but this monitor can not distinguish obstructive sleep apnea (OSA) from central sleep apnea (CSA). We evaluated a new home-type apnomonitor that was able to distinguish OSA from CSA using the change of amplitude in the fingertip plethysmogram and respiratory flow curve attained by oronasal transducer. In this study, the respiratory flow curve became flat under OSA conditions, but the change of amplitude on plethysmogram corresponded to thoracioabdominal motion. On the other hand, the change of amplitude in the plethysmogram did not corresponded with thoracicoabdominal motion under CSA conditions. These findings suggest that it is possible to distinguish between OSA and CSA using an apnomonitor system which records a respiratory flow curve and a plethysmogram, and also to develop a new home-type apnomonitor.

[Current neurophysiological tests and revised JSCN technical standards for clinical EEG].

The purpose of this lecture is to review the development of current neurophysiology and the revised standard of society for clinical EEG. 1. The improvement of neurophysiological tests. 1) EEG and evoked potential: EEG and evoked potential testing includes the routine EEG recording, EEG monitoring in surgical operation, all night sleep polygraph for the diagnosis of sleep apnea syndrome and many kinds of brain evoked potentials. Especially, the P300 component in the ERP(event-related evoked potential) is useful for the testing of essential brain functions. 2) EMG and evoked EMG: These tests are applied for the diagnosis of neurogenic, myogenic and neuromuscular junction disorder, and also the single fiber EMG using micro needle electrode is useful for the diagnosis of myasthenia gravis. Motor and sensory nerve conduction velocity are calculated from the latency of evoked EMGs. Furthermore, the distribution of these conduction velocities in many nerve fibers is measured by the collision technique. 3) Other tests: Near-infrared spectroscopy for the testing of brain functions has made rapid progress, and the transcranial magnetic stimulation method has come to be used for evaluation of functional diseases in the pyramidal tract, cerebellum and the spinal cord. 2. The revised JSCN technical standards for clinical EEG. The revised recording conditions of ECI(electro cerebral inactivity: flat EEG) in brain death are the focus of this lecture.

Equivalent current dipole estimated from SSR potential distribution over the human hand. Sympathetic skin response.

OBJECTIVE: We aimed to determine whether or not the potential distribution of the sympathetic skin response (SSR) on the palm and dorsum of the hand can be described by an equivalent current dipole (ECD) as an SSR source model. METHODS: The SSR of 22 normal subjects were simultaneously obtained from two electrodes placed on the palm and the dorsum of hand, with an indifferent electrode on the thumbnail. We then measured the SSR potential distribution in 10 of the 20 subjects who had responded to stimulation with a clear dorsal SSR. To do this, 18 electrodes were attached to the palm and dorsum of the hand. SSR-evoking stimulation (sound, voice and rapid inspiration) were randomly delivered to the subject at time intervals of more than 1min to minimize the habituation effect. We estimated the ECD from the measured potential distribution. RESULTS AND CONCLUSIONS: The SSR-evoked by stimulation was negative in potential at the palmar sites of all 22 subjects, and was positive in potential at the dorsal sites of the hand in 20 of the 22 subjects. The SSR potential distribution, which was measured in 10 subjects, reached its maximum negative and positive potential near the base of the middle finger on the palm, and near the corresponding site on the dorsum of the hand, respectively. The SSR potential measured on the dorsum of the hand, however, was about 1/3 in amplitude of those on the palmar sites. These results suggest that the SSR source is located on the palm (probably the sweat glands) as confirmed by the estimated ECD (a negative pole on the palm and a positive pole on the dorsum of the hand). We speculate that the SSR may result from the potential difference caused by the Na(+) concentration gradient in the sweat, which results from intracanal reabsorption of Na(+). SIGNIFICANCE: The ECD resulting from the Na(+) concentration gradient within the canal of sweat glands is thought to be the source of the SSR from the negative pole on the palm to the positive pole on the dorsum.