Sixty-four channel wearable acquisition system for long-term surface electromyogram recording with electrode arrays

The use of mono- and bi-dimensional electromyogram (EMG) electrode arrays for the assessment of the neuromuscular system can provide an insight into muscle physiology not achieved with classical bipolar surface EMG. Among the advantages of multichannel EMG detection, there is a) the possibility of estimating muscle fibre conduction velocity, even during motor tasks, and b) the possibility to increase the number of detection points on a muscle, improving the performance of pattern-based EMG decomposition methods. For these reasons, the development and use of multi-channel surface EMG devices and techniques were chosen as the primary goals within the European RTD Project ‘Neuromuscular assessment in the elderly worker’ (NEW). The specific requirements of Project NEW called for the availability of a user-friendly, small-sized EMG acquisition system for field use, suitable for multichannel EMG recording using electrode arrays from one or more muscles. A market survey established that none of the commercially available EMG acquisition systems featured all the desired specifications, nor could they be easily adapted for specific use. The paper describes the design of an innovative acquisition system for long-term multichannel EMG recording fulfilling these requirements and comprising adhesive electrode arrays for artifact-free EMG acquisition during work activity and a portable, user-friendly, battery-powered acquisition system for multichannel EMG recording and storage on a removable PCMCIA card. The system has been used extensively within Project NEW for laboratory and field tests and can find applications in other fields of basic and applied research, including ergonomics, occupational and sports medicine.     

Microcomputer-based system for 24-hour recording of oesophageal motility and pH profile with automated analysis

A system developed for long-term simultaneous recording of eosophageal motility and pH in the ambulant patient is described. The system consists of a microprocessor based data-acquisition and preprocessing device, a personal computer for postprocessing, report generation and data storage, a miniature two-sensor pressure catheter and a pH electrode. Identification and classification of oesophageal contractions are performed in separate steps, using online preprocessing software for identification and offline postprocessing software for categorisation, classification and report generation. Contractions are categorised as peristaltic, simultaneous or nontransmitted and classified according to their amplitude, duration and propagation velocity. The method described reduces the amount of data from 870 kbyte to approximately 40kbyte per 24 hours in a multiparameter recording device, and offers the opportunity for offline postprocessing with different sets of criteria. The system has been found to be accurate and reliable in 24-hour studies in both healthy volunteers and patients with non-cardiac chest pain.     

微机心率变异功率谱测量系统

本文报道在在IBM—PC/XT微型计算机上开发的心率变异(HRV)功率谱测量系统技术,用于无创伤性定量测量心脏植物性神经的活动。系统软件采用菜单方式设计,用8088汇编语言和FORTRAN语言编写。系统在程控下,通过对连续心电信号(ECG)的R—R间期采样计数,并利用傅利叶变换的数字技术,计算出心率变异的时域和频域参数。     

New system for recording ambulatory blood pressure in man

A new perfusion and transducer unit for ambulatory blood-pressure recording is described, followed by reports of both the laboratory evaluation of the unit and experience with its clinical use. The major change from earlier systems is the perfusion system, now based on an electrically driven ‘delta’ pump. Pressure is measured by a semiconductor strain-gauge pressure transducer. Laboratory evaluation has shown that the transducer with associated tubing and cannulae has a satisfactory frequency response, considerably better than that of the recording system normally used. Both quantitatively and qualitatively there was a very close correspondence between signals obtained from the entire Oxford system (including recording and replay) and signals obtained directly by means of a catheter-tip transducer. Small, but consistent, signal drifts attributable to battery behaviour are described. The system appears remarkably insensitive to temperature variations within the range of expected ambient temperatures. Delta pump performance is satisfactory, producing essentially constant perfusion rates. Clinically, the system has been used for the recording of ambulatory blood pressures in 110 patients for periods up to 72 h with satisfactory results. Reliability appears good, with minimal artefacts atributable to the equipment. This transducer and perfusion system appears to be fully satisfactory and considerably more reliable than the earlier designs.     

A system for multiple unit recording during avoidance behavior of the rabbit

This paper describes a system for recording multiple-unit activity during avoidance conditioning of the rabbit. Three major advantages of the system are emphasized. The first is rapid and reliable single-session acquisition of the avoidance response (wheel rotation). A second advantage is the freedom from movement-related artifact provided by combining the recording and behavioral methods. Finally, the techniques of implantation of electrodes maximized the number of large-amplitude unit recordings that were obtained.     

Normal Ambulatory 24-Hour Esophageal pH Values in Koreans -A Multicenter Study-

Ambulatory 24-hr esophageal pH monitoring is considered the gold standard for diagnosing gastroesophageal reflux disease. The aim of this study was to establish normal values for gastroesophageal acid exposure in healthy Koreans. Fifty healthy volunteers (24 males and 26 females; mean age, 45 yr) without reflux symptoms and without reflux esophagitis or hiatal hernia on upper endoscopy underwent ambulatory 24-hr esophageal pH monitoring after esophageal manometry. The 95th percentiles for the reflux parameters were: the percent total time pH <4, 3.7%; the percent upright time pH <4, 5.7%; the percent supine time pH <4, 1.0%; the number of reflux episodes with pH <4, 76.5; the number of reflux episodes with pH <4 for >5 min, 1.5; the duration of the longest episode, 12.5 min; and the composite score, 14.2. Age and gender were not associated with any of the pH parameters. In conclusion, physiological gastroesophageal reflux occurs in healthy Koreans. These normal esophageal pH values will provide reference data for clinical and research studies in Korea.     

Techniques for acute single neuron recording in newborn rats

Techniques are described for artificially respiring, anesthetizing, head-holding, operating on and recording from single neurons in the VIII nerve of newborn rats weighing as little as 4.9 g.     

A microcomputer-based data acquisition system for continuous recording of feeding and drinking by rats

A monitoring system to continuously record the daily pattern of drinking and eating of rats is described. This system, based on a North Star microcomputer, can record the amount of food ingested with a temporal resolution of +/- 1.0 second and quantitative accuracy within +/- 5%. Drinking behavior is detected using a drinkometer which also has a temporal resolution of +/- 1.0 second. Data are analyzed by computer to determine absolute amounts of consumption and patterns of intake. The patterns of feeding and drinking recorded by this system are similar to those observed using other monitoring devices.     

An accelerometer for recording head movement of laboratory animals

The construction of an inexpensive light-weight accelerometer for use as a head-movement transducer with small animals in brain-recording (or brain-stimulation) experiments is described. The accelerometer can simply be taped to the existing cables, thereby furnishing a sensitive measurement of head movement.     

Multiple-electrode nerve cuffs for low-velocity and velocity-selective neural recording

In the paper, a method using multiple-electrode nerve cuffs is presented that enables electroneurographic signals (ENG) to be recorded selectively by action potential velocity. The theory uses a one-dimensional model of the electrodes in the cuff. Using this model, the transfer function for a single tripole is derived, and it is shown that more than one tripole signal can be recorded from within a cuff. When many tripole signals are available and are temporally aligned by artificial delays and summed, there is a significant increase in the amplitude of the recorded action potential, depending on the cuff length and the action potential velocity, with the greatest gain occurring for low velocities. For example, a cuff was considered that was constrained by surgical considerations to 30 mm between the end electrodes. For action potentials with a velocity of 120 ms⁻¹, it was shown that, as the number of tripoles increased from one, the peak energy spectral density of the recorded output increased by a factor of about 1.6 with three tripoles, whereas, for 20 ms⁻¹, the increase was about 19, with ten tripoles. The time delays and summation act as a velocity-selective filter. With consideration of the energy spectral densities at frequencies where are maximum (to give the best signal-to-noise ratio), the tuning curves are presented for these velocity-selective filters and show that useful velocity resolution is possible using this method. For a 30 mm cuff with nine tripoles, it is demonstrated that it is possible to resolve at least five distinct velocity bands in the range 20–120 ms⁻¹.     

Microcomputer Servo-controlled Bicycle Ergometer System for Psychophysiological Research

Steady state exercise is widely used for psychophysiological studies in which a constant heart rate at a predetermined level is desired. We have developed a microcomputer servo-controlled bicycle ergometer system that can be used for administering steady state exercise. Fourteen healthy male subjects, with a wide range of fitness levels (measured by VO2max) were exercised to either a fixed workload (130 watts) or a predetermined heart rate level (servo-heart rate) of 122 bpm (i.e., 65% of maximum calculated heart rate for the sample). Servo-heart rate was implemented using a feedback loop that automatically adjusted workload to compensate for immediate variations in heart rate, resulting in a more consistent heart rate. Heart rate varied from the predetermined value by 17 bpm during fixed workload but only 3 bpm during servo-heart rate (p less than .05). Therefore, by using the microcomputer servo-controlled bicycle ergometer, heart rate was maintained at a predetermined level regardless of the subject's fitness level. VO2max and workload during servo-heart rate were significantly correlated (r = .85, p less than .05). Therefore, the workload necessary to maintain heart rate at a constant level may provide an approximate index of aerobic fitness level.     

Mechanical micromanipulator for single-unit recording in unanaesthetized cat

A mechanical electrode microdrive is described which uses screw rotation of the advancing electrode to reduce adhesion to the tissue. Electrical contact between the fixed and moving parts is provided by a carbon brush. Closed-chamber arrangement keeps brain pulsation to a minimum. The chamber is approached by 7 ready-made penetration channels (jelly-filled hypodermic needles) to allow 7 penetrations without unsealing the chamber.     

Capacitive sensor for lick-by-lick recording of drinking.

An electronic device senses the touching of water by the animal's tongue; and each lick is recorded distinctly as a deflection on paper by an ascillograph. From these traces lick rate and any variations therein may be determined.     

An inexpensive system for continuously recording maternal behavior in the laboratory rat

A system is described for the continuous recording of time spent on the nest by mother rats. Accurate estimates of nursing time are obtained by limiting the space available for nesting and making food and water available only outside of the nesting area. The apparatus may also be used to monitor preparturient circadian activity, and to estimate the time of parturition. It is suggested that continuous monitoring of maternal nesting behavior be an important adjunct to experiments involving manipulation of the mother or litter.     

Whole-cell recording of intracellular pH with silanized and oiled patch-type single or double-barreled microelectrodes

Conventional ion-sensitive microelectrodes cannot be used in small cells, since they create too large an electrical leak at the site of penetration. Membrane potentials can be measured in such cells with the whole-cell configuration of the patch-clamp technique, after obtaining a high-resistance seal (giga-seal) to the cell membrane. Achieving such seals with patch-type microelectrodes silanized and filled with ion-sensitive cocktails has proved very difficult. Since ion-sensitive microelectrodes offer advantages over fluorescent techniques, we have developed a method which enables whole-cell recordings of membrane potential and intracellular pH to be achieved with silanized microelectrodes. We have been able to obtain high-resistance seals with silanized tips by dipping them in mineral oil. We describe the method for both single-barrel and theta-glass double-barreled microelectrodes. Double-barreled microelectrodes can be used to measure and control membrane potential in the whole-cell patch-clamp configuration while also measuring ionic activities with the adjacent barrel. We present illustrative experiments showing intracellular pH recordings in snail neurones and rat dorsal root ganglion cells, and we suggest the method can also be applied to other liquid-sensor ion-sensitive microelectrodes.