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Biomedical subjects

R P Patterson

Publications and source records attributed to R P Patterson.

At least 19 recordsLinked to original sources
PubMed1991

Respiratory effects on cardiac related impedance indices measured under voluntary cardio-respiratory synchronisation (VCRS).

The respiratory effects on impedance-determined cardiac indices ((dZ/dt)min, stroke volume (SV), the Heather index (HI) and the O-wave) were measured at 100 kHz on ten normal males in the supine and sitting positions. The respiration was synchronised to 1/5th of the heart rate using voluntary cardiorespiratory synchronisation (VCRS). Digital filtering was used to eliminate breathing artefacts in the impedance signals. SV, (dZ/dt)min and HI were statistically higher during inspiration than expiration. Ensemble-averaging of (dZ/dt) signals using the R spike of the ECG as reference will lose beat-to-beat information and statistically reduce (dZ/dt)min because of the variation of RZ intervals during respiration. Z0 increased with inspiration and decreased in expiration delayed by one heart beat. The ratio of the O-wave height to (dZ/dt)min changed by 48 per cent from the beginning of inspiration to the end of expiration. Based on the timing and direction of the changes, the data imply that the traditional band impedance measurement is more closely related to the right heart event than to that of the left heart.

Adult↗
PubMed1991

Impedance cardiography using band and regional electrodes in supine, sitting, and during exercise.

The electrical impedance and its first derivative (dZ/dt) were measured at 100 kHz on 10 normal males in supine, sitting, and during upright bicycle exercise in order to compare the contribution of regional electrodes to the standard band electrode signal and to evaluate the possible use of spot electrodes for stroke volume (SV) measurements. Simultaneous measurements were made from band electrodes placed around the neck and lower thorax and from spot electrodes which recorded signals from the neck, upper thorax, and lower thorax. The results showed that approximately equal parts of the dZ/dt waveform came from the neck and upper thorax with the lower thorax contribution small but providing important features of the band signal. Changing from supine to sitting showed percentage decreases of 35% and 46% for the band and neck signals, respectively, with an increase of 19% for the upper thorax signal. The percentage increases in SV with upright exercise were 34%, 52%, and 24% for the bands, neck, and upper thorax signals, respectively. Band signal is made up of different signals from various regions of the thorax. Its ability to predict correct changes in SV may result from some "lucky" coincidences. The use of regional electrodes will probably not give the same SV information but may be important in measuring regional activities of the central circulation.

Cardiography, Impedance↗
PubMed1990

Mapping the cardiogenic impedance signal on the thoracic surface.

The cardiogenic impedance signal from band electrodes placed in the traditional position around the neck and lower thorax was studied by mapping the location of the signal on the sternum using 10 cm strip electrodes in eight male subjects. The band current electrodes on the neck and waist were replaced with 10 cm strip electrodes on the forehead and 10 cm below the xiphisternal joint, respectively, with only small changes in the dZ/dt peak amplitude and Z0. Similarly, using a strip voltage pickup electrode at the level of the xiphisternal joint resulted in very small changes in the waveform. The amplitude of dZ/dt measured between the xiphisternal joint and points along the sternum remains small until approximately 10 cm below the suprasternal notch, after which it increased linearly to the top of the neck. An average of 17 per cent and 24 per cent of the dZ/dt signal and 24 per cent and 22 per cent of the Z0 signal for supine and standing, respectively, occurs above the suprasternal notch. Replacing the current electrodes with strip electrodes on the forehead and waist caused only small changes in the signal. The position of the neck strip electrode is more critical.

Adult↗
PubMed1990

A functional electric stimulation system using an electrode garment.

A functional electric stimulation system for standing and ambulating that uses a commercially available electrode garment has been developed. The garment allows electrodes to be applied rapidly and securely. Two channels of a four-channel stimulator are used to stimulate the quadriceps muscles and permit the user to stand. The other two channels are used to stimulate the peroneal nerve, which causes a flexor withdrawal reflex and permits stepping. The user controls stepping by hand-held switches. The system provides a means for standing, exercising, and limited ambulation.

Clothing↗
PubMed1990

Bicycle pedalling forces as a function of pedalling rate and power output.

Eleven men with recreational bicycling experience rode a bicycle ergometer with instrumented force pedals to determine the effects of pedalling rate and power output on the total resultant pedal force, Fr, and the component of the force perpendicular to the crank arm. The force patterns were obtained at power outputs of 100 W and 200 W for pedalling rates of 40-120 rpm in intervals of 10 rpm. Data were not obtained at 40 rpm at the 200 W power output. The Fr averaged over a crank cycle (Far) was lowest at 90 rpm and 100 W, a value statically different (P less than 0.05) from those at 40, 50, and 120 rpm. At 200 W, the Fr was lowest at 100 rpm, a value statistically different (P less than 0.05) from those at 50, 60, and 70 rpm. The Far varied widely (range of 30% of mean for all subjects) for individuals at a given power output. The results suggest that pedalling at 90-100 rpm may minimize peripheral forces and therefore peripheral muscle fatigue even though this rate may result in higher oxygen uptake.

Adult↗
PubMed1988

A multiple muscle strength testing protocol.

A quick test (QT) protocol was developed to allow for the rapid testing of multiple muscle groups in order to profile body strength. Maximum muscle strength was also obtained using a standard test (ST) protocol. The ST protocol consisted of three five-second trials with a one-minute rest between trials and no more than four muscle groups tested per day. The QT protocol allowed only a five-second rest between trials. Thirteen subjects were evaluated using both protocols. Subjects were positioned either sitting or supine, depending on the muscle groups being evaluated. Stabilization was provided to minimize substitution patterns. Measurements were obtained using a load cell and a computerized recording system. Using the QT protocol and testing 13 muscle groups in one session vs five sessions with the ST protocol resulted in an average reduction of 4% in strength values for the QT protocol. The results suggest that the clinical use of the QT protocol may not significantly reduce the accuracy of repeated measurements even though values obtained may be slightly lower than those obtained using the ST protocol.

Adult↗
PubMed1986

Sitting pressure-time patterns in patients with quadriplegia.

Continuous pressure under each ischial tuberosity was measured on five ulcer-free patients with quadriplegia for four days as they completed their normal daily activities. Results showed many multihour periods without pressure relief. More than 50% of the time the pressure-time periods were outside of previously reported acceptable limits. The results indicate that quadriplegic patients can sit with ischial tuberosity pressures above the previously reported capillary pressure of 32mmHg for long periods of time without getting an ulcer. This study suggests that other factors beside pressure must be studied in order to develop a better resting surface.

Female↗
PubMed1985

Work-rest periods: their effects on normal physiologic response to isometric and dynamic work.

Heart rate (HR) and blood pressure (BP) responses to repeated dynamic and combined dynamic and isometric work bouts of 30 sec, 2 min, and 6 min with equal rest periods at 40% and 80% of Vo2max was studied in five healthy men and five healthy women. Total work duration for each experimental condition was 24 min. The treadmill was used for dynamic work. Subjects pushed a bar horizontally while on the treadmill at 20% of their maximal voluntary strength for isometric work. Results showed that work performed at 40% of Vo2max in 30 sec bouts compared to 6 min bouts reduced HR, BP and the double product (BP X HR) by 11%, 4%, and 14%, respectively. Work performed at 80% of Vo2max in 30 sec bouts of repeated work or rest compared to the 6 min bouts resulted in reducing HR, BP, and double product 28%, 15%, and 39%, respectively. Addition of the isometric load did not significantly change the results. This study suggests that cardiac patients may be able to perform more work safely if it is carried out in short periods alternating with rest periods of equal duration.

Adult↗
PubMed1978

The electrical characteristics of some commercial ECG electrodes.

The impedance and offset potential of six disposable and two non-disposable electrodes were measured on 80 subjects. A total of 160 measurements were made on skin prepared by wiping with alcohol or acetone. For 640 measurements the skin was prepared by lightly sanding. The sanding of the skin reduced the impedance by a factor of approximately 50 for males and 100 for females. The offset potential for sanded skin was reduced by approximately 2. The performance of the disposable electrodes showed no great practical difference when applied on sanded skin. The median impedance ranged from 1500 to 3250 ohms. The median offset potential ranged from 0.5 to 4 mV. It was shown that a small DC current of 100 nA applied to stainless steel electrodes could cause a polarization voltage of approximately 0.5 volts to appear in 25 min.

Disposable Equipment↗