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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
PubMed2003

Impedance cardiographic measurement of the physiological response to the Valsalva manoeuvre.

The Valsalva manoeuvre was performed, with airway pressures of 10, 20, 30, 40 and 50 mmHg, on 11 healthy male subjects in both the standing and supine positions, and was evaluated with impedance cardiography using the Minnesota impedance cardiograph. Along with the impedance waveform, the output of a finger photoplethysmograph was recorded. The ratios of the amplitude of the finger and impedance pulses at the end of a 10s strain phase during the Valsalva manoeuvre were compared with those of the control period. The results in the standing position showed the impedance ratio changed from 0.81 to 0.61 as the airway pressure increased from 10 to 50 mmHg, whereas, over the same pressure range, the finger pulse ratio changed from 0.44 to 0.21. In the supine position, the response was similar to that for standing for most pressures. Upon release of the pressure, the impedance showed an immediate, large decrease, which suggests a significant right-heart and vena cava component in the impedance cardiographic signal. The results show that the impedance signals responded similarly to those of previous studies of central arterial pressure during the Valsalva manoeuvre, whereas the finger pulse decrease was approximately twice as much.

Adult↗
PubMed2001

Variability in the cardiac EIT image as a function of electrode position, lung volume and body position.

A study was conducted using the Sheffield electrical impedance tomography (EIT) portable system DAS-01 P to determine the change in the cardiac image with electrode position, lung volume and body position. Sixteen electrodes were positioned in three transverse planes around the thorax at the level of the second intercostal space, at the level of the xiphisternal joint, and midway between upper and lower locations. Data were collected at each electrode level with the breath held at end expiration and after inspiring 0.5, 1 and 1.5 l of air with the subject in both the supine and sitting position. These data were analysed using a Matlab developed program that calculates the average resistivity change in the cardiac region from automatically determined borders. Results show significant individual variability with electrode position and air volume. The middle electrode most consistently shows an increase in impedance in the region of the heart during systole. In some subjects the change in the ventricular-volume-like curve showed a greater than 50% change as a function of lung volume. The pattern of variability with electrode position was not consistent among subjects. In one subject MRI images were obtained to compare actual structures with those seen in the EIT image. The results suggest that using these electrode locations reliable and consistent data, which could be used in clinical applications, cannot be obtained.

Electric Impedance↗
PubMed1999

Impedance stroke volume compared with dye and electromagnetic flowmeter values during drug-induced inotropic and vascular changes in dogs.

Stroke volumes measured by impedance were compared with values obtained by dye dilution and an electromagnetic flowmeter (EMF) on 14 dogs during drug-induced changes in cardiac contraction strength and peripheral resistance changes. Grouping all data for a total of 305 points showed correlations between dye and EMF, dye and impedance, and EMF and impedance of 0.89, 0.68, and 0.72, respectively. Correlations for individual dogs between dye and EMF, dye and impedance, and EMF and impedance ranged from 0.60 to 0.99, -0.39 to 0.96, and -0.26 to 0.89, respectively. These data suggest that the use of impedance cardiac output measurements to make treatment decisions about individual patients could result in serious error.

Animals↗
PubMed1993

The impaired response of spinal cord injured individuals to repeated surface pressure loads.

Three cyclic pressure loads (10 minutes "on" and 5 minutes "off") of 30 or 75 mmHg were applied to the flat anterior surface of the tibia on 11 able bodied (AB) and nine spinal cord injured (SCI) subjects. Transcutaneous PO2 (TcPO2) and PCO2 (TcPCO2), laser Doppler (LD) skin blood flow, velocity, and volume, and the depth of leg indentation (LI) were recorded. In the AB subjects the mean TcPO2 decreased from 31.5 to 27.2 mmHg with the 30 mmHg load. In contrast for the SCI subjects TcPO2 decreased from 32.3 to 7.3 mmHg (significantly differeNt from AB group at p < 0.05). Means of the LD values for volume, velocity, and flow were normalized, giving the highest value of each of the parameters including both the AB and SCI subject during the entire time period a value of 100%. At 30 mmHg loading, the laser LD normalized volume in the AB subjects were 72.5% and 97.0% for the on and off periods, respectively, whereas for the SCI subjects the values were 43.7% and 69.7% for the on and off periods, respectively (significantly different from the AB group at p < 0.05). At 75 mmHg loading, the volume values for the AB subjects were 59.1% and 95.3% for the on and off periods, respectively, whereas for the SCI subjects, the values were 31.6% and 65.4% for the on and off periods, respectively (significantly different from the AB group at p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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↗
PubMed1987

Nodule activity and allocation of photosynthate of soybean during recovery from water stress.

Nodulated soybean plants (Glycine max [L.] Merr. cv Ransom) in a growth-chamber study were subjected to a leaf water potential (psi w) of -2.0 megapascal during vegetative growth. Changes in nonstructural carbohydrate contents of leaves, stems, roots, and nodules, allocation of dry matter among plant parts, in situ specific nodule activity, and in situ canopy apparent photosynthetic rate were measured in stressed and nonstressed plants during a 7-day period following rewatering. Leaf and nodule psi w also were determined. At the time of maximum stress, concentration of nonstructural carbohydrates had declined in leaves of stressed, relative to nonstressed, plants, and the concentration of nonstructural carbohydrates had increased in stems, roots, and nodules. Sucrose concentrations in roots and nodules of stressed plants were 1.5 and 3 times greater, respectively, than those of nonstressed plants. Within 12 hours after rewatering, leaf and nodule psi w of stressed plants had returned to values of nonstressed plants. Canopy apparent photosynthesis and specific nodule activity of stressed plants recovered to levels for nonstressed plants within 2 days after rewatering. The elevated sucrose concentrations in roots and nodules of stressed plants also declined rapidly upon rehydration. The increase in sucrose concentration in nodules, as well as the increase of carbohydrates in roots and stems, during water stress and the rapid disappearance upon rewatering indicates that inhibition of carbohydrate utilization within the nodule may be associated with loss of nodule activity. Availability of carbohydrates within the nodules and from photosynthetic activity following rehydration of nodules may mediate the rate of recovery of N2-fixation activity.

Acetylene↗
PubMed1986

Temperature and photoperiod responses of soybean embryos cultured in vitro.

Temperature and photoperiod each have direct effects on growth rate of excised embryos of soybean (Glycine max (L.) Merrill). To determine if the effects of photoperiod are altered by temperature, embryos of 'Ransom II' were cultured in vitro at 18, 24, and 30 degrees C under photoperiod durations of 12 and 18 h at an irradiance of 9 W m-2 (700 to 850 nm) and a photosynthetic photon flux density of 58 micromoles m-2 s-1 (400 to 700 nm). Accumulation rates of fresh and dry weight were greater under 18-h than 12-h photoperiods over the entire range of temperature. Water content of the culture embryos was not affected by photoperiod but was greater at 18 and 30 than 24 degrees C. The accumulation rate of dry weight increased from 18 to 26 but declined at 30 degrees C.

Biomass↗
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↗
PubMed1984

Photoperiod effects on growth rate of in vitro cultured soybean embryos.

The growth rate of excised soybean (Glycine max [L.] Merrill) embryos grown in liquid culture increased linearly as photoperiod was increased from 0 to 20 h at an irradiance of 9 W m-2 measured between wavelengths of 700-850 nm from clear incandescent lamps. When irradiance levels were varied between 0.1 and 1.7 W m-2, the maximum growth rates of embryos occurred at ca. 0.5 W m-2 at both 10- and 16-h photoperiods. When the light source was changed from clear incandescent lamps, with a red (600-700 nm) to far-red (700-770 nm) ratio of ca. 1.07, to a BCJ incandescent lamp (Corning Glass dark red, transparent envelope and a red to far-red ratio of ca. 0.19), the growth rate of embryos slowed. These results are consistent with a high irradiance response for growth of soybean embryos.

Infrared Rays↗