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Biomedical subjects

J S Packer

Publications and source records attributed to J S Packer.

At least 19 recordsLinked to original sources
PubMed1999

Pain relief using smart technology: an overview of a new patient-controlled analgesia device.

A new adaptive patient-controlled analgesia (PCA) system designed to improve PCA through the use of a variable bolus dose and a variable background infusion is outlined here. The handset allows patients to rate their pain on a scale of 1-10. Data derived from the handset signals are used by an expert algorithm to repeatedly adapt the drug dosage of the bolus and the background infusion according to both pain intensity and patient response to previous dosages. A feasibility study of the system consisted of a small number of randomized, double-blind, crossover clinical trials. The new system was alternated with a conventional system every 12 h. When the new system was active, 12-h questionnaire pain scores were significantly lower and a trend toward fewer bolus requests was found in alternating intervals. In addition, when the new system was used to commence trials, the number of bolus requests were significantly lower and there was a trend toward lower handset scores, lower questionnaire pain scores, and lower verbal pain scores over the entire trial period. The new adaptive PCA system was well accepted by both patients and clinical staff. The trials successfully established the feasibility of the new system. Further development is being carried out as a result.

Analgesia, Patient-Controlled↗
PubMed1999

Smart technology improves patient-controlled analgesia: a preliminary report.

UNLABELLED: A new adaptive system has been designed to improve patient-controlled analgesia through the use of a variable bolus dose and a variable background infusion of analgesic. A novel hand set allows patients to rate their own pain on a linear scale of 1 to 10. Data derived from the hand set signals are used by an expert algorithm to repeatedly adapt the drug dosage of the bolus and of the background infusion according to both current pain intensity and the patient's response to previous dosage. To test the system, we performed a small pilot clinical study, using a randomized, double-blinded, cross-over design. The new system was alternated with a conventional system every 12 h. Use of the new system was associated with significantly lower pain scores and fewer bolus requests but more analgesic administration, though without increased adverse effects. It was very well accepted by both patients and clinical staff. IMPLICATIONS: Pain relief after surgery is often best provided by patient-controlled analgesia, which uses an IV infusion pump and a patient-activated switch. We have developed a new computer-controlled or "smart" patient-controlled analgesia that rapidly learns a patient's individual needs and provides continuously tailored pain relief.

Adolescent↗
PubMed1991

Clinical evaluation of closed-loop control of blood pressure in seriously ill patients.

OBJECTIVE: To compare the effectiveness of a new method of closed-loop (automatic) control of BP with usual manual control. DESIGN: Within-subject crossover trial. SETTING: General and open heart ICUs in a university teaching hospital. PATIENTS: Convenience sample of 74 seriously ill patients aged 17 to 88 yr. Twenty had hypertension: postoperative (n = 7), neurologic damage (n = 6), miscellaneous (n = 7), and were prescribed nitroprusside (n = 11) or nitroglycerin (n = 9). Fifty-four had hypotension: septic (n = 33), other (n = 21), and were prescribed norepinephrine (n = 30), dopamine (n = 11), epinephrine (n = 8), or dobutamine (n = 5). An additional 21 trials were omitted from analysis because of technical (n = 7), clinical (n = 1), or drug-related problems (n = 13). INTERVENTION: Closed-loop and manual drug administrations 1-hr were studied during periods in each patient. The target and observed mean arterial pressure (MAP) and drug infusion rate were recorded electronically every 30 sec. MAIN OUTCOME MEASUREMENTS: Time taken to achieve initial control (min); fidelity of control (the integral of size and duration of error from target MAP +/- 10% in mm Hg.hr/hr); and average drug dose administered (microgram/min as % maximum possible per drug). RESULTS: Compared with manual control, closed-loop achieved faster initial control (log-rank chi 1 = 5.04, p less than .05) and greater fidelity (mean 1.37 vs. 2.36; F = 7.15, p less than .01). There was no difference in average drug dose administered. There was uniformity in the efficacy advantage of closed-loop drug administration across drugs and patient classifications. CONCLUSION: The new closed-loop system is more effective than the usual manual control in managing acute BP disturbances in the seriously ill patient.

Adolescent↗
PubMed1990

Stimulus miscuing and dishabituation: electrodermal activity and resource allocation.

The present research investigated the effects of miscuing a shock stimulus on dishabituation of the skin conductance response and on the allocation of processing resources. In both experiments, a control group received 21 S1-S2 pairings intermixed with 23 S3-alone presentations. For the experimental group, S2 was miscued on trials 11 and 22 by its presentation following S3. In Experiment 1 (N = 48), S2 was a shock that was either "clearly discernible" or "uncomfortable but not painful". The results indicated increased electrodermal responding when S2 was miscued by S3 and subsequent dishabituation when S2 again followed S1 on the next trial. Miscuing produced dishabituation with both a high- and low-shock S2. A continuous measure of S2 expectancy revealed that expectancy of S2 in the presence of S1 declined as a result of miscuing. Experiment 2 (N = 36) employed reaction time to a white noise probe stimulus as the dependent variable. The critical data came from probes presented 300 ms following S2 onset on the S1-S2 trial immediately following miscuing. They indicated that miscuing produced slowed reaction time to probes presented during S2 on the following S1-S2 trial. Thus, the miscuing of S2 by S3 appears to result in an increase in processing resources devoted to S2, even when S2 is presented in its usual position following S1. The results are discussed in terms of current theories of associative learning.

Adult↗
PubMed1989

The effect of context change on long-term habituation of the skin conductance response to signal and non-signal stimuli in humans.

The present experiment investigated the role of contextual cues in long-term habituation of the skin conductance response. Subjects (N = 65) first underwent a habituation training session in which they received 15 presentations each of a signal and a non-signal stimulus. Signal value was induced by a motor response requirement to stimulus offset. In a test session one week later, the effect of context change on long-term habituation was examined by presenting the habituation stimuli in either the same or in a changed context. Although both short-term (within-session) and long-term (between-session) habituation were demonstrated, the results provided no evidence for context-dependency of long-term habituation. Moreover, there was no evidence of differential long-term habituation as a function of signal value in either the same- or changed-context conditions. The data are discussed in terms of Wagner's (1978) priming theory, and the methodological implications of the experimental manipulations of context change and signal value induction are explored.

Adolescent↗
PubMed1989

Restoration of stimulus associability, electrodermal activity, and processing resource allocation.

Four experiments investigated Pearce and Hall's (1980) proposal that a decrease in the predictive accuracy of a stimulus restores stimulus associability as reflected by increased orienting and controlled processing. The experiments examined the effects of miscuing or omission on stimulus associability as assessed by stimulus expectancy, electrodermal responding, and reaction time (RT) to a secondary task probe stimulus. In Experiments 1 and 2, a control group received 21 S1-S2 trials intermixed with 21 S3-alone presentations. For the experimental group, S2 was miscued by its presentation following S3 on two trials. In Experiments 1 and 2a, S1, S2, and S3 were moderate intensity stimuli, but in Experiment 2b, shock was used as S2. Experiment 1 (N = 24) demonstrated that, although there was uncertainty about whether S2 would follow S3 when S3 was re-presented following miscuing, skin conductance responses to S3 did not differ according to whether or not it had miscued the previous S2. Experiment 2a (N = 48) and Experiment 2b (N = 24) demonstrated that RT to white noise probe stimuli presented during the S3-alone presentation immediately following miscuing did not differ between experimental (miscuing) and control (no miscuing) groups. In Experiments 3 and 4, a control group received 23 S1-S2 trials. For the experimental group, S2 was omitted on two trials. In Experiment 3 (N = 24) S1 and S2 were of moderate intensity, whereas in Experiment 4 (N = 24) shock was used as S2. Reaction time to white noise probes presented during S1 did not differ according to whether or not the previous S2 was omitted. Thus, despite evidence of a reduction in the predictive accuracy of both S3 following miscuing and S1 following omission, there was no evidence of restoration of the associability of either S1 or S3. The results are discussed in terms of current theories of associative learning.

Adolescent↗
PubMed1989

Stimulus miscuing, electrodermal activity, and the allocation of processing resources.

The present research investigated the effects of stimulus miscuing on electrodermal responding, dishabituation, stimulus expectancy, and the allocation of processing resources as assessed by reaction time to a secondary task probe stimulus. In both experiments, a control group received 33 S1-S2 pairings intermixed with 33 S3-alone presentations. For the experimental group, S2 was miscued by its presentation following S3 on 4 trials. Experiment 1 (N = 24) demonstrated reliable electrodermal responding when S2 was miscued by S3 and subsequent dishabituation when S2 was re-presented following S1 on the next trial. A continuous measure of S2 expectancy revealed that S2 was not expected to follow S3 on miscuing trials. On re-presentation trials, S2 was not expected to follow S1. Experiment 2 (N = 24) employed probe reaction time as the dependent variable. White noise probe stimuli of 500-ms duration were presented 300 ms following the onset of S2 on miscued trials and on re-presentation trials. Reaction time to probes presented during miscued presentations of S2 was slower in the experimental group than in the control group. Reaction time on S2 re-presentation trials was also slower in the experimental group than in the control group. The results are interpreted to indicate that both the miscuing of S2 by S3 and its re-presentation following S1 on the next trial command processing resources. The results are discussed in terms of current theories of associative learning.

Adolescent↗
PubMed1987

The effects of signal value on short- and long-term habituation.

The present study examined the effects of signal value on short- and long-term habituation of the skin conductance response. Subjects (N = 48) attended the laboratory at the same time of day on two consecutive days. Day 1 comprised pretraining and training phases, and day 2 comprised the test phase. In the pretraining phase subjects received one presentation each of a tone and a vibration stimulus. In the training and test phases subjects received a randomly ordered sequence of 15 tones and 15 vibrations. All stimuli were of 4 s duration. During the training phase Groups E1 and E2 performed a motor response to the offset of one of the stimuli whereas a third group (Group C) did not. Neither Group E1 nor Group C performed the motor task during the pretraining and test phases. Both between- and within-group analyses of the training phase data indicated that responses were larger and habituation was slower to signal stimuli. Analyses of the test phase data and comparison of pretraining and test phase data indicated that long-term habituation occurred only to nonsignal stimuli. The results are discussed in terms of Wagner's (1978) theory of habituation.

Adolescent↗
PubMed1986

Sodium chloride, water and urea handling in the rat renal medulla: a computer simulation.

A dynamic rat renal medullary model was employed to study how independent control of excretion of various substances is achieved. Salt and water reabsorptive coupling was heterogeneous in the distal nephron. Diversion of filtrate to juxtamedullary nephrons retained salt with little effect on water or urea, a response enhanced by concomitant reduction in inner medullary blood flow. Urine concentration required high permeability and low flow in medullary blood vessels and active inner medullary salt transport. Collecting duct urea movement was closely coupled to that of water and urea recycling was enhanced by incorporation of nephrovascular bundles.

Animals↗