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Biomedical subjects

C R Chapman

Publications and source records attributed to C R Chapman.

At least 55 records · Page 3Linked to original sources
PubMed1985

Stimulus intensity and inter-stimulus interval effects on pain-related cerebral potentials.

The inter-relationship between stimulus intensity and inter-stimulus interval (ISI) on pain-related evoked vertex potentials was studied. Sixteen subjects were tested with 4 stimulus intensities at 4 different ISIs forming 16 averaged event-related potentials for each subject. Data were analyzed in 2 ways: first by multiple regression analysis of peak-to-peak amplitudes and secondly by single-trial analysis for each subject based on a linear model employing principal component loadings as basis functions, from which were derived separate time-dependent functions describing the contributions of intensity and ISI. Peak-to-peak amplitudes of the averaged waves increased with increases in either intensity of ISI. There were no significant interactions. However, single-trial analysis revealed subtle, but consistent, differences in the peak latencies between stimulus and ISI components, suggesting that the components arise from distinct sources.

Adolescent↗
PubMed1985

Pain measurement: an overview.

The practice and theoretical basis of pain measurement is reviewed and critically examined in the areas of animal research, human subjects laboratory investigation and clinical study. The advantages and limitations of both physiological and behavioral methods are discussed in each area, and subjective report procedures are evaluated in human laboratory and clinical areas. The need for procedures that bridge these areas is emphasized and specific issues are identified. Progress in the technology of pain measurement over recent decades is reviewed and directions for future work are suggested.

Animals↗
PubMed1985

Peak latency differences in evoked potentials elicited by painful dental and cutaneous stimulation.

Long-latency evoked potentials (EPs) (50-400 msec) have been obtained from humans during both noxious stimulation of tooth and cutaneous sites in studies of pain and analgesic states. This study investigated whether EPs elicited by tooth and lip stimulation differed in peak latency and whether EPs obtained during painful cutaneous stimulation showed increasing peak latency values with increased conduction distance. Twelve volunteers received painful electrical stimulation at four sites: tooth, lip, thumb, and toe in counterbalanced orders. Evoked potentials recorded at vertex were summation averaged over 128 trials. Multivariate stepwise discriminate analysis was used to determine whether any of the peak latencies of the event-related potentials differed across stimulation sites. No significant latency differences were observed across lip, thumb or toe at any of the major peaks. Since peaks of these EPs did not vary in latency with conduction distance, they appear to reflect processing at higher levels rather than sensory transmission. The negative 140 msec peak of the dental waveform occurred significantly later than the same peak at cutaneous sites.

Adult↗
PubMed1984

New directions in the understanding and management of pain.

Control of pain and the suffering that it causes still eludes us. Despite impressive progress in the prevention and cure of disease and in care of the trauma victim, pain is still a frontier in medical research. It accompanies surgery, various diagnostic procedures and dental care as well as acute injury and disease. For a significant number of patients it persists after injury or illness into a chronic state. Chronic pain is recognized to be the most frequent cause of disability in the United States and many industrialized nations today, and is a major cost to society in both work hours lost and medical expenses. In addition to its social importance, pain is an intimate cause of personal concern for every human being throughout life. The progress, or lack of progress, achieved by medical research in pain control is of interest to us all. Pain disorders may be usefully classified in two categories: acute and chronic. The etiology, physiopathology, symptomatology, diagnosis and therapy of these two types of pain are quite different and require separate consideration. Acute pain is that which arises from an acute injury or disease process and persists only as long as the tissue pathology itself. If acute pain problems are not effectively treated, they may progress to chronic states. Chronic pain is that: (1) associated with chronic tissue pathology; or (2) which persists beyond the normal healing period for an acute injury or disease. There are unique challenges for health care providers associated with each of these two categories of problems, and failure to distinguish between these types of pain has led to a widespread, ongoing mismanagement of patients that can be prevented if strong efforts are made to better educate health care professionals about pain and its therapy. This paper presents an overview of current understanding about the nature of pain and its management. The physiology and psychology of pain are reviewed against a background of the concepts and information taught 25 years ago. Some common acute and chronic pain problems are reviewed and discussed. Finally, several new directions in pain control are described.

Acute Disease↗
PubMed1983

Opiate analgesia and its antagonism in dental event-related potentials: evidence for placebo antagonism.

The analgesic effects of the synthetic opiate fentanyl citrate (0.1 mg) on subjective pain reports (SPR) and late-wave event-related potentials (ERP) recorded during painful dental stimulation were examined in human subjects. Such waves have been shown to reflect the contribution of cognitive variables, such as expectancy and belief, to perception. In addition, the study was intended to demonstrate a dose-related narcotic antagonism with injection of naloxone (1.2 or 0.4 mg) or normal saline (double-blind) following IV fentanyl administration. Fentanyl reduced both ERP waveform amplitudes and SPR as have previously studied analgesic agents, such as nitrous oxide, acupuncture, and aspirin. Naloxone injection reversed both ERP and SPR changes, but surprisingly, a reversal of narcotic analgesia equal to that of 0.4 mg naloxone was seen with saline injection. By chance, all subjects were health-science students or professionals who were knowledgeable in opiate pharmacology, and so placebo reversal was hypothesized. Alternatively, it was hypothesized that fentanyl cleared more rapidly than predicted, thus, producing apparent reveal. In a second experiment involving similarly knowledgeable subjects with identical procedures and testing intervals, subjects received 0.1 mg fentanyl, but no reversal injection. The fentanyl effect was constant across this time period. The data, thus, support the hypothesis where the subjects were knowledgeable in opiate pharmacology, was placebo opiate antagonism.

Adult↗
PubMed1983

Effects of nitrous oxide, transcutaneous electrical stimulation, and their combination on brain potentials elicited by painful stimulation.

Combinations of transcutaneous electrical stimulation (TES) and inhalation of nitrous oxide with oxygen have been used for surgical pain control and this report explored the possible synergism of these two treatments. During painful dental stimulation, 18 subjects gave pain reports while event-related potentials were recorded at vertex. Electrical stimulation was delivered bilaterally at the LI-4 acupuncture points on the hands at 20 Hz, mean = 9.65 mA intensity. Inhalation treatment was nitrous oxide 33% with oxygen. Testing was done on two days to permit evaluation of each treatment alone and their combination. Treatment sequence was counterbalanced. Base-to-peak amplitude and peak latency scores were derived for the event-related potentials under each testing condition. Both stimulation and inhalation treatments altered event-related potential scores and pain report. The combination treatment was significantly more effective than stimulation alone but was not significantly more effective than nitrous oxide alone. Nitrous oxide with oxygen alone reduced peak amplitude at 250 ms and 350 ms, as well as pain report. It increased peak latency at 100 ms. Transcutaneous electrical stimulation alone decreased peak amplitude and latency at 150 ms and increased peak latency at 350 ms. Decreased peak amplitude at 250 ms and increased peak latency at 150 ms were observed when inhalation was added to stimulation, and there was also a significant reduction in pain report. Nine control subjects were studied to demonstrate that analgesic changes were not due to repeated testing. These outcomes demonstrated no synergism between the stimulation and inhalation treatments. The data suggest that nitrous oxide blocks the effects of electrical stimulation at LI-4.

Adult↗
PubMed1982

Effects of nitrous oxide inhalation on brain potentials evoked by auditory and noxious dental stimulation.

1. Effects of inhaling nitrous oxide in oxygen were observed in subjects undergoing noxious dental (N=10) or nonnoxious auditory (N=10) stimulation. Evoked potentials (EPs), 100-500 msec poststimulus, were recorded at vertex, and peak-to-peak amplitudes as well as peak latencies were quantified. 2. Both dental and auditory EPs were reduced by 33% nitrous oxide in oxygen concentration and a dose-related effect was seen in the auditory modality when the concentration was increased to 50%. 3. These observations demonstrate that nitrous oxide inhalation has a broad impact on neurophysiological function in addition to behaviorally determined analgesia.

Acoustic Stimulation↗
PubMed1982

Effect of nitrous oxide concentration on event-related potentials during painful tooth stimulation.

Effects of inhaling three levels of nitrous oxide in oxygen on event-related brain potentials (ERPs) and pain report were examined in 10 volunteers undergoing painful electrical stimulation of tooth pulp. Previous work by the authors demonstrated that inhalation of nitrous oxide 33 per cent in oxygen, iv injection of 0.1 mg fentanyl, oral administration of 975 mg aspirin, and electrical acupunctural stimulation all reduced ERP amplitudes obtained a vertex during painful tooth pulp stimulation. The authors report here the demonstration of a dose-response relationship between increasing concentrations of nitrous oxide in oxygen and measures of ERP amplitude and pain report. Subjects inhaled room air, nitrous oxide 25 per cent, 37 per cent, and 50 per cent in oxygen while ERPs were recorded and pain reports were given. The procedure was repeated on three separate days with each subject experiencing all levels of treatment on each day. Analyses of variance revealed that both ERP amplitude and pain report significantly decreased as dosage increased, and a significant linear trend was observed for the positive-going ERP wave-form deflection between 160 and 240 ms. Pain report scores decreased significantly (P less than 0.001) and proportionally as dosage increased, but there was not a significant linear trend. Inhalation of nitrous oxide in oxygen increased peak latency for the negative component at 50 ms and the positive component at 90 ms but not for later components. These outcomes demonstrate that amplitude measures of the vertex ERP obtained with dental dolorimetry correlate consistently with pain and analgesia. Simultaneous assessment of brain electrical activity and subjective report appears to be a useful approach for the assessment of analgesia in humans.

Adult↗
PubMed1982

Varying electrical acupuncture stimulation intensity: effects on dental pain-evoked potentials.

Electrical acupunctural stimulation (EAS) has repeatedly been shown in the laboratory to diminish human dental pain perception. This study compared the effects of low, medium, and high EAS levels on event-related potentials elicited by painful dental stimulation and on subjective pain report. Acupuncture was performed bilaterally at LI-4 on the hands, and each subject received all EAS levels, counterbalanced for order. Only the highest level of EAS was effective, and it reduced the pain report in addition to the amplitudes of the positive event-related potential deflections from base line at 100 and 250 msec. No dose-response effect was observed for EAS levels. The outcome suggests that the analgesic effect occurs abruptly when stimulation reaches a strong level and a subnoxious pounding sensation is elicited.

Acupuncture Therapy↗
PubMed1981

Rate of stimulus repetition changes evoked potential amplitude: dental and auditory modalities compared.

Vertex evoked potentials (40--500 ms) elicited by painful dental stimulation were compared with those elicited by innocuous auditory stimuli across three rates of stimulus repetition: one second, four seconds, and eight seconds. In both modalities peak amplitude of the major waveform components increased linearly over log rate as stimulus repetition was slowed, and latency of the latest positive component was increased. No changes in subjective stimulus intensity across rate of repetition were reported. These observations demonstrate that the normally close relationship between subjective pain report and EP amplitude is not variant, and they suggest that the development of EP methodology in human pain research should proceed conservatively.

Adult↗
PubMed1981

Studies on the enzymatic cleavage of norethisterone oenanthate.

Norethisterone oenanthate (NET OEN) was extensively hydrolysed in rabbit, rat and guinea pig plasma (99.9%, 76.1% and 46.0% hydrolysed in 90 min, respectively). In contrast, there was negligible hydrolysis (less than 2.5%) in dog, goat and human plasma. Rabbit liver, kidney, gut wall, stomach, heart and muscle showed marked hydrolytic activity in vitro, but there was little hydrolysis of NET OEN by either human muscle or fat. It is proposed that following intramuscular administration of NET OEN to rabbits, the ester is rapidly hydrolysed at the injection site and in the circulation whereas in humans the liver is the main site of hydrolysis since neither muscle nor plasma cause significant breakdown of the ester. The rabbit is not a good model for predicting the pharmacokinetics of NET OEN in humans.

Adipose Tissue↗
PubMed1981

Effects of local anesthetic infiltration on brain potentials evoked by painful dental stimulation.

The effects of lidocaine 2% infiltration on the brain-evoked potential elicited by painful dental stimulation were observed in human subjects. Both the evoked potential wave form and the subjective pain were eliminated by the local anesthetic in 10 volunteers, whereas saline infiltration under identical conditions in 10 others had no effect. These results support our other observations which indicate that brain-evoked potentials recorded during painful dental stimulation are a reliable physiologic correlate of human pain.

Anesthetics, Local↗
PubMed1980

Aspirin analgesia evaluated by event-related potentials in man: possible central action in brain.

The mechanism of aspirin analgesia is still unclear, but it is generally assumed that aspirin exerts its analgesic effect mainly on peripheral nociceptors. In this study, we demonstrate possible brain effects of 975 mg aspirin in man. When brain electrical potentials evoked by painful electrical tooth shocks were examined, aspirin was observed to significantly reduce the amplitude of the late waveform components, but it did not affect the earlier components. Since our earlier findings suggest that early waveform components reflect the energy transmission and the late components manifest the brain activities in an individual's perception of painful information, we postulate that aspirin may act centrally in pain processing.

Adult↗