Multidimensional scaling reveals two dimensions of thermal pain

Thermoregulation and thermal sensation during whole-body water immersion at different water temperatures in healthy individuals: A scoping review

BACKGROUND

Severe thermal discomfort may increase risk of drowning due to hypothermia or hyperthermia from prolonged exposure to noxious water temperatures. The importance of using a behavioral thermoregulation model with thermal sensation may predict the thermal load that the human body receives when exposed to various immersive water conditions. However, there is no thermal sensation "gold standard" model specific for water immersion. This scoping review aims to present a comprehensive overview regarding human physiological and behavioral thermoregulation during whole-body water immersion and explore the feasibility for an accepted defined sensation scale for cold and hot water immersion.

METHODS

A standard literary search was performed on PubMed, Google Scholar, and SCOPUS. The words "Water Immersion," "Thermoregulation," "Cardiovascular responses" were used either as independent searched terms and MeSH terms (Medical Subject Headings) or in combination with other text words. The inclusion criteria for clinical trials terms to thermoregulatory measurements (core or skin temperature), whole-body immersion, 18-60 years old and healthy individuals. The prementioned data were analyzed narratively to achieve the overall study objective.

RESULTS

Twenty-three published articles fulfilled the review inclusion/exclusion criteria (with nine measured behavioral responses). Our outcomes illustrated a homogenous thermal sensation in a variety of water temperatures ranges, that was strongly associated with thermal balance, and observed different thermoregulatory responses. This scoping review highlights the impact of water immersion duration on human thermoneutral zone, thermal comfort zone, and thermal sensation.

CONCLUSION

Our findings enlighten the significance of thermal sensation as a health indicator for establishing a behavioral thermal model applicable for water immersion. This scoping review provides insight for the needed development of subjective thermal model of thermal sensation in relation to human thermal physiology specific to immersive water temperature ranges within and outside the thermal neutral and comfort zone.

Psychological, cognitive factors and contextual influences in pain and pain-related suffering as revealed by a combined qualitative and quantitative assessment approach

Previous psychophysiological research suggests that pain measurement needs to go beyond the assessment of Pain Intensity and Unpleasantness by adding the evaluation of Pain-Related Suffering. Based on this three-dimensional approach, we attempted to elucidate who is more likely to suffer by identifying reasons that may lead individuals to report Pain and Pain-Related Suffering more than others. A sample of 24 healthy participants (age range 18-33) underwent four different sessions involving the evaluation of experimentally induced phasic and tonic pain. We applied two decision tree models to identify variables (selected from psychological questionnaires regarding pain and descriptors from post-session interviews) that provided a qualitative characterization of the degrees of Pain Intensity, Unpleasantness and Suffering and assessed the respective impact of contextual influences. The overall classification accuracy of the decision trees was 75% for Intensity, 77% for Unpleasantness and 78% for Pain-Related Suffering. The reporting of suffering was predominantly associated with fear of pain and active cognitive coping strategies, pain intensity with bodily competence conveying strength and resistance and unpleasantness with the degree of fear of pain and catastrophizing. These results indicate that the appraisal of the three pain dimensions was largely determined by stable psychological constructs. They also suggest that individuals manifesting higher active coping strategies may suffer less despite enhanced pain and those who fear pain may suffer even under low pain. The second decision tree model revealed that suffering did not depend on pain alone, but that the complex rating-related decision making can be shifted by situational factors (context, emotional and cognitive). The impact of coping and fear of pain on individual Pain-Related Suffering may highlight the importance of improving cognitive coping strategies in clinical settings.

Removing carious dentin using a polymer instrument without anesthesia versus a carbide bur with anesthesia

BACKGROUND

The authors describe a new rotary polymer instrument that selectively removes infected dentin. This instrument has the potential to prepare selected cavities without the need for local anesthesia (LA). Patient acceptance has not been investigated in a clinical trial.

METHODS

In this open-label clinical study, the authors enrolled 20 subjects with two Class I carious lesions and randomly assigned them to receive one restoration with the polymer instrument and no LA and the second restoration with a carbide bur and LA. Both procedures were completed in one appointment. Subjects completed dental history, dental anxiety and situational pain questionnaires. At specific points during the procedure, subjects rated their perception of the intensity of cold, heat, pain, pressure, vibration, fear and anxiety. On completion of the restorative procedures and at 48-hour and one-week telephone contacts, subjects indicated which procedure they preferred.

RESULTS

During treatment with the polymer instrument, subjects indicated that they experienced slightly more pain, pressure, vibration and anxiety, but not more heat, cold or fear. Immediately after the procedure, 14 (70 percent) of 20 respondents (binomial test; P = .11) said that they would prefer having no LA and use of the polymer instrument for future dental work. The number of subjects indicating this preference increased to 15 (P < .05) at both the 48-hour and one-week contacts. One subject requested rescue LA during the polymer instrument treatment.

CONCLUSIONS

A significant number of subjects preferred the rotary polymer instrumentation with no LA to the carbide bur instrumentation with LA. They held this preference despite experiencing slightly, but reliably, more pain and pressure when treated with the polymer instrument.

CLINICAL IMPLICATIONS

A polymer (bur-like) rotary instrument with cutting ability limited to infected dentin can be used in Class I cavity preparations without the need for LA.

Descriptors of breathlessness in healthy individuals: distinct and separable constructs

STUDY OBJECTIVES

We tested the hypothesis that descriptors of breathlessness represent distinct and separable cognitive constructs, and predicted that the use of descriptors of breathlessness by healthy individuals is the same as their use by patients with cardiopulmonary disease.

DESIGN

Cluster analyses obtained in healthy individuals were compared with those obtained previously in patients who complained of breathing discomfort. In addition, we used multidimensional scaling (MDS) techniques to analyze relationships among descriptors in healthy individuals.

SETTING

Public university.

PARTICIPANTS

The participants were 100 healthy individuals (48 men and 52 women) ranging in age between 18 and 65 years (mean, 27.9+/-11.7 years).

MEASUREMENTS AND RESULTS

Participants judged the dissimilarity among pairs of 15 descriptors of breathlessness that were used previously to examine the experience of dyspnea in patients who complained of breathing discomfort. Cluster analysis solutions obtained in the healthy individuals were virtually identical to those obtained previously in patients. Three dimensions (attributes) of breathing discomfort were uncovered with MDS: "Depth and frequency of breathing," "Perceived need, or urge, to breathe," and "Difficulty breathing and phase of respiration." The results did not depend on age, sex, levels of education, or the presence of uncomfortable awareness of breathing with activities.

CONCLUSIONS

The relations among descriptors of breathlessness obtained in healthy individuals support the contention that the association of different clusters with different disease states reflects distinct and separable cognitive constructs that are not simply dependent on the presence of an underlying pathophysiology or on a specific disease condition. Our results in healthy individuals also suggest that distinct qualities of breathlessness relate to different physiologic mechanisms underlying respiratory discomfort.

The application of goal attainment scaling in chronic pain settings

Although the multidimensional nature of chronic pain has been recognized since the 1960s, pain management continues to reflect a biomedical model for many chronic pain patients. The application of a biopsychosocial approach would be aided by measurement tools that reflect the multidimensional nature of pain, facilitate interdisciplinary care planning, and focus treatment on the consequences of pain that are important to patients. Goal Attainment Scaling (GAS) is an individualized health outcome measure that is suitable for health problems that warrant a multidimensional and individualized approach to treatment planning and outcome measurement. This paper describes the use of GAS as a treatment and research tool in cancer pain, pediatric pain, work-related nonmalignant pain, and geriatric pain. Unlike the typical process where goals are not explicitly stated, GAS allows goals to be stated in a systematic measurable manner that is relevant and meaningful for each patient, and that can guide individual treatment planning. GAS is an appropriate technique for guiding and monitoring the treatment of individual chronic pain patients, and may provide a useful tool for evaluating chronic pain programs.

Differential effects of hypnotic suggestion on multiple dimensions of pain

Within the framework of multidimensional pain assessment, this study extended an earlier finding that hypnotic analgesia and relaxation suggestions have differential effects on pain reduction by evaluating these strategies in subjects undergoing a cold pressor protocol. Thirty-two highly susceptible subjects were randomly assigned to an analgesia or a relaxation suggestion treatment group. Six pain reports were taken at 10-sec intervals for each experimental condition. The baseline measures served as covariates. A 2 x 2 x 2 x 6 repeated-measures analysis of covariance (ANCOVA) revealed a significant group (analgesia, relaxation) by pain dimension (intensity, unpleasantness), by condition (suggestion alone, hypnotic induction plus suggestion) interaction. Analysis of the simple-simple main effects, holding both group and condition constant, revealed that application of hypnotic analgesia reduced report of pain intensity significantly more than report of pain unpleasantness. Conversely, hypnotic relaxation reduced pain unpleasantness more than intensity. The clinical implications of the study are discussed.

On the absence of correlation between responses to noxious heat, cold, electrical and ischemic stimulation

Is a person's response to one noxious stimulus similar to his/her responses to other noxious stimuli? This long-investigated topic in pain research has provided inconclusive results. In the present study, 2 samples were studied: one using 60 healthy volunteers and the other using 29 patients with coronary artery disease. Results showed near-zero correlations between measures of heat, cold, ischemic, and electrical laboratory pains, as well as between these laboratory pains and an idiopathic pain, the latency to exercise-induced angina in the patients. Power analyses showed that the sample sizes were sufficient to detect a correlation of 0.50 or greater at the 0.05 level 99% of the time in the healthy volunteers, and between 80 and 85% of the time in the patients. Reliability analyses indicated retest correlations on the order of 0.60 for these measures, indicating that the lack of correlation between modalities was not due to unreliability within a measure. These studies fail to demonstrate alternate-forms reliability among these tests, and also fail to support the notion that a person can be characterized as generally stoical or generally complaining to any painful stimulus. In practice, this implies that a battery of tests should generally be used to assess pain sensitivity and also that assessments of one pain modality are not generally useful for making inferences about another.

Multidimensional scaling of painful and innocuous electrocutaneous stimuli: reliability and individual differences

Multidimensional scaling was used to explore whether a single intensity dimension underlies the perception of both nonpainful and painful electrical stimuli, or whether separate dimensions are required. For the scaling (INDSCAL) procedure, 41 healthy volunteers judged the similarity between all pairs of 16 intensities, which ranged from imperceptible levels to pain tolerance. For the property mapping (PREFMAP) analysis, they rated each intensity on each of 16 property scales. INDSCAL revealed four dimensions that showed high levels of both test-retest and split-half reliability. The first dimension scaled stimuli from the lowest intensity to the pain threshold. This dimension was related to property scales of sensation, affect, and arousal, but not pain, suggesting a sensory magnitude dimension. The second dimension ordered the stimuli from mildly to severely painful and was related to the painful property scale, suggesting a pain intensity dimension. Third and fourth dimensions, which refined the scaling of nonpainful stimuli, were also found. Variability in the subjects' use of the painful and nonpainful dimensions was related to their choice of stimulus descriptors. Like clinical pain, laboratory pain requires multidimensional assessment.

The effects of hypnotic suggestion on pain report

Forty-five highly susceptible volunteers rated a series of shocks using 32 pain descriptors. Descriptors were given numerical values using magnitude estimation procedures. We assigned the subjects to one of three conditions, analgesia suggestion, relaxation suggestion, or no suggestion. All subjects were administered the shocks and the suggestion appropriate to the group, in both the waking and hypnotic state. The results support the existence of two dimensions of pain which are differentially responsive to suggestion. Hypnotic-analgesia suggestion altered subjects' perceptions of the intensity without changing their perceptions of the unpleasantness of the shocks. Hypnotic-relaxation suggestion reduced the unpleasantness but not the perceived intensity of the stimuli. These findings imply that research into hypnotic pain relief is more easily interpreted if pain is viewed as multidimensional in nature.

The dimensions of pain: a multidimensional scaling comparison of cancer patients and healthy volunteers

This paper presents a new approach to the measurement and understanding of clinical pain. A multidimensional scaling (MDS) procedure was used to analyze pairwise similarity judgments made to 9 pain descriptors by 24 cancer pain patients and 24 healthy volunteers. The question was whether the dimensions of the global pain space differed between the 2 groups. The Pain Intensity dimension was found to be primary for the patients, but much less important for the volunteers. Otherwise, the group stimulus space revealed broadly similar 3-dimensional solutions. The Pain Intensity dimension placed Mild Pain and Annoying at one pole and Intense and Unbearable Pain at the other. The Emotional Quality dimension grouped the descriptors Sickening and Miserable (and, in part, Intense Pain and Unbearable Pain) at the strong negative affect pole for both groups; they differed, however, with respect to the moderate affect pole. The Somatosensory dimension ranged from Burning to Cramping. The subject weight space revealed that the Pain Intensity dimension was the most important dimension for the patients, while Emotional Quality was more salient for the volunteers. Wide differences were found in the salience of the various dimensions to different individuals; this information may prove useful for tailoring patient treatment. The study demonstrates that MDS procedures such as INDSCAL, in which the subjects (rather than the researcher) determine the number and characteristics of the global pain dimensions, will improve our understanding and treatment of pain.