During COVID-19 pandemic associated with multiple restrictions research performance is significantly hampered. This experiment aimed to verify, whether it is possible to adapt the experimental pain induction technique and observe the spatial summation of pain (SSp) within the field-like environment (so that it is possible to conduct the experiment outside of the laboratory and obtain similar results). Two variants of the Cold Pressor Task (CPT) were chosen to induce the SSp effect: i) using a professional apparatus available in the laboratory and ii) with the use of a commercially available plastic box filled with ice and water and a thermometer to measure the temperature of the water. Volunteers’ (n = 9) hands were divided into 5 segments, which were then subsequently immersed in the cold water (5°C) for 60 seconds (5-minute intertrial interval). Each participant took part in two sessions, i.e., using laboratory equipment and its non-laboratory equivalent. Preliminary observations confirmed that it is possible to induce SSp using both laboratory devices and methods adapted to non-laboratory conditions. SSp effect size was found to be similar in both methods. Small differences in the level of reported pain were observed, but these differences did not affect the SSp effect. The study showed that it is possible to adapt the procedure to induce pain and SSp within non-laboratory environment.

Background The way pain is remembered and reported can affect medical decisions taken by patients and health-care professionals. Memory of pain has been investigated extensively for the past few decades; however, the results of previous studies are highly variable, indicating that the recollection of pain can be accurate, overestimated or underestimated. It is therefore difficult to conclude how well pain is remembered. The aim of this systematic review and meta-analysis is to summarize research findings on memory of pain in healthy adults and patients suffering from acute and chronic pain. Methods The systematic review will be performed by searching for articles indexed in the following databases: PubMed, MEDLINE, PsycINFO, Web of Science, ScienceDirect, PsycARTICLES, Scopus and Academic Search Complete. Studies will be included if (1) they investigated healthy adults or patients with any acute or chronic pain condition and if (2) they assessed experienced pain (pain intensity and/or pain unpleasantness) and its recollection. No restrictions related to the date of publication and recall delay will be applied. Studies will be screened for eligibility and risk of bias by two independent assessors. The risk of bias will be assessed by a modified Downs and Black checklist. A narrative synthesis will be performed in the first stage; in the second stage, the results of studies with comparable designs will be pooled in meta-analytical syntheses. Discussion The question of whether pain is remembered accurately is crucial for valid pain diagnosis, effective treatment and prognosis. So far, a number of studies on memory of pain have been conducted; however, a definitive conclusion on whether memory of pain is accurate is still lacking. In this systematic review and meta-analysis, available data will be pooled together to further inform research and clinical practice. Systematic review registration PROSPERO CRD42018093523 Electronic supplementary material The online version of this article (10.1186/s13643-019-1115-4) contains supplementary material, which is available to authorized users.

No abstract

To calibrate or not to calibrate? This question is raised by almost everyone designing an experimental pain study with supra-threshold stimulation. The dilemma is whether to individualize stimulus intensity to the pain threshold / supra-threshold pain level of each participant or whether to provide the noxious stimulus at a fixed intensity so that everyone receives the identical input. Each approach has unique pros and cons which need to be considered to i) accurately design an experiment, ii) enhance statistical inference in the given data and, iii) reduce bias and the influence of confounding factors in the individual study e.g., body composition, differences in energy absorption and previous experience. Individualization requires calibration, a procedure already irritating the pain system but allowing to match the pain level across individuals. It leads to a higher variability of the stimulus intensity, thereby influencing the encoding of “noxiousness” reaching the central nervous system. Results might be less influenced by statistical phenomena such as ceiling/floor effects and the approach does not seem to rise ethical concerns. On the other hand, applying a fixed (standardized) intensity reduces the problem of intensity encoding leading to a large between-subjects variability in pain responses. Fixed stimulation intensities do not require pre-exposure. It can be proposed that one method is not preferable over another, however the choice depends on the study aim and the desired level of external validity. This paper discusses considerations for choosing the best approach for experimental pain studies and provides recommendations for different study designs.