Yannick Tousignant-Laflamme

A systematic literature review of 10 years of research on sex/gender and experimental pain perception – Part 1: Are there really differences between women and men?

Summary Relatively limited support is provided to the hypothesis that healthy women have greater pain sensitivity than men in most experimental pain modalities. Abstract The purpose of this systematic review was to summarize and critically appraise the results of 10 years of human laboratory research on pain and sex/gender. An electronic search strategy was designed by a medical librarian and conducted in multiple databases. A total of 172 articles published between 1998 and 2008 were retrieved, analyzed, and synthesized. The first set of results (122 articles), which is presented in this paper, examined sex difference in the perception of laboratory‐induced thermal, pressure, ischemic, muscle, electrical, chemical, and visceral pain in healthy subjects. This review suggests that females (F) and males (M) have comparable thresholds for cold and ischemic pain, while pressure pain thresholds are lower in F than M. There is strong evidence that F tolerate less thermal (heat, cold) and pressure pain than M but it is not the case for tolerance to ischemic pain, which is comparable in both sexes. The majority of the studies that measured pain intensity and unpleasantness showed no sex difference in many pain modalities. In summary, 10 years of laboratory research have not been successful in producing a clear and consistent pattern of sex differences in human pain sensitivity, even with the use of deep, tonic, long‐lasting stimuli, which are known to better mimic clinical pain. Whether laboratory studies in healthy subjects are the best paradigm to investigate sex differences in pain perception is open to question and should be discussed with a view to enhancing the clinical relevance of these experiments and developing new research avenues.

A systematic literature review of 10 years of research on sex/gender and pain perception - Part 2: Do biopsychosocial factors alter pain sensitivity differently in women and men?

Summary Ecological validity of laboratory findings in healthy humans about the role of certain biopsychological factors on sex differences in pain perception needs to be assessed/improved. Abstract This systematic review summarizes the results of 10 years of laboratory research on pain and sex/gender. An electronic search strategy was designed by a medical librarian to access multiple databases. A total of 172 articles published between 1998 and 2008 were retrieved, analyzed, and synthesized. The second set of results presented in this review (129 articles) examined various biopsychosocial factors that may contribute to differences in pain sensitivity between healthy women and men. The results revealed that the involvement of hormonal and physiological factors is either inconsistent or absent. Some studies suggest that temporal summation, allodynia, and secondary hyperalgesia may be more pronounced in women than in men. The evidence to support less efficient endogenous pain inhibitory systems in women is mixed and does not necessarily apply to all pain modalities. With regard to psychological factors, depression may not mediate sex differences in pain perception, while the role of anxiety is ambiguous. Cognitive and social factors appear to partly explain some sex‐related differences. Finally, past individual history may be influential in female pain responses. However, these conclusions must be treated with much circumspection for various methodological reasons. Furthermore, some factors/mechanisms remain understudied in the field. There is also a need to assess and improve the ecological validity of findings from laboratory studies on healthy subjects, and perhaps a change of paradigm needs to be considered at this point in time to better understand the factors that influence the experience of women and men who suffer from acute or chronic pain.

An experimental model to measure excitatory and inhibitory pain mechanisms in humans.

Numerous approaches have been used to induce and measure experimental pain perception with the goal of better understanding excitatory and inhibitory pain mechanisms. In this study, the objective was to develop a simple experimental design which would enable us to elicit and measure multiple nociceptive mechanisms that have been reported to play a role in the development and persistency of chronic pain, such as temporal summation (TS) and diffuse noxious inhibitory control (DNIC). Eighty-three healthy subjects (42 men, 41 women) participated in this study where we examined pain perception of two tonic heat pain stimulation (thermode) separated by a 2 minute cold pressor test (CPT) (7 degrees C, 10 degrees C or 12 degrees C) which allowed us to activate DNIC. The heat pain response was characterized by a peak pain during the first 30 s, which was stronger for women (p = 0.001). We also observed a TS phenomenon during the second minute of stimulation. DNICs analgesia was assessed by measuring the difference in pain ratings between the two thermode procedures, before and after inducing DNIC by a cold pressure test on the opposite arm. We found that the mean pain ratings and peak pain but not TS were significantly reduced by DNIC. No sex differences were observed in DNIC analgesia. Our experimental pain design allowed us to measure several excitatory and inhibitory pain mechanisms in one experimental session. We were able to separate the effect of DNIC on the peak pain and on TS. This method is simple, sensitive and can easily be used in different population of either healthy subjects or chronic pain patients.

Excitatory and inhibitory pain mechanisms during the menstrual cycle in healthy women

ABSTRACT Sex differences in pain perception have been clearly documented in the literature during the last decades and it has been shown that women perceived more pain than men. Sex hormones (SHs) are thought to be one of the main mechanisms which explain sex differences in pain. Pain is a dynamic phenomenon involving both excitatory and inhibitory mechanisms. Previous studies have verified the effect of SH on excitatory mechanisms but not on endogenous pain inhibitory mechanisms. The main objective of this study was to establish if pain perception and diffuse noxious inhibitory control (DNIC) vary across the menstrual cycle (MC). Thirty‐two healthy women with a regular MC were tested three times across their MC (days 1–3, days 12–14 and days 19–23). Experimental pain consisted of two tonic heat pain stimulations (thermode) separated by a 2‐min cold pressor test (CPT) (conditioning stimulus activating DNIC). Pain ratings were measured with a visual analogue scale. Heat pain threshold, pain tolerance and mean pain intensity during both the 2‐min thermode test and CPT did not vary throughout the MC. However, we found significantly more pain inhibition (DNIC effectiveness) during the ovulatory phase compared to the menstrual and luteal phases (p = 0.05). The main finding of this study is the observation that only inhibitory mechanisms (DNIC analgesia) and not excitatory pain mechanisms vary throughout the MC, where women have greater DNIC in the ovulatory phase. The higher occurrence of pain and lower pain threshold previously reported during the MC could be related to a reduction in endogenous pain control mechanisms.

Validity study for the cervical range of motion device used for lateral flexion in patients with neck pain.

Study Design. A set of measurements was compared with an accepted gold standard using a methodologic design. Objective. To estimate the criterion validity of the cervical range of motion device used for lateral flexion in patients with neck pain. Summary of Background Data. Reliability of the cervical range of motion device has been well established. At this writing, only validity for flexion and extension of the cervical spine has been investigated with this device. Methods. The sample consisted of 24 volunteer subjects who had previously received physiotherapy for neck pain. In the radiograph department, subjects were stabilized on a chair. A first reading on the cervical range of motion device and a radiograph were taken in a neutral starting position. The subject then was asked to perform a maximal right lateral flexion, which was followed by a reading of the device and a second radiograph. The same procedures were followed for left lateral flexion. Results. The cervical range of motion device demonstrated a very good linear relation with the radiograph measurements: left lateral flexion (r = 0.82,; 95% confidence interval, 0.62–0.92), right lateral flexion (r = 0.84; 95% confidence interval, 0.66–0.93). Conclusions. The cervical range of motion device showed very good validity for measurement of lateral flexion in this population of patients with neck pain. Because the reliability of the cervical range of motion device was established previously, the results of this study suggest that the device be used as an outcome measure for the cervical flexion, and for flexion and extension.

Exploring the validity of the bispectral index, the Critical-Care Pain Observation Tool and vital signs for the detection of pain in sedated and mechanically ventilated critically ill adults: A pilot study

This pilot study aimed to explore the validity of the bispectral (BIS) index, the Critical-Care Pain Observation Tool (CPOT) score, and vital signs (mean arterial pressure, heart rate) during rest and painful procedures in sedated and mechanically ventilated ICU adults. A convenience sample of nine patients with various diagnoses participated in this observational repeated measures study. Patients were observed during 2 minute periods at rest (baseline), and during procedures known to be painful: turning and endotracheal suctioning. Both the BIS index and the CPOT score were found to increase when patients were exposed to procedures compared with rest, and were found to be more sensitive to procedures compared with vital signs. Indeed, vital signs remained quite stable during procedures in this sample. Results from this study support the recommendation that behavioural indicators (i.e. in this case, the use of a behavioural pain scale called the CPOT) be used for the detection of pain in nonverbal ICU patients. However, in some situations (e.g. deep sedation, use of blocking agents), behavioural indicators may no longer be observable, and all that is left are physiologic signs. The BIS seems to be an interesting technique and further research is required in order to establish if it could be used to guide clinicians for the detection of pain in this vulnerable population.

Reliability and criterion validity of two applications of the iPhone™ to measure cervical range of motion in healthy participants

Summary of background dataRecent smartphones, such as the iPhone, are often equipped with an accelerometer and magnetometer, which, through software applications, can perform various inclinometric functions. Although these applications are intended for recreational use, they have the potential to measure and quantify range of motion. The purpose of this study was to estimate the intra and inter-rater reliability as well as the criterion validity of the clinometer and compass applications of the iPhone in the assessment cervical range of motion in healthy participants.MethodsThe sample consisted of 28 healthy participants. Two examiners measured cervical range of motion of each participant twice using the iPhone (for the estimation of intra and inter-reliability) and once with the CROM (for the estimation of criterion validity). Estimates of reliability and validity were then established using the intraclass correlation coefficient (ICC).ResultsWe observed a moderate intra-rater reliability for each movement (ICC = 0.65-0.85) but a poor inter-rater reliability (ICC < 0.60). For the criterion validity, the ICCs are moderate (>0.50) to good (>0.65) for movements of flexion, extension, lateral flexions and right rotation, but poor (<0.50) for the movement left rotation.ConclusionWe found good intra-rater reliability and lower inter-rater reliability. When compared to the gold standard, these applications showed moderate to good validity. However, before using the iPhone as an outcome measure in clinical settings, studies should be done on patients presenting with cervical problems.

Sex differences in cardiac and autonomic response to clinical and experimental pain in LBP patients.

Rehabilitation professionals are currently using heart rate (HR) in order to assess the sincerity of effort in certain evaluations. It has been shown that a relation exists between HR and pain but no study has measured cardiac response during both clinical and experimental pain among a patient population using an intra‐subject design. Thirty patients with low back pain (LBP) participated in this study including 16 men. Clinical pain was induced by applying a postero‐anterior pressure (PA) on a painful lumbar segment for 15 and 30 s in order to reproduce the patients typical LBP at an intensity ranging between 50 and 70/100. Experimental pain was induced with a 15 s thermal stimulus at a temperature which reproduced the same pain intensity as the 15 s PA. For both reproduced clinical pain durations, we observed a rise in HR ranging between 8.5% and 12.67%. However, unlike men, womens cardiac response failed to show a constant rise in HR during the 30 s PA. For all subjects, the rise in HR was much lower during the experimental pain condition (p < 0.001), reaching only 5%. On the other hand, galvanic skin responses were significantly higher during the experimental pain condition (p < 0.001). During this same condition, women also had a greater rise in galvanic skin responses than men (p = 0.04). Finally, a significant correlation was found between both types of pain. These results suggest that pain induced during a clinical evaluation will produce a significant HR augmentation. However, heart rate variability analysis showed greater sympathetic cardiac regulation for men. The sex differences observed in this study call for caution when interpreting HR during pain assessment.

Different autonomic responses to experimental pain in IBS patients and healthy controls.

Background Pain perception ratings in irritable bowel syndrome (IBS) patients suggest that they present either hypoalgesia or hyperalgesia. However, little is known about the physiologic responses these patients present to a somatic painful stimulus. Goals The main goal of this project was to study autonomic nervous system responses and the cardiac response to experimental pain in IBS patients. Study This was addressed by exposing 27 women, 14 IBS, and 13 healthy controls (HCs), to a cold water (7°C) immersion test of the forefoot for 2 minutes. Pain perception, galvanic skin responses (GSR), and heart rate (HR) were monitored during and after the immersion. Results For comparable pain perception, a significant group difference (P<0.02) in the cardiac response was observed during the immersion where the peak rise in HR was much higher for HCs, reaching 22%, whereas it only reached 8% for IBS patients. Moreover, HR variability analysis demonstrated that IBS and HCs had opposite autonomic cardiac reactivity to pain, where IBS had increased parasympathetic/decreased sympathetic reactivity. Conclusions For comparable pain perception, IBS subject demonstrated different autonomic nervous system response to pain, which supports the view of autonomic dysregulation in IBS.

Educational needs of health care providers working in long-term care facilities with regard to pain management

BACKGROUND The prevalence of chronic pain ranges from 40% to 80% in long-term care facilities (LTCF), with the highest proportion being found among older adults and residents with dementia. Unfortunately, pain in older adults is underdiagnosed, undertreated, inadequately treated or not treated at all. A solution to this problem would be to provide effective and innovative interdisciplinary continuing education to health care providers (HCPs). OBJECTIVE To identify the educational needs of HCPs working in LTCF with regard to pain management. METHODS A qualitative research design using the nominal group technique was undertaken. Seventy-two HCPs (21 physicians⁄pharmacists, 15 occupational⁄physical therapists, 24 nurses and 21 orderlies) were recruited from three LTCF in Quebec. Each participant was asked to provide and prioritize a list of the most important topics to be addressed within a continuing education program on chronic pain management in LTCF. RESULTS Forty topics were generated across all groups, and six specific topics were common to at least three out of the four HCP groups. Educational need in pain assessment was ranked the highest by all groups. Other highly rated topics included pharmacological treatment of pain, pain neurophysiology, nonpharmacological treatments and how to distinguish pain expression from other behaviours. CONCLUSION The present study showed that despite an average of more than 10 years of work experience in LTCF, HCPs have significant educational needs in pain management, especially pain assessment. These results will help in the development of a comprehensive pain management educational program for HCPs in LTCF.