Clinical phenotypes and prognostic factors in persons with hip osteoarthritis undergoing total hip arthroplasty: protocol for a longitudinal prospective cohort study (HIPPROCLIPS).

BACKGROUND: Large heterogeneity exists in the clinical manifestation of hip osteoarthritis (OA). It is therefore not surprising that pain and disability in individuals with hip OA and after total hip arthroplasty (THA) cannot be explained by biomedical variables alone. Indeed, also maladaptive pain-related cognitions and emotions can contribute to pain and disability, and can lead to poor treatment outcomes. Traumatic experiences, mental disorders, self-efficacy and social support can influence stress appraisal and strategies to cope with pain, but their influence on pain and disability has not yet been established in individuals with hip OA undergoing THA. This study aims (1) to determine the influence of traumatic experiences and mental disorders on pain processing before and shortly after THA (2) to identify preoperative clinical phenotypes in individuals with hip OA eligible for THA, (3) to identify pre- and early postoperative prognostic factors for outcomes in pain and disability after THA, and (4) to identify postoperative clinical phenotypes in individuals after THA. METHODS: This prospective longitudinal cohort study will investigate 200 individuals undergoing THA for hip OA. Phenotyping variables and candidate prognostic factors include pain-related fear-avoidance behaviour, perceived injustice, mental disorders, traumatic experiences, self-efficacy, and social support. Peripheral and central pain mechanisms will be assessed with thermal quantitative sensory testing. The primary outcome measure is the hip disability and osteoarthritis outcome score. Other outcome measures include performance-based measures, hip muscle strength, the patient-specific functional scale, pain intensity, global perceived effect, and outcome satisfaction. All these measurements will be performed before surgery, as well as 6 weeks, 3 months, and 12 months after surgery. Pain-related cognitions and emotions will additionally be assessed in the early postoperative phase, on the first, third, fifth, and seventh day after THA. Main statistical methods that will be used to answer the respective research questions include: LASSO regression, decision tree learning, gradient boosting algorithms, and recurrent neural networks. DISCUSSION: The identification of clinical phenotypes and prognostic factors for outcomes in pain and disability will be a first step towards pre- and postoperative precision medicine for individuals with hip OA undergoing THA. TRIAL REGISTRATION: ClinicalTrials.gov: NCT05265858. Registered on 04/03/2022.

End-Tidal CO2 in Patients with Panic Disorder, Stress-Related or Functional Syndromes, Versus Healthy Controls.

A dysregulated autonomic stress physiology is hypothesized to play an important role in the etiology and perpetuation of somatic symptoms that cannot be (fully) explained by an organic disease. The aim of this study was to focus on the role of the respiratory system. We examined end-tidal CO2 concentration (PetCO2) in healthy controls (n = 30), patients with panic disorder (n = 36), and patients with stress-related (overstrain; n = 35, burnout; n = 44) or functional syndromes [fibromyalgia (FM) and/or chronic fatigue syndrome (CFS); n = 36]. Participants went through a rest period and a respiratory challenge with recovery, whilst PetCO2 was continuously monitored by a capnograph. Taken together, our results suggest: (1) an overactive respiratory system to be a possible transdiagnostic underlying factor of overstrain, burnout, and panic disorder, and (2) the presence of a less active respiratory fight-flight response in the more chronic and severe functional syndromes (FM/CFS).

The Interoceptive Sensitivity and Attention Questionnaire: Evaluating Aspects of Self-Reported Interoception in Patients With Persistent Somatic Symptoms, Stress-Related Syndromes, and Healthy Controls.

OBJECTIVE: This study aimed to validate the Interoceptive Sensitivity and Attention Questionnaire (ISAQ), a 17-item self-report measure assessing sensitivity and attention to interoceptive signals. METHODS: In study 1, exploratory and confirmatory factor analysis was performed in a student convenience sample (n = 1868). In study 2, ISAQ data of a healthy sample (n = 144) and various patient groups experiencing stress-related syndromes (overstrain, n = 63; burnout, n = 37; panic disorder [PD]. n = 60) and/or persistent somatic symptoms in daily life (irritable bowel syndrome, n = 38; fibromyalgia and/or chronic fatigue syndrome, n = 151; medically unexplained dyspnea [MUD], n = 29) were compared. RESULTS: Three subscales were revealed: (F1) sensitivity to neutral bodily sensations, (F2) attention to unpleasant bodily sensations, and (F3) difficulty disengaging from unpleasant bodily sensations. Overall, patients with fibromyalgia and/or chronic fatigue syndrome and patients with MUD scored significantly higher on F1 (p = .009 and p = .027, respectively) and F2 (p = .002 and p < .001, respectively) than healthy controls. Patients with PD had higher scores on subscales F2 (p < .001) and F3 (p < .001) compared with healthy controls, as well as higher scores on F2 compared with all other patient groups (pPD versus MUD = .008; all other p values < .001). CONCLUSIONS: Interoceptive sensibility-the self-reported aspect of interoception-is not a homogeneous or unitary construct. The subscales of the ISAQ differentiate healthy controls from patients with persistent somatic and/or stress-related complaints in daily life and distinguish different patient groups. The ISAQ can be used as a concise, reliable, and clinically relevant research tool to further disentangle adaptive and maladaptive aspects of interoceptive ability.

Virtual reality distraction induces hypoalgesia in patients with chronic low back pain: a randomized controlled trial.

BACKGROUND: Attentional distraction from pain has been shown to be largely ineffective for obtaining a hypoalgesic effect in patients with chronic pain when compared to a control condition. It has been hypothesized that this may be due to the non-engaging types of distraction that have been used so far. Moreover, it is suggested that the hypoalgesic effects of distraction may be attenuated by pain-related cognitions and emotions, as they may increase the attention to pain. METHODS: In this randomized controlled trial, patients with chronic nonspecific low back pain in the intervention group (n = 42) performed a single exercise session with nonimmersive VR games, while those in the control group (n = 42) performed the same exercises without VR games. We investigated whether VR distraction had a hypoalgesic effect during and immediately after the exercises, and whether it reduced the time spent thinking of pain during the exercises. We further explored whether pain-related fear, pain catastrophizing and baseline pain intensity moderated the effects of VR distraction. RESULTS: VR distraction had a hypoalgesic effect during (Cohen's d = 1.29) and immediately after (Cohen's d = 0.85) the exercises, and it also reduced the time spent thinking of pain (Cohen's d = 1.31). Preliminary exploratory analyses showed that pain-related fear, pain catastrophizing and baseline pain intensity did not moderate the effects of VR distraction. CONCLUSIONS: Large effect sizes of VR distraction induced hypoalgesia were observed. This suggests that nonimmersive VR games can be used when it is deemed important to reduce the pain during exercises in patients with chronic nonspecific low back pain. TRIAL REGISTRATION: NCT02679300. This trial was registered on 10 February 2016.

Relationship Between Different Experimental Measures of Distorted Symptom Perception in Functional Syndrome Patients.

OBJECTIVE: Patients with functional somatic syndromes show reduced correspondence between induced physiological changes and self-reported symptoms in a rebreathing paradigm, as well as elevated symptoms unrelated to physiological changes after induction of negative affective states in an affective picture-viewing paradigm. Detailed results of both paradigms separately were published elsewhere. The main goal of the current report is to describe the relationship between the responses to these two paradigms measuring distortions in symptom perception in a well-described sample of patients with fibromyalgia and/or chronic fatigue syndrome. METHODS: Patients (N = 81) with fibromyalgia and/or chronic fatigue syndrome participated in a test session comprising four well-validated paradigms, including the picture-viewing and rebreathing paradigm. Using mixed model analyses, we tested whether the amount of affective modulation of symptom reporting was related to distorted perception of induced dyspnea. In an exploratory way, we assessed the role of several individual difference variables as moderators. RESULTS: There was no relationship between patients' amount of affective modulation of symptom reporting, as assessed with the picture paradigm, and level of distortion in dyspnea perception, as assessed with the rebreathing paradigm (effect of affective modulation in the subjective recovery from induced dyspnea: F1,70 = 0.16, p = .70; time by affective modulation interaction effect: F4,70 = 0.14, p = .97). CONCLUSIONS: Biased symptom reporting in one paradigm is unrelated to biased symptom reporting in the other paradigm, indicating that distortions in symptom perception in patients with functional somatic syndromes are not a trait-like, cross-situationally stable condition, but a versatile dysfunction that is context dependent.

Endogenous Pain Modulation: Association with Resting Heart Rate Variability and Negative Affectivity.

Objectives: Several chronic pain syndromes are characterized by deficient endogenous pain modulation as well as elevated negative affectivity and reduced resting heart rate variability. In order to elucidate the relationships between these characteristics, we investigated whether negative affectivity and heart rate variability are associated with endogenous pain modulation in a healthy population. Design, Subjects, and Methods: An offset analgesia paradigm with noxious thermal stimulation calibrated to the individual's pain threshold was used to measure endogenous pain modulation magnitude in 63 healthy individuals. Pain ratings during constant noxious heat stimulation to the arm (15 seconds) were compared with ratings during noxious stimulation comprising a 1 °C rise and return of temperature to the initial level (offset trials, 15 seconds). Offset analgesia was defined as the reduction in pain following the 1 °C decrease relative to pain at the same time point during continuous heat stimulation. Results: Evidence for an offset analgesia effect could only be found when noxious stimulation intensity (and, hence, the individual's pain threshold) was intermediate (46 °C or 47 °C). Offset analgesia magnitude was also moderated by resting heart rate variability: a small but significant offset effect was found in participants with high but not low heart rate variability. Negative affectivity was not related to offset analgesia magnitude. Conclusions: These results indicate that resting heart rate variability (HRV) is related to endogenous pain modulation (EPM) in a healthy population. Future research should focus on clarifying the causal relationship between HRV and EPM and chronic pain by using longitudinal study designs.

Inducing Somatic Symptoms in Functional Syndrome Patients: Effects of Manipulating State Negative Affect.

OBJECTIVE: Induction of negative affective states can enhance bodily symptoms in high habitual symptom reporters among healthy persons and in patients with irritable bowel syndrome. The aims of this study were to replicate this effect in patients with fibromyalgia and chronic fatigue syndrome and to investigate the role of moderators, focusing on alexithymia, negative affectivity, and absorption. METHODS: Patients with fibromyalgia and/or chronic fatigue syndrome (n = 81) and HCs (n = 41) viewed series of neutral, positive, and negative affective pictures. After every picture series, participants filled out a somatic symptom checklist and rated emotions experienced during the picture series on valence, arousal, and perceived control. RESULTS: Patients reported more somatic symptoms after viewing negative pictures (least square mean [LSM] = 19.40, standard error (SE) = 0.50) compared with neutral (LSM = 17.59, SE = 0.42, p < .001) or positive (LSM = 17.04, SE = 0.41, p < .001) pictures, whereas somatic symptom ratings of HCs after viewing negative picture series (LSM = 12.07, SE = 0.71) did not differ from ratings after viewing neutral (LSM = 11.07, SE = 0.59, p = .065) or positive (LSM = 11.10, SE = 0.58, p = .93) pictures. Negative affectivity did not moderate the symptom-enhancing effect of negative affective pictures, whereas the alexithymia factor "difficulty identifying feelings" and absorption did (p = .016 and p = .006, respectively). CONCLUSION: Negative affective states elicit elevated somatic symptom reports in patients experiencing fibromyalgia and/or chronic fatigue syndrome. This symptom-enhancing effect is greater in patients having higher difficulty to identify feelings and higher absorption scores. The results are discussed in a predictive coding framework of symptom perception.

Healing Words: Using Affect Labeling to Reduce the Effects of Unpleasant Cues on Symptom Reporting in IBS Patients.

PURPOSE: The present study aimed to induce elevated symptom reports through the presentation of unpleasant cues in patients with irritable bowel syndrome (IBS) and examine whether applying an emotion regulation technique (affect labeling) can reduce symptom reporting in patients. METHODS: Patients diagnosed with IBS (N = 29) and healthy controls (N = 26) were presented with six picture series (three pleasant, three unpleasant) under three within-subject conditions: merely viewing, emotional labeling, or content (non-emotional) labeling. Each picture viewing trial was followed by affect ratings and a symptom checklist, consisting of general arousal and IBS-specific symptoms. RESULTS: Viewing unpleasant pictures led to overall increased symptom reports, both for arousal and gastrointestinal symptoms, in both groups. Labeling the pictures did not reduce these effects significantly, although a trend toward less arousal symptoms after unpleasant cues emerged in the patient group only, especially during emotional labeling. CONCLUSIONS: Current findings indicate that the mere presentation of unpleasant cues can induce elevated symptom reports in IBS patients. The results of the labeling manipulation provide modest support for the effectiveness of emotion regulation strategies in reversing these effects of unpleasant cues in patients suffering from functional syndromes. Methodological issues that may have confounded present results are discussed.

The association between pain-related psychological variables and postural control in low back pain: A systematic review and meta-analysis.

BACKGROUND: Alterations in postural control have been found in individuals with low back pain (LBP), particularly during challenging postural tasks. Moreover, higher levels of negative pain-related psychological variables are associated with increased trunk muscle activity, reduced spinal movement, and worse maximal physical performance in individuals with LBP. RESEARCH QUESTION: Are pain-related psychological variables associated with postural control during static bipedal standing tasks in individuals with LBP? METHODS: A systematic review and meta-analysis were conducted. Pubmed, Web of Science, and PsycINFO were searched until March 2023. Studies were included if they evaluated postural control during static bipedal standing in individuals with LBP by measuring center of pressure (CoP) variables, and reported at least one pain-related psychological variable. Correlation coefficients between pain-related psychological variables and CoP variables were extracted. Study quality was assessed with the "Quality In Prognosis Studies" tool (QUIPS). Random-effect models were used to calculate pooled correlation coefficients for different postural tasks. Sub-analyses were performed for positional or dynamic CoP variables. Certainty of evidence was assessed with an adjusted "Grading of Recommendations, Assessment, Development, and Evaluations" tool (GRADE). The protocol was registered on PROSPERO (CRD42021241739). RESULTS: Sixteen studies (n = 723 participants) were included. Pain-related fear (16 studies) and pain catastrophizing (three studies) were the only reported pain-related psychological variables. Both pain-related fear (-0.04 < pooled r < 0.14) and pain catastrophizing (0.28 < pooled r < 0.29) were weakly associated with CoP variables during different postural tasks. For all associations, the certainty of evidence was very low. SIGNIFICANCE: Pain-related fear and pain catastrophizing are only weakly associated with postural control during static bipedal standing in individuals with LBP, regardless of postural task difficulty. Certainty of evidence is very low thus it is conceivable that future studies accounting for current study limitations might reveal different findings.

Are contextual factors associated with activities and participation after total hip arthroplasty? A systematic review.

OBJECTIVES: After total hip arthroplasty (THA), over 30% of individuals report activity limitations and participation restrictions. This systematic review aimed to determine the association between contextual factors and outcomes in the activity and participation domain after THA for hip osteoarthritis (OA). METHODS: This systematic review was developed according to the PRISMA guidelines for systematic reviews. PubMed, Web of Science, Embase and Scopus were searched until August 2022. Risk of bias was assessed with the Quality in Prognosis Studies tool (QUIPS). RESULTS: Twenty-nine articles were included. Eighteen had a high risk of bias, 3 had a low risk of bias, and 8 had a moderate risk of bias. Anxiety was only investigated in studies with high risk of bias but showed a consistent negative association with activities and participation after THA across multiple studies. Evidence was inconsistent regarding the associations between depression, trait anxiety, sense of coherence, big 5 personality traits, educational level, marital status, employment status, job position, expectations and social support, and the activity and participation domain. Optimism, general self-efficacy, cognitive appraisal processes, illness perception, ethnicity, and positive life events were associated with activities and participation but were only investigated in 1 study. No associations were identified across multiple studies for living or smoking status. Control beliefs, kinesiophobia, race, discharge location, level of poverty in neighbourhood, negative life events and occupational factors, were not associated with the activity and participation domain but were only investigated in 1 study. CONCLUSION: Methodological quality of the included studies was low. Anxiety was the only factor consistently associated with worse outcomes in the activity and participation domain after THA but was only investigated in studies with high risk of bias. Further research is needed to confirm relationships between other contextual factors and activities and participation after THA. REGISTRATION: PROSPERO CRD42020199070.

Brain mediators of negative affect-induced physical symptom reporting in patients with functional somatic syndromes.

Functional somatic syndromes (FSS) include fibromyalgia, irritable bowel syndrome (IBS), and others. In FSS patients, merely viewing negative affective pictures can elicit increased physical symptoms. Our aim was to investigate the neural mechanisms underlying such negative affect-induced physical symptoms in FSS patients. Thirty patients with fibromyalgia and/or IBS and 30 healthy controls (all women) watched neutral, positive and negative affective picture blocks during functional MRI scanning and rated negative affect and physical symptoms after every block. We compared brain-wide activation during negative versus neutral picture viewing in FSS patients versus controls using robust general linear model analysis. Further, we compared neurologic pain signature (NPS), stimulus intensity-independent pain signature (SIIPS) and picture-induced negative emotion signature (PINES) responses to the negative versus neutral affect contrast and investigated whether they mediated between-group differences in affective picture-induced physical symptom reporting. More physical symptoms were reported after viewing negative compared to neutral pictures, and this effect was larger in patients than controls (p = 0.025). Accordingly, patients showed stronger activation in somatosensory regions during negative versus neutral picture viewing. NPS, but not SIIPS nor PINES, responses were higher in patients than controls during negative versus neutral pictures (p = 0.026). These differential NPS responses partially mediated between-group differences in physical symptoms. In conclusion, picture-induced negative affect elicits physical symptoms in FSS patients as a result of activation of somatosensory and nociceptive brain patterns, supporting the idea that affect-driven alterations in processing of somatic signals is a critical mechanism underlying FSS.

Peak-end memory bias in laboratory-induced dyspnea: a comparison of patients with medically unexplained symptoms and healthy controls.

OBJECTIVE: Memory for unpleasant experiences is dominated by intensity at the experience's peak and end, with a relative neglect for its duration. Therefore, unpleasant somatic experiences are expected be remembered as less aversive when they end gradually rather than abruptly, even when they last longer (i.e., the "peak-end effect"). We investigated the peak-end effect for dyspnea in healthy participants and in patients with medically unexplained dyspnea (MUD). METHODS: Two aversive dyspnea-inducing tasks were administered to a clinical MUD sample (n = 29) and a matched healthy control group (n = 29) using a rebreathing paradigm (60-second room air, 150-second rebreathing). In a short trial, the breathing system (mouthpiece) was removed immediately after peak dyspnea. In a long trial, breathing was switched to room air after peak dyspnea and continued in the breathing system for 150 seconds (order was counterbalanced across participants). Respiratory parameters were continuously measured, and dyspnea was rated every 10 seconds. Relative unpleasantness of the dyspneic episode was assessed with forced choice questions. RESULTS: More than 70% of the healthy group found the short episode worse than the long one despite equal maximal dyspnea (p = .02). Patients with MUD did not show this peak-end effect (p = .58). The latter had deficient recovery of dyspnea compared with the controls (42.08 [21.86] versus 17.51 [11.18], p < .001), which could not be explained by differences in respiratory physiology. CONCLUSIONS: The peak-end effect in dyspnea has important implications for dyspnea measurement. Its absence in patients with MUD suggests a critical role of distorted perceptual-cognitive processing of aversive somatic sensations in patients with medically unexplained symptoms.

Generalization of fear of movement-related pain and avoidance behavior as predictors of work resumption after back surgery: a study protocol for a prospective study (WABS).

BACKGROUND: Previous studies indicated that about 20% of the individuals undergoing back surgery are unable to return to work 3 months to 1 year after surgery. The specific factors that predict individual trajectories in postoperative pain, recovery, and work resumption are largely unknown. The aim of this study is to identify modifiable predictors of work resumption after back surgery. METHODS: In this multisite, prospective, longitudinal study, 300 individuals with radicular pain undergoing a lumbar decompression will be followed until 1-year post-surgery. Prior to surgery, participants will perform a computer task to assess fear of movement-related pain, avoidance behavior, and their generalization to novel situations. Before and immediately after surgery, participants will additionally complete questionnaires to assess fear of movement-related pain, avoidance behavior, optimism, expectancies towards recovery and work resumption, and the duration and severity of the pain. Six weeks, 3 months, 6 months, and 12 months after surgery, they will again complete questionnaires to assess sustainable work resumption, pain severity, disability, and quality of life. The primary hypothesis is that (generalization of) fear of movement-related pain and avoidance behavior will negatively affect sustainable work resumption after back surgery. Second, we hypothesize that (generalization of) fear of movement-related pain and avoidance behavior, negative expectancies towards recovery and work resumption, longer pain duration, and more severe pain before the surgery will negatively affect work resumption, pain severity, disability, and quality of life after back surgery. In contrast, optimism and positive expectancies towards recovery and work resumption are expected to predict more favorable work resumption, better quality of life, and lower levels of pain severity and disability after back surgery. DISCUSSION: With the results of this research, we hope to contribute to the development of strategies for early identification of risk factors and appropriate guidance and interventions before and after back surgery. Trial registration The study was preregistered on ClinicalTrials.gov: NCT04747860 on February 9, 2021.

Lumbar range of motion in chronic low back pain is predicted by task-specific, but not by general measures of pain-related fear.

BACKGROUND: Most studies fail to show an association between higher levels of pain-related fear and protective movement behaviour in patients with chronic low back pain (CLBP). This may be explained by the fact that only general measures of pain-related fear have been used to examine the association with movement patterns. This study explored whether task-specific, instead of general measures of pain-related fear can predict movement behaviour. METHODS: Fifty-five patients with CLBP and 54 healthy persons performed a lifting task while kinematic measurements were obtained to assess lumbar range of motion (ROM). Scores on the Photograph Daily Activities Series-Short Electronic Version (PHODA-SeV), Tampa Scale for Kinesiophobia and its Activity Avoidance and Somatic Focus subscales were used as general measures of pain-related fear. The score on a picture of the PHODA-SeV, showing a person lifting a heavy object with a bent back, was used as task-specific measure of pain-related fear. RESULTS: Lumbar ROM was predicted by task-specific, but not by general measures of pain-related fear. Only the scores on one other picture of the PHODA-SeV, similar to the task-specific picture regarding threat value and movement characteristics, predicted the lumbar ROM. Compared to healthy persons, patients with CLBP used significantly less ROM, except the subgroup with a low score on the task-specific measure of pain-related fear, who used a similar ROM. CONCLUSIONS: Our results suggest to use task-specific measures of pain-related fear when assessing the relationship with movement. It would be of interest to investigate whether reducing task-specific fear changes protective movement behaviour. SIGNIFICANCE: This study shows that lumbar range of motion in CLBP is predicted by task-specific, but not by general measures of pain-related fear. This suggests that both in clinical practice and for research purposes, it might be recommended to use task-specific measures of pain-related fear when assessing the relationship with movement behaviour. This may help to disentangle the complex interactions between pain-related fear, movement and disability in patients with CLBP.

Repeated experiences of air hunger and ventilatory behavior in response to hypercapnia in the standardized rebreathing test: effects of anxiety.

In this study, we assessed air hunger (AH) and ventilatory responses to repeated CO(2) exposures in healthy women (N=31), scoring high or low for trait anxiety. A standardized rebreathing test, implying a gradually increasing CO(2) stimulus, was administered three times with 15-min intervals. Respiratory behavior and the intensity of AH perception were measured continuously. Across repeated exposures, maximal tolerance for AH habituated and the slope of AH (increase in AH per unit increase in CO(2)) diminished. Also the dynamics of the breathing response changed across trials. The thresholds for AH and tidal volume (V(T)) moved closer to each other, whereas the threshold for the respiratory rate (RR) was generally postponed. In addition, the association between AH and V(T) was stronger than between AH and RR, and the latter association became weaker over trials, particularly in high anxious persons. This suggests that AH perception became increasingly influenced by psychological factors, especially in high anxious persons. The results suggest that habituation of perceived air hunger is depending on a complex interplay between both changes in respiratory behavior and in perceptual-cognitive processes related to trait anxiety.

High symptom reporters are less interoceptively accurate in a symptom-related context.

OBJECTIVE: We investigated the role of a symptom interpretation frame on the accuracy of interoception and on retrospective symptom reporting in nonclinical high and low reporters of medically unexplained symptoms. METHODS: All participants (N=74) went through two subsequent trials of the Rebreathing Test, inducing altered respiration and other physical sensations as a result of a gradually increasing pCO(2) level in the blood. Each trial consisted of a baseline (60 s), a rebreathing phase (150 s), and a recovery phase (150 s). In one trial, the sensations were framed in a neutral way ("the gas mixture might alter breathing behavior and induce respiratory sensations"). In the other trial, a symptom frame was induced ("the gas mixture might alter breathing behavior and induce respiratory symptoms"). Breathing behavior was continuously monitored, subjective sensations were rated every 10 s, and after each trial, participants filled out a symptom checklist. Within-subject correlations between the subjective rating and its physiological referent were calculated for the rebreathing phase and recovery phase of each trial separately. RESULTS: High symptom reporters had more (retrospective) complaints than low symptom reporters, especially in the symptom trial. Only in the symptom frame were high symptom reporters less accurate than low symptom reporters. The reduction in interoceptive accuracy (IA) in high symptom reporters was most striking in the recovery phase of the symptom frame trial. CONCLUSION: A contextual cue, such as a reference to symptoms, reduced IA in high symptom reporters and this was more so during recovery from the symptom induction.

Breathlessness rating type influences respiratory behavior during hypercapnia in the rebreathing test.

OBJECTIVE: The online rating of perceived breathlessness in a rebreathing test (RT) is a new and powerful technique to analyze the psychological and physiological process related to the mechanisms of breathlessness. The aim of the present study was to assess the influence of rating type on respiratory sensation and behavior during repeated hypercapnic exposures. METHODS: Sixty-one healthy women performed three rebreathing trials. Half of them were auditorily cued to rate breathlessness intensity every 12 s (CR, n=30), the other half was instructed to rate breathlessness each time a change in breathlessness intensity was perceived (UCR, n=31). The ventilatory response was assessed simultaneously. RESULTS: The CR group yielded an earlier threshold in tidal volume (V(T)) than the UCR group. Only in the UCR group did changes occur across rebreathing trials: the V(T) threshold decreased, the respiratory rate (RR) threshold increased, and the sensitivity of the RR increased. CONCLUSIONS: The type of breathlessness rating influences respiratory behavior in the RT. The short-interval cued rating seems to be the best option for a standardized application of this test in research on panic disorder.

Comparing task-induced psychophysiological responses between persons with stress-related complaints and healthy controls: A methodological pilot study.

AIMS: Chronic stress is an important factor for a variety of health problems, highlighting the importance of early detection of stress-related problems. This methodological pilot study investigated whether the physiological response to and recovery from a stress task can differentiate healthy participants and persons with stress-related complaints. METHODS AND RESULTS: Healthy participants (n = 20) and participants with stress-related complaints (n = 12) participated in a laboratory stress test, which included 3 stress tasks. Three physiological signals were recorded: galvanic skin response (GSR), heart rate (HR), and skin temperature (ST). From these signals, 126 features were extracted, including static (eg, mean) and dynamic (eg, recovery time) features. Unsupervised feature selection reduced the set to 26 features. A logistic regression model was developed for 6 feature sets, analysing single-parameter and multiparameter models as well as models using recovery vs response-related features. The highest classification performance (accuracy = 78%) was obtained using the response-related feature set, including all physiological signals and using GSR-related features. A worse performance was obtained using single-signal feature sets based on HR (accuracy = 66%) and ST (accuracy = 59%). Response-related features outperformed recovery-related features (accuracy = 63%). CONCLUSION: Participants with stress-related complaints may be differentiated from healthy controls by physiological responses to stress tasks. We aimed to bring attention to new exploratory methodologies; further research is needed to validate and replicate the results on larger populations and patients on different areas along the stress continuum.

Retrospective memory for symptoms in patients with medically unexplained symptoms.

OBJECTIVE: Clinical assessment and diagnostic processes heavily rely on memory-based symptom reports. The current study investigated memory for symptoms and the peak-end effect for dyspnea in patients with medically unexplained symptoms and healthy participants. METHODS: Female patients with medically unexplained dyspnea (MUD) (n=22) and matched healthy controls (n=22) participated in two dyspnea induction trials (short, long). Dyspnea ratings were collected: (1) continuously during symptom induction (concurrent with respiratory measures), (2) immediately after the experiment, and (3) after 2weeks. Symptoms, negative affect, and anxiety were assessed at baseline and after every trial. The mediating role of state anxiety in symptom reporting was assessed. The peak-end effect was tested with forced-choice questions measuring relative preference for the trials. RESULTS: Compared to controls, dyspnea induction resulted in higher levels of symptoms, anxiety, concurrent dyspnea ratings, and minute ventilation in the patient group. In both groups, immediate retrospective ratings were higher than averaged concurrent ratings. No further increase in dyspnea ratings was observed at 2-week recall. Retrospective dyspnea ratings were mediated by both state anxiety and concurrent dyspnea ratings. Patients did not show a peak-end effect, whereas controls did. CONCLUSION: The findings show that patients' experience of a dyspneic episode is subject to immediate memory bias, but does not change over a longer time period. The results also highlight the importance of affective state during symptom experience for both symptom perception and memory.

Negative Affectivity, Depression, and Resting Heart Rate Variability (HRV) as Possible Moderators of Endogenous Pain Modulation in Functional Somatic Syndromes.

Background: Several studies have shown that patients with functional somatic syndromes (FSS) have, on average, deficient endogenous pain modulation (EPM), as well as elevated levels of negative affectivity (NA) and high comorbidity with depression and reduced resting heart rate variability (HRV) compared to healthy controls (HC). The goals of this study were (1) to replicate these findings and (2) to investigate the moderating role of NA, depression, and resting HRV in EPM efficiency within a patient group with fibromyalgia and/or chronic fatigue syndrome (CFS). Resting HRV was quantified as the root mean square of successive differences between inter-beat intervals (RMSSD) in rest, a vagally mediated time domain measure of HRV. Methods: Seventy-eight patients with fibromyalgia and/or CFS and 33 HC completed a counter-irritation paradigm as a measure of EPM efficiency. Participants rated the painfulness of electrocutaneous stimuli (of individually calibrated intensity) on the ankle before (baseline phase), during (counter-irritation phase) and after (recovery phase) the application of a cold pain stimulus on the forearm. A larger reduction in pain in the counter-irritation phase compared to the baseline phase reflects a more efficient EPM. Results: In contrast to our expectations, there was no difference between pain ratings in the baseline compared to counter-irritation phase for both patients and HC. Therefore, reliable conclusions on the moderating effect of NA, depression, and RMSSD could not be made. Surprisingly, patients reported more pain in the recovery compared to the counter-irritation and baseline phase, while HC did not. This latter effect was more pronounced in patients with comorbid depression, patients who rated the painfulness of the counter-irritation stimulus as high and patients who rated the painfulness of the electrocutaneous stimuli as low. We did not manage to successfully replicate the counter-irritation effect in HC or FSS patients. Therefore, no valid conclusions on the association between RMSSD, depression, NA and EPM efficiency can be drawn from this study. Possible reasons for the lack of the counter-irritation effect are discussed.