Katleen Bogaerts

Distorted Symptom Perception in Patients With Medically Unexplained Symptoms

The present study investigated differences in symptom perception between a clinical sample with medically unexplained symptoms (MUS) and a matched healthy control group. Participants (N = 58, 29 patients) were told that they would inhale different gas mixtures that might induce symptoms. Next, they went through 2 subsequent rebreathing trials consisting of a baseline (60 s room air breathing), a rebreathing phase (150 s, which gradually increased ventilation, PCO2 in the blood, and perceived dyspnea), and a recovery phase (150 s, returning to room air breathing). Breathing behavior was continuously monitored, and dyspnea was rated every 10 s. The within-subject correlations between dyspnea on the one hand and end-tidal CO2 and minute ventilation on the other were used to index the degree to which perceived dyspnea was related to specific relevant respiratory changes. The results showed that perceived symptoms were less strongly related to relevant physiological parameters in MUS patients than in healthy persons, specifically when afferent physiological input was relatively weak. This suggests a stronger role for top-down psychological processes in the symptom perception of patients with MUS.

Negative affective pictures can elicit physical symptoms in high habitual symptom reporters

The present study aimed to explore the role of a brief negative affective state on symptom reporting. Non-clinical high (n = 24) and low (n = 24) habitual symptom reporters viewed four picture series (160 s per series) varying in affective content: neutral, general positive, general negative and symptom-related. Participants rated each picture series on valence, dominance and arousal, and reported their affective state and somatic symptoms experienced during the series. Results showed that all participants reported higher levels of negative affect during the negative and symptom-related picture series compared with the positive and neutral picture series. Only high habitual symptom reporters also reported more bodily symptoms after viewing the negative and symptom-related pictures. The findings allude to a learned association between negative emotional states and symptom reporting in high habitual symptom reporters.

Why do you sigh? Sigh rate during induced stress and relief

Whereas sighing appears to function as a physiological resetter, the psychological function of sighing is largely unknown. Sighing has been suggested to occur both during stress and negative emotions, such as panic and pain, and during positive emotions, such as relaxation and relief. In three experiments, sigh rate was investigated during short imposed states of stress and relief. Stress was induced by exposure to a loud noise stressor or by anticipation of it. Relief was induced by the end of the stressor or the anticipation that no stressor would follow. Breathing parameters were recorded continuously by means of the LifeShirt System. Results consistently showed that more sighing occurred during conditions of relief compared to conditions of stress.

Air hunger and ventilation in response to hypercapnia: effects of repetition and anxiety

We investigated the effects of anxiety on the intensity of air hunger during gradually increasing levels of CO2 until the end-tidal fractional concentration of CO2 was 7.9% or air hunger was intolerable. Normal high and low (trait) anxious participants (N=23) went through three rebreathing trials (15 min interval). Breathing behaviour was continuously monitored and air hunger was rated every 12 s. The threshold for responding to the increased CO2 was always lower for the subjective rating than for the ventilatory response. Habituation across trials was observed for both the ventilatory response and the air hunger rating regardless of anxiety. However, beyond the threshold, the slope in air hunger ratings decreased across trials in low anxious persons and tended to increase in high anxious persons (interaction P<0.05). No differences occurred in the slopes of the breathing responses. The findings documented uncoupling of the physiological and subjective responses during CO2-induced air hunger.

Repeated Breathlessness Experiences Induced by Hypercapnia: Differential Effects on Intensity and Unpleasantness

BACKGROUND The present study investigated the effect of repeated hypercapnic challenges on the sensory (intensity [I]) and affective (unpleasantness [U]) dimensions of breathlessness. METHODS Three subsequent rebreathing trials (Read, 1968) were administered to healthy men and women (n = 39). The I and U of breathlessness were rated every 20 s during the baseline, rebreathing, and recovery phases. Breathing behavior (fractional end-tidal CO(2) [Fetco(2)] and minute ventilation [Ve]) was monitored continuously. Intraindividual linear regression slopes for Fetco(2) and Ve] were calculated and standardized, separately for both rating dimensions. RESULTS Both the absolute magnitude and the slope of the I of breathlessness were higher compared to U (p < 0.05). Across-trial habituation of the peak I and U of breathlessness occurred in both genders (p < 0.001), but habituation was larger for the U than for the I (p = 0.05). CONCLUSIONS The findings show that the sensory and affective dimensions of breathlessness can meaningfully be distinguished during hypercapnic challenges and that repeated exposures have different effects on both dimensions.

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.

Inducing symptoms in high symptom reporters via emotional pictures: The interactive effects of valence and arousal

OBJECTIVE Processing unpleasant emotional cues induces elevated reporting of physical symptoms, especially in people with high habitual symptom reporting. The present study examined the role of valence and arousal of emotional pictorial cues on this effect. METHODS Female participants (N=45; 21 high/24 low habitual symptom reporters) viewed six series of emotional pictures with a homogeneous affective content: low arousal/positive, high arousal/positive, low arousal/negative, high arousal/negative-disgust, high arousal/negative-threat and neutral. Heart rate (HR) and skin conductance level (SCL) were recorded during picture viewing and a symptom checklist and valence and arousal ratings were completed after each trial. RESULTS High habitual symptom reporters reported more symptoms than low habitual symptom reporters overall, but this difference was more pronounced when processing unpleasant high arousing cues. No group differences were found on physiological measures for any of the conditions, while perceived valence and arousal both moderated the relationship between habitual symptom reporting and symptom induction. CONCLUSION These findings show an interactive effect of unpleasantness and high arousal on elevated symptom reporting in high habitual symptom reporters, suggesting that different characteristics of emotional cues contribute to a somatic memory activation process leading to the experience of elevated symptoms.

Sigh rate and respiratory variability during normal breathing and the role of negative affectivity

Spontaneous breathing was measured in healthy persons scoring either high (N=45) or low (N=30) on trait negative affectivity (NA), during a 10 min period of quiet sitting using the LifeShirt System®. Sighing and respiratory variability before and after sighs were assessed. Total respiratory variability of minute ventilation was indexed by the coefficient of variation and structured (correlated) variability was quantified by the autocorrelation. Total variability was higher before a sigh than before a non-sigh, without concomitant differences in structured variability, suggesting more random variability before a sigh. After a sigh, correlated variability increased whereas it remained the same after a non-sigh. Thus sighing acted as a resetter of the respiratory system. However, when comparing the low and the high NA group, this pattern was specific for high NA individuals. We conclude that it is important to take into account individual difference variables when studying the psychophysiological functions of sighing.

Original ResearchDyspneaRepeated Breathlessness Experiences Induced by Hypercapnia: Differential Effects on Intensity and Unpleasantness

BACKGROUND The present study investigated the effect of repeated hypercapnic challenges on the sensory (intensity [I]) and affective (unpleasantness [U]) dimensions of breathlessness. METHODS Three subsequent rebreathing trials (Read, 1968) were administered to healthy men and women (n = 39). The I and U of breathlessness were rated every 20 s during the baseline, rebreathing, and recovery phases. Breathing behavior (fractional end-tidal CO(2) [Fetco(2)] and minute ventilation [Ve]) was monitored continuously. Intraindividual linear regression slopes for Fetco(2) and Ve] were calculated and standardized, separately for both rating dimensions. RESULTS Both the absolute magnitude and the slope of the I of breathlessness were higher compared to U (p < 0.05). Across-trial habituation of the peak I and U of breathlessness occurred in both genders (p < 0.001), but habituation was larger for the U than for the I (p = 0.05). CONCLUSIONS The findings show that the sensory and affective dimensions of breathlessness can meaningfully be distinguished during hypercapnic challenges and that repeated exposures have different effects on both dimensions.

Sensitization in Medically Unexplained Dyspnea: Differential Effects on Intensity and Unpleasantness

BACKGROUND The present study investigated alterations in both the sensory (intensity) and the affective (unpleasantness) components of dyspnea in patients with medically unexplained dyspnea during repeated hypercapnic challenges. METHODS The sensory and affective components were assessed every 20 s during the baseline, rebreathing, and recovery phases of three subsequent trials in patients (n = 17) and matched healthy control subjects (n = 5). Fractional end-tidal carbon dioxide was monitored simultaneously and continuously. Peak intensity and unpleasantness were compared, and intraindividual linear regression slopes between the dyspnea components and fractional end-tidal carbon dioxide were calculated. RESULTS Both intensity and unpleasantness of dyspnea perception were higher in patients than in healthy control subjects. Additionally, the regression slopes were steeper, but this was more prominent for the affective than for the sensory component in patients. Moreover, across-trial increases in unpleasantness of peak dyspnea and slopes of both components were observed in patients. CONCLUSIONS Patients with medically unexplained dyspnea are particularly hypersensitive to the unpleasantness of dyspnea. The elevated breathlessness further increases across repeated challenges, documenting sensitization and suggesting that basic learning mechanisms contribute to exaggerated response to respiratory challenges.