Perceived symptoms and discomfort during induced bronchospasm: the role of temporal adaptation and anxiety

Inaccurate perception of asthma symptoms: a cognitive-affective framework and implications for asthma treatment

Inaccurate perception of respiratory symptoms is often found in asthma patients. Typically, patients who inaccurately perceive asthma symptoms are divided into underperceivers and overperceivers. In this paper we point out that this division is problematic. We argue that little evidence exists for a trait-like stability of under- and overperception and that accuracy of respiratory symptom perception is highly variable within persons and strongly influenced by contextual information. Particularly, expectancy and affective cues appear to have a powerful influence on symptom accuracy. Based on these findings and incorporating recent work on associative learning, attention and mental representations in anxiety and symptom perception, we propose a cognitive-affective model of symptom perception in asthma. The model can act as a framework to understand both normal perception as well as under- and overperception of asthma symptoms and can guide the development of affect-related interventions to improve perceptual accuracy, asthma control and quality of life in asthma patients.

Differentiation between the sensory and affective aspects of histamine-induced bronchoconstriction in asthma

Respiratory symptom perception research has focused mainly on respiratory sensations. Because dyspnea is multidimensional, affective aspects should be investigated. Patients with asthma (N=25) underwent a histamine provocation until a 20% fall in forced expiratory volume in 1s (FEV(1)). After each dose level, 6 symptoms of dyspnea intensity and 6 symptoms of dyspnea affectivity were rated. Individual perceptual sensitivity was determined by calculating the linear slope between the fall in FEV(1) and the increase in the total symptom score, and for affective and sensory symptoms separately [Bijl-Hofland, Folgering, van den Hoogen, et al. Perception of bronchoconstriction in asthma patients measured during histamine challenge test. Eur Respir J 1999;14:1049-54]. Trait anxiety, baseline state anxiety, daily asthma symptoms and catastrophizing during an asthma exacerbation were also assessed. Sensitivity was unrelated to physiological indices of disease severity (i.e., baseline FEV(1) and histamine dose level at 20% fall in FEV(1)), whereas it was positively related to trait anxiety, state anxiety, daily asthma symptoms and catastrophic thinking during an asthma exacerbation in daily life. These relationships were overall much stronger for affective than for sensory symptom slopes. In stepwise multiple regressions, state anxiety was the best predictor of the affective symptom slopes, whereas catastrophic thinking during an asthma exacerbation was the best predictor for the sensory symptom slopes. The differentiation between sensory and affective components of dyspnea adds to the understanding of respiratory symptom perception in asthma.

Dyspnea: the role of psychological processes

Breathlessness or dyspnea-the subjective experience of breathing discomfort-is a symptom in many pulmonary, cardiovascular, and neuromuscular diseases. It occurs in normals as well during intense emotional states and heavy labor or exercise. In clinical cases, it generally causes severe suffering. Dyspnea has multifactorial causes and the explanation for the symptom may differ largely among patients. Explanatory models imply the involvement of mechanisms at several levels of functioning, such as afferent signals from the respiratory muscles or blood gas levels related to hypercapnia and hypoxia. Depending on the relative involvement of specific mechanisms and their interactions, dyspnea may be experienced differently and subtypes can be distinguished. More recently, perceptual-cognitive and emotional processes related to symptom perception and interpretation have been investigated in the context of dyspnea. In this review, we focus on the psychological processes that play part in the perception of dyspnea and formulate some practical guidelines for those who are confronted with dyspnea.

Negative affectivity and the influence of suggestion on asthma symptoms

OBJECTIVE

To investigate the effect of suggestion on subjective and objective asthma symptoms as a function of negative affectivity of the patients.

METHODS

Asthmatics (n=32) took puffs from three separate placebo inhalers, being described as an inert (practice) substance, a bronchoconstrictor, and a bronchodilator. Negative affectivity, social desirability, probability of medication-intake, intensity of asthma symptoms and total respiratory resistance were measured at onset. The latter three measures were repeated after each trial. Heart rate, end tidal PCO(2), and breathing behaviour were measured during each trial.

RESULTS

Asthmatics with high negative affectivity had overall more intense asthma symptoms. They also reported more airway obstruction after suggested bronchoconstriction and less after suggested bronchodilation, whereas persons with low negative affectivity did not show such variation. These effects were unrelated to social desirability. Respiratory symptoms correlated with the odds of medication intake. Neither negative affectivity nor suggestion influenced lung function and only breathing parameters under voluntary control changed as a function of suggestion.

CONCLUSION

Self-reported symptoms of asthmatics with high negative affectivity are more influenced by suggestion than those of patients with low negative affectivity.

Cough, airway inflammation, and mild asthma exacerbation

BACKGROUND

Prospective data on the temporal relation between cough, asthma symptoms, and airway inflammation in childhood asthma is unavailable.

AIMS AND METHODS

Using several clinical (diary, quality of life), lung function (FEV(1), FEV(1) variability, airway hyperresponsiveness), cough (diary, cough receptor sensitivity (CRS)), and inflammatory markers (sputum interleukin 8, eosinophilic cationic protein (ECP), myeloperoxidase; and serum ECP) of asthma severity, we prospectively described the course of these markers in children with asthma during a non-acute, acute, and resolution phase. A total of 21 children with asthma underwent these baseline tests; 11 were retested during days 1, 3, 7, and 28 of an exacerbation.

RESULTS

Asthma exacerbations were characterised by increased asthma and cough symptoms and eosinophilic inflammation. Sputum ECP showed the largest increase and peaked later than clinical scores. Asthma scores consistently related to cough score only early in the exacerbation. Neither CRS nor cough scores related to any inflammatory marker.

CONCLUSION

In mild asthma exacerbations, eosinophilic inflammation is dominant. In asthmatic children who cough as a dominant symptom, cough heralds the onset of an exacerbation and increased eosinophilic inflammation, but cough scores and CRS do not reflect eosinophilic airway inflammation.

Neural substrates for the perception of acutely induced dyspnea

Little is currently known about the brain regions involved in central processing of dyspnea. We performed a functional imaging study with positron emission tomography (PET) to assess brain activation associated with an important component of dyspnea, respiratory discomfort during loaded breathing. We induced respiratory discomfort in eight healthy volunteers by adding external resistive loads during inspiration and expiration. Brain activation was characterized by a significant increase in regional cerebral blood flow (rCBF) (Z score of peak activation > 3.09). As compared with the unloaded control condition, high loaded breathing was associated with neural activation in three distinct brain regions, the right anterior insula, the cerebellar vermis, and the medial pons (respective Z scores = 4.75, 4.44, 4.41). For these brain regions, we further identified a positive correlation between rCBF and the perceived intensity of respiratory discomfort (respective Z scores = 4.45, 4.75, 4.74) as well as between rCBF and the mean amplitude of mouth pressure swings (DeltaPm), the index of the main generating mechanism of the sensation (respective Z scores = 4.67, 4.36, 4.31), suggesting a common activation by these two parameters. Furthermore, we identified an area in the right posterior cingulate cortex where neural activation was specifically associated with perceived intensity of respiratory discomfort that is not related to DeltaPm (Z score = 4.25). Our results suggest that respiratory discomfort related to loaded breathing may be subserved by two distinct neural networks, the first being involved in the concomitant processing of the genesis and perception of respiratory discomfort and the second in the modulation of perceived intensity of the sensation by various factors other than its main generating mechanism, which may include emotional processing.

Reviewing asthma and anxiety

The main characteristic of asthma is sudden and unexpected attacks of impaired breathing. Both the attacks themselves and the prospect of attacks generate much anxiety amongst patients. Several different forms of anxiety can be identified which vary in intensity and the situations in which they appear. Anxiety disorders are more common in asthmatics and have a considerable influence on asthma management because they influence symptom perception. Excessive anxiety about asthma symptoms can affect the patient's response to an asthma attack; anxiety related to asthma triggers can reduce the patient's quality of life and anxiety related to medical treatment can influence compliance. The extent of this influence depends upon an individual's ability to cope. Behavioural therapeutic programmes for patient education offer an opportunity to reduce anxiety and to improve asthma self-management. Physicians should look carefully for anxiety when taking the patient's history, and should support the patient's participation in asthma education programs.

Perception of dyspnea during histamine- and methacholine-induced bronchoconstriction

BACKGROUND

Perception of dyspnea is poorly related to bronchoconstriction and may be influenced by distinct psychophysiologic stimuli.

OBJECTIVE

This study compared the perceived psychophysiologic changes during histamine- and methacholine-induced bronchoconstriction using verbal as well as nonverbal assessment techniques.

METHODS

Perception of dyspnea was studied during induced bronchoconstriction in 40 atopic subjects randomly ascribed to either histamine (n = 20) or methacholine (n = 20) bronchial challenge. A 100% increase in specific airway resistance (sR(aw)) indicated airway hyperresponsiveness (AHR). Dyspnea was verbally assessed by the Borg Scale (BS) and the Asthma Symptom Checklist (ASL). A hand dynamometer (HD) served for nonverbal assessment. Both challenge groups did not differ significantly with respect to age, anthropometric data, smoking and lung function before challenge.

RESULTS

AHR did not differ between groups but groups differed significantly with respect to the number of symptoms and to symptom intensity reported after challenge. Subjects who underwent the histamine challenge scored significantly higher on both measures derived from the ASL. BS ratings and HD scores correlated significantly but were not significantly related to the degree of AHR. Accurate and poor perceivers could be discriminated by analysis of the relationship between BS and sR(aw).

CONCLUSIONS

These findings suggest that perception of induced dyspnea differs between histamine and methacholine when assessed by a symptom report.

Subjective symptomatology of asthma: validation of the asthma symptom checklist in an outpatient Spanish population

The objective of this study was to validate the Asthma Symptom Checklist (ASC) so that it could be reliably used to assess the subjective symptomatology of asthma attacks in our context. Subjective symptomatology of asthma was examined in a group of 100 adult Spanish outpatients (57 women, 43 men; 17-69 years of age) with asthma. All of them completed the modified version of the ASC as well as questionnaires of depression, anxiety, and self-management of asthma (self-efficacy expectancies and health care utilization). Data about duration and severity of asthma, as well as dyspnea and %FEV1, were also recorded. The highest reliability Cronbach alpha indexes were for the panic-fear and fatigue scales. The oblique rotation of the ASC revealed five correlated factors (53% of the total variance explained): 1) panic-fear, 2) airways obstruction, 3) airways obstruction and panic-fear, 4) fatigue and irritability, 5) hyperventilation. The structure of factors was revalidated using orthogonal (varimax) rotation. Construct validity was examined by Person product-moment coefficient correlations, ANOVAs (asthma severity x ASC scores), and t-tests (sex by ASC scores). Panic-fear showed the best construct validity, as it was related to the severity of the asthma and the use of high-cost health care resources. There were no differences in ASC scores either on the basis of the asthma severity or on the sex of patients. The ASC factors represent stable components of subjective symptomatology of asthma attacks, especially with regard to the panic-fear and the hyperventilation subscales; however, the structure of the checklist as a whole was not identical to those reported in other studies. Correlations of the ASC with clinical variables related to asthma severity support the construct validity of the instrument and confirm its utility to evaluate the subjective symptomatology of asthma attacks in outpatients.

Is there a specific relationship between asthma and panic disorder?

The objective of the present study was three-fold: (1) to assess the prevalence of PD in asthmatic patients in comparison with non-asthmatic patients; (2) to investigate possible differences in pulmonary function and anxiety symptomatology between asthmatic patients with PD and those without; and (3) to evaluate possible differences in symptom perception during histamine-induced bronchoconstriction between asthmatic patients with PD versus asthmatic controls without PD matched for age, sex and bronchial responsiveness to histamine (PC20). The study was performed on 123 consecutive patients referred to the lung function laboratory of a university hospital for a histamine challenge test. Firstly, baseline measures for FEV1, anxiety (ADIS-R, ACQ, BSQ, and STAI) and depression (SDS) were collected. Subsequently, before and during induced bronchoconstriction FEV1, perceived breathlessness (Borg scale), subjective anxiety (SUDS), and somatic panic symptoms (PAQ) were assessed. The prevalence of PD in asthmatic patients, although higher than in the general population, was very similar to the rate observed in non-asthmatic patients. Baseline level of FEV1 and bronchial responsiveness to histamine (PC20) were also not significantly different between asthmatic patients with and without PD. Moreover, in comparison with matched controls, PD cases reported significantly higher levels of perceived breathlessness during induced bronchoconstriction, although their mean fall in FEV1 was very comparable. It is concluded that the higher prevalence of PD in asthma is non-specific and probably due to selection bias.