Simon Rietveld

Contribution of tonic vagal modulation of heart rate, central respiratory drive, respiratory depth, and respiratory frequency to respiratory sinus arrhythmia during mental stress and physical exercise

This study tested various sources of changes in respiratory sinus arrhythmia (RSA). Twenty-two healthy participants participated in three experimental conditions (mental stress, relaxation, and mild physical exercise) that each consisted of three breathing parts (normal breathing, breathing compressed room air, and breathing compressed 5% CO2-enriched air). Independent contributions to changes in RSA were found for changes in tonic vagal modulation of heart rate, central respiratory drive (i.e., PaCO2), respiratory depth, and respiratory frequency. The relative contributions to changes in RSA differed for mental stress and physical exercise. It is concluded that uncorrected RSA will suffice to index within-subject changes in tonic vagal modulation of heart rate in most situations. However, if the central respiratory drive is expected to change, RSA should ideally be corrected for changes in PaCO2, respiratory depth, and respiratory frequency.

Stress-induced breathlessness in asthma

BACKGROUND A majority of patients with asthma believe that psychological factors (particularly stress) can induce asthma attacks, but empirical support for actual stress-induced airways obstruction is controversial. This study tested the hypothesis that stress induces breathlessness and not airways obstruction. METHODS Stress was induced by a frustrating computer task in 30 adolescents with asthma and 20 normal controls, aged 14-19 years. Stress measures were self-reported emotions, heart rate, blood pressure. Respiratory measures were respiratory rate (RR), end tidal CO2, deep inspirations and sighs. Asthma measures were lung function, wheeze, cough, breathlessness. RESULTS All measures confirmed high levels of negative emotions and stress. None of the participants developed airways obstruction; they had no reduction in lung function, wheeze was absent and cough negligible. However, breathlessness increased in all participants with asthma and excessively in many. The mean breathlessness was higher than during induction of actual airways obstruction with provocative agents in previous studies. End tidal CO2 showed that breathlessness could not be explained by hypocapnia. CONCLUSION Stress can be sufficient to induce breathlessness in patients with asthma.

Negative thoughts in adults with congenital heart disease.

BACKGROUND Many patients with congenital heart disease have persistent cardiac defects, psychosocial adjustment problems, and a poor quality of life. This study tested the relationship between negative thoughts and adaptation to congenital heart disease. METHODS Eighty-two adult out-Patients with congenital heart disease were divided on the basis of few, moderate or many negative thoughts. Group differences were tested in medical and psychosocial adjustment variables (including negative emotions), and quality of life. RESULTS Patients with many negative thoughts scored worse on psychosocial adjustment and quality of life, irrespective of severity of cardiac deviation, according to the cardiologist, New York Heart Association classification, number of passed and expected surgery, or use of medication. CONCLUSION Negative affect in general, rather than negative thoughts is decisive in psychosocial adjustment and quality of life. Psychological intervention would be helpful for many patients.

Symptom Perception in Asthma: A Multidisciplinary Review

Clinical observations and research show that symptom perception in asthma is, at worst, inaccurate or often biased in two directions: (1) blunted perception, (2) overperception (both involving airway obstruction manifested in low or high breathlessness). Theoretically breathlessness occurs during respiratory labor or blood gas changes. However, pathophysiological factors and asthma severity are inconsistently related to perceptual accuracy. Consequently, symptom perception within the biomedical perspective is not well understood. Possible psychological influences, varying from the stimulus level to emotions and high-order reasoning, are discussed.

Classification of asthmatic breath sounds: preliminary results of the classifying capacity of human examiners versus artificial neural networks

For continuous monitoring of the respiratory condition of patients, e.g., at the intensive care unit, computer assistance is required. Existing mechanical devices, such as the peak expiratory flow meter, provide only with incidental measurements. Moreover, such methods require cooperation of the patient, which at, e.g., the ICU is usually not possible. The evaluation of complicated phenomena such as asthmatic respiratory sounds may be accomplished by use of artificial neural networks. To investigate the merit of artificial neural networks, the capacities of neural networks and human examiners to classify breath sounds were compared in this study. Breath sounds were in vivo recorded from 50 school-age children with asthma and from 10 controls. Sound intervals with a duration of 20 seconds were randomly sampled from asthmatics during exacerbation, asthmatics in remission, and controls. The samples were digitized and related to peak expiratory flow. From each interval, two full breath cycles were selected. Of each selected breath cycle, a Fourier power spectrum was calculated. The so-obtained set of spectral vectors was classified by means of artificial neural networks. Humans evaluated graphic displays of the spectra. Human examiners could not clearly discriminate between the three groups by inspecting the spectrograms. Classification by self-classifying neural networks confirmed the existence of at least three classes; however, discrimination of 11 classes seemed more appropriate. Good results were obtained with supervised networks: as much as 95% of the training vectors could be classified correctly, and 43% of the test vectors. The three patient groups, as discriminated in advance, do not correspond with three sharply separated sets of spectrograms. More than three classes seem to be present. Humans cannot take up the spectral complexity and showed negative classification results. Artificial neural networks, however, are able to handle classification tasks and show positive results.

Psychiatric factors in asthma: Implications for diagnosis and therapy

Emotional factors are an obstacle in the diagnosis and management of asthma. This review discusses three problem patterns: negative emotions in relatively normal patients with asthma; patients presenting possible functional symptoms and; patients presenting asthma in conjunction with psychiatric deviations. Negative emotions influence the symptoms and management of asthma, even in relatively normal patients. Psychogenic symptoms appear normal, but culminate in functional symptoms in a minority of patients. Diagnosing and treating asthma in patients with comorbid asthma and psychiatric symptoms is very difficult. On the one hand, treating asthma may often be just treating the emotions. On the other hand, negative emotions make the treatment of asthma guesswork.Physicians should estimate emotional influences in their patients’ symptoms for an optimal evaluation of medication efficacy. Assessment and analysis of emotional factors surrounding exacerbations seems essential, e.g. emotional precipitants of asthma and asthma-evoked negative emotions. Moreover, patients should be informed about stress-induced breathlessness and the consequences of overuse of bronchodilators. When patients present with atypical symptoms, or do not properly respond to asthma medication, functional symptoms should be suspected. Psychiatric analysis may often lead to the conclusion that symptoms have a functional basis. In patients with comorbid asthma and anxiety disorders, asthma should be the focus for treatment since difficult-to-control asthma often causes anxiety problems in the first place. Moreover, panic-like symptoms in asthma are often related to sudden onset asthma exacerbations. However, in patients with comorbid asthma and depression, depression should become the focus of treatment. The reason is that optimal treatment of depressive asthmatics is probably impossible. Special issues include specific problems with children, compliance problems, and physicians’ dilemmas regarding the simultaneous treatment of asthma and psychiatric symptoms.

The influence of respiratory sounds on breathlessness in children with asthma: a symptom-perception approach.

The discordance between the objective and subjective symptoms of asthma has major effects on proper medication and management. In 2 studies the influence of respiratory sounds in the process of symptom perception underlying breathlessness was investigated in children aged 7-17 years. In Experiment 1, asthmatic wheezing sounds were recorded in 16 children during histamine-induced airway obstruction. Breathlessness correlated significantly with rank order of amount of wheezing, but not with lung function. In Experiment 2, after standardized physical exercise, 45 asthmatic and 45 nonasthmatic children were randomly assigned to (a) false feedback of wheezing, (b) quiet respiratory sounds, or (c) no sound. Asthmatic children reported significantly more breathlessness in the 1st versus the 3rd condition. In conclusion, many asthmatic children were easily influenced by wheezing in their estimation of asthma severity, reflected in breathlessness.

Exaggerated perception of normal physiological responses to stress and hypercapnia in young women with numerous functional somatic symptoms

OBJECTIVE This study tested whether functional somatic symptoms are associated with exaggerated increases in self-reported anxiety and somatic complaints in response to stress and CO(2)-enriched air breathing, and whether this association exists in parallel to or in the absence of exaggerated physiological responses. METHODS Out of 499 young somatically healthy undergraduate women, 18 participants high in functional somatic symptoms (HSS group) and 18 participants low in symptoms (LSS) were selected. They were submitted to mental stress, mild physical exercise and relaxation during conditions of normal breathing, breathing compressed normal air, and breathing compressed 5% CO(2)-enriched air. In all conditions, self-reported anxiety and somatic symptoms and respiratory and autonomic responses were assessed. RESULTS HSS participants reported, as compared to LSS, more tenseness, anxiety, and somatic symptoms at baseline and increased responses to mental stress and during 5% CO(2) breathing, but not in response to exercise. However, no evidence was found for a corresponding exaggerated respiratory or autonomic response. CONCLUSIONS A young, female, and nonclinical population with numerous functional somatic symptoms and high levels of anxiety is characterized by an exaggerated perception of a normal physiological response.

The impact of severe asthma on schoolchildren

Episodic airway obstruction and hypoxia are potentially life-threatening to children with asthma and may account for neuropsychological impairment. Moreover, living with this chronic disease may severely disrupt childrens emotional functioning. The general functioning of 25 children with severe asthma aged 10-13 years was tested by a comparison with 25 matched normal controls. Testing included variables with relevance to normal daily functioning: memory, concentration, school performance, physical condition, subjective symptoms after exercise, and negative emotions. The results showed that children with asthma did not significantly deviate from controls. They reported more dyspnea after physical exercise, which could not be attributed to lung function. Differences in school performance were not significant. It was concluded that children may generally adapt well to living with asthma.

Excessive breathlessness through emotional imagery in asthma.

Breathlessness and negative emotions during asthma attacks interact in complex patterns. This study tested the influence of emotional imagery on breathlessness during voluntary breath holding. Adolescents with and without asthma (n = 36 + 36) were assigned to positive imagery, negative imagery, or no imagery. There were four trials with close to thresholds for breath holding combined with imagery. Breathlessness and quality of imagery were measured by the end of breath holding. Additional measures were lung function and anxiety. The results showed that positive and negative imagery were only influencing breathlessness in participants with asthma. Although threshold duration for the groups were not significantly different, participants with asthma reported more breathlessness. The intensity of imagery enhanced breathlessness but diminished the accuracy of symptom perception. Positive imagery diminished breathlessness in participants with asthma, but also the difference in breathlessness between 75% and 95% of threshold duration. Breathlessness did not correlate with lung function, anxiety or other variables. It was concluded that emotional imagery during asthma attacks distracts from accurate introspection or enhances breathlessness, irrespective of anxiety.