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Biomedical subjects

B Dahme

Publications and source records attributed to B Dahme.

At least 19 recordsLinked to original sources
PubMed2001

Experimentally induced emotions, facial muscle activity, and respiratory resistance in asthmatic and non-asthmatic individuals.

We studied the effects of emotion induction on total respiratory resistance, and their relationship with cardiac vagal activity and facial muscle activity in asthma. Groups of 20 asthmatic and 20 non-asthmatic participants were exposed to series of happy and depressing pictures or self-referent Velten statements. Facial electromyographic activity over corrugator supercilii, orbicularis oculi, and zygomaticus major regions was recorded during periods of presentation and imagery of each stimulus. Following each stimulus series, mood, respiratory resistance, ventilation, and cardiac activity including respiratory sinus arrhythmia (RSA) were recorded. Significant increases of respiratory resistance were observed in asthmatic patients following depressing stimulation. Resistance increases were positively correlated with RSA and heart period. No substantial group differences were found in facial response to emotional stimuli. Changes in facial target muscle sites during positive stimulation were inversely correlated with RSA following stimulation. We conclude that respiratory resistance increases in asthmatics following depressing stimulation are dependent on vagal activity. Greater facial muscle activation during emotional stimulation can reduce vagal activation, which is consistent with claims in the clinical literature of the benefits of emotional expression in asthma.

Adult↗
PubMed2001

Modulation of respiratory sinus arrhythmia by respiration rate and volume: stability across posture and volume variations.

We tested the assumption that the slope of the within-individual regression equation of respiratory sinus arrhythmia (RSA) normalized by tidal volume (V(T)) upon respiratory cycle length (T(TOT)) can characterize ventilatory RSA modulation independent of cardiac vagal tone, whereas the intercept is varying as a function of vagal tone. We also explored whether a variation of V(T) is necessary to estimate slopes reliably. Four 3-min sequences paced at 8-18 cycles/min were performed supine and standing. Participants also breathed the same sequences in supine posture with voluntarily varying V(T). The mean slope of RSA/V(T) upon T(TOT) was identical, and the mean intercept was lower for standing than supine (spontaneous V(T)) conditions. Stability of slopes was low between body postures, and was higher between spontaneous V(T) versus varying V(T) at the same body posture. The regression of RSA/V(T) upon T(TOT) allows for a valid estimation of ventilatory influences on RSA.

Adult↗
PubMed2000

Increases in total respiratory resistance during forehead temperature stimulation.

We investigated the effects of forehead temperature stimulation on total respiratory resistance in healthy individuals. In two experiments involving a total of 38 participants we studied the time course and stability of the response at moderate temperature (20-23 degrees C). Small plastic bags filled with water were positioned on the forehead for a duration of 60 s. Oscillatory resistance (R(os)), heart period (HP), respiratory sinus arrhythmia (RSA), and ventilatory parameters were measured continuously. Experiment 1 showed similar phasic increases in R(os) during the first 20 s of stimulation with moderate (20-23 degrees C) as compared to cold (8-11 degrees C) temperature. Phasic increases by moderate temperature were replicated in Experiment 2 over five successive stimulation trials. Within-session stability of individual differences in response was only modest. Ventilatory adjustments did not facilitate the phasic R(os) increases. As increases were mainly due to the inspiratory component of R(os), a substantial contribution of upper airway artifacts was less likely. Increases in HP were the most pronounced responses to all stimulation conditions, while RSA did not increase significantly.

Adult↗
PubMed2000

Respiratory resistance during emotional stimulation: evidence for a nonspecific effect of experienced arousal?

We investigated the effects of phasic emotional stimuli on total respiratory resistance (TRR) in 16 nonasthmatic students. Six series of happy, neutral, and depressing affective pictures and self-referent Velten statements were presented. Each stimulus was presented for 12 s and subsequently imagined for 12 s. TRR was measured by forced oscillations throughout the stimulus series, together with ventilation, cardiac activity (including respiratory sinus arrhythmia), and facial EMGs (corrugator supercilii, orbicularis oculi, and masseter). In addition, self-reports of mood, pleasure and arousal were obtained. TRR was increased during happy and depressing stimuli compared to neutral stimuli, with stronger effects for the inspiratory component of TRR. Ventilatory parameters did not explain the changes observed in TRR. Discrimination of affective categories by facial EMG was weak. Although EMG masseter activity did not account for this result, an influence of the respiration measurement procedure on facial EMG cannot be ruled out. The TRR results are in accordance with clinical reports of asthmatic symptom aggravation due to positive or negative emotional arousal.

Adult↗
PubMed1999

Body image in eating disorders and analysis of its relevance: a preliminary study.

The purpose of the present study was to assess body perception in eating disorders and its meaning in therapy. A total of 44 patients, 25 bulimia nervosa and 19 anorexia nervosa, admitted at a specialized in-patient treatment center participated in the present study. Body size estimation procedures (video-distortion and image-marking techniques) and self-report questionnaires were used for the assessment. No significant differences were found in actual body size estimation between the two eating disorder groups, either before or after therapy. It emerged after therapy that the outcome was not related to body size estimation. These findings suggest that there is no evidence for a serious impairment of body perception (size estimation) in eating-disordered patients, but rather for a disturbance in the emotional aspect of body image, as expressed in negative body attitudes. Body size perception does not appear to be a predictor of treatment outcome in eating disorders.

Adolescent↗
PubMed1999

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.

Adult↗
PubMed1998

Stability of total respiratory resistance under multiple baseline conditions, isometric arm exercise and voluntary deep breathing.

Little is known about total respiratory resistance (TRR) as a psychophysiological parameter in normal subjects. Therefore, we investigated TRR in 45 healthy students under multiple baseline conditions, isometric arm muscle tension and voluntary deep breathing (VDB). TRR was measured by the forced oscillation technique. In addition, heart rate (HR) as well as volume and time components of the respiratory cycle, respiratory timing and respiratory drive were monitored. Subjects repeated the protocol 14 days later. Coefficients of stability and dependability were calculated for 20 s measurement epochs within and between both sessions. Increases of HR and shortening of time components of the respiratory cycle were found during muscle tension, prolongation of time components and increases in volume were found for deep breathing. During both experimental tasks TRR increased significantly. Short-term as well as long-term stability of absolute TRR scores proved to be comparable or even better than reliability of other physiological parameters, however, difference scores from baseline revealed only low coefficients.

Adult↗
PubMed1998

Effects of static forehead and forearm muscle tension on total respiratory resistance in healthy and asthmatic participants.

The impact of static muscle tension on total respiratory resistance (TRR) was examined. Participants (24 healthy, 24 asthmatic) performed biofeedback-assisted sequences of tensing (15 s) and relaxing (20 s) forehead and forearm muscles. Muscle tension levels were 40% or 80% of the maximum individual force. Oscillatory TRR, electromyograms, ventilation, heart period, and respiratory sinus arrhythmia were recorded. Baseline TRR did not change over the session as a whole. Decreases in TRR during forehead tension in both groups were accompanied by increases in end-expiratory volume, which could have mediated TRR changes. During forearm tension, decreases in TRR with minimal ventilation changes were only observed in healthy participants, whereas asthmatic patients revealed marked increases in respiratory volume and flow. These results indicate that static muscle activity and TRR are negatively related. Ventilatory changes can exaggerate or diminish evidence for this relationship.

Adult↗
PubMed1996

'Interoception' of heart rate, blood pressure, and myocardial metabolism during ergometric work load in healthy young subjects.

In a laboratory experiment intensities of 25, 50, and 75% of the individual range of a cardiovascular parameter (heart rate, blood pressure, and Robinson-index as an index of myocardial metabolism) were demonstrated during bicycle ergometer testing with healthy young subjects. In a subsequent phase they had to reproduce the same value of the parameter in question by regulating the physical work load of the ergometer. Reproduction accuracy was taken as an interoceptive index. We concluded from our data that subjects reproduced heart rate with high internal consistency but with a systematic bias. There is no linear consistency in blood pressure reproduction, and a moderate one in the reproduction of the index of myocardial metabolism. The physiological processes, upon which the interoception and reproduction is based, remain a question of further research.

Adult↗
PubMed1996

Interoception of respiratory resistance in asthmatic patients.

The interoception of respiratory obstruction was investigated in three different experimental or quasi-experimental studies. In two experiments of the first study, the psychophysics of the perception of externally added flow resistive loads were examined by using a signal detection approach. Asthmatic patients displayed a decreased sensitivity in the discrimination of such loads. The second study assessed the individual consistency of dyspnea ratings at different levels of bronchoconstriction provoked by allergic agents. A great variation in subjects' ability to discriminate consistently between various levels of airway resistance was observed. This ability was found to be relevant for coping with asthma. In the third study the visceral perception hypothesis of J. Brener was examined. This theory states that biofeedback training of voluntary control of respiratory resistance is accompanied by an improvement in perception of airway obstruction. No specific effect on load perception resulted from this training. The results of these three studies are of specific relevance to symptom perception in asthmatic patients. Further experimental studies should be directed towards the interoception of real bronchoconstriction instead of the perception of added loads which only partially models the clinical situation.

Adult↗
PubMed1996

Biofeedback-induced voluntary reduction of respiratory resistance in severe bronchial asthma.

Attempts to reduce asthmatic symptoms with respiratory resistance (Ros) biofeedback yielded heterogeneous results. The nature of treatment effects remained unclear (e.g. unspecific relaxation, visceral learning); little is known about clinical long-term effects. The present study investigated the suitability of a statistical single-case approach for an adequate evaluation. A female asthmatic underwent 12 Ros biofeedback sessions. Several breathing parameters were recorded during all sessions and pre/post investigations. The clinical course was observed with symptom diaries for 100 days. The subject achieved considerable voluntary control over her Ros, this control was based upon the expiratory flow. In general, the effects on the clinical course were weak; however, asthmatic attacks decreased in the follow-up period. Careful analyses of physiological, psychophysiological, and course variables allowed the identification of the main processes underlying the biofeedback effects. Further studies should investigate the worth of the expiratory flow as feedback variable.

Aged↗
PubMed1994

[Subjective stress factors and dyspnea in asthma patients over time].

The share of psychological factors involved in the disease pattern of asthma bronchiale is considered to be about one to two thirds, according to the literature. It is only rarely that a distinction is made between causative psychogenetic factors and such factors that exercise an influence on the course of the pattern of symptoms. The aim of the present study was to cover prospectively the possible--including the psychological--parameters influencing the pattern of symptoms of asthma in relation to time. To this end a symptom diary was kept for 35 asthma patients for an average time of 8 weeks. The entries were made daily. The points noted and counted were the concurrent occurrence of dyspnoea and various subjective influencing factors such as everyday stress, weather, etc. or their coincidence with a time lag of one day. There were surprisingly few links between dyspnoea and mental stress/stressors in relation to time. On the other hand, there was a high coincidence in relation to impairment of the quality of life and to a lesser extent also in relation to subjectively experienced weather and local conditions. The results show that stress factors--contrary to the aetiological beliefs held by laymen--are not represented by a simple relationship between psyche and asthma as time-concurrent or time-lagging coincidences to shortness of breath. However, clarification of complex socio-psychosomatic linkups in the psychogenesis of asthma bronchiale were not the subject of this study.

Adaptation, Psychological↗
PubMed1994

[Assessment of current cardiovascular stress in healthy, young people].

Forty-three young healthy subjects' estimates of their own heart rate, systolic blood pressure, and myocardial oxygen consumption at various intensities of physical work load were investigated. Their estimates were assessed using an ipsative scale, while the physiological parameters were measured continuously and simultaneously. Subjects tended to underestimate their heart rate at every intensity level, men misinterpreting less than women. Blood pressure was underestimated only at moderate physical work loads; with increasing work load blood pressure was overestimated. Estimates of myocardial oxygen consumption were the least biased. This result indicates that parameters other than the heart rate influence cardiac interoception. It seems that estimation of cardiovascular parameters influences the self regulation of physical activities.

Adult↗
PubMed1993

Clinical evaluation of a respiratory resistance biofeedback training.

This study evaluated the effectiveness of a respiratory resistance biofeedback training. Fifteen adult asthmatic subjects participated in a feedback training program including twelve feedback sessions (three sessions weekly). Respiratory resistance (Ros) was measured using the forced oscillation method; to prevent subjects from lung hyperinflation, feedback was interrupted when functional residual capacity increased. One-second forced expiratory volume (FEV1), usage of self-administered medication, degree of asthmatic dyspnoea, and general activity were daily recorded in symptom diaries for at least three months, starting four weeks before the first feedback session. Seven subjects showed significant average Ros decreases within the sessions, while mean Ros in two subjects was increased. However, these direct feedback effects were not related to transfer effects outside the laboratory: e.g., not one of the seven successful subjects showed FEV1 improvements, and only in one of them were within-session Ros reductions accompanied by a decreased frequency of self-administered medication during the training period. These results lead to the conclusion that Ros feedback may not be an effective technique for the treatment of bronchial asthma in adults.

Adult↗
PubMed1993

An algorithm establishing a defined ergometric cardiovascular load.

A computer-aided procedure is presented to regulate the workload on an ergometric bicycle to an individually fixed level of heart rate as the criterion, applying an integral controller algorithm. The workload is incremented in a few variable steps asymptotically to the target heart rate. A free parameter of the algorithm has been fixed empirically. In the empirical evaluation of the quality of this procedure, a strictly linear relationship of individual Watt increment and rise in heart rate was found in 27 subjects, with a median correlation of 0.95. The procedure is recommended for specific ergometric workload regulation in which an upper limit of rise in heart rate should not be surpassed, e.g. in cardiac rehabilitation. The procedure can also be generalized to comparable regulation tasks, e.g. in the management of blood pressure to avoid an hypertensive crisis.

Adult↗
PubMed1992

[Comparison of two different methods for measuring interoception of obstructions in asthma patients].

For measuring the interoception of airway resistance, bronchial obstructions are often simulated by flow-resistive loads applied externally (i.e. outside the body) into the respiratory flow. However, it is open to doubt whether interoception characteristics obtained in this manner are really related to the clinical pattern of complaints of asthmatic patients. Possibly such externally applied resistance simulates merely an aspect of the physics of apnoea but not a clinical and hence also psychological aspect of the same. To estimate the significance of these aspects for the perception of obstructions, this ability was measured in 25 asthmatic patients first by means of external added loads; this test was then repeated by noting the subjective assessment of bronchial obstructions caused during a routine histamine provocation test. Both interoception parameters correlated only slightly (rxy = 0.31) which is discussed as a pointer to the assumption that, among other parameters, psychological factors may considerably modify the perception of flow resistivity. No correlations were seen between the characteristic interoception value obtained by means of mesh resistivities and the different variables of the clinical pattern of symptoms. On the other hand, the interoception parameter measured on the basis of bronchial obstructions revealed significant connections with several clinical variables: the greatly increased incidence of respiratory distress at night or during certain external conditions, coping medication, physical exercise and style. It is concluded that only such parameters of perception of obstructions are clinically relevant for patients suffering from asthma, which consider not only the somaticophysical but also the psychic component of asthmatic respiratory distress.

Adolescent↗
PubMed1991

A device for functional residual capacity controlled biofeedback of respiratory resistance.

A computer-aided procedure is presented providing subjects with analogous visual feedback of respiratory resistance, which is continuously measured using the forced oscillation method. Simultaneous pneumotachographical control of the breathing volume curve makes it possible to prevent reinforcement for decreases of respiratory resistance which are due to increases of functional residual capacity (FRC). Lung hyperinflation is an unsuitable way to reduce respiratory resistance; if it occurs, feedback is interrupted until the subject decreases his FRC to its initial level. Analysis of the data of 15 adult asthmatic subjects which underwent a 12-sessions feedback training showed that no substantial changes of FRC appeared within feedback trials. Advantages of this new biofeedback technique compared to other procedures are discussed with regard to volume control and feedback signal.

Airway Resistance↗