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Biomedical subjects

B Dahme

Publications and source records attributed to B Dahme.

At least 19 recordsLinked to original sources
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↗
PubMed1991

[Do asthmatic patients have deficits in symptom perception? Quasi-experimental and experimental findings on introception of airway obstruction].

Symptom perception of asthmatic patients was investigated in a quasi-experimental and in two experimental studies. Simultaneous ratings and measurements of airways obstruction assessed during an inhalative provocation test were correlated in the first study, in the two latter studies psychophysical parameters of the perception of external flow-resistive loads were determined for asthmatic patients and normal controls. These are the main results: 1. Most of the asthmatic patients are rather poor in discriminating provoked airways obstructions which results in a negative coping with the illness. 2. Asthmatic patients are slightly poorer in discriminating flow-resistive loads than healthy controls. 3. A distinct tendency of asthmatic patients to dissimulation found in the first study could not be confirmed in the two experiments.

Adult↗
PubMed1990

[Central nervous system risk factors in heart surgery].

Serious complications involving the central nervous system in the course of cardiac surgical procedures have become rare. Nevertheless, CNS dysfunctions still are observed in a considerable number of patients, exceeding by far the number of those at risk from preoperative neurological hazards. The influence of extracorporeal circulation performance and hypothermia on the physiology of cerebral autoregulation, as well as microembolization events seem to be crucial factors in this context. The resulting regional or global posthypoxic changes in brain metabolism may lead to the manifestation of various neurologic and psychiatric disorders in the postoperative course. These often minor disturbances of CNS function can only be detected regularly and diagnosed correctly in a prospective way by consulting specialists in neurology, psychiatry and psychology, as performed at the Department of Thoracic- and Cardiovascular Surgery of the University Hospital in Hamburg since 1974, and currently in use an international multicenter study. We found postoperative neurological abnormalities in more than 50% of our patients. While irreversible brain damage occurred in only 0.5% of cases, about twothird exhibited transient symptoms that were no longer apparent after 8-10 days postoperatively. Obvious psychopathological symptoms were noted in 10% of cases after surgery, and minor, likewise transient, psychiatric disturbances were seen in up to 50% of patients; 20% suffered from long-lasting psychic problems. The subjective complaints in these cases exceeded the results of objective assessments to a remarkable amount. The discussion focuses on a critical valuation of clinical and supplementary examination techniques and on the potential pathophysiologic mechanisms induced by extracorporal circulation.

Brain Damage, Chronic↗
PubMed1990

[Psychophysiologic microperspective in the psychotherapy process--a sequential approach of investigation].

To Investigate the interpersonal psychophysiology in the psychotherapeutic process a sequential approach using single case analysis is presented. During 18 psychoanalytic-psychosomatic initial interviews simultaneous recordings of heart periods (IBI) and arrhythmia scores (from ecg) and the psychotherapeutic dialogue were made from 10 patients with cardiac neurosis and their interviewers. The general finding is that therapists were able to forecast those segments better, in which their own physiological activity was involved than the segments of their patients. Consideration is given to the consequences which should be drawn from these results for psychophysiological psychotherapy research.

Adult↗
PubMed1990

[Diagnosis and prevalence of latent hepatic encephalopathy].

To compare the efficacy of various psychometric and neurophysiological tests in the detection of latent hepatic encephalopathy (LHE) cerebral functions were studied in 146 patients with liver cirrhosis but without overt encephalopathy and in 146 matched controls. Patients with liver cirrhosis scored significantly worse than controls in 8 out of 11 tests. Best discrimination between patients with cirrhosis and controls was obtained by testing for reaction time to white and colored light with a reaction time apparatus (DTG), and with the digit symbol (UT1) and block design test (UT4), i.e. with two Wechsler adult intelligence scale performance tests. Thirtyseven out of 146 (25%) patients with cirrhosis reveiled an abnormal result with the DTG alone. A combination of the DTG, UT1 and UT4 yielded the diagnosis in 44 (30%) patients. LHE correlated with the severity of the disease (Child-Pugh classification) but not with its etiology or with portasystemic shunting. In the Federal Republic of Germany about 300,000 subjects suffer from liver cirrhosis. Based on our results 100,000 of them may have LHE.

Adult↗
PubMed1985

[The Hamburg Rating Scale for psychiatric disorders following heart operations (HRPD)].

A brief psychiatric inventory has been developed from the AMP/AMDP system for the assessment and classification of psychic disturbances after open heart surgery in a random sample of 99 patients operated upon. By means of item analysis in accordance with classic test theory, a list of 36 symptoms (items) was selected. Factor analysis of this brief inventory resulted in eight factors: disorientation, impaired concentration and thinking, paranoid-hallucinatory symptoms, anxiety, sullen inadequacy (restraint depression), hostility, loss of control, giving up. By cluster analysis the sample was divided into six subgroups: "unnoticeable", "rather unnoticeable", "slight psycho-organic symptoms with affective-emotional disturbances", "severe psycho-organic symptoms with loss of control", "hostility with paranoid and hallucinatory and psycho-organic symptoms", "delirious symptoms". Some results agree well with the descriptions of syndromes given by other AMP/AMDP reports. Other divergent results probably reflect the particular situation of the patients after open heart surgery.

Adult↗