Heart rate variability biofeedback therapy and graded exercise training in management of chronic fatigue syndrome: An exploratory pilot study
Introduction
Chronic fatigue syndrome (CFS) is characterised by intense, disabling fatigue persisting more than six months that is not explained by on-going exertion or organic disease and that cannot be alleviated within a normal period by rest or distraction [1], [2]. In addition, several physical or somatic symptoms, such as muscular pain, dizziness, headache, sleep disorder, inability to relax and/or irritability have to exist [3]. The prevalence of CFS varies widely depending on disease definition, but it is assumed that the syndrome could affect 1% of the adult population [1], and is more often seen in women and in adults [4], [5], [6]. Furthermore, there is an increased risk of completed suicide in patients with CFS [7]. Until now, no distinct agents either exclusively physiological or exclusively psychopathological have been identified [8]. Most promising theoretical concepts assume that the experience of fatigue and chronic physical symptoms combined with loss of functioning is influenced by multiple biological, affective, behavioural, cognitive, and social factors [6], [8], [9]. Wyller et al. [10] proposed a model of sustained arousal in patients with CFS based on the cognitive activation theory of stress (CATS) by Ursin and Eriksen [11]. This model takes into account predisposing (e.g. genetic traits such as polymorphisms in the autonomic and endocrine systems and personality traits such as inappropriate illness perceptions), precipitating (e.g. long-lasting infections, critical life events, and perceived chronic difficulties), perpetuating, and associated factors (e.g. hemodynamic, immune, endocrine, muscle, and cognitive alterations) [10]. The authors suggest that patients with CFS experience homeostatic instability as a result of precipitating factors, followed by vicious cycles of reinforced arousal response and dysfunctional cognitive beliefs that elicit a state of sustained arousal [10]. Similarly, Hyland [12] developed an extended network learning error theory of CFS to combine the psychological and immunological perspectives as well as that concerning the hypothalamic-pituitary-adrenal axis. He proposed that those three mechanisms interact and should be treated as complementary rather than as competing explanations within a network system. Knoop et al. [13] focused on the cognitive components. The authors described three different cognitive processes that may play a role in the maintenance of CFS: a general cognitive representation averse to fatigue, a process of focusing on fatigue, and specific dysfunctional beliefs about fatigue and activity.
Therapeutic approaches in patients with CFS are very limited. Three Cochrane reviews published thus far have summarised the evidence and suggested that cognitive behavioural therapy (CBT) and graded exercise training (GET) are effective therapies for patients with CFS [14], [15], [16]. The meta-analysis of Castell et al. [17] shows positive effect sizes for both CBT and GET and replicates the findings of previous reviews [18], [19], but the research did not manage to find any significant difference between the two intervention types [17]. However, CBT seemed to emphasise the role of emotional aspects as perpetuating factors of fatigue and resulted in a greater reduction in depression and in anxiety [17]. In another randomised controlled trial that included 641 patients, White et al. [20] found CBT, GET, and adaptive pacing therapy (APT) in combination with specified medical care (SMC) to be more effective compared to SMC alone as a non-specific control condition. The long-term follow-up from this trial shows that the beneficial effects of CBT and GET were maintained for a median of 2.5 years after randomisation [21]. Moss-Morris et al. [22] analysed 49 CFS patients after a 12-week graded exercise programme in comparison to standard medical care. Patients showed less mental and physical fatigue and improved physical functioning. The authors stated that a decrease in symptom focusing, rather than an increase in fitness, mediated this treatment effect. Recently, Christensen et al. [23] highlighted the changes of illness perception as an important process in CBT for severe functional somatic syndromes (FSS). Concerning complementary medicine a recent systematic review provides limited evidence for the effectiveness of complementary and alternative-medicine therapy in relieving symptoms of CFS [24].
Biofeedback therapy (BF) is a treatment method that includes cognitive and behavioural strategies, and thus – based on the above mentioned – can be considered for application in the management of CFS patients. It comprises psychoeducational and interoceptive aspects, stress reduction and relaxation training, and improvement of self-efficacy in addition to the training of one or several specific parameters [25], [26], [27]. Heart rate variability biofeedback (HRV-BF) is a subtype of biofeedback training that aims to control ones breathing frequency at the level of 6 to 7 cycles per minute. Slow pace breathing has shown to increase a vagal tone, stimulate baroreflex regulation and contribute to the “restoration” of sympathetic/parasympathetic shift [28]. The most comprehensive review of HRV-BF by Wheat and Larkin [29] points out that changes in baroreflex activity could be the underlying physiological mechanism that explains beneficial effects of HRV-BF on health. HRV-BF has shown to be efficient in management of stress-related psychiatric disorders [30], [31], chronic pain [32], [33] as well as for the stress modulation in postpartum period [34] and in healthy subjects [35].
Surprisingly, our literature research revealed very few data about elaborated treatment protocols using HRV-BF in adult patients with CFS. In one study, 50 adolescents (ages 10–14) with CFS were treated with Electromyography- (EMG-) and HRV-biofeedback and compared with wait-list controls (n = 42), showing a significant reduction in fatigue severity and higher school attendance after intervention [36]. James and Folen [37] and Hammond [38] each reported single-case studies with EEG- biofeedback in a woman with CFS. Both reported considerable improvement in fatigue and cognitive functioning.
This led us to the idea to develop a HRV-biofeedback treatment manual for patients with CFS and to test its effect on fatigue perception as well as on self-estimated mental and physical functioning. Based on the evidence that HRV and respiratory sinus arrhythmia (RSA) trainings improve the regulation of the autonomic nervous system [28], [39] which is affected in FSS as CFS [40], we chose breathing and heart rate as specific training parameters [25]. In regard to the maintaining cognitive and affective processes of CFS [13], [41], we hypothesize that HRV-BF might help to normalise individual physiological reactions, to reflect specific dysfunctional beliefs about fatigue and activity, and to shift the point of concentration from fatigue to other aspects [42], [43]. Based on Hyland's extended network learning error theory of CFS, HRV-BF might promote self-organisational learning at the interface between physiological and psychological events [12]. Finally, we thought about HRV-BF having an effect on the positive belief of personal control over one's symptoms, which has been proven to be an important mediating factor in the treatment of FSS [23], [44].
If our HRV-BF protocol shall proof its efficacy in this pilot-study it could be used in further randomised placebo-controlled or “head-to-head” trials. Having this scope in mind, we added a well-established treatment for CFS management – graded exercise training – in order to observe their influence on our variables of interest. We aim to explore the impact of both treatment methods on subjective fatigue, mental and physical functioning as well as on depression. As a secondary outcome we compare the two interventions with regard to above mentioned mental and physical parameters.
Section snippets
Study population
The study was conducted at the Department of Psychosomatic Medicine and Psychotherapy, in collaboration with the Department of Sports Medicine, University Hospital Tübingen (Germany). Patients were recruited through advertisements in local newspapers and by an Internet web page. The local ethics committee of the medical faculty approved the study protocol (project number 310/2009BO2) in accordance with the Helsinki Declaration. All participants provided written informed consent prior to study
Description of participants
A total of 115 females and 3 males responded to the study announcement. According to exclusion criteria no male persons were included. Study information was provided to interested females via email or telephone. Subsequently, 57 individuals cancelled their participation because of the treatment frequency and training intensity, the long distance to the study centre, or the randomisation or ongoing psychotherapy or other regular exercise training. Finally, 58 persons were invited to an expert
Discussion
In this exploratory pilot trial patients with CFS received either HRV-BF training or GET. Results show an improvement in fatigue scores that last for at least 5 months in both intervention groups. Large to medium effect sizes suggest a clinical significance of the proven statistical changes. No significant differences between groups regarding general fatigue or any subtypes of fatigue in general and at any particular observation point were observed.
At the same time the treatments seem to differ
Conclusion
In conclusion, in this pilot study we evaluated a manualised programme for the HRV-biofeedback training for patients with CFS. We also investigated the impact of HRV-BF and GET on fatigue as well as on several other mental and physical parameters. Results show that both treatments improve fatigue as a core symptom of CFS with medium to large effect sizes. Moreover, HRV-BF training seems to have a specific positive influence on mental functioning and cognitive components, whereas GET seems to
Conflicting interests
The author(s) declare that they have no competing interests.
Acknowledgements
The study was funded by a grant from the Alfred-Teufel-Foundation (3012425), Nagold, Germany. We are grateful for all the help we received from the clinic personnel, especially from Ms. Karin von Hacht (sports therapist).
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Authors contributed to the paper equally.