Behavioral interventions in asthma. Breathing training

Breath Rate Variability: A Novel Measure to Study the Meditation Effects

Context:

Reliable quantitative measure of meditation is still elusive. Although electroencephalogram (EEG) and heart rate variability (HRV) are known as quantitative measures of meditation, effects of meditation on EEG and HRV may well take long time as these measures are involuntarily controlled. Effect of mediation on respiration is well known; however, quantitative measures of respiration during meditation have not been studied.

Aims:

Breath rate variability (BRV) as an alternate measure of meditation even over a short duration is proposed. The main objective of this study is to test the hypothesis that BRV is a simple measure that differentiates between meditators and nonmeditators.

Settings and Design:

This was a nonrandomized, controlled trial. Volunteers meditate in their natural habitat during signal acquisition.

Subjects and Methods:

We used Photo-Plythysmo-Gram (PPG) signal acquisition system from BIO-PAC and recorded video of chest and abdomen movement due to respiration during a short meditation (15 min) session for 12 individuals (all males) meditating in a relaxed sitting posture. Seven of the 12 individuals had substantial experience in meditation, while others are controls without any experience in meditation. Respiratory signal from PPG signal was derived and matched with that of the video respiratory signal. This derived respiratory signal is used for calculating BRV parameters in time, frequency, nonlinear, and time-frequency domain.

Statistical Analysis Used:

First, breath-to-breath interval (BBI) was calculated from the respiration signal, then time domain parameters such as standard deviation of BBI (SDBB), root mean square value of SDBB (RMSSD), and standard deviation of SDBB (SDSD) were calculated. We performed spectral analysis to calculate frequency domain parameters (power spectral density [PSD], power of each band, peak frequency of each band, and normalized frequency) using Burg, Welch, and Lomb–Scargle (LS) method. We calculated nonlinear parameters (sample entropy, approximate entropy, Poincare plot, and Renyi entropy). We calculated time frequency parameters (global PSD, low frequency-high frequency [LF-HF] ratio, and LF-HF power) by Burg LS and wavelet method.

Results:

The results show that the mediated individuals have high value of SDSD (+24%), SDBB (+29%), and RMSSD (+26%). Frequency domain analysis shows substantial increment in LFHF power (+73%) and LFHF ratio (+33%). Nonlinear parameters such as SD1 and SD2 were also more (>20%) for meditated persons.

Conclusions:

As compared to HRV, BRV can provide short-term effect on anatomic nervous system meditation, while HRV shows long-term effects. Improved autonomic function is one of the long-term effects of meditation in which an increase in parasympathetic activity and decrease in sympathetic dominance are observed. In future works, BRV could also be used for measuring stress.

Asthma - A Disease of How We Breathe: Role of Breathing Exercises and Pranayam

To describe the role of breathing exercises or yoga and/or pranayama in the management of childhood asthma. We conducted an updated literature search and retrieved relevant literature on the role of breathing exercises or yoga and/or pranayama in the management of childhood asthma. We found that the breathing exercises or yoga and/or pranayama are generally multi-component packaged interventions, and are described as follows: Papworth technique, Buteyko technique, Yoga and/or Pranayam. These techniques primarily modify the pattern of breathing to reduce hyperventilation resulting in normalisation of CO2 level, reduction of bronchospasm and resulting breathlessness. In addition they also change the behaviour, decrease anxiety, improve immunological parameters, and improve endurance of the respiratory muscles that may ultimately help asthmatic children. We found 10 clinical trials conducted in children with asthma of varying severity, and found to benefit children with chronic (mild and moderate) and uncontrolled asthma, but not acute severe asthma. Breathing exercises or yoga and/or pranayama may benefit children with chronic (mild and moderate) and uncontrolled asthma, but not acute severe asthma. Before these techniques can be incorporated into the standard care of asthmatic children, important outcomes like quality of life, medication use, and patient reported outcomes need to be evaluated in future clinical trials.

A Behavioral-Educational Intervention to Promote Pediatric Sleep During Hospitalization: A Pilot Randomized Controlled Trial

OBJECTIVE/BACKGROUND

Hospitalization can contribute to common sleep difficulties in children. Interventions aimed at hospitalized children need to be developed and piloted with rigorous evaluative methods. The primary purpose of this study was to examine the feasibility and acceptability of a behavioral-educational intervention aimed at increasing nighttime sleep for hospitalized children.

PARTICIPANTS

Hospitalized children aged 4-10 years and their caregivers.

METHODS

A pilot randomized, controlled trial with concealed-group allocation was conducted. Forty-eight hospitalized children (ages 4-10) and their care-givers were randomized to either the Relax to Sleep (RTS) intervention group (n = 24) or the Usual Care (UC) comparison group (n = 24). The RTS intervention was comprised of a one-on-one educational session for the parent that was guided by a standardized booklet containing information on sleep and instructions for training the child in the use of a diaphragmatic breathing exercise. UC participants received no information about sleep or relaxation. Children wore actigraphs for 3 days and nights and completed sleep diaries. Outcome measures included feasibility, acceptability, and sleep outcomes.

RESULTS

Parental reports indicated they enjoyed the discussion on sleep, found the information helpful, and their child found diaphragmatic breathing easy to use, and would use it again in the future. Children in the RTS group averaged 50 minutes more nighttime sleep, and had less wake after sleep onset time compared to children in the UC group.

CONCLUSION

Sleep is critically important to children's health and well-being and should be given important consideration during hospitalization. Although the results of this pilot trial seem promising, more interventional studies are needed.

A Sleep Hygiene and Relaxation Intervention for Children With Acute Lymphoblastic Leukemia: A Pilot Randomized Controlled Trial

Background:

Sleep disturbance and fatigue are common and distressing pediatric cancer-related outcomes. Sleep hygiene education and relaxation techniques are recommended to improve sleep in healthy children and adult cancer survivors. No studies have tested these interventions to improve sleep and fatigue for children with acute lymphoblastic leukemia (ALL) in the home setting.

Objectives:

The aim of this study is to establish the feasibility and acceptability of a sleep hygiene and relaxation intervention to improve sleep and fatigue for children receiving maintenance chemotherapy for ALL. The child's fatigue and sleep data were collected to inform sample size calculations for a future trial.

Methods:

In this pilot randomized controlled trial, 20 children were allocated randomly to the sleep intervention or control group. The sleep intervention group received a 60-minute educational session to discuss sleep and fatigue in children with cancer and strategies to improve sleep, including use of 2 storybooks to teach deep breathing and progressive muscle relaxation. Objective sleep data were collected using actigraphy and fatigue was measured using the Childhood Cancer Fatigue Scale.

Results:

The intervention was acceptable to families, and feasibility of the intervention and data collection was clearly established. Although not statistically significant, increases in mean nighttime sleep and decreases in mean wake time after sleep onset in the sleep intervention group represented clinically important improvements.

Conclusions:

This pilot study demonstrated the feasibility and acceptability of a sleep hygiene and relaxation intervention for children undergoing maintenance chemotherapy for ALL.

Implications for practice:

Given the clinically important improvements in sleep observed, replication in a larger, adequately powered randomized controlled trial is merited.

Breathing pattern recordings using respiratory inductive plethysmography, before and after a physiotherapy breathing retraining program for asthma: A case report

Breathing retraining (BR) improves symptoms, psychological well-being and quality of life in adults with asthma; but there remains uncertainty as to mechanism of effect. One of the intuitively logical theories is that BR works through altering breathing pattern. There is currently no evidence, however, that BR does result in measurable changes in breathing pattern. In this case report we describe the effects of physiotherapy BR on a 57-year-old female with a 10-year history of asthma. Data were collected before and after a physiotherapy BR program comprising three sessions over 18 weeks: breathing pattern (respiratory inductive plethysmography (RIP); physiology (end tidal carbon dioxide (ETCO₂), heart rate, oxygen saturations, spirometric lung function); questionnaires (Asthma Control Questionnaire (ACQ), Hospital Anxiety and Depression Score, Nijmegen Questionnaire); and medication usage. After BR, the patient's symptoms improved. Her physiology was largely unchanged, although her FEV₁ increased by 0.12L, peak flow by 21L/min. The patient reported using less Salbutamol, yet her asthma control improved (ACQ down 1.5). Her Nijmegen score dropped from positive to negative for hyperventilation (from 39 to 7). Her anxiety-depression levels both reduced into 'normal' ranges. The patient's expiratory time increased, with longer respiratory cycles and slower respiratory rate. No changes were seen in relative contributions of ribcage and abdomen. Controlled trials are now needed to determine the generalizability of these findings.

The role of inspiratory muscle training in the management of asthma and exercise-induced bronchoconstriction

Asthma is a pathological condition comprising of a variety of symptoms which affect the ability to function in daily life. Due to the high prevalence of asthma and associated healthcare costs, it is important to identify low-cost alternatives to traditional pharmacotherapy. One of these low cost alternatives is the use of inspiratory muscle training (IMT), which is a technique aimed at increasing the strength and endurance of the diaphragm and accessory muscles of respiration. IMT typically consists of taking voluntary inspirations against a resistive load across the entire range of vital capacity while at rest. In healthy individuals, the most notable benefits of IMT are an increase in diaphragm thickness and strength, a decrease in exertional dyspnea, and a decrease in the oxygen cost of breathing. Due to the presence of expiratory flow limitation in asthma and exercise-induced bronchoconstriction, dynamic lung hyperinflation is common. As a result of varying operational lung volumes, due in part to hyperinflation, the respiratory muscles may operate far from the optimal portion of the length-tension curve, and thus may be forced to operate against a low pulmonary compliance. Therefore, the ability of these muscles to generate tension is reduced, and for any given level of ventilation, the work of breathing is increased as compared to non-asthmatics. Evidence that IMT is an effective treatment for asthma is inconclusive, due to limited data and a wide variation in study methodologies. However, IMT has been shown to decrease dyspnea, increase inspiratory muscle strength, and improve exercise capacity in asthmatic individuals. In order to develop more concrete recommendations regarding IMT as an effective low-cost adjunct in addition to traditional asthma treatments, we recommend that a standard treatment protocol be developed and tested in a placebo-controlled clinical trial with a large representative sample.

Breathing exercises for asthma

Educational aims

To summarise the evidence of the role of breathing control approaches in the management of asthma

To provide information on the content of evidence-based breathing exercises programmes

Summary

Asthma is a complex, multi-dimensional condition that affects patients in many ways. Having asthma is inherently stressful and psychological problems are common and associated with poor asthma outcomes. Although most patients in clinical trials can achieve high levels of control with optimised pharmacotherapy, in “real-life” practice, poor control is common, with over-reliance on rescue bronchodilator medication and ongoing symptoms and quality-of-life impairment. Many patients are interested in non-pharmacological treatments to improve asthma control, particularly breathing control exercises but, until recently, the evidence base has been inadequate. The place of breathing exercises has been controversial, partly because some proponents have made exaggerated, implausible claims of effectiveness. Recent evidence, however, has resulted in endorsement of breathing exercises as add-on treatment in asthma in systematic reviews and guidelines.

This review summarises the current evidence of effectiveness of breathing exercises programmes as an adjuvant treatment to pharmacological strategies for people with asthma. The types of breathing training programmes used and the content of effective programmes are discussed. We conclude that patients whose asthma continues to cause symptoms and quality-of-life impairment, despite adequate pharmacological treatment, or who have high bronchodilator use, should be offered access to an effective breathing training programme as a part of holistic, integrated asthma care.

Key points

Asthma is frequently poorly controlled despite effective modern medication

Psychological factors can be as important as physiological ones in affecting symptom perception and disease impact

Breathing exercises can improve patient-reported outcomes and psychological state

Breathing exercises should be offered to all asthma patients with symptoms or impaired quality of life despite standard treatment

Psychosocial factors and behavioral medicine interventions in asthma

OBJECTIVE

This review examines the evidence for psychosocial influences in asthma and behavioral medicine approaches to its treatment.

METHOD

We conducted a systematic review of the literature on psychosocial influences and the evidence for behavioral interventions in asthma with a focus on research in the past 10 years and clinical trials. Additional attention was directed at promising new developments in the field.

RESULTS

Psychosocial factors can influence the pathogenesis and pathophysiology of asthma, either directly through autonomic, endocrine, immunological, and central nervous system mechanisms or indirectly through lifestyle factors, health behaviors, illness cognitions, and disease management, including medication adherence and trigger avoidance. The recent decade has witnessed surging interest in behavioral interventions that target the various pathways of influence. Among these, self-management training, breathing training, and exercise or physical activation programs have proved particularly useful, whereas other essential or promising interventions, such as smoking cessation, dietary programs, perception and biofeedback training, and suggestive or expressive psychotherapy, require further, more rigorous evaluation. Given the high comorbidity with anxiety and mood disorders, further evaluation of illness-specific cognitive behavior therapy is of particular importance. Progress has also been made in devising community-based and culturally tailored intervention programs.

CONCLUSION

In concert with an essential medication treatment, behavioral medicine treatment of asthma is moving closer toward an integrated biopsychosocial approach to disease management.

The effect of physiotherapy-based breathing retraining on asthma control

BACKGROUND

The mechanism of the breathing retraining effect on asthma control is not adequately based on evidence.

OBJECTIVE

The present study was designed to evaluate the effect of physiotherapy-based breathing retraining on asthma control and on asthma physiological indices across time.

STUDY DESIGN

A 6-month controlled study was conducted. Adult patients with stable, mild to moderate asthma (n = 40), under the same specialist's care, were randomized either to be trained as one group receiving 12 individual breathing retraining sessions (n = 20), or to have usual asthma care (n = 20). The main outcome was the Asthma Control Test score, with secondary outcomes the end-tidal carbon dioxide, respiratory rate, spirometry, and the scores of Nijmegen Hyperventilation Questionnaire, Medical Research Council scale, and SF-36v2 quality-of-life questionnaire.

RESULTS

The 2 × 4 ANOVA showed significant interaction between intervention and time in asthma control (F = 9.03, p < .001, η(2) = 0.19), end-tidal carbon dioxide (p < .001), respiratory rate (p < .001), symptoms of hypocapnia (p = .001), FEV1% predicted (p = .022), and breathlessness disability (p = .023). The 2 × 4 MANOVA showed significant interaction between intervention and time, with respect to the two components of the SF-36v2 (p < .001).

CONCLUSION

Breathing retraining resulted in improvement not only in asthma control but in physiological indices across time as well. Further studies are needed to confirm the benefits of this training in order to help patients with stable asthma achieve the control of their disease.

The role of breathing training in asthma management

PURPOSE OF REVIEW

There is considerable public interest in the use of breathing modification techniques in the treatment of asthma. Surveys suggest many people with asthma use them, often without the knowledge of their medical attendants. Extravagant claims have been made about the effectiveness of some techniques, resulting in scepticism from orthodox clinicians. The evidence supporting breathing training for asthma was previously weak, and limited by the small size and methodological limitations of published research.

RECENT FINDINGS

The evidence base for the effectiveness of breathing training has recently improved, with reports from several larger and more methodologically robust controlled trials. These trials are reviewed in this study, and the findings placed in context. Trials have investigated a variety of breathing training programmes delivered by different therapists in different ways. All incorporate some instruction in breathing pattern, usually focusing on slow, regular, nasal, abdominal breathing and reduced ventilation, with patients instructed to practise exercises at home and when symptomatic.

SUMMARY

Current evidence suggests that breathing training programmes can be effective in improving patient-reported outcomes such as symptoms, quality of life and psychological impact; and may reduce the use of rescue bronchodilator medication. There is little evidence that airways physiology, hyper-responsiveness or inflammation is affected by such training. The optimal way of providing breathing training within the context of routine asthma care is still uncertain.

Hyperventilation in panic disorder and asthma: empirical evidence and clinical strategies

Sustained or spontaneous hyperventilation has been associated with a variety of physical symptoms and has been linked to a number of organic illnesses and mental disorders. Theories of panic disorder hold that hyperventilation either produces feared symptoms of hypocapnia or protects against feared suffocation symptoms of hypercapnia. Although the evidence for both theories is inconclusive, findings from observational, experimental, and therapeutic studies suggest an important role of low carbon dioxide (CO2) levels in this disorder. Similarly, hypocapnia and associated hyperpnia are linked to bronchoconstriction, symptom exacerbation, and lower quality of life in patients with asthma. Raising CO2 levels by means of therapeutic capnometry has proven beneficial effects in both disorders, and the reversing of hyperventilation has emerged as a potent mediator for reductions in panic symptom severity and treatment success.

Changes in pCO2, symptoms, and lung function of asthma patients during capnometry-assisted breathing training

In a recent pilot study with asthma patients we demonstrated beneficial outcomes of a breathing training using capnometry biofeedback and paced breathing assistance to increase pCO(2) levels and reduce hyperventilation. Here we explored the time course changes in pCO(2), respiration rate, symptoms and lung function across treatment weeks, in order to determine how long training needs to continue. We analyzed in eight asthma patients whether gains in pCO(2) and reductions in respiration rate achieved in home exercises with paced breathing tapes followed a linear trend across the 4-week treatment period. We also explored the extent to which gains at home were manifest in weekly training sessions in the clinic, in terms of improvement in symptoms and spirometric lung function. The increases in pCO(2) and respiration rate were linear across treatment weeks for home exercises. Similar increases were seen for in-session measurements, together with gradual decreases in symptoms from week to week. Basal lung function remained stable throughout treatment. With our current protocol of paced breathing and capnometry-assisted biofeedback at least 4 weeks are needed to achieve a normalization of pCO(2) levels and reduction in symptoms in asthma patients.

Studying noninvasive indices of vagal control: the need for respiratory control and the problem of target specificity

Respiratory sinus arrhythmia (RSA) is a popular index of cardiac vagal control; however, research has rarely adequately addressed respiratory influences on RSA. In addition, simplistic views of the parasympathetic system have resulted in an overinterpretation of RSA as a general indicator of vagal control. Research using a respiration-corrected time-domain index of RSA has yielded plausible findings that substantially deviate from uncorrected RSA. Paced breathing, which is used for baseline calibration of RSA in this correction procedure, allows for a representative sampling of respiratory influences on RSA and has minimal impact on autonomic regulation. Past research has largely focused on cardiac vagal activity and ignored the extent of target specificity in the parasympathetic system. More research is needed on new noninvasive indices of vagal control at other organ sites. Studies also need to address muscarinic receptor sensitivity before noninvasive vagal indices can be interpreted as markers of central vagal outflow.

Hyperventilation symptoms are linked to a lower perceived health in asthma patients

BACKGROUND

Hyperventilation symptoms are among the sensations asthma patients tend to report during exacerbations of their disease. However, little is known about their importance for the patients' perceived well-being.

METHOD

We therefore studied the association of reported hyperventilation symptoms (Asthma Symptom Checklist) with perceived physical and mental health (36-item Short-form Health Survey) in a sample of primary care asthma patients (N = 190). We also studied the potential role of perceived control of asthma (Perceived Control of Asthma Questionnaire) in mediating any association between these variables.

RESULTS

In hierarchical multiple regression analyses controlling for demographics, asthma severity, and other asthma symptoms (obstruction, congestion, panic-fear, irritation, and fatigue), hyperventilation symptoms were significantly associated with both physical and mental health status. This association was partially mediated by perceived control of asthma.

CONCLUSION

It is possible that hypocapnia creates symptoms that asthma patients cannot control by using their antiasthmatic medication, thus compromising their perceived control over the management of their asthma, and consequently their perceived health. Behavioral interventions should address the problem of hyperventilation in asthma.

Targeting pCO(2) in asthma: pilot evaluation of a capnometry-assisted breathing training

OBJECTIVES

This pilot study aimed to evaluate the feasibility and potential benefits of a novel biofeedback breathing training for achieving sustained increases in pCO(2) levels.

METHODS

Twelve asthma patients were randomly assigned to an immediate 4-week treatment group or waiting list control. Patients were instructed to modify their respiration in order to change levels of end-tidal pCO(2) using a hand-held capnometer. Treatment outcome was assessed in frequency and distress of symptoms, asthma control, lung function, and variability of peak expiratory flow (PEF).

RESULTS

We found stable increases in pCO(2) and reductions in respiration rate during treatment and 2-month follow-up. Mean pCO(2) levels rose from a hypocapnic to a normocapnic range at follow-up. Frequency and distress of symptoms was reduced and reported asthma control increased. In addition, mean PEF variability decreased significantly in the treatment group.

CONCLUSIONS

Our pilot intervention provided evidence for the feasibility of pCO(2)-biofeedback training in asthma patients.

Psychological aspects in the perception of dyspnea in obstructive pulmonary diseases

Dyspnea is an impairing symptom in obstructive pulmonary diseases. Besides multiple physiological pathways contributing to this sensation recent research has demonstrated an important role of psychological factors in the perception of dyspnea. The present review article synthesizes the research literature with regard to psychological aspects of the perception of dyspnea as well as other dyspnea-related issues such as course of disease, neuropsychological correlates and interventions that focus on psychological or behavioural changes. The available data show that inaccurate perception of dyspnea is related to poorer treatment outcome in obstructive pulmonary diseases and is impacted upon by emotional, attentional and learning processes. Neuropsychological deficits might further contribute to this association. Different psychological and behavioural interventions might reduce comorbid psychological disorders and thus improve the perception of dyspnea. However, future research is clearly required to substantiate current findings.

Airways, respiration, and respiratory sinus arrhythmia during picture viewing

Emotional stimuli can cause airway constriction; however, it is uncertain whether a dimensional or categorical model of emotion can better describe airway changes. Also, little is known about the affective modulation of respiration and vagal activity, which can influence airway tone. We studied changes in oscillatory resistance (Ros), respiration, and respiratory sinus arrhythmia (RSA) in asthmatics and controls during viewing of affective pictures eliciting anxiety, depression, disgust, happiness, contentment, erotic tension, or neutral affect. Ros, respiration, cardiac activity, and self-report were measured during picture presentations. Ros increased monotonically with picture unpleasantness mainly due to disgust pictures. RSA and respiratory timing parameters were particularly sensitive to erotic pictures. Differences between asthmatics and controls were minimal, suggesting that airway responses to unpleasant pictures are not specific to asthma.

Clinical decision-support for diagnosing stress-related disorders by applying psychophysiological medical knowledge to an instance-based learning system

OBJECTIVE

An important procedure in diagnosing stress-related disorders caused by dysfunction in the interaction of the heart with breathing, i.e., respiratory sinus arrhythmia (RSA), is to analyse the breathing first and then the heart rate. Analysing these measurements is a time-consuming task for the diagnosing clinician. A decision-support system in this area would reduce the analysis task of the clinician and enable him/her to give more attention to the patient. We have created a decision-support system which contains a signal classifier and a pattern identifier. The system performs an analysis of the physiological time series concerned which would otherwise be performed manually by the clinician.

METHODS

The signal-classifier, HR3Modul, classifies heart-rate patterns by analysing both cardio- and pulmonary signals, i.e., physiological time series. HR3Modul uses case-based reasoning (CBR), using a wavelet-based method for retrieving features from the signals. The system searches for familiar shapes in the signals by comparing them with shapes already stored. We have applied a best fit scheme for handling signals of different lengths, as the length of a breath is highly dynamic. We also apply automatic weighting to the features to obtain a more autonomous system. The classified heart signals indicate if a patient may be suffering from a stress-related disorder and the nature of the disorder. These classified signals are thereafter sent to the second subsystem, the pattern-identifier. The pattern-identifier analyses the classified signals and searches for familiar patterns by identifying sequences in the classified signals. The identified sequences give clinicians a more complete analysis of the measurements, providing them with a better basis for diagnosis.

RESULTS AND CONCLUSION

We have shown that a case-based classifier with a wavelet feature extractor and automatic weighting is a viable option for building a decision-support system for the psychophysiological domain, as it is at par, or even outperforms other retrieval techniques and is less complex.

Probing the psychophysiology of the airways: physical activity, experienced emotion, and facially expressed emotion

This article reviews research on airway reactivity in health and asthma within a psychophysiological context, including the effects of physical activity, emotion induction, and manipulation of facial expression of emotion. Skeletal muscle activation leads to airway dilation, with vagal withdrawal being the most likely mechanism. Emotional arousal, in particular negative affect, leads to airway constriction, with evidence for a vagal pathway in depressive states and ventilatory contributions in positive affect. Laboratory-induced airway responses covary with reports of emotion-induced asthma and with lung function decline during negative mood in the field. Like physical activity, facial expression of emotion leads to airway dilation. However, these effects are small and less consistent in posed emotional expressions. The mechanisms of emotion-induced airway responses and potential benefits of emotional expression in asthma deserve further study.

Behavioral interventions in asthma: biofeedback techniques

OBJECTIVES

Biofeedback techniques have long been recommended as an adjunctive treatment for bronchial asthma. Techniques that target lung function directly, or indirectly by altering facial muscle tension, heart rate, heart rate variability (HRV) or inspiratory volume together with accessory muscle tension, have been proposed. We review evidence for the effectiveness of these biofeedback interventions and discuss the psychophysiological rationale behind individual techniques.

METHOD

Controlled studies of biofeedback in asthma were retrieved using relevant search engines and reference lists of published articles. Effect sizes comparing intervention with control groups were calculated where appropriate.

RESULTS

Most of the studies suffer from methodological inadequacies or poor reporting of methods and results. Interventions targeting respiratory resistance directly have yielded only small and inconsistent changes in lung function and are difficult to implement without producing dynamic hyperinflation. Biofeedback-assisted facial muscle relaxation as an indirect intervention has yielded mixed results across studies, with only half of the studies showing significant albeit very small and clinically irrelevant improvements in lung function. The underlying physiological assumptions of the technique are questionable in the light of current knowledge of respiratory physiology. For other indirect techniques, only preliminary evidence of small effects is available.

CONCLUSION

Currently, there is little good evidence that biofeedback techniques can contribute substantially to the treatment of asthma.