To assess the effectiveness of Buteyko Breathing Technique (BBT) and Conventional Physical Therapy (Conventional PT) for improving pulmonary functions and Health Related Quality of Life (HRQoL) in the management of chronic bronchial asthma.
STUDY DESIGN & SAMPLING TECHNIQUE
It is a Randomized Control Trial. Patients were selected through Simple Random Sampling.
STUDY SETTING & PARTICIPANTS
24 patients diagnosed as chronic bronchial asthma were recruited from the outpatient department, pulmonary clinics of tertiary care hospital.
Subjects were randomly assigned into two groups, BBT (n=12) and conventional PT (n=12). FEV1, FVC and FEV1/FVC ratio were measured at the start and end of the treatment through MIR Spirolab-III. HRQoL was also measured using St George Respiratory Questionnaire (SGRQ) at start and end of treatment session.
No statistically significant changes were observed in FVC, FEV1 and FEV1/FVC ratio in BBT as well as in Conventional PT whereas significant changes in HRQoL through SGRQ is revealed in BBT (p <0.05).
BBT is found to be more effective in assessing HRQoL through SGRQ, whereas a larger sample size is required in patients with chronic bronchial asthma to evaluate the effectiveness of BBT as no significant difference was shown in the study.
Bronchial Asthma, Buteyko Breathing Technique, Conventional Physical Therapy, FEV1, FVC, St George Respiratory Questionnaire
Qurat ul Ain Ausaf
Ziauddin College of Physical Therapy
Ghazala Noor Nizami
Ziauddin College of Physical Therapy
Amna Aamir Khan
Ziauddin College of Physical Therapy
[Ausaf QA, Nizami GN, Khan AA. Effects of Buteyko Breathing Technique and Conventional Physical Therapy in Adult Bronchial Asthma: A Randomized Control Trail. Pak. j. rehabil. 2017;6(1) :36-44]
Asthma is a chronic respiratory disease that affects approximately 334 million people globally belonging to all age groups. Low and middle-income countries are considered to be most affected where the prevalence is increasing day by day 1. Variation in intensity and frequency of symptoms over period of time including dyspnea, cough, wheezing and tightness of chest among individuals leads to difference in disease progression. When managed poorly, asthma compromises quality of life and increase the health care socioeconomic Burden 2,3.
Apprehension about the side effects and drug dependence due to prolong use of medication, steroids and inhalers have been witnessed in studies conducted on patients with asthma 4-6. Many studies have advocated the use of alternative therapies in combination with medicines that control the asthma4-10. These include relaxation therapy breathing techniques, herbal medication, homeopathy and manual therapy. The breathing exercises are considered as one of the most popular method of these alternative therapies for individual suffering from asthma11. Globally recognized respiratory techniques include Pursed lip breathing, Buteyko reduced breathing, Frolov device, Resperate and Strelnikova respiratory gymnastic. All the above mentioned breathing exercises regime have been introduced to benefit asthma but BBT, which support individual to control their breathing rate that increases due to hypocapnia and hyperventilation 11,12.
Buteyko Breathing Technique (BBT) comprises of a set of breathing exercises developed basically for the treatment of Asthma by the Russian doctor, Konstanin Pavlovich Buteyko13,14. Multiple clinical
trials have been done internationally and proved its efficacy in reduction of symptoms of asthma, improvement in quality of life and in some cases reduction in frequency of acute exacerbations and
need for reliever medications has also been noticed13,15,16. According to the Buteyko Institute of Breathing and Health in Australia, the excessive breathing among the asthmatics has four primary effects including a decrease in carbon dioxide that causing spasm, a decrease in the release of oxygen that causing breathlessness, sensitivity in the mast cells that causing inflammation and formation of mucus due to inflamed airway. The BBT has increased its popularity in past few years with patients suffering with respiratory disorders, especially asthma, aiming to reverse chronic hyperventilation13. In a randomized controlled trial, based on the utilization of BBT video has also revealed that use of beta 2 – agonist is effectively reduced13. The purpose of BBT is to correct the breathing pattern by improving hyperventilation and maintaining CO2 levels. BBT mainly involves the series of breath holding periods with low paced breathing to improve the CO2 level further14-16.
Pulmonary functions abnormalities were frequently observed in Asthmatics patients where reduced ventilatory functions were observed during exacerbations and post exacerbations as well. Reduction of Forced Expiratory Volume in 1 second (FEV1) and Forced Vital Capacity (FVC) are common findings17. Marked improvement in ventilatory function has been reported in group treated with respiratory training18. BBT focuses on normalizing breathing patterns, reducing breathing rate and accessory muscle work9-10. As per Global Initiative of Asthma (GINA) guidelines there is level B evidence in support of breathing exercises and can be recommended as management strategy for asthma11. Renata André Laurino et al, in 2012, reported improvement of respiratory symptoms and anxiety in groups being treated with the breathing techniques18.
In Pakistan, conventional therapies are more in trend for the management of asthma. Conventional PT may include Active Cycle of Breathing Technique (ACBT), pursed lip breathing, tissue blowing exercises, interdigital technique, relaxation therapies and manual techniques. The aim of all these exercises is to improve pattern of breathing and functional residual capacity, relieve the symptoms of wheezing and clear sputum from the airways19. ACBT comprises of breathing control followed by thoracic expansion exercises and huffing (forced expiratory techniques), the integral phases of this technique. Inter digital technique is at times combined with ACBT to increase the rib cage expansion during active exhalation phase20. Pursed lip breathing is another effective method of controlling shortness of breath by asking patient to relax neck and shoulders followed by breathing in through the nose and count till 2 keeping mouth closed. Pursed or pucker lips can be performed by blowing a candle, breath out slowly through pursed lips and count till four21. Deep breathing and prolong exhalation exercise are taught by tissue or balloon22 blowing in order to improve the breathing pattern and to train respiratory muscles. Combination of certain positioning and exercises, diaphragmatic breathing and breathing through nose have proved to relax patients suffering from mild to moderate asthma, by providing beneficial effects especially in reduction of symptoms arising from hypocapnia and anxiety. Percussion, vibration, chest tapping and shaking in different postural drainage positions are commonly used manual techniques by physical therapists in both outpatient clinics and admitted patients for the clearance of sputum from air way passage23.
Approximately 7.5 million adults and 15 million children were suffering from asthma in 2011. Its increasing unfortunately around 5% annually and among them 20-30% are children and most of them are from urban areas11. The traditional treatment given to asthmatic patients also increases the economic burden on the suffering families19. The BBT has received substantial devotion but still there is a need of rigorous research evidence to support the use of different breathing techniques. BBT has been debated in a number of studies but still the use of this technique in Asian countries is limited and no significant research work has been found in Pakistan. This aim of the study is to determine the efficacy of BBT and conventional PT for improving pulmonary functions and Health related Quality of Life (HRQoL) in asthmatic patients.
Patients were recruited from out-patient pulmonary clinic of tertiary care hospital, diagnosed as Chronic Bronchial Asthma by Physician.
The study was conducted at Physical Therapy Department of tertiary care hospital.
A sample size of 24 individuals has been selected.
Data has been collected, compiled and analyzed in the period of eight months.
Selection of Sample
A two-arm randomized control trail was conducted on 24 adult asthmatic patients visiting at the pulmonary clinic that were equally randomized into 2 groups, Group A as BBT group (n=12) and Group B as Conventional PT group (n=12). This randomization was undertaken through the card placed in an envelope having treatment technique and picked for each patient.
Inclusion and Exclusion Criteria
Patients aged between 16-60 years, known case of Chronic Asthma, with no serious co-morbidities and willing to give their written informed consent were
included in the study.
Patients with an acute exacerbation of asthma, any other respiratory illness and history of taking breathing training were excluded from the study. Pregnant women and smokers were also excluded from the study.
Patients were randomly allocated to two treatment groups, BBT (Group A) and Conventional PT (Group B). Participant information sheet were provided to the patients. Consent was taken before the start of the treatment session. Patient assessment and treatment was undertaken by the assigned physical therapist. Standardized protocols of performing spirometry was ensured and explained to all participants. Participant information was recorded on assessment forms. Both the groups continued their regular asthmatics medications. It was ensured that conventional treatment group may not include any advice about their breathing exercises regarding BBT.
All patients have to perform 40-60 minutes exercises twice a day. All patients came to the physical therapy department for 5 consecutive days to learn and perform the treatment technique under supervision of the assigned physical therapist. Patients were instructed to perform 2nd session at home. After performing 5 days treatment at physical therapy department, they were instructed to performthat exercises twice at home for 3 months. After 15 days, they came for follow up and perform a session in front of Physical Therapist. Reinforcement was given to patients where required. The assessments were undertaken at baseline and end of treatment.
Buteyko Breathing Technique (Group A)
Each patient performed the standard protocols of BBT13, 24 as mentioned in Table 1.
Conventional Physical Therapy (Group B) Patients in the conventional PT group follow the routine protocols as instructed by their physical therapist, consisting of two cycles of ACBT, interdigital technique, pursed lip breathing and relaxation technique. Steps of Active cycle of breathing technique25 are shown in table2.
Data Collection Tools
- Demographic Details
Demographic details including age, height, weight, profession and co-morbid were recorded.
- St George’s Respiratory Questionnaire (SGRQ)
One of the prime outcome measures is the standardized St George’s Respiratory Questionnaire (SGRQ). This questionnaire is used to assess the impaired respiratory symptoms and quality of life. Three sub-scales are also defined in the questionnaire relating to the experience of symptoms, their impact and the level of impairment to find the total score. Score ranges from 0-100 with higher scores indicating more limitations. The questionnaire is divided into 2 parts where part 1 is the symptoms comprise of question 1-8 and part 2 consists of the activity and impact. Activity component comprise of question no 11-15 whereas impact comprises of question no 9, 10, 12-14 and 16-17. The scores of the symptoms revealed the perception of the patients towards their respiratory problem and scores of activity and impact were revealed the current health status. Total scores were calculated by summing all positive responses in the questionnaire. SGRQ reliability coefficient Cronbach’s alpha was >0.7 for symptoms, activity and impact score. It was > 0.9 for overall total scores26.
- Pulmonary Functions Measurement
Pulmonary functions were measured by Medical International Research (MIR) Spirolab III27. Spirometer facilitates the evaluation of lung functions, severity of respiratory disease and the response to therapy13. Forced Expiratory Volumes in 1 second (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio were measured.
An automatic analysis of spirometry test for each patient was carried out to compare with the Normal or Predicted values, based on the anthropometric pometric details of the patients27. This was helpful in identifying the severity of disease. Pulmonary functions parameters including FEV1, FVC and FEV1/FVC ratio were measured and recorded in the assessment form.
Data Analysis Strategies
Data was analyzed in SPSS (Statistical Software for Social Sciences) version 20. Gender distribution was measured in term of frequency and percentages. Mean ± Standard Deviation (SD) were used for quantitative variables including height, weight, age, FVC, FEV1, FEV1/FVC ratio and SGRQ scores. To find out the mean differences of FVC, FEV1, FEV1/FVC ratio and scores of SGRQ of before and after treatments, paired T test was run after getting significant result for normality assumptions over data. Normality of data was assessed by using Kolmogorov-Smirnov and Shapiro-Wilk Tests. Wilcoxon signed-rank test was applied, in case of violation of normality assumption. P-value of less than 0.05 was considered statistically significant. Mann-Whitney Test was applied individually on all post variables of all the parameter to assess significant difference in the dependent variable by a single dichotomous independent variable.
Ethical issues considered in this study are as followed:
1-Privacy and confidentiality statement were issued to all participants because confidentiality and privacy of identity was an important aspect of personal security.
2-Consent form was obtained from participants to ensure that the patient knows all of the risks and costs regarding the treatment.
3- Participants had the right to withdraw from study at any time.
4- Data collection and intervention in the hospital were done after taking permission from HOD of Physiotherapy.
In this study 24 adults with primary diagnosis of Chronic Asthma were recruited. 4 patients from both the groups were withdrawn at the start of study due to exacerbation of asthma. Demographic data is presented in Table 3. Age, height and weight are presented in Mean with SD. Results revealed that average age, height and weight of patients were nearly similar between the two groups.
Table 4 shows the result for checking the normality of data set and the results of tests of normality reveal that data was not symmetric, so Wilcoxson Signed-Rank test is also applied.
Ausaf QA et al. Effects of BBT & Conventional PT in Adult Bronchial Asthma: A RCT Result of Wilcoxson signed-rank test showed that treatment of 3 months did not elicit statistically significant changes in both groups, as shown in Table 5 and 6. Indeed, the median of all variables were found similar in both pre and post treatments of both groups.
Slight improvement has been observed in patients of both treatment techniques. On the basis of the results of lung function as shown in table 5, it was observed that p-value of FVC in the BBT group was 0.85 and in Conventional PT group it was 0.73. It showed that Conventional PT is slightly better than BBT. Similarly p-value of FEV1 showed that results of BBT group (0.10) was better than Conventional PT group (0.49). Results of FEV1/FVC ratio was better to some extent in BBT group (p-value = 0.23) as compared to Conventional PT group (p-value = 0.67).
Results of assessing health related quality of life through SGRQ are as shown in Table 6. Result of BBT group (p value = 0.001) was found significant with total scores of SGRQ as compared to Conventional PT (p value = 0.06). Improvement in Symptoms, Activity and Impact scores of patients have been observed with both the techniques. Indeed the median pain score rating in all variables are same in both pre and post treatments of both group. On the basis of the results it was observed that Symptoms score were significant in the BBT group (0.007) and in conventional PT group (0.037). It showed that BBT is better than Con PT. Results of activity Scores were found significant in BBT group (0.009), whereas it was found insignificant in Conventional PT group (0.97). Impact scores of both groups shows significant improvement that is p value is less than 0.05.
Mann-Whitney Test was applied on post treatment variables of all the parameter to find which group was showing better improvement, although above result shows insignificant improvement in some variables. Results of Mann-Whitney Test for lung functions and SGRQ are shown in table 7. Result shows that the BBT received the higher rank with most of the variables as compared to Conventional physical therapy techniques. However, data shows statistically insignificant improvement in parameters (p-value > 0.05). Rank of impact score was similar in both groups, whereas, Conventional PT received the higher rank in total score of SGRQ as compared to BBT.
This study was conducted to analyze the effects of BBT in patients of chronic asthma as compared to convention PT. The results of our study shows slight improvement in terms of FVC, FEV1, FEV1/FVC ratio and scores of SGRQ among patients of both treatment techniques.
Results of FEV1 in our study were not significant (Table 5 and 6) for BBT as per the study conducted by McHugh28 whereas out of 38 patients 4 patients were withdrawn from the study in 6 months of duration. The sample size was found to be higher with twice the duration. Cooper et al29 found no difference in FEV1 when compared between the groups. In the study sample of ninety patients were taken and divided into three groups BBT, Pink City Lung Exercise (PCLE) and PCLE placebo group. Out of 90 samples, 69 patients completed the study. Researcher found no significant difference in-between these groups but BBT group showed reduction in the symptoms. The study was conducted for the period of 6 months and found no significant difference in lung functions that is similar to our study.
Gudjonsdottir and Monique van Oosten reported no change in FEV1 and FVC in both groups on 18 asthmatic patients30. The sample size was small as per our study and we found slight changes in lung functions that are not significant statistically. McGowan J conducted a study on a larger sample size with 384 patients and divided then into three groups, Buteyko, Placebo and Control. Researcher found significant improvement in symptoms, medication and quality of life31. Moreover, the study
showed 98% reduction in reliever medication, 92% reduction in preventer medications and 98% reduction in asthma symptoms. Slight improvement was found in lung functions as appeared in this study. Elnanaggar RK and Shendy MA conducted another study on children of age group 8-14 years. It comprised of three treatment techniques, BBT, ACBT and Thoracic Lymphatic Pump Technique (TLPT). They found significant results with post treatment differences in FVC, FEV1 and FEV1/FVC ratio in BBT group as compared to ACBT. When comparing BBT with TLPT no significant post treatment difference was found in FVC and FEV1/FVC ratio but significant difference was found in FEV1 of BBT group32. Alfe GM and Grover SK33 in 2014 reported significant improvement in FEV1, FEV1/FVC and PEFR in group treated with BBT in comparison with diaphragmatic breathing. Statistical analysis of our study shows insignificant result for FVC, FEV1 and FEV1 /FVC ratio in patients of both treatments techniques. The result of the study conducted by Prasanna KB et al 2016, reported that significant difference was found in asthma control questionnaire among BBT group. This study was conducted for 2 months and effectively reduced the symptoms of patients and also improved the lung compliance in patients irrespective of age and sex distribution among acute asthmatic population in Tagore Medical College and Hospital34. The study also provided significant evidences in support of results of our study regarding SGRQ as they also assessed quality of life through Asthma control questionnaire.
Studies conducted by Hassan et al13, Prem et al15 and Bruton A & Thomas M35 found improvement in symptoms of asthma or reduction of medications by using BBT. We also found slight improvement in asthma symptoms of our patients with BBT and Conventional PT group. Weiner et al also found that sixteen weeks of conventional physical therapy intervention is found to be effective not only in plummeting the asthmatic attack intensity but also in intake of asthmatic medication by 50%36. Similar result has also been obtained by Weiner et al (2002) in another study in which 4-6 months of training with conventional physical therapy approach improved FEV1, FVC and Borg Dyspnoea Score with reduction in the use of bronchodilators37. Cowie RL in a conclusion of a randomized controlled trial established that Buteyko technique is widely recognized intervention strategy for the management of asthma in adult patients and stated that Buteyko techniques can be used as an adjunct to conventional management of asthma38.
According to the result obtained from this research where 3 months sessions provide a significant result in improving SGRQ in BBT group. However BBT are markedly more beneficial in terms of St George respiratory questionnaire in comparison to conventional PT. In previous researches breathing techniques are found to be effective in the management of asthma. Since Buteyko is cheap, safe and effective method to control asthma symptoms so awareness programs and special trainings should be started among the physical therapy students and clinical therapist to ensure that all such techniques are only be included as a part of interventional strategies once it fulfills the criterion of ethical decision making as forwarded in Belmont report39.
BBT is found to be clinically as well as statistically effective in assessing HRQoL in patients with chronic bronchial asthma. More researchers are required in future to evaluate the effectiveness of BBT on larger scale in order to be generalized to the asthmatic population. The young researchers as well as clinicians should be appreciated to teach Buyteko in their routine practice as being cost effective.
 Holland AE, Wadell K, Spruit MA. How to adapt the pulmonary rehabilitation programme to patients with chronic respiratory disease other than COPD. Eur Respir Rev. 2013;22(130): 577-586
 The Global Asthma Report 2014. Auckland, New Zealand: Global Asthma Network; 2014
 Thomas M, McKinley RK, Freeman E, Foy C. Prevalence of dysfunctional breathing in patients treated for asthma in primary care: cross sectional survey. BMJ. 2001;322(7294): 1098-1100
 Yanez A, Cho SH, Soriano JB, Rosenwasser L J, Rodrigo GJ, Rabe KF, Et al. Asthma in elderly: What we know and what we have yet to know. World Allergy Organ J. 2014;7(1):8
 Abramson MJ, Perret JL, Dharmage SC, McDonald VM, McDonald CF. Distinguishing adult-onset asthma from COPD: a review and a new approach. Int J Chron Obstruct Pulmon Dis. 2014;9:945-962
 Azab NY, El Mahalawy II, Abd El Aal GA, Taha MH. Breathing patterns in asthmatic patients during exercise. Egypt J Chest Dis Tuberc. 2015;64(3)521-527
 Hagman C, Janson C, Emtner M. Breathing retraining-a five years follow-up of patients with dysfunctional breathing. Respir Med. 2011; 105(8):1153-1159
 El-Helaly N, Aboel-magd FM. Ventilatory functions response to breathing training versus aerobic training in asthmatic children. Egypt J Pediatr Allergy Immunol. 2012;10(1):33-37
 Thomas M, Bruton A. Breathing exercises for asthma. Breathe. 2014;10(4):312-322.
 Slader CA, Reddel HK, Spencer LM, Belousova EG, Armour CL, Bosnic- Anticevish SZ, et al. Double blind randomized controlled trial of two different breathing techniques in the management of asthma. Thorax. 2006;61(8): 651-656
 Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention. 2017. Availablefrom: www.ginasthma.org
 Currie GP, Devereux GS, Lee DK, Ayres JG. Recent developments in asthma management. BMJ. 2005;12;330(7491): 585-589
 Hassan ZM, Riad NM, Ahmed FH. Effect of Buteyko breathing technique on patient with Bronchial Asthma. Egypt J Chest Dis Tuberc. 2012;61(4);235-241
 McKeown P. Close Your Mouth Buteyko Breathing Clinic Self Help Manual. Loughwell, Moycullen, Co Galway: Buteyko Books; 2004
 Prem V, Sahoo RC, Adhikari P. Comparison of the effects of Buteyko and pranayama breathing techniques on quality of life in patients with asthma – A randomized controlled trial. Clin Rehabil. 2013;27(2):133- 141
 Freitas DA, Holloway EA, Bruno SS, Chaves GS, Fregonezi GA, Mendonca KP. Breathing exercise for adults withAsthma. Cochrane Database Syst Rev. 2013;(10):CD001227
 Oga T, Tsukino M, Hajiro T, Ikeda A, Koyama H, Mishima M et al. Multidimensional analyses of longterm clinical courses of asthma and chronic obstructive pulmonary disease. Allergol Int. 2010;59(3):257- 265
 Laurino RA, Barnabe V, Saraiva- Romanholo BM, Stelmach R, Cukier A, et al. Respiratory rehabilitation: a physiotherapy approach to the control of asthma symptoms and anxiety. Clinics (Sao Paulo). 2012;67(11):1291-1297
 Kim J, Park JH, Yim J. Effects of respiratory muscles and endurance training using an individualized training device on the pulmonary function and exercise capacity in stroke patients. Med Sci Monit. 2014; 20:2543-2549
 Kirilloff LH, Owens GR, Rogers RM, Mazzocco MC. Does chest physical therapy work? Chest. 1985;88(3):436-444
 Lewis LK, Williams MT, Olds TS. The active cycle of breathing technique: a systemic review and Meta-analysis. Respir Med. 2012;106(2):155-172
 Borge CR, Hagen KB, Mengshoel AM, Omenaas E, Moum T, Wahl AK. Effects of controlled breathing exercises and respiratory muscles training in people with chronic obstructive pulmonary disease: results from evaluating the quality of evidence in systematic reviews. BMC Pulm Med. 2014;14:184
 Boyle KL, Olinick J, Lewis C. The value of blowing up a balloon. N Am J Sports PhysTher. 2010;5(3):179-188
 Brindley JL. Buteyko Practice Diary and Quick Reference Guide. Buteyko Breathing Association; 2010
 The Active Cycle of Breathing Techniques. United Kingdom: Association of Chartered Physiotherapists in Respiratory Care; 2011
 Bae YJ. Reliability and validity of the St George’s Respiratory Questionnaire for asthma: Int J Tuberc Lung Dis. 2011;15(7):966-971
 Spirolab III – User Manual Code MIR 980067 REV 1.6 (brochure). Italy: Medical International Research; 2007
 McHugh P, Aitcheson F, Duncan B, Houghton F. Buteyko Breathing Technique for asthma: an effective intervention. N Z Med J. 2003;116 (1187):U710
 Cooper S, Oborne J, Newton S, Harrison V, Thompson Coon J, Lewis S, Tattersfield A. Effect of two breathing exercises (Buteyko and pranayama) in asthma: a randomized controlled trial. Thorax. 2003;58(8):674–679
 Gudjonsdottir M, Oosten MV. Effects of Buteyko breathing retraining method on resting ventilation and asthma control in asthma patients. Eur Respir J. 2015;46:2282
 McGowan J. Health Education in Asthma Management – Does the Buteyko Institute Method Make a Difference? Thorax. 2003;58(Suppl III):iii28
 Elnaggar RK, Shendy MA. Efficacy of noninvasive respiratory techniques in the treatment of children with bronchial asthma: a randomized controlled trial. Bull Fac Phys Ther 2016;21: 1-10
 Afle GM, Grover SK. To study the effectiveness of buteyko breathing technique versus diaphragmatic breathing in asthmatics. Int J Physiother. 2014;1(3):116-119
 Prasanna KB, Sowmiya KR, Dhileeban CM. Effect of Buteyko breathing exercise in newly diagnosed asthmatic patients. Int. J. Med. Public Health. 2015;5(1):77-81
 Bruton A, Thomas M. The role of breathing training in asthma management. Curr Opin Allergy Clin Immunol. 2011;11(1): 53-57
 Weiner P, Berar-Yanay N, Davidovich A, Magadle R, Weiner M. Specific inspiratory muscle training in patients with mild asthma with high consumption of inhaled beta 2- agonists. Chest. 2000;117(3):722–727
Weiner P, Magadle R, Massarwa F, Beckerman M, Berar-Yanay N. Influence of gender and inspiratory muscle training on the perception of dyspnea in patients with asthma. Chest. 2002;122(1),197-201
 Cowie RL, Conley DP, Underwood MF, Reader PG. A randomized controlled trial of the Buteyko technique as an adjunct to conventional management of asthma. Respir Med. 2008;102(5):726-732
 Markham A, Buchanan E. Ethical decision-making and internet research: Recommendations from the AoIR ethics working committee (version 2.0). 2012