Abstract
Background
Prolonged exposure to biomass smoke is a leading cause of respiratory morbidity among women living in low and middle-income countries, resulting in progressive lung damage and increased risk for chronic respiratory diseases.
Purpose
To develop, validate, and evaluate the feasibility of a Pranayama-based voluntarily regulated breathing technique (VRBT) module specifically tailored for women exposed to biomass smoke.
Methods
The VRBT module was developed through a yoga literature review and scientific evidence, and then evaluated for content validity by 22 yoga experts using Lawshe’s CVR method. One month pre-post feasibility trial of the module was conducted among 12 rural non-smoking women mean age of 50.42 ± 8.05 years; Biomass Exposure Index ≥ 60 hour-years. Pulmonary function was measured at baseline and post-intervention using Spirometer RMS Helios 401. Statistical analyses were conducted using paired t-tests (p < .05).
Results
Fourteen practices met the CVR threshold of 0.45; the final module duration is 40 minutes. After one month, significant improvements were observed in FVC (1.43 ± 0.41 L to 1.94 ± 0.37 L, p < .001), FEV1 (1.31 ± 0.40 L to 1.57 ± 0.34 L, p = .037), FEV1/FVC ratio (91.7 ± 7.96 to 80.6 ± 1.63, p < .001), and PEFR (2.83 ± 0.97 to 3.60 ± 0.96 L/s, p = .040). FEF25-75% did not show any significant change (p = .554). Pranayama was found to be a safe intervention with no adverse effects observed.
Conclusion
The module was designed for simplicity and ease of adoption by women, ensuring its accessibility. Hence, the VRBT module can be administered to the women exposed to biomass smoke.
Introduction
Biomass cooking smoke is a pervasive health hazard. About one-third of the world’s ~2.1 billion people still rely on open fires or inefficient stoves using wood, dung, or crop waste.1, 2 Household air pollution from this smoke causes ~3.2 million premature deaths annually, largely among women and young children. 2 In particular, chronic inhalation of biomass smoke is strongly associated with progressive lung damage in women, including chronic bronchitis, airflow obstruction, and COPD, as well as pneumonia, lung cancer, and cardiovascular disease. 3 Long-term exposures, often 30-40 years as a primary cook, result in airway inflammation, oxidative stress, and structural remodelling, like wall thickening and reduced lung function. 4 Rural women spend more time near indoor fires, and studies in India and Africa report higher rates of chronic bronchitis, dyspnoea, and impaired lung function in biomass-exposed women than in those using cleaner fuels.1, 5 Moreover, WHO estimates that nearly one-quarter of adult COPD deaths in low- and middle-income countries are attributable to household smoke, and notes that women in LMICs ‘disproportionately bear the greatest health burden’ from polluting cookstoves. 2 In India, 50.2% of rural households use biomass fuels like wood and dung for cooking. 6 A 2016 study found a COPD prevalence of 18.4% among rural women using biomass for over 10 years, which increased threefold after 25 years of exposure. 7 Systematic review and meta-analysis of 24 community-based studies of South Asia, including India, sub-Saharan Africa and Latin America, reported that women cooking with biomass fuel had a 1.38 times increased risk of COPD and were 2.11 times more likely to develop chronic bronchitis compared with unexposed women. 8 The prevalence of obstructive pulmonary disease attributable to biomass smoke exposure in India represents a major respiratory health burden. A recent systematic review and meta-analysis study of India reported a pooled prevalence of COPD among biomass fuel-exposed individuals is 10%. 9 People using biomass fuels for cooking in India have a 17%–60% higher chance of developing respiratory diseases compared to those using cleaner fuels. The risk is also higher for respiratory conditions like asthma, tuberculosis (TB), and chronic respiratory failure. 10 These findings underscore that biomass smoke causes insidious and often respiratory injury, especially in women. To reduce the direct exposure of biomass to households, improved biomass cookstoves with chimneys and fuels like LPG or biogas are widely promoted. Field evaluations show that many improved cookstoves can cut particulate emissions somewhat, but levels typically remain above WHO safe targets. 11 In practice, adoption is uneven: a Ghana RCT found minimal health gains because households continued using traditional stoves, and the improved stoves did not consistently lower smoke exposure. 12 However, a recent scoping review notes that about 87% of improved cookstoves produce less smoke than traditional open fires, but still do not reduce pollution to meet WHO air quality standards. 11
Simple measures like cooking outdoors, using chimneys, opening windows, or timing cooking to disperse smoke are also advised. In a long-term Chinese cohort study, households that switched to cleaner biogas and added improved kitchen ventilation saw significantly less annual FEV1 decline and a lower COPD incidence than those with biomass stoves. 13 However, such improvements often require structural changes or behavioural shifts that are hard to sustain in developing countries. The study reported that even well-designed stove or ventilation interventions did not yield significant outcomes because personal and local beliefs, economic, and sociocultural conditions limited the adoption of the administered interventions. 3 These changes can slow progressive damage, but do not affect impaired lung function. As a consequence, millions of women with long-standing biomass exposure continue to suffer from chronic cough, dyspnoea, and reduced lung capacity despite the said interventions. This highlights that no current intervention specifically rehabilitates lungs already injured by biomass smoke in women.
Growing evidence suggests that Pranayama, a voluntarily regulated breathing technique (VRBT), offers therapeutic benefits for individuals with both acute and chronic respiratory conditions. Systematic reviews and meta-analyses have demonstrated that yoga-based interventions, including Pranayama, lead to significant improvements in pulmonary function and exercise tolerance, particularly in patients with chronic obstructive pulmonary disease (COPD). For instance, a meta-analysis reported that 3–9 months of yoga practice led to greater improvements in forced expiratory volume in one second (FEV1) and six-minute walk distance compared to usual care in patients with COPD. 14 Similarly, a recent meta-analysis involving adults with asthma found that yoga interventions significantly enhanced lung function parameters, including FEV1, forced vital capacity (FVC), and peak expiratory flow rate (PEFR), as well as asthma control scores and health-related quality of life. 15 At the physiological level, Pranayama, which involves the conscious regulation of breathing, has been shown to increase vital capacity, maximal voluntary ventilation (MVV), breath-holding time, and respiratory-muscle strength. 16 Despite these promising findings, no targeted Pranayama-based intervention has yet been developed or validated specifically for women suffering from biomass smoke-induced lung impairment with distinct needs and vulnerabilities. To the best of our knowledge, no clinical trials or established guidelines have specifically addressed respiratory rehabilitation in this population using non-invasive, cost-effective Pranayama techniques. To address this critical gap, our study was designed to develop, validate, and evaluate the efficacy of a structured Pranayama module aimed at improving lung function and overall respiratory health in this vulnerable group.
Methods
Study Design
We developed a module for pulmonary rehabilitation involving VRBTs tailored to address the target population’s health issues, then sent it to a panel of experts, who evaluated its usefulness using a Likert scale. 17 Content validity was calculated using Lawshe’s formula. 18 The schematic representation of the development and content validation process is illustrated in Figure 1.
Schematic Presentationof the Development and Content Validation Process.
Development of VRBT Protocol
For the development of the VRBT intervention, we first reviewed both classical and contemporary yoga texts. Classical sources included Hatha Yoga Pradipika, 19 Gheraṇḍa Saṃhita, 20 and Patanjali’s Yogasūtras. 21 Contemporary texts included Prana and Pranayama, Asana Pranayama Mudra Bandh, 22 Light on Pranayama, 23 Yoga for Promotion of Positive Health, 24 and Yoga for Bronchial Asthma. 25 Thereafter, we conducted systematic searches of Google Scholar, PubMed, ScienceDirect, and the Cochrane Library using keywords such as Pranayama, ‘yogic breathing’, ‘breathing practices’, ‘psychic breath’, ‘voluntarily regulated breathing’, ‘lung function test’, ‘pulmonary function test’ and ‘biomass’. Complex breathing practices with no clear description were excluded. The VRBT module included standing, sitting, and prone breathing practices; Sectional Breathing; Cleansing Breathing; Cooling, Heating, and Balancing Pranayama; and Swara Pranayama. Finally, practices were sent to a panel of Yoga experts for validation.
Methodology for Validation
The process began with contacting experts over the phone, briefing them about the study, and obtaining their consent to participate. A Google Form was created for all the practices and sent via email for validation. Experts were asked to rate each practice using a Likert scale (not necessary, useful but not essential, essential). Practices rated as ‘essential’ were selected for content validation. 17
Expert Committee Validation
An expert panel of 22 yoga professionals, including 13 males and 9 females with specialised backgrounds in clinical practice and research in yoga therapy, is detailed in Table 1. All the panel members have a minimum of five years of experience in therapy, research, and yoga education. The distribution of years of yoga experience among the yoga experts involved in the content validation process is illustrated in Figure 2.
Characteristic Features of the Experts.
Years of Experience of Experts in Yoga.
VRBT Module Feasibility Testing
To assess the feasibility of the VRBT module, women who were regularly exposed to biomass smoke during cooking were enrolled in this study. Participants received a one-month VRBT module intervention, with 40-minute supervised sessions conducted physically, five days per week, by a certified yoga instructor.
Study Objective
The study objective was to assess the effect of the VRBT module on lung function in women exposed to biomass smoke.
Study Design and Setting
This pre-post study was conducted in a rural village in Ajmer district, Rajasthan. Ethical approval was obtained from the Institutional Ethics Committee of the Central University of Rajasthan.
Participant Selection
Participant selection was conducted through community outreach in the rural village based on the following inclusion–exclusion criteria. Inclusion criteria comprised rural women aged 25–60 years who provided informed consent with high biomass exposure index BEI > 60 calculated as years of exposure multiplied by hours of daily used biomass fuels (wood, dung, or crop residues) for cooking on traditional stove (chullha), a threshold BEI of 60 hour-years was identified as the minimum level significantly associated to lung function decrement. 26 Exclusion criteria included cooking with both biomass and LPG, a diagnosed chronic lung disease (e.g., COPD, asthma, or interstitial lung disease), serious comorbid health conditions, pregnancy, current psychiatric illness, regular yoga or Pranayama practice, and current or former smoking.
Data Collection
Socio-demographic data were collected once (age, education, household income, family size, and biomass smoke exposure details, including type of biomass fuel, years of use, hours per day, location of kitchen, and ventilation in kitchen). Pulmonary function was assessed at baseline (pre-intervention) and again after one month of VRBT, following American Thoracic Society/European Respiratory Society guidelines with a portable RMS Helios 401 spirometer. Participants were asked to avoid heavy meals for at least two hours before testing. At the beginning, height and weight were recorded, and then women were asked to sit upright with feet flat on the floor and back straight, wearing a nose clip. After a deep inhalation, she was instructed to exhale forcefully and completely to the best of her capacity into the spirometer. At least three acceptable manoeuvres were performed to determine FEV1, FVC, FEV1/FVC ratio, PEFR, and FEF25%–75%. The socio-demographic characteristics and biomass smoke exposure details of the study participants are summarized in Table 2.
Socio-demographic Data and Biomass Smoke Exposure Details of Participants (n = 12).
Statistical Analysis
The cutoff value of 0.45 was determined using Lawshe’s formula for the Content Validity Ratio (CVR): CVR = (Ne - N/2) / (N/2). Ne is the number of panellists who rated a practice as ‘essential’, and N is the total number of panellists.17, 18 Statistical analyses of spirometry and demographic data were conducted in JASP (version 0.17.1, 2023). Variables are presented as mean ± SD, and the normality of each outcome was assessed with the Shapiro–Wilk test. Within-group comparisons of baseline versus one-month post-VRBT spirometry measures were made using two-tailed paired t-tests at a significance level of 0.05. CVR scores obtained for individual practices under different categories of the VRBT module, reflecting their level of expert agreement illustrated in Figure 3.
The CVR Scores of All Practices Across Different VRBT Categories.
Results
Content Validity Ratio
A total of 22 experts evaluated the selected VRBT practices for individuals exposed to biomass smoke. Details of each practice and its individual CVR values are presented in Table 3.
List of Voluntarily Regulated Breathing Technique (VRBT) Practices for Biomass-exposed Individuals: Findings from Literature Review (Development Phase) with Content Validity Ratio (CVR) Scores.
A CVR threshold of 0.45, based on Lawshe’s minimum criteria, 27 ensured that only practices deemed essential by the majority of experts were retained. Of the 20 practices assessed, 14 met or exceeded this threshold (CVR ≥ 0.45) and were incorporated into the protocol, while the six practices with lower CVR values were excluded.
The total duration of the module is 40 minutes, recommended for five sessions per week. Detailed information on each practice, including the number of cycles and duration, is provided in Table 4.
Final VRBT Module Based on the Inclusion Criteria (CVR ≥ 0.45).
*Participants were instructed to breathe comfortably; they can adjust inhalation, exhalation time, and overall pace according to individual capacity. Round - A set of cycles performed consecutively. Cycle - A single complete performance of a specific practice.
Practiced Retained in Each VRBT Category
The CVR analysis (Figure 4) categorised 20 practices into seven groups: Breathing Practices (6 retained, 1 excluded), Sectional Breathing (4 retained, 0 excluded), Cleansing (1 retained, 0 excluded), Heating Pranayama (1 retained, 2 excluded), Cooling Pranayama (0 retained, 3 excluded), Balancing Pranayama (1 retained, 0 excluded) and Swara Pranayama (1 retained, 0 excluded).
Illustrates the Number of Practices Excluded and Retained Across Different VRBT Categories (CVR ≥ 0.45).
Acceptability and Feasibility of the Final Module
Of the 27 women screened for the study, 19 met the eligibility criteria and were invited to participate in the study. Fifteen agreed to enrol with an acceptance rate: 78.9% and 12 completed the study, yielding an attrition rate of 20%.
Effectiveness of the VRBT Module
The effectiveness of the VRBT module was evaluated by comparing lung function parameters (FVC, FEV1, FVC/FVC, PEFR, and FEF25–75) before and after the intervention. After one month of VRBT intervention, FVC increased significantly from 1.43 ± 0.41 L to 1.94 ± 0.37 L (p < .001; small-to-medium effect), and FEV1 rose from 1.31 ± 0.40 L to 1.57 ± 0.34 L (p = .037; small effect). The FEV1/FVC ratio decreased from 91.7 ± 7.96 to 80.6 ± 1.63 (p < .001; medium effect), and PEFR improved from 2.83 ± 0.97 L/s to 3.60 ± 0.96 L/s (p = .040; small-to-medium effect). FEF25–75 remained essentially unchanged (1.73 ± 0.78 L/s to 1.63 ± 0.67 L/s; p = .554). These small-to-moderate effect sizes indicate that the VRBT module effectively enhanced key aspects of pulmonary function. Pranayama is generally considered safe, and no adverse effects were observed in our study. Detailed results are presented in Table 5.
Table Showing the Mean ± SD Scores of the Measures of Spirometry Before and After the Intervention.
Discussion
The CVR results for the VRBT module elements indicate that the experts agree these practices are essential for women regularly exposed to biomass smoke during cooking. To evaluate the module’s efficacy, it was tested as an alternative strategy to mitigate the harmful effects of biomass smoke and improve lung function. After one month of intervention, FVC increased significantly an expected outcome, since biomass smoke exposure can cause restrictive lung disease by inducing pulmonary fibrosis and reducing lung elasticity, thereby limiting full lung expansion. 28 Chest-expanding practices in this module—such as ‘Hands In-and-Out’, ‘Hand Stretch’, ‘Tiger-Pose’, Shashankasana and Bhujangasana likely contributed to this improvement by enhancing thoracic flexibility and strengthening the intercostal muscles. This aligns with a 2016 study showing that a yoga-based pulmonary rehabilitation programme incorporating similar techniques significantly improved FVC in coal miners with COPD. 29 Enhanced chest expansion during inhalation generates more negative intrapleural pressure, recruiting previously collapsed alveoli, while controlled exhalation helps maintain ventilation-perfusion balance. 30 Concurrent respiratory-muscle strengthening and autonomic modulation further boost lung compliance and vital capacity, counteracting biomass-induced pulmonary compromise. 31 Moreover, the module incorporates sectional breathing techniques, abdominal, thoracic, and clavicular, that promote coordinated diaphragmatic and chest wall expansion through deep, controlled inhalations directed toward specific regions of the lungs, followed by prolonged exhalations. This breathing pattern activates slowly adapting pulmonary stretch receptors (SARs), which transmit afferent signals via the vagus nerve to the nucleus tractus solitarius (NTS). 31 In turn, the NTS stimulates key respiratory centres, including the parafacial respiratory group and the retrotrapezoid nucleus, modulating respiratory rhythm through bombesin-like peptides that act on the preBötzinger Complex. 32 This neurophysiological cascade enhances respiratory drive, stabilises rhythmogenesis, and increases tidal volume, collectively contributing to the observed improvements in FVC.33, 34 The observed improvements in FEV1 among biomass-exposed women indicate enhanced airflow through the larger airways. Exposure to biomass smoke is known to cause airway inflammation and mucus hypersecretion, leading to bronchial obstruction. 35 In our intervention, the inclusion of Bhastrika Pranayama and Kapalabhati, both involving forceful exhalations, likely contributed to mucus clearance and reduced bronchial inflammation. Notably, a previous yoga-based respiratory training programme incorporating these techniques also demonstrated significant improvements in FEV1 among elderly participants. 36 Additionally, the high-frequency breathing patterns employed in these practices may stimulate the Hering–Breuer reflex, which is often blunted in individuals with obstructive lung disorders. Activation of this reflex enhances carbon dioxide clearance and contributes to a shift in autonomic balance, helping to reduce physiological stress on compromised lungs.37–39 The FEV1/FVC ratio, initially elevated due to a restrictive ventilatory pattern, decreased into the normal range following the intervention. Chronic exposure to biomass smoke often results in pulmonary fibrosis, which disproportionately reduces FVC, thereby elevating the FEV1/FVC ratio.40, 41 The greater relative improvement in FVC achieved through the Pranayama module effectively normalised this ratio.
Furthermore, PEFR showed significant improvement, indicating enhanced large-airway function in individuals vulnerable to airway narrowing caused by chronic respiratory irritation. 42 Breathing practices such as Anuloma-Viloma and Bhramari Pranayama, previously shown to improve PEFR among industrial workers, emphasise diaphragmatic control and extended exhalation. These techniques likely generate positive end-expiratory pressure (PEEP), which aids in recruiting collapsed alveoli and improving oxygenation, an essential therapeutic mechanism in addressing emphysematous changes associated with biomass smoke exposure. 43 Slow, rhythmic breathing, as practiced in the module, stimulates pulmonary stretch receptors, thereby enhancing vagal afferent signalling to the NTS. 31 This increased vagal input suppresses sympathetic hyperactivity commonly triggered by chronic airway irritation, promoting autonomic balance. The resulting vagal dominance reduces bronchoconstriction and helps counteract the airway hyperreactivity characteristic of biomass-related COPD. Additionally, the emphasis on Bhramari Pranayama within these practices offers further therapeutic benefit. Nitric oxide, released from the paranasal sinuses during nasal airflow, serves as an endogenous bronchodilator, helping to alleviate small airway resistance is often worsened by the deposition of biomass particulates. 44 The Bhramari Pranayama, centred on sustained humming, generates low-frequency vibrations that resonate within the paranasal sinuses, acting similarly to Helmholtz resonators. 44 This resonance increases turbulence and cyclic pressure fluctuations within the sinus cavities, effectively ‘pumping’ the NO-rich air, synthesised by nitric oxide synthase enzymes in the sinus mucosa, into the nasal passages. 44 Research has shown that such humming can amplify nasal NO production up to 15-fold compared to normal exhalation. 45 Once inhaled, this NO-enriched air is carried into the lower respiratory tract, where NO diffuses into airway smooth muscle cells and activates soluble guanylate cyclase, subsequently in the formation of cyclic GMP. The resulting decrease in intracellular calcium facilitates smooth muscle relaxation and bronchodilation, enhancing airflow and improving spirometry measures like peak flow rates. 46 Concurrently, the slow and prolonged exhalation of Bhramari Pranayama engages the vagus nerve, thereby enhancing parasympathetic activity and increasing heart rate variability, attributed to autonomic balance. 47 Moreover, Bhramari Pranayama integrates nitric oxide-mediated bronchodilation with autonomic regulation, working synergistically to restore lung compliance, improve gas exchange, and mitigate the harmful effects of chronic biomass exposure. However, forced expiratory flow 25%–75% did not show a statistically significant improvement, indicating that a longer duration of intervention may be required to produce measurable benefits in small airway function.
Conclusion
The module was designed for simplicity and ease of adoption by women exposed to biomass smoke, ensuring its accessibility in resource-constrained rural settings where such exposure is prevalent. It has demonstrated efficacy in improving lung function parameters (FVC, FEV1, FEV1/FVC ratio, and PEFR). As this study was limited to module development, validation, and feasibility testing, we recommend conducting a full-scale randomised controlled trial with a longer intervention period to comprehensively evaluate its effects.
Footnotes
Acknowledgement
The author acknowledges the contributions of all the experts for their valuable feedback on the VRBT Module, as well as the women participants for their participation, which were crucial to the study. The address(es) from which the work originated: Department of Yoga, Central University of Rajasthan, Bandarsindri, Ajmer (305817), India.
Authors’ Contribution
Harish Sharma: Study design and conceptualization; VRBT module development and validation; recruitment and screening of participants; module delivery; data collection and analysis; writing the original manuscript.
Arjun Ram Roj: Articulation of physiological mechanisms of VRBT; data management; manuscript refinement and editing.
Ragini Rai: Module development; participant monitoring; data entry and management; assisted in preparing tables and figures.
Sanjib Patra: Study design and overall supervision; manuscript refinement & drafting; clinical oversight and methodological guidance.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.
Data Availability
The datasets of the current study are available from the corresponding author upon reasonable request.
Funding
The authors received no financial support for the research, authorship and/or publication of this article.
Patient Consent
Informed consent was obtained from all study participants.
Statement of Ethics
Ethical approval was taken from the Ethics Committee of the Central University of Rajasthan, India with reference no with reference number CURAJ/H-IEC/25/03/0013.
