Buteyko Breathing Technique for Exertion-Induced Paradoxical Vocal Fold Motion (EI-PVFM)
Introduction
Paradoxical Vocal Fold Motion (PVFM) is one type of episodic upper airway obstruction thought to result from true vocal fold adduction during inspiration. Dyspnea (shortness of breath) is the hallmark symptom.1, 2, 3, 4 The exertion-induced variant—the focus of the present study—is typically referred to as exercise-induced PVFM (EI-PVFM)5 or exertion-induced laryngeal obstruction.6, 7 Although neurological, anatomical, biochemical, and psychogenic mechanisms have all been proposed, there has been little formal consensus about the etiology of PVFM,2, 8 or the treatment approach.9 Because of the altered biomechanical pattern during inspiration, Barker and Everard defined PVFM as a form of extrathoracic dysfunctional breathing disorder,8 associated with hyperventilation: “In some patients minute volume increases to induce hypocapnia (hyperventilation) either very transiently with sighs that commonly accompany PBD [pattern disordered breathing], or more persistently during periods of stress.”8 (p. 54).
Clinically, hyperventilation is characterized by rapid and shallow or deep breathing,10 and like PVFM results in dyspnea and respiratory distress. Mechanistically, hyperventilation is breathing beyond metabolic needs; the result is abnormally low blood gas CO2 levels (<35–45 mmHg).11, 12 In a retrospective study, Parker and Berg13 found that 41 of 54 patients (76%) with PVFM seen in their medical practice also exhibited symptoms of hyperventilation, including dizziness and limb paresthesia. Forty-eight percent of this cohort also had end-tidal carbon dioxide (ETCO2) levels below the 30 mmHg indicative of hyperventilation. Because of the high prevalence of hyperventilation found by Parker and Berg13 in patients with PVFM and acknowledged in other studies,14 a behavioral intervention aimed at reducing hyperventilation15 may also be applicable for PVFM. While specific claims about the natural course of the disorder and physiologic, mechanistic, or behavioral connections between PVFM and hyperventilation require further study to define, we will address a part of the gap in knowledge in this study of response to a behavioral intervention.
One behavioral intervention paradigm aimed at the treatment of a wide array of breathing disorders including hyperventilation is Buteyko breathing technique (BBT), developed by Dr. Konstantin Buteyko in the 1950s. Based both on accordance with literature on hyperventilation and efficacy studies,16 BBT therapists claim chronic, subclinical hyperventilation may be an underlying cause for various breathing disorders, and that in patients with asthma and hyperventilation, BBT practice has been shown to result in increased ETCO2, and decreases in both heart rate (HR) and respiratory tidal minute volume (RTMV).17 Efficacy trials on BBT have previously been shown to mitigate asthma-related dyspneic symptoms, reduce self-reported inhaler use, and improve quality of life in individuals with asthma.18, 19, 20, 21 In particular, one study on the efficacy of BBT has shown a reduction in RTMV and HR in patients with asthma and hyperventilation.22 In addition, guidelines for the physiotherapy management of the adult, medical, spontaneously breathing patient include treatment methods for mitigation of hyperventilation, which include reduced RTMV.15 The BBT approach aims to increase blood gas CO2 levels and reduce HR and RTMV, which is ultimately said to mitigate hyperventilation and frequency and severity dyspnea. A specific BBT exercise, “relaxed breathing,” promotes a reduced HR23 (p. 242) as well as reduced tension of the neck, shoulders, and abdomen.24 Relaxed breathing also promotes a naturally occurring short pause between the expiratory and inspiratory cycles. A lengthier pause is considered a sign of healthy breathing and good oxygen-carbon dioxide balance. This claim can be seen both in respiratory physiology literature10 and in the underlying theoretical basis for BBT.17 Buteyko breathing is similar in many ways to the standard treatment for PVFM—so-called “respiratory retraining” (RR), but at the same time presents treatment aspects that are markedly different from traditional RR. The ultimate goal of both approaches is to address physiological respiratory behaviors in order to mitigate frequency and severity of dyspnea symptoms through altered breathing patterns.3, 25, 26, 27, 28, 29, 30 Both approaches focus on nasal breathing, as well as body alignment and posture, and address symptoms of anxiety through mindfulness/awareness, when applicable. Indirect therapy, such as psychoeducational counseling and knowledge of basic respiratory anatomy and physiology, is also typically implemented in both BBT and traditional RR. However, the presumed underlying physiological targets differ between traditional RR and BBT, which may introduce the possibility that BBT can be regarded as a variant of RR, which suggests ventilatory and metabolic aspects of respiratory physiology as an underlying cause. The proposed theory addresses underlying metabolic respiratory mechanisms that may lead to the clinical presentations of PVFM (eg, dyspnea, respiratory distress). At present, there is insufficient evidence to support either traditional RR9 or BBT31, 32 in the treatment of PVFM, nor has the effect of BBT on PVFM been reported.33 Further investigations into the role of these behavioral interventions for PVFM, hyperventilation, and other forms of dysfunctional breathing are critically warranted. Particularly in individuals with PVFM associated with hyperventilation, BBT may reduce dyspnea and improve respiratory homeostasis.
The goal of the current study was to determine the usefulness of BBT in patients with PVFM, specifically exercise-induced PVFM (EI-PVFM). EI-PVFM was chosen due to exertion's natural impact on respiratory drive, metabolic demands, and respiratory volume, which likely predisposes individuals to hyperventilation syndrome.34 The primary objective of the study was to assess the effects of BBT on dyspnea severity using the Dyspnea Index (DI) and dyspnea frequency in people with EI-PVFM, using a number log of the frequency of dyspneic episodic events. The second objective was to assess the physiological basis of the treatment, namely whether BBT can improve markers of hyperventilation in persons with concomitant EI-PVFM and hyperventilation.
Section snippets
Participants
The target sample size was nine participants, based on a power analysis of anticipated pre- to post-therapy changes in DI scores at 10.4 (±9.34) points35 and a power of 0.9. A total of 15 participants were recruited for the study over a period of 20 months (between October 2015 and June 2017), with the expectation of up to 20% attrition after enrollment. Primary recruitment involved patients diagnosed with EI-PVFM by laryngoscopic observation of vocal fold approximation during the inspiratory
Participants
Of the 15 participants who were enrolled in the study, three participants were lost to attrition before treatment began. Ten of the remaining 12 participants completed the protocol in its entirety. Two participants did not complete the final post2 stage. Therefore, analysis of treatment effect was performed on 12 participants and treatment retention on 10 participants. Data from one male and 11 females were analyzed. Three participants were using asthma inhalers but exhibited no evidence of
Discussion
The findings provide preliminary support for both the treatment efficacy and the theorized physiological underpinnings of the BBT approach for persons with EI-PVFM. The cohort was consistent with speculations on high prevalence of EI-PVFM and hyperventilation.39 Following BBT, dyspnea severity was reduced, suggesting BBT efficacy, with reductions in RTMV and HR; these secondary outcomes are consistent with the changes expected based on alleviation of hyperventilation and suggestions regarding
Conclusion
The current study's preliminary findings suggest BBT may be useful in reducing dyspnea severity and RTMV in patients with EI-PVFM, who also presented with hyperventilation. BBT may also positively impact other cardiopulmonary parameters, such as RTMV and HR. Further research is needed to test the efficacy of BBT using a larger and more authoritative clinical trial. Future investigations should also directly compare the efficacy of BBT to traditional RR approaches. Further study is needed to
Author contributions
D.H.K., O.S., H.G. K.B., and K.V.A. designed the study as part of the first author's Master's thesis. H.G. carried out BBT treatment at Boston Medical Center (BMC). G.P.K. supervised research administration at BMC. J.V.S. advised on respiratory disorders. Data analysis was conducted by D.H.K. O.S., and K.V.A. D.H. wrote the manuscript. All authors commented and participated in preparing the manuscript for publication.
Acknowledgments
The Wright Mark 14 Respirometer used in this study was donated by nSpire Health, Inc with thanks to Mr. Dan Graff. Our sincere appreciation and gratitude go to Adrianna Shembel, PhD, for her long-standing contribution to this research study and manuscript. We thank to Ms. Sigalit Mangut Leiba for her assistance with statistical analysis, and to Mrs. Tasha Watson-Coughlin for assisting with questions pertaining to REDCAP. Finally, we thank to the research assistants at Boston Medical Center and
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