disorders, which enables them to detect and address abnormalities in laryngeal and respiratory function.4
In the voice-clinic setting, the treatment of chronic cough has become a significant part of the SLP caseload, and SLP intervention provides options for patients who have either exhausted conventional management or who may require behavioral management in conjunction with medical therapies.
In this chapter the literature related to the behavioral management of chronic cough and associated laryngeal conditions by SLPs will be reviewed. The assessment process of the behavioral manifestations associated with patient complaints will be described, and treatment options starting with traditional SLP approaches and continuing with less traditional but increasingly more commonly used modalities will be discussed.
Data from systematic review of nonpharmacological interventions for chronic cough by Chamberlain et al support the use of two to four speech therapy sessions that include education, cough suppression techniques, breathing exercises, vocal hygiene and hydration, and counseling. These interventions have been found to significantly reduce cough reflex sensitivity, in turn leading to reductions in cough severity and frequency, and improving the cough-related quality of life in people with chronic cough.5 One randomized-control trial involving 87 patients with chronic cough demonstrated significant improvements in cough-symptom scores yielded by these interventions relative to control patients, who received healthy lifestyle advice and education alone.6
UNDERLYING MECHANISMS OF COUGH ADDRESSED IN SLP TREATMENT
SLP management of chronic cough is designed to increase patient self-efficacy in their ability to break the vicious cycle of cough-induced irritation. Lee et al describe cough as a “complex respiratory response,” involving a mixture of involuntary brainstem reflexes and voluntary cortical control.7 Studies on capsaicin-induced cough, and cough associated with upper respiratory tract infection (URTI), have shown that cough is under the control of the cerebral cortex and can be voluntarily inhibited or initiated.8 Deliberate cough in response to laryngeal irritation, rather than for the purpose of clearing the lungs, may lead to a positive feedback loop in which irritation leads to coughing, causing more irritation, and so on, hypersensitizing the afferent nerve receptors that results in a decreased cough threshold. Speech pathology treatment aims to increase voluntary control of the cough and to reduce cough-reflex sensitivity.1 Using capsaicin cough-sensitivity testing, ambulatory cough monitoring, and self-ratings of cough, Ryan et al demonstrated that the active suppression of cough raises the cough threshold. As their patients learned to voluntarily suppress their cough through speech pathology training and broke this cycle, their cough-reflex sensitivity and cough frequency lessened and their cough-related quality of life improved.9
UPPER AIRWAYS DISORDERS LINKED TO CHRONIC COUGH
Other laryngeal disorders often coexist in patients with chronic cough that affect their breathing, swallowing, and voice. There is a complex relationship among chronic cough, paradoxical vocal fold motion disorder (PVFMD) (also known as vocal cord dysfunction), globus pharyngeus, and muscle tension dysphonia (MTD). These conditions are, in part or in total, all viewed as manifestations of laryngeal hypersensitivity syndrome and respond similarly to speech pathology intervention.1, 10
Several theoretical models have been proposed to better characterize these conditions. The irritable larynx syndrome (ILS) model, introduced by Morrison and Rammage,11 proposes that ILS is a central sensitivity syndrome resulting from central neural plasticity due to nerve or tissue injury. This manifests as a normally structured larynx that is dysfunctional due to abnormal laryngeal posturing and palpable muscle tension involving intrinsic and extrinsic laryngeal muscles. Causes may include habitual muscle misuse, emotional distress, viral illness, and chronic gastroesophageal reflux (GER) stimulation. ILS occurs when the neuronal networks in the brainstem responsible for laryngeal control are maintained in a hyperexcitable state, resulting in an exaggerated response by the laryngeal and paralaryngeal muscles to normal sensory input. Associated symptoms can include episodic laryngospasm, MTD, globus pharyngeus, and chronic cough, and may be triggered by various stimuli. Murry et al proposed that chronic cough in patients with PVFMD was associated with aberrant laryngeal sensation; the larynx is actually edematous and desensitized from chronic acid irritation caused by LPR, leading to paradoxical adduction of the vocal folds during inspiration as a protective response against the inhalation of irritants.12
A second model, periodic occurrence of laryngeal obstruction (POLO), refers to episodic dyspnea as the primary symptom in response to triggers. In this model, cough is considered a concomitant symptom along with noisy breathing (stridor), chest and/or throat tightness, and dysphonia.13 In a recently published article, Shembel et al proposed an integrated theoretical algorithmic paradigm classifying the key clinical features of this spectrum of disorders, termed episodic laryngeal breathing disorders (ELBDs). It includes clinical subgroups to explain the considerable individual variability in symptom presentations, laryngoscopic findings, and triggers. They called for an interdisciplinary approach to improve diagnostic criteria and for future study of the underlying pathophysiological mechanisms of ELBDs.14
Chronic cough has been associated with PVFMD. These two conditions may commonly co-occur: Chronic cough has been described in as many as 80% of patients with PVFMD.15 In one study, patients with PVFMD had cough as the primary symptom in 59% of the subjects,16 and in another, adduction of the vocal folds during inspiration was present in 56% of subjects with chronic cough.17 Vertigan et al proposed a model depicting chronic cough and PVFMD on a continuum, with pure cough and pure PVFMD at either end of the continuum, and some combination of the two in the middle.18 For this reason PVFMD will be included in the discussion of the evaluation and of the different treatment modalities of chronic cough later on in this chapter.
Once a patient has been appropriately referred to an SLP, a comprehensive evaluation will be conducted, leading to treatment recommendations.
SLPs can play an important role in evaluating chronic cough, even if the etiology is unknown or multifactorial. In their book Speech Pathology Management of Chronic Refractory Cough and Related Disorders, Vertigan and Gibson describe inclusion and exclusion criteria for referral to an SLP for treatment of chronic cough and PVFMD.1 These may be useful for healthcare providers to familiarize themselves with prior to making such a referral, especially so they are able to rule out serious underlying disease and/or to adjust the dosing of medication for asthma and GER, to substitute other medications for those that may themselves trigger cough (such as ACE inhibitors), and to consider testing for nonacid pepsin-induced pharyngeal reflux.
■ Cough qualifies as chronic cough (8+ weeks since onset)
■ Cough is problematic for the patient
■ Cough persists despite medical treatment for common causes of cough
■ Untreated asthma, GERD/LPR, allergies, rhinitis (can occur concurrently with SLP treatment)
■ Current upper respiratory tract infection
■ Spirometry not conducted; asthma not reviewed in last 2 years
■ Trial of ACE inhibitor withdrawal not yet undertaken
■ Patient not reviewed by/referred by respiratory physician or otolaryngologist
The American Speech-Language Hearing Association has provided an expertly vetted, consensus-based template for SLPs to use when assessing voice and laryngeal disorders. The questions included can help guide the practitioner in determining the overall function of the larynx.19
Information provided by the patient at the time of initial evaluation should include medical diagnosis, date of onset of cough, relevant medical and surgical history, medications, and allergies. Questionnaires such as the Cough Severity Index (CSI)20 (Table 8–1), Leicester Cough Questionnaire (LCQ),21 Voice Handicap Index-10 (VHI-10)22 (Table 8–2), Dyspnea Index (DI)23 (Table 8–3), and Reflux Symptom Index (RSI)24 (Table 8–4) provide indications of the severity of the chronic cough and its impact on the patient’s life.
Vocal hygiene information, including water, caffeine, alcohol and other beverage intake; smoking and recreational drug history; and vocal activities at work, at home, and socially, provide details that may help the SLP understand the patient’s total laryngeal demand. Reflux history and exposure to environmental triggers (temperature changes, smoke, chemicals, and allergens) may also contribute valuable information.
In addition to questions about voice use, the clinician should also include questions about breathing and swallowing, as well as cough-specific questions such as:
■ When did the cough start and was there any specific event associated with it?
■ What happens just before you cough?
■ Do you initiate the cough in response to irritation, or does the cough just “explode”?
■ Are there specific events, settings, or severity of stress that usually trigger a coughing episode?
■ What strategies have you used to try to suppress the cough, or to break a cycle of coughing?
■ Has the severity and/or duration of a coughing episode caused urinary incontinence or vomiting?
■ Is your cough triggered by talking, laughing, walking, or yawning?
■ Is your cough triggered by eating in general? Eating specific foods?
■ Do you have any difficulty swallowing saliva, certain food consistencies, or liquids?
■ Do you have any difficulty breathing? Is it harder to breathe in or to breathe out?
Table 8–1. Cough Severity Index (CSI)
Table 8–2. The Voice Handicap Index 10-Item (VHI-10)
Table 8–3. Dyspnea Index (DI)
1. De Guzman V, Ballif CL, Maurer R, Hartnick CJ, Raol N. Validation of the Dyspnea Index in adolescents with exercise-induced paradoxical vocal fold motion. JAMA Otolaryngol Head Neck Surg. 2014; 140(9):823–828.
2. Shembel AC, Hartnick, C, Bunting G, et al. Perceptual clinical features in exercise-induced laryngeal obstruction (EILO): towards improving diagnostic approaches. Journal of Voice. 2018.
Table 8–4. The RSI
SLP Clinician Observations
The evaluating clinician includes observations of posture, respiratory, cough-related and vocal behaviors. For example: Does the patient exhibit noisy breathing? Does talking trigger cough? Additional observations that may help the clinician structure the treatment plan include:
■ Diaphragmatic/upper chest/clavicular
■ Inhalation:exhalation ratio
■ Route (mouth/nose)
■ Breath holding
■ Paradoxical abdominal movement during deep breathing
■ Sighing, gasping, excessive yawning
■ A lot of visible respiratory movement
■ Breathing pattern change after a short exercise challenge
■ Frequent throat clearing
■ Speaking too long on one breath
■ Running out of air when speaking
■ Voice-use habits
■ Rate of speech
■ Resonance pattern
Muscle tension assessment noted by the SLP in the upper body, abdomen, neck, jaw, face, lips, or base of tongue may help to better understand patterns of dysfunction. This may be expanded to observation of the posture while seated and standing (addressed in detail later in this chapter), and observations made during laryngeal palpation, such as tenderness/pain, reduction in thyrohyoid space, elevation during speech, and whether or not laryngeal palpation elicits coughing.
Because dysphonia is common in chronic cough, voice assessment is part of the evaluation session. A comprehensive assessment including instrumental measures is indicated in individuals who report voice changes or present with dysphonia. For those with access to specialized equipment, analysis of acoustic and aerodynamic measures of laryngeal function can provide the evaluating clinician with objective data gathered during a prescribed menu of tasks, such as vowel prolongation, pitch glides, subglottal air pressure, mean airflow during voicing, and vital capacity, to name a few. These indirect measures of voice production offer a more complete understanding of laryngeal behavior and function and allow the clinician to make inferences about laryngeal and vocal fold physiology. In the hands of a skilled clinician with appropriate training and experience, these functional measures may also help determine etiology, diagnosis, severity, and measurable changes in vocal fold physiology after a course of therapy.25
Videostroboscopic evaluation of the larynx is done routinely in voice clinics to provide information regarding laryngeal structure and function. Laryngoscopy helps to detect abnormal laryngeal movements during respiration and phonation. The addition of a stroboscopic light source provides clinicians with the illusion of a slow-motion view of vocal fold vibration allowing them to detect subtle alterations in vibratory behavior of the vocal folds. Videostroboscopy is essential to rule out laryngeal pathology such as gross or subtle vocal fold lesions, mobility issues, or airway obstruction.26 Laryngoscopy is also considered the gold standard for diagnosing PVFMD. If the patient is asymptomatic at the time of laryngoscopic examination, asking them to pant, breathe deeply, or to perform an exercise challenge, including something as sedentary as counting as quickly as possible from zero to 100 in as few breaths as possible, may sometimes elicit symptoms.27
Giliberto et al noted that in 80% of patients with chronic cough believed to be attributable to vagal neuropathy, vocal fold motion asymmetry was noted during videostroboscopic examination.28
For clinicians without a voice lab at their disposal, measures such as s:z ratio, maximum phonation time, presence of delayed onset, pitch glide, and average pitch during speech can offer insight into laryngeal behaviors. In addition, there are new smartphone applications and digital programs that can be downloaded and used by clinicians who invest the time to familiarize themselves with the technology.
Traditional Speech Pathology Intervention
The rationale for speech therapy should be understood by the patient to increase motivation and compliance. Long-term goals of therapy are reducing laryngeal irritation affecting cough and improving voluntary control of cough and general control of respiratory symptoms,6 so as to reduce and eliminate laryngeal and cough-reflex hypersensitivity,1 and the frequency and severity of the cough. The SLP should also address posture and laryngeal, neck, and shoulder muscle tension.
Treatment paradigms for chronic cough described in the literature2, 3, 6, 10 employ techniques adapted from treating functional voice disorders and PVFMD, since the primary goals are similar for all three.
■ Patient education, identification of, and strategies to manage triggers of cough
■ vocal hygiene
■ cough suppression techniques
■ postural modification
■ respiratory retraining
■ psychoeducational counseling
■ voice therapy
■ manual techniques to reduce paralaryngeal muscle tension.
Patients should be educated to recognize chronic cough as a manifestation of laryngeal hypersensitivity that doesn’t serve any physiological function (ie, airway protection), and that continuous coughing lowers their cough threshold to such a level that coughing is triggered by progressively smaller stimuli. Learning that cough is both involuntary and voluntary helps to demystify the cough as a reflex beyond the patient’s control and increases patient willingness to accept behavioral therapy.
Reviewing the patient’s answers on the CSI (and VHI-10, DI, and RSI, where applicable) will give the SLP insight into the impact of cough and priorities for each individual patient, furthering the paradigm of treating the patient and not just the disorder. The patient and the SLP should work together to identify all of the steps involved in the pattern of chronic cough that has developed, and the SLP will teach strategies to break the cycle at any of the points identified.
Vocal hygiene counseling targets reduction of laryngeal irritation to minimize stimulation of cough receptors, and improvement of hydration. SLPs can provide dietary counseling, promote behavioral management of previously diagnosed acid reflux, encourage smoking cessation and the reduction of secondhand tobacco smoke exposure, and promote nasal breathing to reduce laryngeal dryness and irritation. Helping a patient to identify vocal behaviors that may trigger a cough, such as speaking too long on one breath, or speaking at a consistently loud volume, may reduce the demands made on the larynx and contribute to decreasing the frequency and duration of the cough.
SLPs in the clinical setting often describe systemic and surface hydration as beneficial for vocal fold health. Most SLPs include recommendations about optimal hydration (64 ounces of water intake daily), avoiding presumed drying substances such as caffeine (not supported in the literature), and use of humidified air to improve vocal function. However, there is no conclusive evidence this is true, and more targeted research is needed to study the biological mechanisms influencing vocal fold hydration before a conclusive hydration regimen can be validated.29
A literature review across many disciplines by Hartley and Thibeault revealed that there is no clear understanding of the underlying mechanisms regarding the effects of euhydration (normal state of body water content/absence of relative hydration or dehydration), hypohydration, or hyperhydration across the lifespan, or of the connection between surface and systemic hydration.29 However, literature about vocal health has successfully demonstrated, in both animal and human-subject studies, the ill effects of both surface and systemic dehydration, primarily related to increased effort of phonation. Clinical advice regarding adequate surface hydration for patients with chronic cough may be based on studies showing that known cough behaviors, such as rapid deep breathing through the mouth or the breathing of poorly humidified air, can lead to dehydration of tissues in the larynx, increasing laryngeal dryness and irritation and vocal effort.30
Strategies to Control the Cough
SLPs use various breathing retraining programs and cough suppression techniques to address cough with or without PVFMD.
Cough Suppression or Distracting Techniques
With these techniques, patients learn to identify the physical sensations that precede the cough, such as a tickle, and try to suppress or delay the cough. They can implement one of the following symptom control techniques according to their preference:
■ Substitute the throat clear or cough with an effortful swallow (dry or with water), swallow while manually lowering the larynx, sucking on ice, or sucking a nonmedicated, sugar-free lozenge to increase the frequency of saliva swallows, in an attempt to delay the cough.
■ Sniff to inhale and abduct the vocal folds (some suggest a brisk sniff, others recommend a slow, drawn-out inhalation).
■ Pursed lip breathing (PLB): exhale through pursed lips or gentle prolonged fricatives in order to maximize expiratory flow through the larynx and provide positive-end expiratory pressure to maintain the vocal folds in an abducted/separated position.
■ Inhaling with PLB or through a straw helps to regulate the airflow and shift the constriction to the lips rather than the larynx.31
Laryngeal Deconstriction Techniques
■ “Silent laughing” adapted from the Estill Voice Model. With this, patients increase their awareness of laryngeal constriction by contrasting it with an open-throat sensation and learn how to maintain the open throat posture. This may also help to improve awareness of breath holding patterns, which themselves may trigger cough or PVFM episode.32
■ Relaxed throat breathing designed to shift attention away from the larynx by emphasizing diaphragmatic breathing, and to maintain vocal fold abduction throughout the breathing cycle to prevent adduction and consequent cough. Patients are guided to release tension in the upper body, shoulders, neck, jaw, and abdominal muscles, maintain an open throat sensation, and notice the gentle natural expansion and deflation in the diaphragm and or abdominal area.33
Patients are instructed to practice these techniques frequently during their daily activities when asymptomatic to facilitate automatic recall at the first sense of the urge to cough. Lastly, they are gradually exposed to their known triggers in the clinic in order to desensitize the cough response.1
Postural alignment is an important component in treating and optimizing respiratory and laryngeal function.34 Respiratory muscles have a dual function in both posture and spinal stabilization, and there are close links between breathing and musculoskeletal function. Habitually poor posture such as a slumping over may compromise the action of the diaphragm by abdominal compression.35 Alternately, posture may be influenced by altered breathing patterns. Solow et al. noted that children who are mouth breathers due to obstructed upper airways, for example, commonly exhibit habitual forward head posture (FHP) to increase the size of the airways and to facilitate breathing.36–38 Moreover, FHP is known to influence respiratory function by weakening respiratory muscles such as the sternocleidomastoid (SCM), scalene, and trapezius muscles, as well as increasing muscle tension around the thoracic spine and reducing its mobility. FHP and associated chronic neck pain have been shown in studies to reduce vital capacity.39, 40
Regarding laryngeal function, postural imbalances in the neck and head structures can have a strong effect on vocal effort, and even subtle shifts in the position of the head may significantly impact the efficiency of laryngeal movement.41 Patients with MTD often have excessive tension in their extrinsic or paralaryngeal musculature, which leads to the elevation of the larynx in the neck. Additionally, a disturbed alignment of the laryngeal cartilages (hyoid, thyroid, cricoid, and arytenoid) may affect the intrinsic laryngeal muscles, which in turn may alter the tension of the vocal folds, impairing control and resonance of the voice.34, 42 It is the authors’ anecdotal clinical observation that patients with PVFM, chronic cough, and globus share similar dysfunctional postural and muscle patterns that may aggravate their laryngeal symptoms.
It is also observed that patients with a global postviral vagal neuropathy with chronic cough may also demonstrate a vocal fold paresis with MTD secondary to glottic insufficiency that ultimately leads to the changes previously mentioned; thus, it is not always clear if these changes are primary or secondary problems.43
SLPs should try to facilitate optimal postural alignment, which allows ease, freedom, and flexibility. They should also address the ergonomics of the patients’ regular activities and encourage awareness of posture throughout the day. In more serious spinal conditions, a referral to a physical therapist is warranted.
Inspiratory muscle strength training devices (IMT) have been suggested for management of PVFMD and chronic cough.
Inspiratory muscle training has been shown to improve inspiratory muscle strength and to reduce the sensation of exertional dyspnea. IMT may facilitate a more desirable respiratory pattern and promote improved diaphragm relaxation and mechanical efficiency.44 The use of IMT for people with chronic cough warrants further research.
Comprehensive breathing retraining programs, such as the Buteyko breathing technique, are described later in the chapter. Their goal is to restore physiologically normal minute and tidal volume and to correct carbon dioxide (CO2) levels.
Motivational Interviewing (MI) is an evidence-based, person-centered counselling style used to increase intrinsic motivation by helping patients to explore and to resolve ambivalence to change.45 SLPs can effectively use MI techniques to increase patients’ adherence to cough behavioral therapy and to facilitate behavioral changes.46
Instead of taking responsibility for changing patient behavior, the SLP uses MI techniques to support and empower the patient to take an active role in their healing process. Through thinking and talking about the patient’s reasons for and means of making changes and supporting their self-efficacy—the belief they can achieve change—MI complements and ensures sustainability of treatment.
The SLP may address emotional issues associated with the cough and refer the patient to a mental health professional when these exceed the SLP’s scope of practice.
Voice therapy can be effective for patients with chronic cough in the following ways:
■ Cough and throat clearing are considered phonotraumatic behaviors that may cause vocal fold edema or hemorrhage, or lesions such as nodules and polyps. Clinically significant voice disorders are present in up to 40% of patients with chronic cough and PVFMD.1
■ The movement of the vocal folds or an alteration in the normal movement with glottic insufficiency47 and a patient’s pattern of phonation, such as hyperadduction, may stimulate pressure receptors in the larynx enough to trigger cough.1
■ Inflammatory mediators have been shown to increase following vocally fatiguing tasks and to decrease following resonant voice therapy, indicating that airway inflammation can be affected negatively or positively by phonatory patterns, therefore affecting cough.1
■ Supraglottic constriction, which is present in primary MTD and is more likely evidence of secondary MTD due to glottic insufficiency, might sometimes act as an irritant and result in throat clearing or cough. MTD often makes it feel as if there is something in the throat, especially when swallowing. The concept of muscle tension dysphagia is novel but requires further research and understanding but may be a significant contributor to the globus sensation.48
■ Cough often subsides when MTD is resolved.1
Voice symptoms may themselves resolve following treatment of the cough if they were integral to the cough. If not, dysphonia is likely a separate condition and needs to be treated.1
SLPs often consider the use of expanded modality therapies beyond those taught in SLP graduate programs, such as hypnosis, manual techniques, and Buteyko breathing techniques. The three modalities we have chosen to highlight below require special training.
Hypnosis has been shown as a viable tool in the treatment of chronic cough. Defined as “a state of consciousness involving focused attention and reduced peripheral awareness characterized by an enhanced capacity for response to suggestion,”49 hypnosis has been officially recognized by the American Medical Association as a legitimate medical tool since 1958. This shift in consciousness enables the person to tap into the natural abilities and allows them to more easily modify sensations, perceptions, thoughts, feelings, and behaviors.
A hypnotic state is usually established by an induction procedure. Most inductions include suggestions for relaxation, calmness, and well-being. People experience hypnosis differently, with some describing it as an altered state of consciousness, and others as a relaxed state of focused attention resembling a meditative state.50 Contrary to common myths and misconceptions regarding hypnosis, people who have been hypnotized do not lose control over their behavior, and usually remember what transpired during hypnosis.
The American Society of Clinical Hypnosis (ASCH) offers certification programs for licensed practitioners, including SLPs.
A retrospective chart review described 56 children and adolescents with habit cough who were treated in two different institutions by a pediatric pulmonologist or a child psychologist. In 78% of these patients, the cough resolved during or immediately after the initial hypnosis session, and within a month, an additional 12% of the patients experienced resolution of their cough. The patients were followed for an average of 13 months. The cough recurred 1 to 3 times in 22% of the patients, and all but one used hypnosis to manage it. The authors concluded that self-hypnosis offers a safe, efficient means of resolving habit cough.51
Elevated laryngeal position in the pharynx has repeatedly been noted to contribute to or, possibly more accurately stated, is one of the physical representations of MTD. This is why traditional voice therapy includes manual circumlaryngeal techniques intended to reduce musculoskeletal tension and hyperfunction by re-posturing the larynx.52, 53 This treatment involves kneading the extralaryngeal musculature in an anterior-posterior direction at specific locations while exerting a downward pull on the larynx while the patient is phonating.
Behavioral therapy incorporating manual laryngeal reposturing by an experienced voice clinician has been shown to be an effective primary modality for MTD with consistently improved perceptual and acoustic measurements of vocal function during the follow-up period.54 Anecdotally, people with chronic cough often report that the lower laryngeal position following these techniques allows for a stronger swallow, which helps them to clear mucus more effectively and reduce laryngeal irritation.
More recently, some specialized SLPs have been utilizing holistic and comprehensive physical therapy and osteopathic manual therapy techniques such as myofascial release (MFR) to facilitate improved respiratory and laryngeal function. Osteopathic principles and practice are based upon the interrelationship of structure and function and the body’s natural ability to self-regulate and heal itself.37, 55 There are different ideas about how manual therapy works, and researchers and clinicians are now beginning to look at issues of swallow and voice from a more neurocentric perspective. Tight muscles are the result of protective responses produced by the nervous system. Manual therapists use the skin and deeper structures to affect neural tension via accepted neurodynamic techniques.
When clinicians apply manual therapy/MFR to a patient with issues of chronic cough, they may be treating neuromuscular tension generated as a result of injury, disuse, surgery, or chronic disease.56 Additionally, this “safe touch” may reduce tension, allowing the muscles to relax and to communicate this relaxed state to the nervous system. When the nervous system no longer receives the feedback loop indicating a need for “protection,” it can instruct the muscle tone to change from hypertonic to a more normal tone.57
To further address excessive overall body tension, SLPs may encourage patients to become more aware of their specific tension-holding patterns, and to monitor these throughout the day. Patients can learn different strategies to release neck, tongue, and jaw tension, such as stretches and self-circumlaryngeal massage.
Dysfunctional Breathing and the Buteyko Breathing Method
This section will outline dysfunctional breathing (DB), discuss its parameters and its symptoms, and show the connection between DB and chronic cough/PVFMD. It will also describe how correcting DB can help with chronic cough/PVFMD, and introduce the Buteyko method as a means for addressing DB.
Chronic cough and other laryngeal conditions such as PVFMD and globus have been linked to DB and are among the most common symptoms associated with it.58 There is no consensus on a precise definition of DB, but the term generally describes breathing disorders where chronic or recurrent changes in breathing pattern cause respiratory and nonrespiratory symptoms in absence or in excess of organic respiratory or cardiac disease.59, 60 The disordered breathing pattern may reflect abnormalities in rate or depth of breathing, or in breathing mechanics that may involve the nose, oropharynx, larynx, chest wall muscles, and/or diaphragm.60 PVFMD is considered a form of DB.61 Barker and Everard proposed that DB can be subdivided into either thoracic or extrathoracic forms. Thoracic DB is characterized by predominantly upper chest breathing. Extrathoracic DB involves the upper airway in addition to the upper thoracic breathing pattern, and includes PVFMD and exercise-induced laryngomalacia.61 Dysfunctional breathing may contribute to disproportionate dyspnea and other medically “unexplained” symptoms that don’t respond to asthma medications.62
Some of the older literature focused on hyperventilation syndrome (HVS) and hypocapnia; however, it is recognized now that HVS and its associated signs and symptoms cannot always be attributed to, and have weak correlations with, CO2 levels. Instead, a broader characterization of symptoms should include the biochemical, biomechanical, and psychophysiological dimensions of breathing.63 The biochemical dimension refers to hyperventilation with symptoms arising from respiratory alkalosis and hypocapnia. The biomechanical dimension refers to respiratory muscle and breathing pattern dysfunction, and the psychophysiological dimension refers to interactions of physiology with mental and emotional factors. These dimensions can be related or distinct and produce the unexplained symptoms.64
Symptoms of Dysfunctional Breathing
Dysfunctional breathing can affect individuals in different ways. Some people complain of mental distress; others may experience musculoskeletal and physical symptoms such as neck and shoulder problems, chronic pain, and fatigue. Many report a combination of both mental and physical factors.65
Biochemical changes in the body due to DB may seriously impact emotional well-being, circulation, digestive function, and the musculoskeletal structures involved in respiration.37 DB may result in: cough, significant dyspnea, chest pain and tightness, exercise-induced breathlessness, frequent yawning or sighing, anxiety, lightheadedness, palpitations, muscle spasm, and fatigue.
Nonrespiratory neurovascular symptoms such as dizziness, numbness and tingling have the strongest relationship to low CO2, the biochemical dimension of breathing.
Respiratory symptoms such as inability to take a deep breath, chest tightness, and shortness of breath are typically related to the biomechanical and psychophysiological dimensions of DB.64
Prevalence of Dysfunctional Breathing
Diagnosis of Dysfunctional Breathing
The diagnosis of DB first requires the exclusion and/or treatment of organic pathology. Only then can a functional diagnosis be entertained.70 A variety of methods may be used to evaluate breathing function clinically, including instrumentation, observation, and palpation.
End-tidal capnography measures end-tidal carbon dioxide (ETCO2) in exhaled nasal air to determine the presence of chronic or intermittent hyperventilation. ETCO2 correlates with alveolar carbon dioxide concentration (PACO2), which in turn correlates with arterial levels of CO2 (PaCO2). Capnography also provides information about respiratory rate and rhythm, and whether the breathing is smooth and rhythmical or choppy and irregular.37, 71
The Manual Assessment of Respiratory Motion (MARM) is a manual procedure used for assessing chest and abdominal movement during breathing. It quantifies the extent of thoracic breathing. The examiner can also gauge various aspects of breathing such as rate, volume, and regularity.74
Symptoms questionnaires such as the Nijmegen questionnaire (NQ)63 and the Self-Evaluation of Breathing Questionnaire (SEBQ)63 have been developed to evaluate all dimensions of breathing-related symptoms and their severity.
An accurate diagnosis in itself can provide significant reassurance and relief of anxiety, and may reduce symptoms.59
Hyperventilation and PVFM/Vocal Cord Dysfunction (VCD)
Hyperventilation is common among patients with PVFMD, and likely accounts for symptoms of lightheadedness, visual changes, numbness, tingling, extremity heaviness, dizziness, and near-syncope or syncope described by these patients. The PaCO2 of patients with PVFMD is typically lower than normal because of the hyperventilation that accompanies most attacks.75 In a retrospective study of 54 patients with exercise-induced PVFMD, 76% had concomitant hyperventilation as measured by a symptom questionnaire. An end-tidal CO2 of less than 30 mm Hg, a physiologic consequence of hyperventilation, was seen in 48% of the patients.76
It is interesting to note that clinics use voluntary hyperventilation when trying to provoke PVFM symptoms during the laryngeal exam. The fact that cough and PVFM symptoms can be reproduced by hyperventilation suggests that hyperventilation may contribute to symptoms. Parker and Berg have suggested that hyperventilation may be a possible mechanism for explaining PVFMD and may require alternative therapeutic approaches in people unresponsive to traditional SLP therapy.76 The Buteyko breathing program discussed next is designed to reverse hyperventilation and may be a viable treatment option for these patients.
Buteyko Breathing Retraining
One form of respiratory retraining is the Buteyko Breathing Technique (BBT). It is based on Ukranian physician Dr. Konstantin Buteyko’s theories that many symptoms and disease processes may be caused by chronic “overbreathing” or hidden hyperventilation, and the resultant CO2 deficiency. Due to the Bohr effect, the lowered levels of CO2 inhibit the release of oxygen from hemoglobin to the tissue cells which, in turn, may lead to ischemia, fatigue, and other symptoms.78 BBT is an educational program designed to restore normal breathing patterns. It consists of breathing exercises and lifestyle factors of physical exercise, food, speech, and sleeping as they relate to healthy breathing.
The BBT’s approach for cough management is similar to the traditional SLP management of cough suppression and restoring relaxed nasal diaphragmatic breathing. In the context of the BBT theoretical model, cough can manifest as both the cause and effect of overbreathing. The BBT intends to address the underlying causes of overbreathing, while SLP intervention for cough is designed to addresses symptoms.6
The BBT aims to reprogram the respiratory center to adapt to higher levels of CO2 and thus to improve the symptoms caused by the chronic hyperventilation. BBT exercises involve the voluntary reduction of the volume of breathing through the relaxation of the respiratory muscles in combination with breath-holding techniques. The improvement in breathing control and function experienced with the BBT may be explained by mechanisms other than raising CO2 alone. For example, the biomechanical problem of hyperinflation of the lungs and the anxiety surrounding symptoms are both likely to decrease with this treatment methodology.64
The BBT is best known as a treatment for asthma. Several clinical trials on BBT showed that patients substantially reduced their medication use with no deterioration in lung function and improvement in asthma symptoms.79–81 The BBT is also used as a supportive therapy for people with chronic mouth breathing, nasal symptoms, COPD, obstructive sleep apnea and snoring, and stress-related disorders. Its principles and techniques are also increasingly being used to help improve athletic performance.82
To address chronic cough, patients are educated about the negative impact that excessive breathing and harsh cough can have on the tissue linings of the nose, throat, and lungs. These can cause dehydration and inflammation of the tissues and, consequently, an increase in mucus production to protect the drying airways. With ongoing overbreathing, this mucus may thicken and become harder to clear, exacerbating the original cough, creating a vicious cycle (Figure 8–1). Mouth breathing, common in patients with chronic cough,3 may also cause the throat to become dry and raw if sustained, causing a tickling sensation, which patients report often leads to coughing. This can cause a persistent cycle of dry throat, coughing, irritated and dry throat, coughing, and so on. Coughing is considered a hyperventilation behavior because of the excessive loss of CO2 with the fast and forceful exhalation followed by the large inhalation through the mouth, often repeatedly as in coughing fits. The excessive loss of CO2 aggravates smooth muscle constriction in the airways of susceptible people.37, 83
The BBT emphasizes establishing and maintaining gentle nasal breathing at all times, including during exercise, speech inhalation, and sleep. This may be beneficial for patients with chronic cough, since studies have shown that as many as 50% of these patients are habitual mouth breathers, which may, in turn, further exacerbate laryngeal symptoms.3, 84 As gentle nasal breathing is habituated, tissue dryness and irritation and excessive mucus production may diminish, allowing the cough to subside.
Nasal breathing may improve lung function and reduce asthma exacerbations.85 In one study of young people with asthma who were required to breathe only through the nose during exercise, post-exercise bronchoconstriction was almost completely inhibited. When instructed to breathe only through the mouth during exercise, an increased bronchoconstriction occurred, as measured by spirometry, flow-volume relationships, and body plethysmography.86
Open-mouth breathing caused by chronic nasal obstruction has also been identified as a risk factor for the collapse of the pharyngeal airway and may also be an important factor in the pathogenesis of obstructive sleep apnea. The airway dilator muscles lose some of their efficiency when the mouth is open. With nasal breathing, neural activity in the airway dilator muscles stabilizes the upper airway.87 Future research is needed to explore how similar mechanisms may also affect the upper airways in PVFMD and cough.
Another way in which BBT reduces chronic cough is related to the psychological triggers, which may coexist and in many cases have been implicated in chronic cough.1 Current research associates emotional disorders with decreased vagal tone as indicated by heart rate variability.88 Breathing modification has been suggested to balance the autonomic nervous system by reducing sympathetic and increasing parasympathetic nervous system activity. This may assist with recovery and restoration of function in body systems disturbed by stress.89
Despite the relation of the BBT’s core principles with its stated outcomes as proven by external studies, the BBT therapy itself has not been empirically tested for the treatment of chronic cough without asthma.