Download - Seeing the Forest Through the Wheeze: Laryngeal Involvement in

Seeing the Forest Through

the Wheeze:

Laryngeal Involvement in

Episodes of Dyspnea

Marc Haxer, M.A., CCC-Sp

Departments of Speech-Language Pathology and Otolaryngology/Head and Neck Surgery

University of Michigan Health System

Introduction

• Goals/Objectives – Become familiar with upper versus lower

airway etiologies for dyspnea

– Become able to differentially diagnose upper airway involvement in dyspnea

– Become familiar with chronic cough, involuntary vocal fold closure, laryngospasm, adductory laryngeal breathing dystonia and irritable larynx syndrome as they relate to compromised respiration

Larynx

• Cartilaginous tube – Connects inferiorly to respiratory system

• Trachea, lungs

– Connects superiorly to vocal tract • Pharynx, oropharynx, nasopharynx

• Anatomic orientation important – Highlights interactive relationship between vocal

subsystems • Pulmonary mechanism

• Laryngeal valve

• Supraglottic vocal tract resonator

Larynx

• Complex arrangement of muscles, mucus membranes, and other connective tissue – Soft tissues responsible for airway preservation

– Cartilage housing serves as columnar protective shield for laryngeal valve

• Muscles and cartilages provide three levels of “folds” – Serve as sphincters which provide communicative and

vegetative functions

– Angles of closure multidimensional (valve in horizontal and vertical planes)

Larynx

• Upper rim of larynx formed by aryepiglottic folds

– Fibrous membrane extending from epiglottis to arytenoid towers

– Thus serves as lateral boundary of larynx

– Epiglottic inversion posteriorly/inferiorly over laryngeal vestibule results in separation of larynx from pharynx and serves as most superior level of airway protection

Larynx

• Second sphincter formed by ventricular folds – Not normally active during phonation – Can become hyperfunctional during episodes of

increased vocal effort/extreme vegetative closure – Directly superior to ventricle/true vocal folds – Form double layer of medial closure w/TVFs if needed – Principle function is to increase intrathoracic pressure

by blocking exhalatory airflow from lungs – Compress tightly during sneezing/coughing, lifting,

emesis, childbirth, defecation – Also provide medial level of airway protection during

swallows

Larynx

• Most inferiorly are true vocal folds

– Provide vibrating source for phonation

– Also close tightly for nonspeech and vegetative tasks

• Thus, larynx and vocal folds function as variable valve

– Modulate airflow through VFs during phonation

– Close off trachea/lungs to prevent soiling of airway during swallows

– Provide resistance to increased abdominal pressure during effortful activities

Neurologic Supply

• Cranial nerve X innervates larynx peripherally

– Vagus = “wanderer”

– Innervates sites from skull to abdomen

• Innervates larynx through two important branches

– Superior laryngeal nerve (SLN)

– Recurrent laryngeal nerve (RLN)

Neurologic Supply

• Superior laryngeal nerve

– Branches off vagus near nodose ganglia in neck

– Course alongside carotid artery

– Forms internal/external branches

• Internal branch inserts through thyrohyoid membrane superior to VFs and provides all sensory information to larynx

• External branch is motor nerve to cricothyroid (CT) muscle

Neurologic Supply

• Recurrent laryngeal nerve – Extends to thorax

– Forms long loop under heart before coursing superiorly under thyroid gland and into larynx

– Different on right/left sides of body • L RLN courses under aorta

• R RLN course under subclavian artery

– Nerves (especially left) susceptible to injury

– Supplies all sensory information to area below VFs and all motor innervation to PCA, TA, LCA, and IA muscles

Larynx

Where/What’s the Problem?

• Upper airway issue?

• Lower airway issue?

• Problem w/inhalation?

• Problem w/exhalation?

• Problem w/both?

• Acute versus chronic issue?

• Episodes same/different w/regard to presentation?

• Episodes same/different w/regard to severity?

Upper Airway Issues that can Compromise Respiration

• Unilateral vocal fold motion impairment (abductory) • Bilateral vocal fold motion impairment (abductory) • Reinke’s edema • Laryngeal papilloma • Laryngeal carcinoma • Vocal Fold Granuloma • Laryngospasm • Involuntary vocal fold closure • Cough • Adductory Laryngeal Breathing Dystonia • Acute infection (eg croup, laryngitis, epiglottitis) • Allergies • Laryngomalacia • Tracheomalacia/Stenosis • Foreign body in airway • Extrinsic/intrinsic airway compression by tumor inferior to glottis

Unilateral Vocal Fold Paralysis

Bilateral Vocal Fold Paralysis

Reinke’s Edema

Laryngeal Papilloma

Laryngeal Carcinoma

Vocal Fold Granuloma

Laryngitis

Laryngomalacia

Tracheal Stenosis

http://homepage.mac.com/changcy/voicebreathing.htm

Lower Airway Issues that can Compromise Respiration

• Asthma

• COPD

• Emphysema

• Restrictive Airway Disease

• Lung Cancer

• Interstitial lung disease

Chronic Illnesses/Disorders That Can Affect Laryngeal Function

• Chronic sinusitis/URI

– Cough/throat clear

• Can cause trauma to laryngeal tissues

– Antihistamines

• Dry secretions

• Resultant dehydration of VFs

– Anti-cough medications

• Drying agents

• Contribute to VF dehydration


• Asthma

• Chronic obstructive pulmonary disease

• Emphysema

• Lung CA – Above can be direct/indirect cause of laryngeal

problems • Vocal fold tissue abuse

• Poor breath support

• Vocal fold dryness secondary to medication use

• VF paresis/paralysis

• Cough


• Allergies

– Congestion/edema of VFs

– VF dehydration

– VF tissue trauma

• cough/throat clear


• Laryngopharyngeal reflux disease – Is GERD that affects pharynx/larynx

– Occult chronic reflux is etiologic factor in high percentage of patients w/laryngologic complaints

– Reflux involves multiple anatomic sites • LES

• Entire esophagus

• UES

• Larynx/pharynx/oral cavity

• Trachea

• Lungs


• Laryngopharyngeal reflux disease – Symptoms

• Chronic hoarseness • Voice fatigue • Cough • Chronic throat clearing • Globus sensation • Sensation of choking • Edema • Ulceration/granulation of laryngeal mucosa • Hyperkeratosis • Carcinoma of larynx


• Laryngopharyngeal reflux disease – LPRD best managed via multidisciplinary team

• Otolaryngologist

• Internist/PCP

• Gastroenterologist

• Allergist

• Pulmonologist

• Speech Pathologist

• Nutritionist


• Laryngopharyngeal reflux disease

– Almost always associated w/some degree of aspiration

• Amount of aspiration may be clinically insignificant

• Or, may be clinically significant enough to cause:

– Chronic cough

– Involuntary vocal fold closure

– Reactive airway disease

– Difficult to control asthma

– Pneumonia

– Bronchiectasis



– Evaluation

• Esophagram

• Dual 24-hour pH probe

• Bravo capsule study

• Flexible fiberoptic endoscopy



– Treatment

• Behavioral

• Chewable antacids

• Viscous antacids

• H2-receptor antagonists

• Proton pump inhibitors

• Nissen fundoplication/Stretta procedure


• Smoking/alcohol abuse/illicit drug use

– Erythema/edema

– Generalized inflammation

– Drying of mucous membranes

– Incoordination/dysarthria/impaired judgment

– LPRD

– Chronic cough

Primary Disorder Etiologies That Can Affect Laryngeal Function

• Environmental stress – Loss of employment – Death of spouse/significant other – Family conflict

• Conversion behaviors – Avoidance behavior(s) developed to counteract stressful

situation(s) – Whispering, muteness, unusual dysphonias

• Identity conflict – Establishment of own personality

• High-pitched falsetto in post-pubescent adolescent • Weak, juvenile, thin-sounding voice of adult female • Raised pitch in male-to-female transsexual

Case Study #1

• 41 year-old female • Presenting Dx of “difficult to control asthma” • Trialed on multiple courses of different asthma

medications over a # of months w/no appreciable improvement in respiratory function

• No hx of smoking/excessive alcohol use • Presenting symptoms

– Chronic sense of chest tightness – Chronic restriction of inhalation/exhalation – Sense of “elephant sitting on chest” – Chronic hoarseness X12 months w/no Otolaryngologic

examination – Denied sense of throat constriction

Case Study #1

• Presenting symptoms not consistent with upper airway involvement

• Extended duration of hoarseness concerning

• Referral to Otolaryngology

• Fiberoptic endoscopic exam results – Marked endolaryngeal erythema/edema

– Laryngeal candidiasis

– No concerning lesions

Case Study #1

• Treatment

– Speech Pathology not involved in Tx

– Aggressive pharmacologic management of LPRD/candidiasis for six months

• Oral anti-fungal medication (swish/swallow)

• Anti-reflux management

– Rigid behavioral strategies

– 40mg PPI b.i.d. 30 minutes prior to oral intake

Case Study #1

• Results of treatment

– 40 lb. weight loss

– Return of baseline vocal functioning

– Return of baseline respiratory functioning

– Secondary to tx, QOL markedly improved

Irritable Larynx Syndrome

Laryngospasm

IVFC

Chronic Cough

Chronic Throat Clearing


• Postulated by Morrison, Rammage, and Emami in 1999

• Suggests that various laryngeal behaviors can be categorized within the context of “hyperkinetic laryngeal dysfunction”

These Behaviors Include:

• Muscle Tension Dysphonia

• Episodic laryngospasm

• Globus sensation

• Cough

Muscle Tension Dysphonia

• Incoordination between respiration and phonation

• Above results in elevated levels of laryngeal/throat muscle tension

• In turn, contributes to general laryngeal hyperfunction – Laryngeal pain/discomfort

– Increased vocal effort

– Vocal fatigue

Muscle Tension Dysphonia

• In addition to elevated levels of tension in larynx/throat, can also contribute to increased tension in neck, shoulder, and upper chest musculature

– Can then masquerade as sensation of limited movement of air through the neck/throat area during inhalation

Episodic Laryngospasm

• Adduction of VFs during inhalatory phase of respiration • In differential Dx

– Involuntary Vocal Fold Closure – Adductory Laryngeal Breathing Dystonia – Closure of VFs as protective mechanism during reflux episode

• Somatoform/anxiety disorder? – Intrinsic/extrinsic stress vs. psychological issue – Larynx “Achilles heel” for stress/anxiety?

• Variations on a theme? – Asthma variant

• Functional? – Implies normal structure/function of larynx but inappropriate behavior

of the same

Globus

• “Lump in throat” sensation

• Secondary to increased levels of muscle tension in larynx? – Inappropriate resting or holding position of

laryngeal musculature

• Secondary to laryngopharyngeal reflux disease? – Laryngeal erythema/edema masquerading as

sensation of mucous

Cough

• Secondary to respiratory disease?

– Acute vs. chronic

– Productive vs. non-productive

• Secondary to laryngopharyngeal reflux disease?

• Increase in stress/anxiety?

– Stress vs. psychogenic

– Functional?

• Secondary to allergies?

• Neuropathic?

For All of These Behaviors

• Larynx appears structurally normal on visualization

• Abnormal laryngeal muscle posture present – Anteroposterior “squeeze” of laryngeal

complex

• Palpable laryngeal muscle tension present – Massage of thyroid cartilage/hyoid bone

results in pain, discomfort


• Defined as:

– “hyperkinetic laryngeal dysfunction resulting from an assorted collection of causes in response to a definitive triggering stimulus”

ILS – Inclusion Criteria

• Symptoms attributable to laryngeal tension – Dysphonia and/or laryngospasm

• With or without chronic cough • Visible and palpable evidence of tension

– Lateral and A/P compression of larynx during laryngoscopic examination

– Discomfort during laryngeal palpation

• Presence of sensory trigger(s) – Airborne substance – Esophageal irritant – Odors

ILS – Exclusion Criteria

• Apparent organic laryngeal pathology

• Identifiable neurologic disease

• Identifiable psychiatric diagnosis

Patients with Dx of ILS

• Tend to have complex combination of signs, symptoms, and background factors

• Laryngospasm and dysphonia are two major ILS symptoms – Laryngospasm most distressing to patient

• More minor symptoms – Globus

– Cough

– Perilaryngeal pain

• Above will vary from patient to patient

ILS Symptom Complex Grouping

• Laryngospasm alone

• Laryngospasm with dysphonia, globus, or cough

• Dysphonia alone

• Dysphonia with laryngospasm, globus, or cough

• Other

– Globus and/or cough

Triggering Stimuli

• Airborne irritants

• Reflux

• Perfumes/colognes

• Foods

• Emotions

• Voice use

• Exertion

Possible Etiologic Factors

• Reflux

• Viral

• Stress/Psychogenic

• Asthma

• Environmental allergy(ies)

• Torsion injury to neck/throat/larynx

Hypothesis for ILS

• Develops as reaction to some sort of CNS change that leaves sensorimotor pathways in state of hypersensitivity

• # of possible causative factors

• Several can be active in any one patient

• Most prevalent – Emotional distress

• Stress component vs. psychogenic cause

– Habitual inappropriate resting posture of laryngeal musculature

– LPRD

– Post-viral illness • Viral neuropathy

Treatment

• Reflux management – Behavioral/pharmacologic

• Exercises

• Stress management

• Massage/manipulation

• Non-reflux pharmacologic management – Botulinum Toxin A

– Nebulized topical anesthetic

– Amitriptyline/Gabepentin

Cough

• Important respiratory defense mechanism

• Responsible for clearance of excessive secretions, fluids, or foreign materials from the airway

• Despite this protective role, excessive coughing can result in multisystem issues

– Anxiety, dysphonia, fatigue, urinary incontinence, emesis, rib fracture(s), etc.

Cough – Differential Diagnosis

• Upper Respiratory Tract

• Allergic or vasomotor rhinitis, postnasal drip syndrome, infectious/post-infectious cough, sinusitis


• Lower Respiratory Tract • Abscess, allergic inflammation, aspiration, asthma, bronchiectasis, bronchitis, COPD, cystic fibrosis, drugs, eosinophilic bronchitis, interstitial lung disease, pertussis, primary or metastatic lung tumors, sarcoidosis, tuberculosis


• Cardiovascular system

• Gastrointestinal system

• Left ventricular failure, mitral stenosis, medications (ACE inhibitors)

• Reflux disease (laryngopharyngeal)


• Central Nervous System (psychological response)

• D’Urzo and Jugovic (2002)

• Habit cough, chronic cough, psychogenic cough, neuropathic cough

Cough – Clinical Presentation

• School age children to older adults

• Average length of cough months to years

• Most pts have attempted multiple interventions w/o resolving of cough

• Most have associated fatigue

• Most do not have accompanying hoarseness

• Most have been treated for reflux for a short period of time w/o success

Cough

• Habit/chronic cough – Larynx engaged in disordered loop of behavior

• Psychogenic cough – Cough occurs secondary to emotional/psychological issues

• Laryngeal hypersensitivity/hyper-reactivity – Larynx over-reacts to triggering stimuli secondary to irritation of

the larynx by refluxed stomach contents

• Neuropathic cough – Cough occurs secondary to viral neuropathy

• Cough Hypersensitivity Syndrome (Morice, 2009) – Th2-type immune response vs. reflux symptoms

Behavioral/Environmental History

• Nature of cough – Light dry coughs throughout the day – Severe/overwhelming cough “attacks”

• Pattern of cough – Occurs at specific time(s) of day? – Follow meals or specific activity(ies)? – Getting worse/remaining stable?

• Work/home/social environment – New building materials? – Ventilation relative to work space? – Dusty and/or dry environment?

Cough - Tx

• Habit/chronic cough – Behaviorally reposture larynx into appropriate pattern of functioning – Improve laryngeal environment – Improve awareness of sensations/behaviors that precipitate cough – Implement behavior to delay/eliminate the cough before it

“recalibrates” laryngeal sensitivity threshold

• Psychogenic cough – Behavioral/psychological treatment

• Laryngeal hypersensitivity/hyper-reactivity – Behavioral/aggressive reflux tx

• Neuropathic cough – Amitriptyline, Gabepentin

• Cough Hypersensitivity Syndrome – Treat causal phenotype appropriately

Involuntary Vocal Fold Closure

• Confusing disorder that is frequently mistaken for asthma or organic obstructive upper airway conditions

• Fully 78 different names for disorder in the literature

• Encompasses inappropriate vocal fold adduction during inhalation

IVFC - Symptoms

• Sudden onset

• Compromised inhalation

• Sensation of throat closure/tightness

• Inhalatory stridor

IVFC Mimicking Asthma

• IVFC

– Throat tightness, dysphonia during episodes – esp inhalation

– Little/no improvement w/use of bronchodilators during episodes

– No night awakening or cough unless associated with reflux-induced laryngospasm

• Asthma

– Chest tightness – esp exhalation

– Improvement w/use of bronchodilators

– Nighttime symptoms frequent

IVFC Mimicking Asthma

– Symptoms early in exercise – Recovery period 5-10

minutes – Turbulence at level of

larynx, +/- stridor – Pt able to pant/breath hold

during episode – may improve symptoms

– PFTs characterized by truncated inspiratory loop w/normal exhalatory loop w/no bronchodilator response

– Normal lung volumes – Female preponderance

– Symptoms later in exercise – Recovery period 15-60

minutes – Turbulence in lungs

w/wheeze, no stridor – Pt unable to pant/breath

hold when symptomatic – PFTs abnormal (airflow

obstruction) w/bronchodilator response

– Increased residual lung volume

– Males/females equally affected

IVFC

• Causal factors

– Functional or psychogenic issue?

– Laryngeal hypersensitivity/hyper-reactivity?

– Laryngospasm?

– Adductor laryngeal breathing dystonia (Blitzer and Brin, 1991; Grillone, et.al., 1994)

• Rare disorder whose symptoms are similar to IVFC

• Neurological issue

• Behavioral intervention not efficacious in management

IVFC - Evaluation

• History – Acute versus chronic issue?

– Episodes same/different w/regard to presentation?

– Episodes same/different w/regard to severity?

– Triggers

• Flexible endoscopy during/subsequent to challenge

• Spirometry

IVFC - Treatment

• Functional issue – Behavioral intervention

• Psychogenic issue – Behavioral/psychological treatment

• Laryngeal hypersensitivity/hyper-reactivity – Aggressive reflux management

• Laryngospasm – Aggressive reflux management, behavioral management, use of

Heliox if severe, tracheotomy if life-threatening

• Adductory laryngeal breathing disorder – Botulinum Toxin A injections

Case Study #2

• 13 year-old female

• Placed into foster care/living w/supportive foster mother

• Reason for placement – ongoing sexual/psychological abuse at hands of one parent w/other parent/family members unable/unwilling to intervene

• Patient actively pursuing legal severance of parental rights/involvement w/family

Case Study #2

• Parents/other family members under court order not to contact patient

• When court order violated, patient experienced episodes of dyspnea: sudden onset, sensation of throat constriction, compromised inhalation, and inhalatory stridor

Case Study #2

• During flexible endoscopy, sudden onset of VF adduction occurred

• Use of behavioral intervention efficacious in alleviating episode

• Episodes continued to occur but were effectively managed w/behavioral strategies

• Episodes ceased subsequent to legal severance of parental/family rights, adoption of patient by foster mother, and 18 months of psychotherapy

Thank you!

Bibliography

• Christopher, K.L., Wood II, R.P., Eckert, R.C., Blager, F.L., Raney, R.A., Souhrada, J.F.: Vocal Cord Dysfunction Presenting as Asthma. New England Journal of Medicine, 308: 1566-1570 (1983)

• Martin, R.J., Blager, F.L., Gay, M.L., Wood II, R.P.: Paradoxic Vocal Cord Motion in Presumed Asthmatics. Seminars in Respiratory Medicine, 8: 332-337 (1987)

• Grillone, G.A., Blitzer, A., Brin, M.F., Annino, D.J., Saint-Hilaire, M.H.: Treatment of Adductor Laryngeal Breathing Dystonia with Botulinum Toxin Type A. Laryngoscope, 104: 30-32 (1994)

• Bless, D.M., Swift, E.: Vocal Fold Dysfunction: Diagnosis and Management. Paper presented at the 4th Biennial Phonosurgery Symposium: Madison, WI (1996)

• Irwin, R.S., Boulet, L.P., Cloutier, M.M., Fuller, R., Gold, P.M., Hoffstein, V., Ing, A.J., McCool, D., O’Byrne, P., Poe, R.H., Prakash, U.B.S., Pratter, M.R., Rubin, B.K.: Managing Cough as a Defense Mechanism and as a Symptom: A Consensus Report of the American College of Chest Physicians. Chest, 133-207 (1998)

Bibliography

• Abaza, W.: Vocal Cord Dysfunction: Diagnosis and Treatment. Grand Rounds presentation to Faculty and Staff of the Department of Pediatric Pulmonary Medicine, University of Michigan Health System (1999)

• Morrison, M., Rammage, L., Emami, A.J.: The Irritable Larynx Syndrome. Journal of Voice, 13: 447-455 (1999)

• Sandage, M., Swift, E.: A New Look at Assessment and Treatment of Paradoxical Vocal Cord Dysfunction. Short Course presented at the Annual Convention of the American Speech-Language-Hearing Association. San Francisco, CA (1999)

• Altman, K.W., Mirza, M., Ruiz, C., Sataloff, R.T.: Paradoxical Vocal Fold Motion: Presentation and Treatment Options. Journal of Voice, 14: 99-103 (2000)

• Andrianopoulos, M.V., Gallivan, G.J., Gallivan, K.H.: PVCM, PVCD, EPL, and Irritable Larynx Syndrome: What are we Talking About and How do we Treat it? Journal of Voice, 14: 607-618 (2000)

Bibliography

• Altman, K.W., Simpson, C.B., Amin, M.R., Balkissoon, R., Casiano, R.R.: Cough and Paradoxical Vocal Fold Motion. Otolaryngology-Head and Neck Surgery, 127: 501-511 (2002)

• D’Urzo, A., Jugovic, P.: Chronic Cough. Canadian Family Physician, 48: 1311-1316 (2002)

• Newsham, K.R., Klaben B.K., Miller, V.J.: Paradoxical Vocal-Cord Dysfunction: Management in Athletes. Journal of Athletic Training, 37: 325-328 (2002)

• Sandage, M., Zelazny, S.K.: Paradoxical Vocal Fold Motion in Children and Athletics. Language, Speech, and Hearing Services in Schools, 35: 353-362 (2004)

• Sataloff, R.T., Castell, D.O., Katz, P.O., Sataloff, D.M.: Reflux Laryngitis and Related Disorders. San Diego; Plural Publishing (2006)

• Simpson, C.B., Amin, M.R.: Chronic Cough: State of the Art Review. Otolaryngology-Head and Neck Surgery, 134: 693-700 (2006)

Bibliography

• Johnston, N., Dettmar, P.W., Bishwokarma, B., Lively, M.O., Koufman, J.A.: Activity/Stability of Human Pepsin: Implications for Reflux Attributed Laryngeal Disease. Laryngoscope, 117: 1036-1039 (2007)

• Rank, M.A., Kelkar, P., Oppenheimer, J.J.: Taming Chronic Cough. Annals of Allergy, Asthma, and Immunology, 98: 305-313 (2007)

• Bastian, R.W.: Neurogenic Cough and Other Sensory/Pain disorders of the Head and Neck – 20 Year’s Experience. Paper presented at the Annual Convention of the American Speech-Language-Hearing Association, Chicago, IL (2008)

• Birchall, M.A., Bailey, M., Gutowska-Owsiak, D., Johnston, N., Inman, C.F., Stokes, C.R., Postma, G., Pazmany, L., Koufman, J.A., Phillips, A., Rees, L.E.: Immunologic Response of the Laryngeal Mucosa to Extraesophageal Reflux. Annals of Otology, Rhinology, and Laryngology, 117: 891-895 (2008)

• Blager, F.B.: Symptoms and Treatment of Vocal Cord Dysfunction/Paradoxical Vocal Fold Motion. Short Course presented at the Annual Convention of the American Speech-Language-Hearing Association, Chicago, IL (2008)

Bibliography

• Brugman, S.M.: What’s This Thing Called Vocal Cord Dysfunction? Retrieved 6/24/2008 at http://chestnet.org/education/online/pccu/vol20/lessons25_27/print26.php

• Cukier-Blaj, S., Bewley, A., Aviv, J.E., Murry, T.: Paradoxical Vocal Fold Motion: A Sensory-Motor Laryngeal Disorder. Laryngoscope, 118: 367-370 (2008)

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• Ramanuja, S., Kelkar, P.: Habit Cough. Annals of Allergy, Asthma, and Immunology, 102: 91-95 (2009)

• Morice, A.H.: The Cough Hypersensitivity Syndrome: A Novel Paradigm for Understanding Cough. Lung, published online on October 7, 2009

• Sandage, M.: Sniffs, Gasps and Cough: Treatment of Irritable Larynx Syndrome Across the Lifespan. Paper presented at the Concepts in Voice Therapy Conference, New Orleans, LA (2009).

http://chestnet.org/education/online/pccu/vol20/lessons25_27/print26.php

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