Exercise Induced Exercise Induced Paradoxical Vocal Cord DysfunctionParadoxical Vocal Cord Dysfunction

(EI-PVCD)(EI-PVCD)

Dale R. Gregore Dale R. Gregore

M.S., CCC-SLPM.S., CCC-SLPSpeech Language PathologistSpeech Language Pathologist

Clinical Rehabilitation Specialist - VoiceClinical Rehabilitation Specialist - Voice

NORMAL RespirationNORMAL Respiration 101 101

On inhalation, the vocal cords (folds) On inhalation, the vocal cords (folds) ABductABduct allowing air to flow into the allowing air to flow into the trachea, bronchial tubes, lungstrachea, bronchial tubes, lungs

On exhalation, the vocal folds may On exhalation, the vocal folds may close slightly, however should and do close slightly, however should and do remain remain ABductedABducted

Normal LarynxNormal Larynx

Vocal fold ABDUCTION occurs during respiration

Vocal fold ADDUCTION

Occurs during

swallowing, coughing, etc…

Strobe exam

Paradoxical Vocal Fold Movement Paradoxical Vocal Fold Movement (PVFM)(PVFM)

The cord function is The cord function is reversed reversed in that the in that the vocal folds ADDuct on vocal folds ADDuct on inspiration versus inspiration versus ABduct ABduct Leads to tightness or Leads to tightness or spasm in the larynxspasm in the larynxInspiratory wheeze Inspiratory wheeze evidentevident

Definition of EI-VCDDefinition of EI-VCD

““Inappropriate closure of the Inappropriate closure of the vocal folds upon inspiration vocal folds upon inspiration resulting in stridor, dyspnea resulting in stridor, dyspnea and shortness of breath (SOB) and shortness of breath (SOB) during strenuous activity”during strenuous activity”

– Matthers-Schmidt, 2001; Sandage Matthers-Schmidt, 2001; Sandage et al, 2004et al, 2004

PseudonymsPseudonyms

Vocal Cord Dysfunction (VCD)Vocal Cord Dysfunction (VCD)– Most common termMost common term

Munchausen’s StridorMunchausen’s Stridor

Emotional Laryngeal WheezingEmotional Laryngeal Wheezing

Pseudo-asthmaPseudo-asthma

Fictitious Asthma Fictitious Asthma

Episodic Laryngeal DyskinesiaEpisodic Laryngeal Dyskinesia

Patient description Patient description of VCD episodesof VCD episodes

– ““in the top of my throat I see a McDonalds in the top of my throat I see a McDonalds straw surrounded by darkness. The straw straw surrounded by darkness. The straw ends in a pool of thick, sticky liquid that is ends in a pool of thick, sticky liquid that is encased by a wall of rubber bands and encased by a wall of rubber bands and outside of the rubber bands is air that I outside of the rubber bands is air that I can’t access”.can’t access”.

– ““The top part of my throat is complete The top part of my throat is complete darkness, at the back part of the darkness darkness, at the back part of the darkness there are cotton balls. These are holding there are cotton balls. These are holding my fear”. my fear”.

PVFM VisualizedPVFM VisualizedAnterior portion of the Anterior portion of the vocal folds are vocal folds are ADDuctedADDucted

Only a small area of Only a small area of opening at the opening at the

Posterior aspect of Posterior aspect of the vocal foldsthe vocal folds

Diamond shaped Diamond shaped ‘CHINK’‘CHINK’

May be evident on May be evident on both inhalation and both inhalation and exhalationexhalation

Essential FeaturesEssential Features

Vocal fold adduct (close) during Vocal fold adduct (close) during respiration instead of abducting respiration instead of abducting (opening)(opening)

Laryngeal instability while patient is Laryngeal instability while patient is asymptomaticasymptomatic

– Treole,K. et. al. 1999Treole,K. et. al. 1999

Episodic respiratory distressEpisodic respiratory distress

SymptomsSymptoms

StridorStridor

Difficulty with inspiratory phaseDifficulty with inspiratory phase

Throat tightening > bronchial/ chestThroat tightening > bronchial/ chest

Dysphonia during/following an attackDysphonia during/following an attack

Abrupt onset and resolutionAbrupt onset and resolution

Little or NO response to medical Little or NO response to medical treatment (inhalers, bronchodilators)treatment (inhalers, bronchodilators)

Various EtiologiesVarious Etiologies

Laryngo-Pharyngeal Reflux (LPR)Laryngo-Pharyngeal Reflux (LPR)– Food/ liquid/ acid refluxes from the Food/ liquid/ acid refluxes from the

stomach up the esophagus into the stomach up the esophagus into the pharynx (throat)pharynx (throat)

– Can spill over and into the larynx Can spill over and into the larynx – causes coughing, choking, breathing and causes coughing, choking, breathing and

voice changes, swelling, irritation, voice changes, swelling, irritation, – Can be SILENT or sensed when it happensCan be SILENT or sensed when it happens– WATERBRASHWATERBRASH

LPR, continuedLPR, continued

Clinical characteristics can be Clinical characteristics can be observed using observed using videolaryngoscopic or videolaryngoscopic or stroboscopic visualization of stroboscopic visualization of the larynxthe larynx

Ideally, diagnosed by a 24-Ideally, diagnosed by a 24-hour pH. Probe or EGDhour pH. Probe or EGD

LPR and AthletesLPR and AthletesWell documented occurrence in weight Well documented occurrence in weight liftinglifting

Can be aggravated by bending, pushing/ Can be aggravated by bending, pushing/ resisting (tackling, etc…), tight clothing, resisting (tackling, etc…), tight clothing, even drinking water during a game/ meet/ even drinking water during a game/ meet/ matchmatch

Timing of meals before exercise is Timing of meals before exercise is importantimportant

Type of foods/ liquids should be monitoredType of foods/ liquids should be monitored

Laryngopharyngeal Reflux: Laryngopharyngeal Reflux: Clinical Signs Clinical Signs

Vocal Fold Edema

Lx Erythema

Interarytenoid Edema

Other potential causes of Other potential causes of Paradoxical Vocal Cord Paradoxical Vocal Cord

DysfunctionDysfunction

Allergic rhinitis or reactionAllergic rhinitis or reaction

Conversion disorder Conversion disorder

AnxietyAnxiety

Respiratory-type or drug-Respiratory-type or drug-induced laryngeal dystoniainduced laryngeal dystonia

Etiologies (cont.)Etiologies (cont.)

Asthma-associated Asthma-associated laryngeal dysfunctionlaryngeal dysfunction

Brainstem dysfunctionBrainstem dysfunctionCVA or injuryCVA or injury

Chronic laryngeal Chronic laryngeal instability, sensitivity & instability, sensitivity & tensiontension

Athlete Profile for EI-VCDAthlete Profile for EI-VCD

Onset between 11-18 Onset between 11-18

Females have a greater incidence Females have a greater incidence (generally 3:1) (generally 3:1)

High achievingHigh achieving

““Type A” personalitiesType A” personalities

High personal standards and/or High personal standards and/or social pressuressocial pressures

Intolerant to personal failureIntolerant to personal failure

Athlete Profile, cont…Athlete Profile, cont…CompetitiveCompetitive

Self demandingSelf demanding

Perceives family pressure to achieve a Perceives family pressure to achieve a high level of successhigh level of success

““Choke” under pressureChoke” under pressure

May have recently graduated to higher May have recently graduated to higher level of competition within their sport (JV level of competition within their sport (JV to Varsity: Rep to Travel team; college to Varsity: Rep to Travel team; college level sports, etc)level sports, etc)

EI-VCD versus AsthmaEI-VCD versus Asthma

Recalcitrant to asthma medicationsRecalcitrant to asthma medicationsi.e. does not respond to i.e. does not respond to Individuals with “asthma” after long Individuals with “asthma” after long term steroid use might not truly have term steroid use might not truly have asthma, but VCDasthma, but VCDIndividuals with significant anxiety: Individuals with significant anxiety: is it LIVE OR MEMOREX? Which is it LIVE OR MEMOREX? Which causes which?causes which?

Differential Diagnosis of EI-VCDDifferential Diagnosis of EI-VCDIncludes a detailed Case History Includes a detailed Case History

Pulmonary function StudiesPulmonary function Studies

Lab Test Lab Test

ENT/ Pulmonary/ Allergy evaluations ENT/ Pulmonary/ Allergy evaluations

Flexible Laryngoscopy/ videostroboscopyFlexible Laryngoscopy/ videostroboscopy

Speech-language pathology evaluation Speech-language pathology evaluation

Supplemental as needed: Supplemental as needed: Psychological evaluationPsychological evaluation

Differential Diagnosis of VCDDifferential Diagnosis of VCD Team Must Rule Out:Team Must Rule Out: – Mass ObstructionMass Obstruction– Bilateral vocal fold paralysisBilateral vocal fold paralysis– Anaphylactic laryngeal edemaAnaphylactic laryngeal edema– Extrinsic airway compressionExtrinsic airway compression– Foreign body aspirationForeign body aspiration– Infectious croupInfectious croup– LaryngomalaciaLaryngomalacia– Exercise Induced Asthma/ Exercise Induced Asthma/

AsthmaAsthma

Diagnosis of EI-VCDDiagnosis of EI-VCD

Often mistaken for asthmaOften mistaken for asthma

Diagnosis of EI-PVCD is by Diagnosis of EI-PVCD is by exclusionexclusion = when patient = when patient fails to respond to asthma fails to respond to asthma or allergy medication, then or allergy medication, then VCD is finally consideredVCD is finally considered

EI-VCD and AsthmaEI-VCD and Asthma

Can exist independently Can exist independently

Can also coexistCan also coexist– Patient may experience LPR which Patient may experience LPR which

causes Asthma flare-up and then causes Asthma flare-up and then laryngospasm (VCD) from coughinglaryngospasm (VCD) from coughing

– May experience chest (asthma) and/or May experience chest (asthma) and/or laryngeal (VCD) tightnesslaryngeal (VCD) tightness

EI-PVCD versusEI-PVCD versus Exercise Induced Asthma Exercise Induced Asthma

Feature PVCM EIAFemale Preponderance + -Chest Tightness +/- -Throat Tightness + -Stridor + -Usual onset of symptoms after beginning exercise (min) <5 >5-10Recovery period (min) 5-10 15-60Refractory period - +Late-phase response - +Response to beta-agonist - +

Typical Spirometry Findings for Typical Spirometry Findings for PVCDPVCD

AsymptomaticAsymptomatic– Flow-volume loops are normal Flow-volume loops are normal

Symptomatic: Symptomatic: – Blunted inspiratory curveBlunted inspiratory curve– Inspiratory curves highly varied Inspiratory curves highly varied – Expiratory portion may be bluntedExpiratory portion may be blunted– Ratio of forced expiratory to inspiratory Ratio of forced expiratory to inspiratory

flow at 50% VC can be greater than 1.0flow at 50% VC can be greater than 1.0

Inspiratory cut-off, flattening of the Inspiratory cut-off, flattening of the inspiratory limb (curve)inspiratory limb (curve)

NORMAL VCD

Case History QuestionsCase History Questions– Do you have more trouble breathing in Do you have more trouble breathing in

than out?than out?– Do you experience throat tightness?Do you experience throat tightness?– Do you have a sensation of choking or Do you have a sensation of choking or

suffocation?suffocation?– Do you have hoarseness?Do you have hoarseness?– Do you make a breathing-in noise Do you make a breathing-in noise

(stridor) when you are having (stridor) when you are having symptoms?symptoms?

Questions (cont.)Questions (cont.)– How soon after exercise starts do your How soon after exercise starts do your

symptoms begin?symptoms begin?– How quickly do symptoms subside?How quickly do symptoms subside?– Do symptoms recur to the same degree Do symptoms recur to the same degree

when you resume exercise?when you resume exercise?– Do inhaled bronchodilators prevent or Do inhaled bronchodilators prevent or

abort attacks?abort attacks?– Do you experience numbness and/or Do you experience numbness and/or

tingling in your hands or feet or around tingling in your hands or feet or around your mouth with attacksyour mouth with attacks

Questions (cont.)Questions (cont.)– Do symptoms ever occur during sleep?Do symptoms ever occur during sleep?– Do you routinely experience nasal Do you routinely experience nasal

symptoms (postnasal drip, nasal symptoms (postnasal drip, nasal congestion, runny nose, sneezing)?congestion, runny nose, sneezing)?

– Do you experience reflux symptoms?Do you experience reflux symptoms?

Videostroboscopic ExaminationVideostroboscopic ExaminationInstrumentationInstrumentation– Flexible fiberoptic laryngeal endoscope with Flexible fiberoptic laryngeal endoscope with

stroboscopic capabilitystroboscopic capability

ObservationsObservations– Movement of arytenoids during respiration Movement of arytenoids during respiration

at rest: Complete closure; Posterior at rest: Complete closure; Posterior diamonddiamond

– Signs of laryngopharyngeal reflux disorder Signs of laryngopharyngeal reflux disorder (LPR)(LPR)

– Degree of laryngeal instabilityDegree of laryngeal instability

Laryngeal Supraglottic Laryngeal Supraglottic HyperfunctionHyperfunction

arytenoid arytenoid compressioncompression

ventricular ventricular compressioncompression

Limited airway for Limited airway for phonationphonation

VCD appearance on direct VCD appearance on direct examinationexamination

Laryngeal Laryngeal Supraglottic Supraglottic HyperfunctionHyperfunction

Abnormal Abnormal ventricular ventricular compression compression during speech during speech

Laryngeal Supraglottic Laryngeal Supraglottic HyperfunctionHyperfunction

Sphincteric Sphincteric contraction of the contraction of the supraglottis during supraglottis during speech productionspeech production

PVCM VisualizedPVCM Visualized

Rounded arytenoids, but normal abduction

Posterior ‘chink’

Diagnostic Features PVFM Asthma

Flow-volume loop Inspiratory cut-off, Reduced expiratory perhaps some expiratory limb only limb reduction *

Bronchial provocation Negative Positive test

Laryngoscopic Inspiratory adduction Vocal folds may observations adduct during of anterior 2/3 of vocal exhalation folds; posterior diamond- shaped chink; perhaps medialization of ventricular folds; inspiratory adduction may carry over to expiration

Diagnostic Features PVFM Asthma

Precipitators (triggers) Exercise, extreme Exercise, extreme temperatures, airway

temperatures, irritants, emotional airway irritants, stressors emotional stressors,

allergens

Number of triggers Usually one Usually multiple

Breathing obstruction Laryngeal area Chest area location

Timing of breathing Stridor on Wheezing on noises inspiration exhalation

Pattern of dyspneic Sudden onset and More gradual onset event relatively rapid longer recovery

cessation period

Nocturnal awakening Rarely Almost always with symptoms

Response to broncho- No response Good response dilators and/or systemiccorticosteroids

Acute Management of EI-VCD Acute Management of EI-VCD in the fieldin the field

Approach to the Approach to the patient is importantpatient is important

It is generally agreed It is generally agreed that patients do not that patients do not consciously consciously manipulate or control manipulate or control their upper airway their upper airway obstruction obstruction

Acute Management of EI-VCD Acute Management of EI-VCD

During an episode, they usually feel During an episode, they usually feel helpless and terrifiedhelpless and terrified

Implying that it is “in their head” is Implying that it is “in their head” is incorrect and counterproductive to incorrect and counterproductive to their recoverytheir recovery

Coach them through, help them outCoach them through, help them out

Be positiveBe positive

Acute Management of AttacksAcute Management of Attacks

– Offer reassurance and empathyOffer reassurance and empathy– Eliminate activity and people from Eliminate activity and people from

environmentenvironment– Prompt for EASY BREATHINGPrompt for EASY BREATHING– Elicit controlled ‘Panting’Elicit controlled ‘Panting’

Relaxed jawRelaxed jaw

Tongue on floor of mouth behind bottom Tongue on floor of mouth behind bottom teethteeth

Acute Management in the GameAcute Management in the Game

Visualize WIDE OPEN AIRWAY Visualize WIDE OPEN AIRWAY

6 lane highway with no roadblocks6 lane highway with no roadblocks

Air goes in and circles around, goes outAir goes in and circles around, goes out

Shoulders relaxedShoulders relaxed

Standing w/ open chest, hands on hips, Standing w/ open chest, hands on hips, or bent over/ hands on knees….which or bent over/ hands on knees….which position works best?position works best?

Quick Sniff TechniqueQuick Sniff Technique– Sniff then Blow….talk the athlete through this– Sniff in with focal emphasis at the tip of the

noseSniff = ABduction

– Then exhale with pursed lips on “ssssss” “shhhhhh” “ffffffff”“whhhhhhhh” = Back pressure respiration

ACUTE treatment, cont…ACUTE treatment, cont…– Breathing against pressure (hand on Breathing against pressure (hand on

abdomen)abdomen)Resistance and focus on pressure against / Resistance and focus on pressure against / in another body partin another body part

– HelioxHelioxAdministered by Paramedics or ER MDsAdministered by Paramedics or ER MDs

– Sedatives and psychotropic medicationsSedatives and psychotropic medicationsLast resortLast resort

Calming effectCalming effect

Eliminates tension/ constrictionEliminates tension/ constriction

Treatment: Speech TherapyTreatment: Speech Therapy

Patient counseling, education Patient counseling, education

Respiratory retrainingRespiratory retraining

Focal and whole body relaxationFocal and whole body relaxation

Phonatory retrainingPhonatory retraining

Monitor reflux Sx or anxietyMonitor reflux Sx or anxiety

Develop / outline a ‘Game Plan’ = Develop / outline a ‘Game Plan’ = practice when asymptomatic; practice when asymptomatic; implement at the onset of sximplement at the onset of sx

Therapeutic goals and methodsTherapeutic goals and methodsGoalGoal– Ability to Ability to

overcome fear overcome fear and helplessnessand helplessness

– Reduced tension Reduced tension in- extrinsic in- extrinsic laryngeal muscleslaryngeal muscles

– Diversion of Diversion of attention from attention from larynxlarynx

MethodMethod– Mastery of Mastery of

breathing breathing techniquestechniques

– Open throat Open throat breathing; breathing; resonant voice resonant voice techniquetechnique

– Diaphragmatic Diaphragmatic breathing and breathing and active exhalationactive exhalation

Therapeutic goals and methodsTherapeutic goals and methodsGoalGoal– Reduced tension Reduced tension

in neck, in neck, shoulders and shoulders and chestchest

– Ability to use Ability to use techniques to techniques to reduce severity reduce severity and frequency of and frequency of attacksattacks

MethodMethod– Movement, Movement,

stretching, stretching, progressive progressive relaxationrelaxation

– Increase Increase awareness of early awareness of early warning warning symptoms; symptoms; Rehearse action Rehearse action planplan

Speech TherapySpeech Therapy

Patient Counseling & EducationPatient Counseling & Education– Description of laryngeal eventsDescription of laryngeal events– Viewing of laryngoscopy tapeViewing of laryngoscopy tape– Relate parallels to other stress induced Relate parallels to other stress induced

disorders: migraine, irritable colon, disorders: migraine, irritable colon, muscle tension dysphonia, muscle tension dysphonia, GERefluxGEReflux

– Flexible endoscopic biofeedbackFlexible endoscopic biofeedback– Sensory biofeedback (sEMG)Sensory biofeedback (sEMG)

Speech TherapySpeech Therapy

Respiratory trainingRespiratory training– Low “diaphragmatic” breathing versus Low “diaphragmatic” breathing versus

“high” clavicular thoracic “high” clavicular thoracic – Rhythmic respiratory cyclesRhythmic respiratory cycles– Use resistance exhale (draw attention Use resistance exhale (draw attention

away from larynx and extend exhale)away from larynx and extend exhale)– Prevention and coping strategies during Prevention and coping strategies during

episodes = Action Planepisodes = Action Plan

Back Pressure BreathingBack Pressure Breathing

Nasal Sniff = OPEN cordsNasal Sniff = OPEN cords

Prolonged exhalation /w/, /f/, /sh/, /s/ Prolonged exhalation /w/, /f/, /sh/, /s/

Shoulders relaxedShoulders relaxed

Throat openThroat open

Implement when laying, sitting, Implement when laying, sitting, standing, walking, jogging, running, standing, walking, jogging, running, playing sports, etcplaying sports, etc

RelaxationRelaxation TrainingTraining

GoalGoal– Teach the patient to relax focal areas Teach the patient to relax focal areas

then the entire body during an episode then the entire body during an episode of respiratory distressof respiratory distress

MethodsMethods– Use progressive relaxation with guided Use progressive relaxation with guided

imageryimagery– Explore the patient’s visual concept of Explore the patient’s visual concept of

their disorder and altertheir disorder and alter

ST Duration: The CCHS ApproachST Duration: The CCHS Approach

2-8 sessions2-8 sessions

Average 4 sessionsAverage 4 sessions

Followed by clinical observation Followed by clinical observation during sport/ gameduring sport/ game

Followup phone / email contact: tell Followup phone / email contact: tell me how it is going? me how it is going?

Re-evaluation as necessary, if Re-evaluation as necessary, if symptoms reoccur (rarely)symptoms reoccur (rarely)

CASE DISCUSSIONCASE DISCUSSION

14 year old female14 year old female

Sports: field hockey, soccerSports: field hockey, soccer

Travel soccer U-17 team/ midfiledTravel soccer U-17 team/ midfiled

Initial symptoms: ‘throat closes’ ~5 Initial symptoms: ‘throat closes’ ~5 minutes in to game; hand on throat; minutes in to game; hand on throat; signals coach; pulled from game; 20 signals coach; pulled from game; 20 minute recovery: lying on sidelineminute recovery: lying on sideline

Therapy Focus and OutcomeTherapy Focus and Outcome5 sessions5 sessions

Breathing 101Breathing 101

Training from static to active movement/ Training from static to active movement/ runningrunning

Full coaching then observation of strategy Full coaching then observation of strategy implemetation in therapy and during gameimplemetation in therapy and during game

Outcome:Outcome: (-) sx during mile run; cool (-) sx during mile run; cool down routine implemented; 20-30 minute down routine implemented; 20-30 minute game play/ no EI-VCD w/ ‘game plan’ game play/ no EI-VCD w/ ‘game plan’

Case Discussion #2Case Discussion #2

14 year old female14 year old female

Sports: cross country; basketballSports: cross country; basketball

Initial Symptoms: ‘throat closed’ Initial Symptoms: ‘throat closed’ during CC trials; had to ‘drop out’during CC trials; had to ‘drop out’

Secondary Symptoms: inspiratory Secondary Symptoms: inspiratory stridor when wearing mouth guard/ stridor when wearing mouth guard/ basketball; felt ‘faint’basketball; felt ‘faint’

Therapy Focus and OutcomeTherapy Focus and Outcome

5 sessions5 sessionsGoals: establish ‘low’ AD breathing/ Goals: establish ‘low’ AD breathing/ eliminate shoulder elevation and CT eliminate shoulder elevation and CT respiration pattern; train in back respiration pattern; train in back pressure breathing w/ and w/out pressure breathing w/ and w/out mouthguard during activities of mouthguard during activities of progressive effort including walk; jog; progressive effort including walk; jog; stairs, treadmill; suicide drills; BB stairs, treadmill; suicide drills; BB drills; sprints, etcdrills; sprints, etc

OutcomeOutcomeSuccessful resolution of PVFM during Successful resolution of PVFM during 20 minute runs and when playing BB20 minute runs and when playing BBIncreased awareness of AD versus CT Increased awareness of AD versus CT respirationrespirationHabituated alternate use of sniff/ Habituated alternate use of sniff/ pant – blow, etc. pant – blow, etc. Increased perceived ‘control’ over Increased perceived ‘control’ over breathing and performancebreathing and performanceSpring Sport pending: soccerSpring Sport pending: soccer

REFERENCESREFERENCESBrugman, S. M., & Newman, K. (1993).Brugman, S. M., & Newman, K. (1993). Vocal cord Vocal cord dysfunction. Medical/Scientific Update. 11. 5. 1-5. dysfunction. Medical/Scientific Update. 11. 5. 1-5.

Christopher, K. L., WoodII, R. P., Eckert, R. C., Christopher, K. L., WoodII, R. P., Eckert, R. C., Blager, F. B., Raney, R. A., & Souhrada, J. F. (1983).Blager, F. B., Raney, R. A., & Souhrada, J. F. (1983). Vocal-cord dysfunction presenting as asthma. The New Vocal-cord dysfunction presenting as asthma. The New England Journal of Medicine. 308. 1556-1570. England Journal of Medicine. 308. 1556-1570.

Gavin, L. A., Wamboldt, M., Brugman, S., Roesler, T. Gavin, L. A., Wamboldt, M., Brugman, S., Roesler, T. A., & Wamboldt, F. (1998).A., & Wamboldt, F. (1998). Psychological and family Psychological and family characteristics of adolescents with vocal cord dysfunction. characteristics of adolescents with vocal cord dysfunction. Journal of Asthma. 35. 409-417.Journal of Asthma. 35. 409-417.

Martin, R. J., Blager, F. B., Gay, M. L., & WoodII, R. P. Martin, R. J., Blager, F. B., Gay, M. L., & WoodII, R. P. (1987).(1987). Paradoxic vocal cord motion in presumed Paradoxic vocal cord motion in presumed asthmatics. Seminars in Respiratory Medicine. 8. 332-337.asthmatics. Seminars in Respiratory Medicine. 8. 332-337.

Matthers-Schmidt B.AMatthers-Schmidt B.A Paradoxical Vocal Fold Motion: A Paradoxical Vocal Fold Motion: A Tutorial on a Complex Disorder and the Speech Language Tutorial on a Complex Disorder and the Speech Language Pathologist’s Role. American Journal of Speech-Language Pathologist’s Role. American Journal of Speech-Language Pathology 2001; 10:111-25.Pathology 2001; 10:111-25.

Sandage et. al.Sandage et. al. Paradoxical vocal fold motion in children Paradoxical vocal fold motion in children and adolescents. Lang. Speech Hear. Serv. Sch. 2004: 35 and adolescents. Lang. Speech Hear. Serv. Sch. 2004: 35 (4) 353-62(4) 353-62

Vlahakis NE, Patel AM, Maragos NE, Beck KC.Vlahakis NE, Patel AM, Maragos NE, Beck KC. Diagnosis of Vocal Cord Dysfunction: The Utility of Diagnosis of Vocal Cord Dysfunction: The Utility of Spirometry and Plethysmography. Chest 2002; 122: 2246-Spirometry and Plethysmography. Chest 2002; 122: 2246-2249.2249.

Nastasi, K. J., Howard, D. A., Raby, R. B., Lew, D. B., Nastasi, K. J., Howard, D. A., Raby, R. B., Lew, D. B., & Blaiss, M. S. (1997).& Blaiss, M. S. (1997). Airway fluoroscopic diagnosis of Airway fluoroscopic diagnosis of vocal cord dysfunction syndrome. Annals of Allergy, vocal cord dysfunction syndrome. Annals of Allergy, Asthma, Immunology. 78. 586-588. Asthma, Immunology. 78. 586-588.

Powell DM, Karanfilov BI, Beechler KB, Treole K, Powell DM, Karanfilov BI, Beechler KB, Treole K, Trudeau MD, Forrest L.Trudeau MD, Forrest L. Paradoxical vocal cord Paradoxical vocal cord dysfunction in Juveniles.Arch. Otolaryngol Head Neck Surg. dysfunction in Juveniles.Arch. Otolaryngol Head Neck Surg. 2000 Jan; 126 (1): 29-342000 Jan; 126 (1): 29-34

Morris MJ, Deal LE, Bean DR, Grbach VX, Morgan JA.Morris MJ, Deal LE, Bean DR, Grbach VX, Morgan JA. Vocal Cord Dysfunction in Patients with Exertional Dyspnea. Vocal Cord Dysfunction in Patients with Exertional Dyspnea. Chest 1999; 116: 1676-1682. Chest 1999; 116: 1676-1682.