What’s our child’s physical system like? Considerations about structure, biology,

biomechanics

K. Verdolini Abbott, Ph.D., CCC-SLPUniversity of Pittsburgh

2010

Discussion in three parts

• (1) General developmental information

• (2) Information pertinent to “indirect therapy”

• (3) Information pertinent to “direct therapy”

Image from http://fit.bethlin.com/wp-content/uploads/2009/04/funny-pictures-cat-is-three-steps-into-an-epic-journey.jpg

Developmental issues

• Very young children (< 2-3 yr) appear to have phonotrauma infrequently

Image from http://supermon.files.wordpress.com/2010/01/baby.jpg

Developmental issues

• More broadly– Babies/infants low risk– Children high risk– Adults

• Males low risk• Females high risk

(Percent; approximate)

Developmental issues

• We will try to figure out if there are physical changes over time that might help to explain these shifts in risk (special interest is increased risk in children)

• If so, maybe we can use the information to shed light on prevention and treatment of phonotrauma in children

http://technology.amis.nl/blog/wp-content/images/data_miner_collage_10gr2.jpg

Laryngeal macrostructure (and vocal tract)

• Neonatal vs adult– Pharynx short– Cricoid cartilage is high (C4)– Tip of the epiglottis is high (C1)– Approximation of epiglottis and soft

palate thought to allow sucking and simultaneous respiration

– Hyolaryngeal area is compact

– Age 2: Lower border of larynx descends to C5

– Age 6: Lower border of larynx descends to C6

– Age 15: Lower border of larynx descends to final position C6-7; thyroid cartilage and hyoid bone separate during descent

– Epiglottis: Increases curvature until age 3, then gradually flattens

• Isaacson, 1996

• Possible implication: Source-filter interactions may vary with age; details not well studied for children. Relevance for phonotrauma???

Laryngeal macrostructure

• Neonatal vs adult– Aryepiglottic folds thick and

bulky– Arytenoids appear

prominent– Glottis is 7 mm AP and 4

mm lateral– Isaacson, 1996

• Possible implication: Mostly relevant for swallowing; epiglottis squashed against the VFs in infants. Relevance for phonotrauma???

Laryngeal macrostructure

• Child vs adolescent• Prepubertal vs pubertal

larynx, male and female (ages 9-18; Kahane, 1978)

• Angle of the thyroid cartilage decreases in boys with age; therefore the relative posterior glottal gap is reduced, compared to the relative gap in females

• Possible implication: PGG is thought to contribute to phonotrauma (e.g. Morrison & Rammage, 1993); may help explain risk of phonotrauma in children and decreased risk in adult males (but decreased risk in infants???)

Adult vocal fold Membrane: Cartilage

(5.5:1 male and 4:1 female)(images courtesy Christopher Hartnick, p.c.)

Laryngeal macrostructure:Membranous vs Cartilaginous Vocal Folds

Infant vocal foldMembrane: Cartilage

1.5:1 at birth with relative growth of membranous folds

Laryngeal macrostructure

• Possible implication– Reduced motor control of

voice in infancy and childhood?

– Small changes in control parameters should produce large proportional changes in tissue

– Poor control might somehow increase risk of injury in infancy?

• Possible implication– High frequency of VF

vibration due to small mass of membranous folds should also increase the risk of phonotrauma in infants (more vibrations per unit time)

Laryngeal macrostructure

• So far how are we doing in trying to find a physical basis to explain changes in risk of phonotrauma with age and gender?

• Mostly poorly.• Batting 0.001 at best.

http://education.baseballhalloffame.org/experience/thematic_units/science/assets/Gill_Batting.jpg

Laryngeal microstructure

• Neonatal vs adult– Hyaluronic acid (cushioning

in adults): Minimal in infants. Speculatively actively produced in maculae flavae of infants from phonation (Sato et al., 2001).

– Collagen: About 51% of the collagen found in adults (Hammond et al., 2000)

– Elastin: About 23% of the elastin found in adults (Hammond et al., 1998)

– Image from Gray, 1996

• Possible implication (especially for HLA): Less cushioning in the vocal folds in babies. Should have higher risk for injury.

• Batting 0.00 here.

Laryngeal microstructure

• Differentiated tri-layered structure of the lamina propria not present at birth

• Gradually develops over first 17 yr of life– Monolayer -->– Bilaminar structure – Trilaminar structure

• Hartnick CJ et al. Development and maturation of the pediatric human vocal fold lamina propria. Laryngoscope. 2005 Jan; 115(1):4-15. • Next slides courtesy C. Hartnick, p.c.

2 day

3 year

2 month

7 year

13 year old

Laryngeal microstructure

• Possible implication: Maybe “harder striking surface” with increasing age, increasing risk of injury?

• But what about decreased risk in adult males? (Possibly attributable to another factor, i.e. sharp increase in hyaluronic acid.)

• (Batting 0.001 again, barely?)

Laryngeal microstructure

• Neonatal vs adult, cont’d– Fibroblasts: Inactive in

producing fibers in newborn.

– (Speculation that fibroblasts and macula flavae may contribute to development of ligament over time.)

– Hirano et al., 1999

• Possible implication: Maybe infants don’t have the biological machinery to produce a lot of fibrous tissue that are the physical basis of chronic phonotrauma.

• Batting 0.002?

Laryngeal macro- and microstructure

• Summary:– What is the physical basis for

changes in risk for phonotrauma with gender and age (for now focus is decreased risk in infants and increased risk in children)?

– For now we have to admire the question without a lot of good answers

• Biology/biomechanics:

C/w decreased risk in infant

C/w increased risk in infant

Infant No hard striking surface (LP)

High Fo

Child Limited capacity for fiber production

Reduced cushion

Laryngeal structure

• The situation is more complex than we’d like

• Biomechanically:– Maybe infant crying isn’t the same

as adult screaming – Maybe it’s relevant babies use

voice less or differently than older children and adults

Laryngeal microstructure

• Aside: Much of current knowledge about laryngeal microstructure is based on pathology model in cadavers (see Hartnick)

• Tissue processing concerns– Prolonged tissue fixation

– Prolonged intubation pre-mortem

– Dessication

• Functional approach to be taken in coming years with novel technology (Optical Coherence Tomography; Hartnick, p.c.; image courtesy Hartnick)

Vocal tract structure

• Dimensions increase• Formant frequencies

decrease

• Possible implications: Source-filter interactions may change quantitatively (NB: Such interactions affect (a) adduction; and (b) amplitude of VF vibration; see Titze)

• Details not well worked out specifically for children

http://users.uom.gr/~toutios/assets/vocal-tract.gif

Vocal tract/articulatory function

• Ages 1-6: Changes in coordinative relationships of articulators– Young children: Jaw

predominated– Older children: Increasing

independence of upper and lower lip; increasing use of lip movement for bilabial closure

– Green et al., 2000; Green et al., 2002

http://www.orthodontics.org/lipbumper.jpg

Vocal tract/articulatory function

• Possible implication: Evidence is seen of increasing differentiation in motor control– Is one implication that very

young children may have difficulty differentially altering voice independent of articulation, meaning we might want to manipulate both together in therapy “en bloc?”

– I.e. laryngeal function might benefit from articulatory manipulations?

• http://www.speech-solutions.com/images/prompt.JPG

Respiratory structure/function• Decreasing compliance of rib cage• Changes in general shape and

orientation of rib cage• Papastamelos et al., 1995; Sharp

et al., 1970

• Toddlers– Rest breathing:

• Paradoxing in inspiration (collapse of chest), probably due to high rib compliance (Gaultier et al., 1987)

• Toddlers to children – Rest versus speech breathing (15

mo): • Rest: Relative synchrony between

rib and abdomen• Speech: Oppositional

(paradoxical) movement between rib and abdomen in speech breathing

– Variability: • Large intra- and intersubject

variability (5 wk to 1 yr; 1 yr to 3 yr)

» Moore et al., 2001; Boliek et al., 1996, 1997)

http://www.luxfitness.com/Figures/muscles_of_the_abdomen.jpg

Respiratory function

• Toddlers and children (9-48 mo)

– Increasing independence of rib and abdomen during speech (not rest) breathing (coupling decreased 15% over 3 yr)

– Increasing rib expansion in speech (7% over 3 yr)

– Increase in oppositional movement (paradoxing) of rib and abdomen, abdomen possibly decreasing dissipation of air and this limiting speech Ps (my speculation)

– Changes were gradual, suggesting attribution to structural changes, not motor control changes

» Moore et al., 2001; 2004

• Possible implication: With age, increased capability to limit dissipation of air during speech, and thus limit Ps – which should limit VF impact stress? (e.g. Jiang & Titze, 1994)

• Doesn’t help to explain increased risk of phonotrauma from infancy to childhood.

So far

• A tiny bit of heat and not much light

Indirect therapy

• “Voice hygiene”• Adventures in Voice hygiene

differs from traditional hygiene education programs

– Adventures in Voice hygiene understood as care of tissue mostly independent of phonation

– Adventures in Voice hygiene program is lean and mean: (a) hydration; (b) exogenous inflammation control; (c) yelling and screaming

– Adventures in Voice hygiene program is tailored to individual child

http://www.bigmusclesbuilding.com/image-files/anabolicsteroids-1.jpg

Vocal hygiene: Dehydration (bad)

• Increases the subglottic pressure required to oscillate the vocal foldsFisher et al., 2001; Jiang et al., 2000; Titze, 1988; Verdolini-Marston et al., 1990; Verdolini et al., 1994; Verdolini et al., 2002

• May increase the risk of phonotraumaTitze, 1981

http://web.hcsps.sa.edu.au/projects/deserts/projects/group13/namib%20desert%201.jpg

Vocal hygiene: Hydration (good)

• Reduces the subglottic pressure required to oscillate the vocal foldsJiang et al., 2000; Verdolini-Marston et al., 1990; Verdolini et al., 1994

• May diminish phonotraumatic lesions Verdolini-Marston et al., 1994

http://lomophilly.files.wordpress.com/2009/09/water-drop-a.jpg

Vocal hygiene: Inflammation (bad)Laryngopharyngeal reflux

• LPR could increase the risk of phonotraumatic lesions and other conditions (e.g. cancer; paralysis)

• According to some data,

effective treatment of LPR may improve vocal fold condition and voice(Koufman, 1991; Shaw et al., 1996, 1997)

http://science.nayland.school.nz/SimonPa/Webpage/Year11/Acid_and_base_image/Acid_med.jpg

Vocal hygiene: Inflammation (bad)Laryngopharyngeal reflux

http://images.icanhascheezburger.com/completestore/2009/4/5/128834617768108870.jpg

• However– Scary (next page)

                       Laryngoscope. 2006 Jan;116(1):144-8. LinksEmpiric treatment of laryngopharyngeal reflux with proton pump inhibitors: a systematic review.Karkos PD, Wilson JA.Department of Otolaryngology, The Freeman Hospital, Newcastle upon Tyne, UK.OBJECTIVE: The objective of this study was to define the outcome of empiric treatment of suspected laryngopharyngeal reflux (LPR) symptoms with proton pump inhibitors (PPIs). DESIGN: The authors conducted a systematic review of the English and foreign literature. Studies that used PPIs as an empiric treatment modality for suspected LPR, whether alone or in combination with other acid suppressants and/or placebo, were included. Studies that did not include PPIs as a treatment option were excluded. MAIN OUTCOME MEASURES: A lack of common outcome measures was evident in the uncontrolled studies. In the randomized, controlled trials, outcome measures included symptom questionnaires and videolaryngoscopy. Only one study used computerized voice analysis. RESULTS: Fourteen uncontrolled studies together with one unblinded, nonrandomized study with a control group of healthy volunteers and six double-blind, placebo-controlled randomized trials were identified from 1994 to 2004. Selection bias, blinding of the results, and lack of common outcome measures were some of the problems preventing a formal metaanalysis. Although uncontrolled series reported positive results, randomized, controlled trials demonstrated no statistically significant differences for changes in severity or frequency of symptoms associated with suspected reflux between PPIs and placebo. CONCLUSIONS: Recommendations for empiric treatment of suspected LPR with PPIs, by far the most common ear, nose and throat practice in the United Kingdom, are based on poor levels of evidence from uncontrolled studies. The few randomized, controlled trials have failed to demonstrate superiority of PPIs over placebo for treatment of suspected LPR.

Vocal hygiene: Inflammation (bad)Smoking and other

• Don’t do it!

• Consider also other environmental issues (petrol pollution, allergies, chemicals, etc.)

– E.g. Richter et al.

http://i.treehugger.com/images/2007-2-28/smoking.jpg

Vocal hygiene:Screaming like crazy (bad)

• Don’t do it!

• Unless you have specialized training in screaming by a knowledgeable theatre trainer (use of epiglottis as noise source; vocalization in falsetto) – E.g. Ufema & Montequin,

unpublished data http://thepeoplebrand.com/blog/wp-content/uploads/2007/03/holler2.jpg

Vocal hygiene:Screaming like crazy (bad)

• A trick: Earplug in one ear in background noise

• Increases bone conduction; you hear yourself better and don’t scream

• Two earplugs even better than one (hear others’ speech better too)

http://www.activevibrant.com/catalog/images/hearing/Reusable%20Ear%20Plug%201260.jpg

Voice hygiene

• But wait!• There’s a 64,000 lb

elephant in the driveway

• All of the foregoing data and observations were based on adults

• Do they apply to children?

Voice hygiene

• Give it up???

• Evidence-based practice and all….

• Nooooo: There’s the principle of first principles!

http://www.mathhelpforum.com/math-help/attachments/calculus/6661d1212778861-first-principles-calculus-1.12.jpg

Direct voice therapySwitching gears

• Voice work• Adventures in Voice

differs from traditional voice work for children– Emphasis is vocal

function rather than conservation

Biomechanics

• Basic question: Is there an ideal biomechanical set-up to optimize voice across a range of people?

Biomechanics

• What do we mean by “biomechanical set-up?”– In this case we mean

amount of VF adduction

• What do we mean by “optimizing voice?”

• Implicit goal for most people:– Intense voice– Clear voice– Limited potential for

injury– Limited effort

BiomechanicsHow do we operationalize these desired outcomes?

• (a.)– Voice intensity and clarity are

interrelated, so we can collapse them into one variable

– We can operationalize that variable as “dB

• (b.)– Perpendicular VF impact stress is

the factor thought most directly causal to VF injury

– We can thus operationalize that variable as SI (force/area)

• (c.)– A chief factor predicting vocal

effort is phonatory PL– We can thus operationalize that

variable as PL

Biomechanics

• Going at the issues sequentially

– First question: What VF configuration (adduction) will give us the greatest ratio of dB/SI?

– Second question: What VF configuration (adduction) will give us the least PL?

– Third question: Will the ideal configuration to optimize dB/SI be similar to the configuration to minimize PL?

http://www.hellowood.com/images/Steps3WR.jpg

Biomechanics

• Question approached from converging studies– Simulation– Excised– HumanBerry et al., 2001

http://www.ust.ucla.edu/ustweb/Homepage_imgs/ucla_04.jpg

Biomechanics• Methodology

(excised)

Jiang, J.J, Zhang, Yu, & Ford, C.N. (2003). Nonlinear dynamics of phonations in excised larynx experimentsJ. Acoust. Soc. Am. 114, 2198 (2003)

Biomechanics• Results for output:

excised studies

Biomechanics• Results for output:

excised + simulation studies

Biomechanics• Results for impact

stress: excised studies

Biomechanics• Results for ratio of

output/impact intensity (“vocal economy) (combined excised/simulation)

Biomechanics• Summary: • Vocal fold posturing yielding

best ratio of output to impact intensity involves barely separated vocal folds (~0.6-0.7 mm), for conditions tested

• Precisely replicated results for independent human study

• Generally similar results expected for other fundamental frequencies, possibly with slight shifts (existing studies run with Fo ~ 155 – 196 Hz)

http://www.stammeringlife.com/Images/Vocal%20Folds%20(vf)%20Opening%20and%20Closing.JPG

Biomechanics• Problem: We wanted

best ratio of– Strong output– Limited impact and

effort

• Pick 2 out of 3???

Biomechanics• Nope. • PL > 2k/T B c w/2

– Titze, 1988

Biomechanics• Summary • Barely touching or barely

separated VF posture gives us biomechanical target relevant for wide sector of population with voice disorders

• Glossing over vocal tract for the moment

http://www.stammeringlife.com/Images/Vocal%20Folds%20(vf)%20Opening%20and%20Closing.JPG

Biomechanics• As chance would

have it• Performing arts,

classical singing technique, “resonant voice” – produced with this general posturing– Peterson et al., 1994– Verdolini et al., 1998

http://api.ning.com/files/vlzj-gWGwag4ns0bp0kF-GRoztWyRSrxo78oTwyb9rO3-28SsjXn5aOOtT9C0j*clTfJTE8-SiaRPWY0pByJ7xMTTK-adcrj/singer.jpg

Biomechanics• Resonant voice • Voice produced with

perceptible anterior oral vibrations, in the context of “easy” voice– Verdolini-Marston et al.,

1995

– Verdolini, 2000

– Video

Biomechanics• Link between

perception and production

Complete vocal fold closure

Incomplete vocal fold closure

Biomechanics• Summary to this point • Barely ad/abducted vocal folds

optimize relation between voice output intensity (strong) and impact stress (small). Same configuration relatively minimizes vocal effort as well.

• Target configuration

corresponds to percept of “resonant voice” (anterior oral vibrations, easy voice)

http://www.stammeringlife.com/Images/Vocal%20Folds%20(vf)%20Opening%20and%20Closing.JPG

Biomechanics

• But wait!

• Oops. All the foregoing data refer to adults.

• Tentatively, no reason to think they don’t apply to children

• But data are sorely lacking

Biomechanics

• Data forthcoming

• Initial observations indicate the data appear to apply to children as well (D. Berry, p.c.)

Biomechanics

• But wait!• There’s another little

guy in the yard

• The SI involved in resonant voice might be relatively small, but it’s still “non-zero”

• Is it sufficiently small not only to hopefully help prevent phonotrauma, but also to help heal existing phonotrauma?

Biology• Stated differently: What

about value of resonant voice (“tissue mobilization”) for recovery from injury?

http://ramanathan.files.wordpress.com/2007/12/lifesaver.jpg

Biology• First study showed

we detect (presumably) VF inflammatory mediator concentrations in vocal fold secretions

Interleukin-1beta (pg/mg protein)

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TimePre 10 Min. 20 Min

Tumor Necrosis Factor-alpha (pg/mg protein)

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Matrix Metalloproteinase-8 (pg/mg protein)

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Pre 10 Min 20 Min

Verdolini et al., 2003

Biology• A next study showed vocal fold

mobilization in the form of “resonant voice” exercises (large-amplitude low-impact VF vibrations) reduced inflammation

• (Scream study; Verdolini et al., in preparation)

http://s3.hubimg.com/u/337798_f260.jpg

Biology• Scream study

Verdolini et al., in preparation

IL-1beta

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Spontaneous Speech Voice Rest Resonant Voice

Treatment Condition

No

rma

lize

d V

alu

e

IL-1beta baseline

IL-1beta post-loading

IL-1 beta 4-hr post-treatment

IL-1beta 24-hr post-treatment

IL-6

0.00

10.00

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30.00

40.00

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70.00

Spontaneous Speech Voice Rest Resonant Voice

Treatment Condition

No

rma

lize

d V

alu

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IL-6 baseline

IL-6 post-loading

IL-6 4-hr poast-treatment

IL-6 24-hr post-treatment

MMP-8

0.00

2.00

4.00

6.00

8.00

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Spontaneous Speech Voice Rest Resonant Voice

Treatment Condition

No

rma

lize

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alu

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MMP-8 baseline

MMP-8 post-loading

MMP-8 4-hr post-treatment

MMP-8 24-hr post-treatment

Biology

• Summary so far for biology of resonant voice:– Low VF impact, helping to

minimize (further) tissue damage = biological prevention factor

– Large-amplitude VF oscillations (tissue mobilization) = biological healing factor

http://www.creatingpositivelives.co.uk/assets/Healing%20Hands%20Larger%201.jpg

Biology• Branski et al. (2007;

Best Basic Science paper, J Voice)

Biology• Branski et al. (2007;

cont’d)

Biology• Li: ABM simulation in

phonotrauma

Based on Li et al., 2005

Biology

• One last wait!• We‘ve talked about value of

resonant voice for acute injury

• What about chronic injury, which is most of what we see?

• Phases of healing– Inflammation (several

days)

– Protein synthesis (a few weeks)

– Tissue remodelling (year or longer) proteins align according to force vectors applied during healing

Question• How do we get

people to acquire the target vocal fold configuration???

• See motor learning!