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

What’s our child’s physical system like? Considerations about structure, biology, biomechanics. K. Verdolini Abbott, Ph.D., CCC-SLP University of Pittsburgh 2010. Discussion in three parts. (1) General developmental information (2) Information pertinent to “indirect therapy”

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

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  1. What’s our child’s physical system like? Considerations about structure, biology, biomechanics K. Verdolini Abbott, Ph.D., CCC-SLP University of Pittsburgh 2010

  2. 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

  3. Developmental issues • Very young children (< 2-3 yr) appear to have phonotrauma infrequently Image from http://supermon.files.wordpress.com/2010/01/baby.jpg

  4. Developmental issues • More broadly • Babies/infants low risk • Children high risk • Adults • Males low risk • Females high risk (Percent; approximate)

  5. 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

  6. 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???

  7. 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

  8. 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???) Laryngeal macrostructure

  9. 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: Cartilage1.5:1 at birth with relative growth of membranous folds

  10. 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)

  11. 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

  12. 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

  13. 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.

  14. 2 day 2 month 3 year 7 year

  15. 13 year old

  16. 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?)

  17. 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?

  18. 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: Laryngeal macro- and microstructure

  19. 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

  20. 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)

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

  22. 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

  23. 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

  24. 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) Respiratory structure/function http://www.luxfitness.com/Figures/muscles_of_the_abdomen.jpg

  25. 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. Respiratory function

  26. So far • A tiny bit of heat and not much light

  27. 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

  28. Increases the subglottic pressure required to oscillate the vocal folds Fisher 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 phonotrauma Titze, 1981 http://web.hcsps.sa.edu.au/projects/deserts/projects/group13/namib%20desert%201.jpg Vocal hygiene: Dehydration (bad)

  29. Reduces the subglottic pressure required to oscillate the vocal folds Jiang 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: Hydration (good)

  30. 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

  31. Vocal hygiene: Inflammation (bad)Laryngopharyngeal reflux http://images.icanhascheezburger.com/completestore/2009/4/5/128834617768108870.jpg • However • Scary (next page)

  32. Laryngoscope. 2006 Jan;116(1):144-8. Links • Empiric 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.

  33. 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

  34. 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)

  35. 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 Vocal hygiene:Screaming like crazy (bad)

  36. 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?

  37. 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

  38. Direct voice therapySwitching gears • Voice work • Adventures in Voice differs from traditional voice work for children • Emphasis is vocal function rather than conservation

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

  40. 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

  41. 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

  42. 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

  43. Biomechanics • Question approached from converging studies • Simulation • Excised • Human Berry et al., 2001 http://www.ust.ucla.edu/ustweb/Homepage_imgs/ucla_04.jpg

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

  45. Results for output: excised studies Biomechanics

  46. Results for output: excised + simulation studies Biomechanics

  47. Results for impact stress: excised studies Biomechanics

  48. Results for ratio of output/impact intensity (“vocal economy) (combined excised/simulation) Biomechanics

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

  50. Problem: We wanted best ratio of Strong output Limited impact and effort Pick 2 out of 3??? Biomechanics

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