HYDRATION

 When the vocal fold tissues are dehydrated, their viscosity increases.  This makes the tissue of the vocal fold cover less pliable and more difficult to displace.  Additionally, when subglottic air pressure is exerted against the inferior margin of the fold, a convergent glottis may not form.  When the folds are closing, a divergent glottis may not be accomplished.  The combined effects of increased viscosity and the lack of a convergent/divergent glottis could raise the phonation threshold pressure.  The patient has to "work" more to initiate and maintain phonation.
 

REFLUX

 Gastroesophageal reflux occurs when stomach acids are not retained in the stomach and travel up the esophagus.  The acid may spill onto the posterior region of the larynx.  The mucosa in this region can become irritated and pathological conditions may develop.  Reflux has been identified as an etiologic factor for chronic throat clearing, contact ulcers, laryngitis, cancer, granulomas hoarseness and other disorders of the larynx.

WARM-UP\COOL-DOWN

 During warm-up, arteries dilate to allow increased flow of oxygen-rich blood to the working muscles.  The temperature of the muscle rises and its viscosity (resistance to displacement) decreases.  This and other factors have potential to reduce phonation threshold pressure.  Also, speakers report subjective/emotional benefits to a warm-up.  A cool-down is a gradual reduction in activity.  Blood vessels remain somewhat dilated, providing oxygen-rich blood.  The oxygen facilitates removal of lactic acid and speeds recovery.
 

CAFFEINE

 Caffeine acts as a diuretic, meaning that fluids may pass from the body before adequately hydrating the tissues.  When the cover of the vocal folds is relatively dehydrated, the phonation threshold pressure becomes higher.  Additionally, caffeine is a central nervous system stimulant.  This effect on the CNS could sabotage therapeutic efforts that encourage relaxation.  Finally, caffeine can aggravate reflux because it weakens the lower esophageal sphincter.

ALCOHOL

 Alcohol is a 'CNS depressant.  It may impair fine motor coordination and reduce sensation.  These effects are dangerous since slight pain and "tickling" may signal potentially damaging phonatory patterns.  Alcohol is also a diuretic and can contribute to dehydration of the laryngeal mucosa.

SMOKING

 The heat and irritants found in smoke result in erythema (redness due to dilation of the superficial capillaries), edema (swelling of tissues) and general inflammation.  Long term exposure to the irritants could lead to cellular changes of the mucosa that could signal the development of cancer.

REFERENCES

1. McArdle, W.D., Katch, V.L. and Katch, F.I. (1991). Essentials of Exercise Physiology.  Malvern, PA: Lee and Febiger.

2. Olson, N. (1991).  Laryngopharyngeal manifestations of gastroesophageal reflux disease. Otolarngologic Clinics of North America, 24, 1201-1213

3. Sataloff, R.T. (1991).  Professional Voice: The Science and Art of Clinical Care. New York: Raven Press.

4. Sataloff, R.T. (1987).  Common diagnoses and treatments in professional singers. Ear Nose and Throat Journal, 66, 28-46.

5. Stemple, J.C., Glaze, L.E. and Gerdeman, B.K. (1995).  Clinical Voice Pathology: Theory and Management. San Diego: Singular Publishing Group, Inc.

6. Verdonlini, K., Titze, I. and Fennel, A. (1994).  Dependance of phonatory effort on hydration level.  Jounal of Speech and Hearing Research, 7, 1001-1007.

7. Verdonlini-Marston, K. Titze, I. and Druker, D. (1990).  Changes in phonation threshold pressure with induced conditions of hydration.  Journal of Voice, 4, 142.