Biomedical subjects

Thomas J Hixon

Publications and source records attributed to Thomas J Hixon.

6 recordsLinked to original sources

PubMed2006

A clinical method for the detection and quantification of quick respiratory hyperkinesia.

PURPOSE: Quick respiratory hyperkinesia can be difficult to detect with the naked eye. A clinical method is described for the detection and quantification of quick respiratory hyperkinesia. METHOD: Flow at the airway opening is sensed during spontaneous apnea (rest), voluntary breath holding (postural fixation), and voluntary volume displacement (intentional movement). The method is designed to reveal quick respiratory hyperkinesia independent of the function of the larynx and/or upper airway. Theory underlying the method is discussed, and a protocol is offered for clinical use. CONCLUSIONS: This method may be useful to neurologists, pulmonologists, and speech-language pathologists. Because it depends on nonspeech observations, its application to speech and/or voice production must be inferred.

Airway Resistance↗

PubMed2006

Listener perception of respiratory-induced voice tremor.

PURPOSE: The purpose of this study was to determine the relation of respiratory oscillation to the perception of voice tremor. METHOD: Forced oscillation of the respiratory system was used to simulate variations in alveolar pressure such as are characteristic of voice tremor of respiratory origin. Five healthy men served as speakers, and 6 clinically experienced women served as listeners. Speakers produced utterances while forced sinusoidal pressure changes were applied to the surface of the respiratory system. Utterances included vowels and sentences produced using usual loudness, pitch, quality, and rate, and vowels produced using different loudness, pitch, and quality. Perceptual tasks included detection threshold for voice tremor and pair comparison judgments in which listeners identified the sample with the greater magnitude of voice tremor. RESULTS: The mean detection threshold for voice tremor was 1.37 cmH(2)O (SD = 0.47) for vowel utterances and 2.16 cmH(2)O (SD = 1.52) for sentence utterances. Tremor magnitude was judged to be different for vowel and sentence utterances, but not for different vowels. Results revealed differential effects for loudness, pitch, and quality. CONCLUSIONS: These findings offer implications for the evaluation and management of voice tremor of respiratory causation.

Adult↗

PubMed2006

The Hardy Effect.

PURPOSE: The late James C. Hardy completed an extensive investigation of respiratory muscle activity during speech production. The data set that resulted was probably the most comprehensive and instructive that has ever existed. One aspect of the data puzzled Hardy and caused him to question the validity of his findings and withhold his observations from publication. METHOD: This research note chronicles Hardy's thinking at the time (based on personal communications) and points out how the aspect of the data that puzzled him turned out to be a seminal discovery of a fundamental mechanism of speech breathing. CONCLUSION: It is proposed that, in his honor, this discovery be referred to as the Hardy Effect.

Biomechanical Phenomena↗

PubMed2006

Rib torque does not assist resting tidal expiration or most conversational speech expiration.

PURPOSE: This research note discusses a common misconception in speech science and speech-language pathology textbooks that rib torque (i.e., rotational stress) assists resting tidal expiration and conversational speech production. METHOD: The nature of this misconception is considered. CONCLUSION: An alternate conceptualization is offered that is consistent with knowledge from respiratory biomechanics.

Biomechanical Phenomena↗

PubMed2006

Velopharyngeal function during vocalization in infants.

OBJECTIVE: To determine the age at which infants achieve velopharyngeal closure during vocalization. DESIGN: Longitudinal with repeated measures. SETTING: Laboratory. PARTICIPANTS: Six healthy infants were studied monthly from ages 2 to 6 months while they interacted with a parent and an investigator. MAIN OUTCOME MEASURES: The presence or absence of velopharyngeal closure, as determined by sensing ram pressure at the anterior nares. RESULTS: The velopharynx was open for windups, whimpers, and laughs, and it was closed for cries, screams, and raspberries, regardless of age. The frequency with which the velopharynx closed during syllable utterances increased significantly with age. CONCLUSIONS: Velopharyngeal closure for speech-like utterance increases with age, but is not complete and is still undergoing development at 6 months of age. Velopharyngeal closure during infancy may be influenced by pressure demands of the utterance; however, support for this speculation is stronger for other types of utterances than it is for speech-like utterances. The method used in this study holds promise for evaluating infants with suspected velopharyngeal impairment.

Age Factors↗

PubMed2003

Clinical ventilator adjustments that improve speech.

STUDY OBJECTIVES: We sought to improve speech in tracheostomized individuals receiving positive-pressure ventilation. Such individuals often speak with short phrases, long pauses, and have problems with loudness and voice quality. SUBJECTS: We studied 15 adults with spinal cord injuries or neuromuscular diseases receiving long-term ventilation. INTERVENTIONS: The ventilator was adjusted using lengthened inspiratory time (TI), positive end-expiratory pressure (PEEP), and combinations thereof. RESULTS: When TI was lengthened (by 8 to 35% of the ventilator cycle), speaking time increased by 19% and pause time decreased by 12%. When PEEP was added (5 to 10 cm H(2)O), speaking time was 25% longer and obligatory pauses were 21% shorter. When lengthened TI and PEEP were combined (with or without reduced tidal volume), their effects were additive, increasing speaking time by 55% and decreasing pause time by 36%. The combined intervention improved speech timing, loudness, voice quality, and articulation. Individual differences in subject response to the interventions were substantial in some cases. We also tested high PEEP (15 cm H(2)O) in three subjects and found speech to be essentially identical to that produced with a one-way valve. CONCLUSIONS: These simple interventions markedly improve ventilator-supported speech and are safe, at least when used on a short-term basis. High PEEP is a safer alternative than a one-way valve.

Adult↗