Laryngeal Airway Resistance Research Articles

Aerodynamic and acoustic changes following intensive voice therapy for patients with Parkinson’s disease: A case study

A 50‐year‐old patient with Parkinson’s disease received a 4‐week course of intensive voice and respiratory therapy aimed at improving functional communication through increased laryngeal adduction. Aerodynamic and acoustic data were gathered on two occasions before treatment, two after the completion of therapy, and at 6‐ and 12‐month follow‐up sessions. There were increases in subglottal pressure and laryngeal airway resistance after the treatment. Maximum flow declination rate (MFDR) also increased, as did the sound pressure level of utterances that the subject produced at a ‘‘comfortable’’ effort level. Fundamental frequency variability and conversational intensity levels were higher post therapy. Video‐stroboscopic examination before and after treatment showed improvements in adduction and a decreased level of supraglottic hyperfunction. Possible physiological mechanisms are discussed to account for these changes. [Work supported by NIH Grant No. R01 DC01150‐03 and NIDCD Grant No. DC00976.]

Aerodynamic assessment of the speech of adults undergoing multichannel cochlear implantation.

This investigation was designed to evaluate the aerodynamic characteristics of the speech of adult multichannel cochlear implant (Nucleus, 21-channel) recipients. Five adults with an acquired profound sensorineural hearing loss were tested before implantation, immediately following implantation, and 3, 6, 9, and 12 months after implantation. A commercially available computerized pressure-flow instrumentation system was employed to assess the respiratory, laryngeal, velopharyngeal, and oral articulatory subsystems of speech of the implantees. The results of the investigation indicated 1) a slight increase in airflow rate values for sustained vowel /a/phonation after implantation, 2) a slight increase in duration of sustained vowel phonation from the preimplant period to the last postimplant period, 3) an increase in laryngeal airway resistance after implantation that resulted from a larger increase in estimated transglottal pressure than in transglottal airflow, 4) maintenance of normal velopharyngeal closure in oral-nasal contrastive contexts, and 5) slight increases in oral orifice area for fricative syllable utterances following implantation. Individual strategies for coordinated control of the speech mechanism appear to be potent variables to consider when assessing speech production.

Respiratory and Laryngeal Function of Women and Men During Vocal Intensity Variation

Simultaneous procedures for making aerodynamic and kinematic observations of the laryngeal and chest wall systems were used to investigate variations in vocal intensity in normal women and men. Laryngeal results indicate that significant increases of maximum flow declination rate and laryngeal airway resistance and significant decreases in open quotient occur when higher intensity levels are produced. Respiratory results indicate that tracheal pressure, percent rib cage contribution, lung volume, and rib cage volume initiations are higher, and lung and rib cage volume excursions are larger when higher vocal intensity levels are produced. Laryngeal and respiratory function results indicate that some measures are different for women than for men. Mean data support the notion that increases in tracheal pressure are achieved by inhaling to higher lung and rib cage volumes. Individual subject data provide alternative respiratory and laryngeal patterns for changing the shape of the glottal airflow waveform.

Age and laryngeal airway resistance during vowel production in women.

An investigation was conducted to determine if laryngeal valving economy, as reflected in measures of laryngeal airway resistance during vowel production, differs with age in women. Seventy healthy women were studied, 10 each at age 25, 35, 45, 55, 65, 75, and 85 years. Results indicated that laryngeal airway resistance did not differ significantly with age, although it was noted that the 45-year-old women generally had lower laryngeal airway resistance values. This pattern of function differs from that observed in men (Melcon, Hoit, & Hixon, 1989). Discussion of findings includes consideration of factors that might influence laryngeal function during speech production in women. Clinical implications are offered.

Voice Analysis of Patients with Endoscopically Treated Early Laryngeal Carcinoma

Endoscopic laser resection of early (T1) laryngeal carcinoma has been advocated as an alternative to radiotherapy. Heretofore, the voice characteristics following this procedure have been addressed in only one review, which included patients treated by irradiation and laser resection. We present the first review of voice findings in 22 patients treated only by endoscopic laser resection of their vocal cord carcinomas. Laser resection of selected vocal cord carcinomas produced voice function results acceptable to the patients and was rated by them to be normal to almost normal. Speech pathologists rated the voices to be near-normal to mildly abnormal. Voices after laser resection of vocal carcinoma exhibited a slightly higher fundamental frequency, a decrease in intensity and phonatory duration, and markedly higher laryngeal airway resistance. The percentage of voicing showed little deviation from normal, as did mean percentage of perturbations.

Changes in laryngeal airway resistance in young adult men and women as a function of vocal sound pressure level and syllable context

<h2>Summary</h2> A noninvasive pressure-flow technique was used to assess laryngeal airway resistance (R_law) in eight young adult women and seven men. Syllable structures used were consonant-vowel (/pi/) and consonant-vowel-consonant (/bip/). The data were obtained from oscillographic records of intraoral air pressure and transglottal airflow over 2 consecutive days. Repetitions of each syllable context were produced at each subject's 25th, 50th, and 75th percentiles of vocal sound pressure level. No significant differences in R_law were found across days for the two groups. Women had significantly greater R_law than did men for the /pi/ and /bip/ contexts. Men showed a significantly greater average airflow rate than did women for both syllable contexts. Airflow, air pressure, and the ratio R_law increased as the sound pressure level of voice increased. The technique appears to be useful for characterizing certain features of laryngeal airway resistance for men and women.

Laryngeal Airway Resistance: The Relationships of Airflow, Pressure, and Aperture

In the surgical treatment of the paralyzed larynx, a compromise often needs to be made between an orifice size needed to preserve voice and that needed for adequate inspiratory airflow rates. To assess the negative pressures needed to generate normal airflows across a narrowed vocal cord aperture, we measured pressure and flow changes across cadaveric larynges while altering aperture size. Best-fit quadratic equations for each aperture area selected were derived and showed that if the aperture were 0.5 cm2 or less, the resistance to normal breathing would be significantly increased. Aperture sizes of 0.67 cm2 or greater are not associated with such an increase in resistance.

Pressure-flow relationships during phonation in the canine larynx

Summary Measurements of air pressure and flow were made using an in vivo canine model of the larynx. Subglottic pressures at varying flow rates were taken during phonation induced by laryngeal nerve stimulation. Results showed that during constant vocal fold stiffness, subglottic pressure rose slightly with increased air flow. The larynx in the in vivo canine model exhibited a flow-dependent decrease in laryngeal airway resistance. Increasing flow rate was associated with an increase in frequency of phonation and open quotient, as measured glottographically. Results from this experiment were compared with a theoretical two-mass model of the larynx and other theoretical models of phonation. The influence of aerodynamic forces on glottal vibration is explained by increased lateral excursion of the vocal folds during the open interval and shortening of the closed interval during the glottal cycle.

Effect of maturation on the sensitivity of laryngeal resistance to chemoreceptor stimulation in the dog.

The respiratory system undergoes many changes with maturation, resulting in increased capacity and efficiency. In an effort to determine the effects of maturation on airway control, laryngeal airway resistance was studied from infancy to adulthood in dogs. Reflex regulation of laryngeal airway resistance in response to chemoreceptor stimulation was found in puppies 1 day of age and older. Chemoreceptor-mediated laryngeal reflexes were qualitatively similar in all age groups. However, a significant quantitative difference was found. With maturation, an increase in the sensitivity of both central and peripheral chemoreceptors regulating laryngeal resistance is realized.

Age-related responses of laryngeal airway resistance to peripheral and central chemoreceptor stimulation.

Laryngeal airway resistance was measured in anesthetized dogs ranging in age from one day to adult during central and peripheral chemoreceptor stimulation by hypoxia and hypercapnia. Chemoreceptor-mediated regulation of airway resistance was found to be qualitatively similar in all age groups; however, there was a progressive increased sensitivity to both hypoxia and hypercapnia with increasing age. The reduced sensitivity of the laryngeal airway to hypoxic and hypercapnic stimulation in the young animal may predispose the young animal to airway obstruction during periods of hypoxia or hypercapnia. This may bear some relevance to the etiology of certain cases of sudden infant death syndrome.

Consistency of laryngeal airway resistance in adult women

Fifteen young adult women performed a noninvasive clinical technique for measurement of laryngeal airway resistance (R law) during syllable (consonant plus vowel) production. The data were recorded from oscillographic records of translaryngeal air pressure (P tr – P ph) and translaryngeal airflow (V̇ tl) over 2 days, during two time periods on each day. The overall mean R law for the experimental sessions was 38.3 cmH 2O/LPS (SD = 9.24). No significant differences were found within or between days or time of day for the subjects. The obtained values were similar to mean values obtained for men in a previous study (Smitheran and Hixon, 1981). Single subject phonation data were also gathered during a controlled intensity condition. The R law range and standard deviation figures decreased significantly from the uncontrolled condition during syllable productions to the midrange intensity (75 dB SPL). This finding suggests that control of intensity is an important variable to consider during clinical sampling. The measurement procedure shows promise clinically as an index of actual laryngeal resistance under selected control conditions and in relation to simultaneous comparison of patient strategies used to regulate translaryngeal pressure and airflow.

Response of laryngeal airway resistance to chemoreceptor stimulation: effect of pulmonary afferent denervation.

The response of laryngeal airway resistance to chemoreceptor stimulation was measured before and after vagotomy in ten anesthetized dogs. With the vagus nerves intact, stimulation of chemoreceptors produced a decrease in both inspiratory and expiratory laryngeal resistance. After bilateral vagotomy below the origin of the recurrent laryngeal nerves, stimulation of chemoreceptors produced a smaller decrease in inspiratory laryngeal resistance and an increase in expiratory laryngeal resistance. We concluded that pulmonary afferent input to the respiratory neurons maintains a low airway resistance during chemoreceptor stimulation.

Laryngeal airway resistance as a function of phonation type

An indirect method to estimate laryngeal airway resistance was investigated. The ratio of the intraoral pressure (IOP) for the voiceless stop and the volume velocity air flow (V0) for the open vowel in the CV utterance /pa/ was suggested to give an estimate of the laryngeal airway resistance (Rlaw); Rlaw = IOP/V0. The primary variable was phonation type. It was hypothesized that the Rlaw value would reflect the laryngeal airway resistance during: (1) normal, (2) pressed, and (3) breathy phonation. Other controlled variables were intensity and fundamental frequency. The results suggested that the Rlaw value was highest for pressed phonation and lowest for breathy phonation irrespective of intensity and fundamental frequency. Good discrimination in the Rlaw value between high and low intensity was also found. These results were interpreted to give evidence that the Rlaw value obtained with this method was a good index of actual resistance.

Laryngeal Regulation of Airway Resistance

The response of laryngeal airway resistance to pulmonary receptor stimulation was studied in 20 mongrel dogs anesthetized with alpha-chloralose (80 mg/kg). Stimulation of pulmonary stretch receptors by lung inflation inhibited the phasic variation of laryngeal resistance during respiration and produced a sustained reduction of laryngeal resistance, which was related to lung inflation pressure. Stimulation of pulmonary J-receptors with capsaicin produced apnea and a large increase in laryngea resistance. Capsaicin produced this reflex when injected into the pulmonary circulation but not when injected into the systemic circulation. Irritant receptor stimulation with histamine hydrochloride produced tachypnea and a reduction in inspiratory laryngeal resistance. Pulmonary receptor reflexes were abolished by dividing the vagus nerves distal to the origin of the recurrent laryngeal nerves. Laryngeal reflexes may be important in the regulation of respiration and the production of physiologic and pathologic alterations in pumonary function.

Laryngeal regulation of airway resistance. I. Chemoreceptor reflexes.

The resistance of the larynx to airflow was measured during hypercapnia, hypoxemia, and stimulation of peripheral chemoreceptors by sodium cyanide and phenyl diguanide in 15 dogs anesthetized with alpha-chloralose (80 mg/kg). Laryngeal airway resistance (R1x) was obtained by measuring the pressure difference between the subglottic region and the mouth while a constant flow of humidified air was passed through the larynx. During spontaneous respiration, R1x varies with the phase of the respiratory cycle: R1x is high during expiration (mean +/- SEM = 0.79 +/- 0.19 cm H2O/L/sec) and falls just before inspiration (0.49 +/- 0.14 cm H2O/L/sec) and remains low until the end of inspiration. Hypercapnia, hypoxemia, and chemoreceptor stimulation each stimulated respiration and simultaneously decreased R1x during both inspiration and expiration. Chemoreceptor stimulation with phenyl diguanide (100 microgram/kg) and sodium cyanide (100 microgram/kg) produced similar decreases in R1x whether injected into the right atrium or left ventricle, indicating that these agents are not stimulating pulmonary receptors. The decrease in R1x during stimulation of chemoreceptors will decrease the work of ventilation. This study suggests that the control of ventilation involves the active regulation of the resistance of the laryngeal airway.