Laryngeal Airway Resistance Research Articles

Exploring the phonatory effects of external superior laryngeal nerve paralysis: An In vivo model

Little is known regarding the phonatory consequences of unilateral external superior laryngeal nerve (ESLN) paralysis. By selectively blocking the ESLN with lidocaine HCl (with laryngeal electromyography verification), we modeled acute, unilateral cricothyroid (CT) muscle dysfunction to explore possible acoustic, aerodynamic, auditory-perceptual and auto-perceptive effects. Prospective, repeated measures, experimental design. Ten, vocally-normal adult males underwent lidocaine block of the right ESLN. Multiple measures of phonatory function across a variety of vocal tasks/conditions were acquired before and during the block using standard data acquisition and analysis protocols. During ESLN block, phonatory frequency range was significantly reduced with compression of both upper and lowermost regions of the pitch range. Mean speaking fundamental frequency increased significantly during oral reading. Acoustic analysis, aerodynamic assessment, and auditory- perceptual evaluation by blinded listeners revealed modest increases in phonatory instability (jitter), increased laryngeal airway resistance with no objective evidence of glottic insufficiency, and mild deterioration in voice quality most evident during high pitched voice productions, respectively. Participants uniformly rated their speaking and singing voices as worse during the block with significant weakness, effort, and tightness that they perceived as a mild level of impairment. These data support generally mild changes to the speaking voice, which extend beyond reductions in pitch range only, and shed light on the potential untoward phonatory effects of acute, unilateral CT dysfunction.

Voice Production during a Weightlifting and Support Task

Although effort closure techniques have a long history in the treatment of hypofunctional and psychogenic voice disorders, there have been surprisingly few studies of their specific laryngeal and phonatory effects. The present study was designed to provide preliminary data on physiologic changes in voice production associated with a weightlifting and support maneuver. Twenty vocally healthy subjects (10 men and 10 women) lifted hand-held weights and steadily supported them with outstretched arms as they either sustained comfortable phonation or repeated the syllable /pi/. Both the male and female subjects showed an increase in the electroglottographic contact quotient, long-term F₀ variability, and estimated laryngeal airway resistance attributable to an elevated driving pressure. Conversely, there were no significant changes in mean F₀, pitch perturbation quotient (jitter), or phonatory airflow between the pre-lift and lift portions of their voice production, regardless of the amount of weight supported. The results of this study indicate that simultaneous phonation and weightlifting is associated with increased laryngeal airway resistance characterized by an elevation in driving pressure and medial compression of the vocal folds. Implications for an improved understanding of normal vocal physiology and for the therapeutic use of such air-trapping exercises are addressed.

Direct measurement of onset and offset phonation threshold pressure in normal subjects

Phonation threshold pressures were directly measured in five normal subjects in a variety of voicing conditions. The effects of fundamental frequency, intensity, closure speed of the vocal folds, and laryngeal airway resistance on phonation threshold pressures were determined. Subglottic air pressures were measured using percutaneous puncture of the cricothyroid membrane. Both onset and offset of phonation were studied to see if a hysteresis effect produced lower offset pressures than onset pressures. Univariate analysis showed that phonation threshold pressure was influenced most strongly by fundamental frequency and intensity. Multiple linear regression showed that these two variables, as well as laryngeal airway resistance, most strongly predicted phonation threshold pressure. Two of the five subjects demonstrated a significant hysteresis effect, but one subject actually had higher offset pressures than onset pressures.

Respiratory and laryngeal contributions to maximum phonation duration

Maximum phonation duration (MPD) is a common assessment procedure in speech-language pathology. However, the specific contributions of the respiratory and phonatory components of the speech-production mechanism to this task are not typically assessed. Six women and 6 men with normal speech and voice were monitored for lung volume during a standard MPD task, and for laryngeal airway resistance (Rlaw) during a modified MPD (slow syllable-repetition) task. On average, subjects used 90% of their vital capacity (VC) for their best MPD trial. There was no systematic relation between MPD and VC for these subjects. Rlaw was strongly correlated with MPD for the men (r(s) = 0.886 for /a/; r(s) = 0.829 for /i/), but not for the women. Rlaw increased linearly as lung volume decreased (slope > 0.15) for a subset of trials (32%). This was a common pattern for four of the subjects. The clinical utility of MPD to assess breathing for speech is questioned because of the lack of association between MPD and VC, and some atypical laryngeal-valving strategies.

Modulations in respiratory and laryngeal activity associated with changes in vocal intensity during speech.

We tested the hypothesis that different strategies are used to alter tracheal pressure (Pt) during sustained and transient increases in intensity. It has been suggested that the respiratory system plays the primary role in Pt changes associated with alteration in overall intensity, whereas laryngeal adjustment is primary for transient change in Pt related to emphasis. Tracheal pressure, obtained via tracheal puncture, airflow (U), and laryngeal electromyography from the thyroarytenoid muscle (TA EMG) were collected from 6 subjects during sentence production at different intensity levels and with various stress patterns. Using a technique described in a previous study, we computed lower airway resistance (Rlaw) from measures of Pt and U obtained during a sudden change in upper airway resistance. We used this resistance value, together with direct measures of Pt and U during speech, to derive a time-varying measure of alveolar pressure (Pa), the pressure created by respiratory muscle activity and elastic recoil of the lungs. Pa provided a measure of respiratory drive that was unaffected by laryngeal activity. Laryngeal airway resistance (Rlx) and TA EMG provided measures of laryngeal activity. The results of this study indicated that, contrary to the outcome predicted by the hypothesis, there was no difference in the strategies used to alter Pt during sustained and transient increases in intensity. Although changes in both Pa and Rlx contributed to increase in Pt, the contribution of Pa was substantially greater. On average, Pa contributed to 94% and Rlx to 6% of the increase in Pt associated with vocal intensity. A secondary purpose of the study was to determine the extent to which laryngeal muscle activity was related to Rlx during speech. We found TA EMG activity increased with intensity but was not well correlated with Rlx, suggesting that when it contracts, the TA muscle may affect intensity by loosening the cover, which allows for greater amplitude of vocal fold vibration, without necessarily increasing laryngeal airway resistance.

Laryngeal Airway Resistance in Cleft Palate Children with Complete and Incomplete Velopharyngeal Closure

Abstract Objective: This study investigated the effect of velopharyngeal insufficiency on aerodynamic measures of laryngeal function in children with cleft palate. Design: Data were analyzed using analysis of covariance. The independent variable was velopharyngeal closure, and the dependent variables were laryngeal resistance, laryngeal airflow, and transglottal pressure. Age and gender were covariates. Setting: The data were collected at The Craniofacial Center, University of Illinois, a tertiary health care center located in Chicago. Patients: Thirty-six children with cleft palate were recruited from among the patients at The Craniofacial Center. Ten children with velopharyngeal areas > 5 mm2 during oral speech were placed in the incomplete closure group, while 26 children with areas < 1 mm2 were placed in the complete closure group. Outcome Measures: The three dependent variables (transglottal pressure, transglottal airflow, and laryngeal resistance) were measured. Results: Laryngeal resistance and tra...

Laryngeal Airway Resistance in Cleft Palate Children with Complete and Incomplete Velopharyngeal Closure

This study investigated the effect of velopharyngeal insufficiency on aerodynamic measures of laryngeal function in children with cleft palate. Data were analyzed using analysis of covariance. The independent variable was velopharyngeal closure, and the dependent variables were laryngeal resistance, laryngeal airflow, and transglottal pressure. Age and gender were covariates. The data were collected at The Craniofacial Center, University of Illinois, a tertiary health care center located in Chicago. Thirty-six children with cleft palate were recruited from among the patients at The Craniofacial Center. Ten children with velopharyngeal areas >5 mm2 during oral speech were placed in the incomplete closure group, while 26 children with areas <1 mm2 were placed in the complete closure group. The three dependent variables (transglottal pressure, transglottal airflow, and laryngeal resistance) were measured. Laryngeal resistance and transglottal pressure were significantly higher, and transglottal airflow was significantly lower in the group with complete closure. In summary, cleft palate patients with complete velopharyngeal closure exhibited higher laryngeal resistances than those with incomplete closure.

Acoustic characteristics of voice after severe traumatic brain injury.

To describe the acoustic characteristics of voice in individuals with motor speech disorders after traumatic brain injury (TBI). Prospective study of 100 individuals with TBI based on consecutive referrals for motor speech evaluations. Subjects were audio tape-recorded while producing sustained vowels and single word and sentence intelligibility tests. Laryngeal airway resistance was estimated, and voice quality was rated perceptually. None of the subjects evidenced vocal parameters within normal limits. The most frequently occurring abnormal parameter across subjects was amplitude perturbation, followed by voice turbulence index. Twenty-three percent of subjects evidenced deviation in all five parameters measured. The perceptual ratings of breathiness were significantly correlated with both the amplitude perturbation quotient and the noise-to-harmonics ratio. Vocal quality deviation is common in motor speech disorders after TBI and may impact intelligibility.

Effects of medialization laryngoplasty on airway resistance: a pilot study.

To investigate the effects of medialization laryngoplasty on laryngeal airway resistance at various clinically relevant flow rates. This study was conducted using a total of 13 laboratory experiments. Two of the experiments were used to validate the cadaveric model employed. Eleven experiments were used to quantify airway resistance relative to increasing medialization laryngoplasty stent size. With autopsy consent the authors obtained 13 consecutive and anatomically complete larynges for experimentation. A thyrotomy window measuring 8 x 6 mm was made on the left side of the thyroid cartilage. A #4 laryngeal mask was secured to the pharyngeal airway with sutures. Eleven experiments were conducted at the same flow rates using increasingly larger stents from 1 mm to 11 mm in size. Using the Bernoulli equation, the pressure measured at the proximal end of the laryngeal mask is representative of the pressure drop across the airway. The experimental model was validated in two experiments using flow rates between 5 and 50 L/min and stents measured at 5, 10, 15, and 20 mm. Average results from the 11 experiments indicate that at increasing levels of medialization, from 0 to 11 mm, there is essentially the same pressure drop across the larynx at a given flow rate. At physiologic airflow rates in a cadaveric model, medialization laryngoplasty implants of 11 mm or less seem to have no obvious effect on airway resistance.

Arytenoid adduction as an adjunct to type I thyroplasty for unilateral vocal cord paralysis

Background. Surgical management of unilateral vocal cord paralysis has evolved over the last three decades. The recent use of type I thyroplasty has resulted in improvements in voice, swallowing, and respiration. The study was performed to evaluate our experience in 28 patients undergoing arytenoid adduction as part of their surgical rehabilitation of unilateral vocal cord paralysis. Methods. Patients undergoing arytenoid adduction with or without silastic medialization for unilateral vocal cord paralysis were entered into a prospective data base. Evaluation included symptomatic improvement in hoarseness, aspiration, dysphagia, dyspnea, and the radiographic documentation of pneumonia. Objective evaluation included mean phonatory air flow and acoustic analysis. Complications associated with surgery were recorded. Results A satisfactory result was obtained in 27 of 28 (96%) patients. By symptom, improvement in hoarseness was evident in 96%, dyspnea 80%, dysphagia 94%, and aspiration 84%. Improvements in phonatory flow rate (p <.001), estimated mean laryngeal airway resistance (p <.001), and maximally prolonged phonation (p <.01) were identified. Complications occurred in 18% and consisted of local wound sepsis (n = 1 ), hematoma (n = 1), seroma (n = 1), and transient airway edema (n = 2). There were no episodes of airway obstruction requiring tracheostomy or implant extrusion. Conclusions. Arytenoid adduction as part of type I thyroplasty is a safe and effective procedure. Subjective analysis confirms marked improvement in laryngeal function in the form of speech, swallowing, and respiration. Objective analysis confirms improvement in voice parameters. Future directions will focus on determination of those patients best served by arytenoid adduction.

Arytenoid adduction as an adjunct to type I thyroplasty for unilateral vocal cord paralysis.

Surgical management of unilateral vocal cord paralysis has evolved over the last three decades. The recent use of type I thyroplasty has resulted in improvements in voice, swallowing, and respiration. The study was performed to evaluate our experience in 28 patients undergoing arytenoid adduction as part of their surgical rehabilitation of unilateral vocal cord paralysis. Patients undergoing arytenoid adduction with or without silastic medialization for unilateral vocal cord paralysis were entered into a prospective data base. Evaluation included symptomatic improvement in hoarseness, aspiration, dysphagia, dyspnea, and the radiographic documentation of pneumonia. Objective evaluation included mean phonatory air flow and acoustic analysis. Complications associated with surgery were recorded. A satisfactory result was obtained in 27 of 28 (96%) patients. By symptom, improvement in hoarseness was evident in 96%, dyspnea 80%, dysphagia 94%, and aspiration 84%. Improvements in phonatory flow rate (p < .001), estimated mean laryngeal airway resistance (p < .001), and maximally prolonged phonation (p < .01) were identified. Complications occurred in 18% and consisted of local wound sepsis (n = 1), hematoma (n = 1), seroma (n = 1), and transient airway edema (n = 2). There were no episodes of airway obstruction requiring tracheostomy or implant extrusion. Arytenoid adduction as part of type I thyroplasty is a safe and effective procedure. Subjective analysis confirms marked improvement in laryngeal function in the form of speech, swallowing, and respiration. Objective analysis confirms improvement in voice parameters. Future directions will focus on determination of those patients best served by arytenoid adduction.

Effects of a pressure target on laryngeal airway resistance in children

The purpose of this study was to determine the effects of an intraoral air pressure target on estimation of laryngeal airway resistance (LAR) in normal children. Ten children produced the syllable /pi/ (a) with self-determined normal loudness, (b) with increased loudness, and (c) at a predetermined intraoral air pressure level of 6.5 to 7.5 cm of water. The target pressure level was selected because it was expected to result in estimated subglottal pressures that were lower than those associated with self-determined loudness levels. Results indicated significant differences in estimated subglottal pressure among the three conditions. As expected, estimated subglottal pressures were highest during loud speech and lowest during the pressure target task. LAR values associated with normal loudness were similar to values previously reported for children. The use of the pressure target resulted in LAR values that were reduced by 31% from normal loudness. These resistance values, however, were still greater than those reported for adult speakers at similar subglottal pressure levels. The results are explained relative to preferred loudness levels and vocal tract size differences in children and adults. It is suggested that use of a pressure target during estimation of LAR in children may provide additional data that more accurately reflect the aerodynamic integrity of the larynx. Implications for clinical assessment are discussed.

Direct measurement of subglottic pressure and laryngealresistance in normal subjects and in spasmodic dysphonia

This study tested the accuracy of indirect methods of measurement of laryngeal airway resistance in normal subjects and in spasmodic dysphonia (SD). The indirect method assumes that subglottic air pressure remains constant during the voiced segment of a syllable. In this study subglottic air pressure was directly measured via puncture of the cricothyroid membrane in seven normal subjects and seven subjects with SD. The true laryngeal airway resistance was calculated and compared with airway resistance measured using indirect techniques based on intraoral air pressure. In five of the seven normal subjects, subglottic air pressure did not remain constant during the voiced segment. As a result, the error produced using indirect method of calculating average laryngeal resistance for the normal subjects varied from -44% to +50%. For SD subjects the error ranged from -49% to +22%. In general, the indirect technique overestimated laryngeal airway resistance in normal subjects and underestimated the resistance in subjects with SD.

Laryngeal airway resistance in teacherswith vocal fatigue: A preliminary study

A noninvasive pressure-flow technique was used to compare laryngeal airway resistances in nine female classroom teachers with symptoms of vocal fatigue and seven teachers without symptoms of vocal fatigue. Data were collected two times per day on the Monday, Wednesday, and Friday of a typical work-week. No significant between-group differences were found, but two within-group differences were notable. Airflow in the fatigued subjects decreased across the sampling period (p = .0009). In the controls, air pressure increased across the sampling period (p = .021). These findings suggest that both groups may have reacted to vocal demands during the week by employing two different strategies to maintain habitual laryngeal airway resistance: laryngeal adjustments alone or laryngeal adjustments plus increased respiratory drive. The first strategy, employed by the fatigued subjects, may have been less efficient, thereby provoking conditions associated with their vocal fatigue.

Laryngeal and phonatory dysfunction in Parkinson's disease

The vocal function of 20 speech-disordered subjects with idiopathic Parkinson's disease (PD) was assessed using both perceptual and instrumental techniques. The instrumental analysis included electroglottography and the use of a computerized airflow/air pressure analysis system (Aerophone II). Variables measured included parameters of the Lx waveform (F0, duty cycle, and closing time) as well as aerodynamic parameters such as subglottal pressure, laryngeal airway resistance, average phonatory sound pressure level, phonatory flow rate and ad/abduction rate. Values were compared to those recorded from a group of non-neurologically impaired controls matched for age and sex. Perceptual assessment revealed that 89·5% of the PD subjects exhibited deviant laryngeal features. None of the electroglottography (EGG) parameters differed significantly between the PD and control groups. However four of the five aerophone parameters did differentiate between the two subject groups. The PD group was characterized by higher levels of glottal resistance than the control subjects and lower values for subglottal pressure, average phonatory sound pressure level and phonatory flow rate. A cluster analysis based on the EGG and aerodynamic measures identified the presence of four subgroups, two which represented different expressions of hyperfunction of the larynx within the PD group. The results are discussed with reference to the expected effects of PD on vocal function.

Phonatory and articulatory changes associated with increased vocal intensity in Parkinson disease: a case study.

This study examined changes in voice and speech production in a patient with Parkinson disease as he increased vocal intensity following 1 month of intensive voice treatment. Phonatory function and articulatory acoustic measures were made before and after treatment as well as 6 and 12 months later. Pre- to post-treatment increases were documented in sound pressure level in sustained phonation, syllable repetition, reading, and monologue. Consistent with mechanisms of intensity change reported in normal speakers, corresponding improvements were measured in estimated subglottal pressure, maximum flow declination rate, laryngeal airway resistance, open quotient, EGGW-25, harmonic-spectral slope, and maximum vowel duration. Measures of phonatory stability in sustained phonation and semitone standard deviation in reading and speaking showed changes accompanying increased vocal intensity. In addition, changes were measured in articulatory acoustic parameters (vowel and whole word duration, transition duration, extent and rate, and frication duration and rise time) in single-word productions. These findings indicate that this patient increased his vocal intensity using phonatory mechanisms that have been associated with the nondisordered larynx. In addition, the increased vocal intensity led to changes in articulation that were not targeted in treatment.

Laryngeal Airway Resistance in Children with Cleft Palate and Adequate Velopharyngeal Function

Laryngeal airway resistance during vowel production was determined for 10 children without cleft palate and 14 children with cleft palate and adequate velopharyngeal function. The children with cleft palate were further grouped according to either complete or incomplete velopharyngeal closure. All children performed a syllable repetition task with nostrils occluded at self-determined effort and a targeted effort typical of adult speech. Results indicated that all children exhibited significantly greater laryngeal resistance at self-determined effort. No significant differences occurred among the groups of children at either effort level. Some children with incomplete velopharyngeal closure, however, tended to exhibit relatively increased laryngeal resistance at the targeted effort level when their nostrils were unoccluded. Implications for a regulation-control model of speech production and clinical assessment are discussed.

Laryngeal airway resistance in children with cleft palate and adequate velopharyngeal function.

Laryngeal airway resistance during vowel production was determined for 10 children without cleft palate and 14 children with cleft palate and adequate velopharyngeal function. The children with cleft palate were further grouped according to either complete or incomplete velopharyngeal closure. All children performed a syllable repetition task with nostrils occluded at self-determined effort and a targeted effort typical of adult speech. Results indicated that all children exhibited significantly greater laryngeal resistance at self-determined effort. No significant differences occurred among the groups of children at either effort level. Some children with incomplete velopharyngeal closure, however, tended to exhibit relatively increased laryngeal resistance at the targeted effort level when their nostrils were unoccluded. Implications for a regulation-control model of speech production and clinical assessment are discussed.

Effect of hypercapnia on laryngeal airway resistance in normal adult humans

Laryngeal airway resistance (Rlar) was measured in eight normal adult humans during progressive hyperoxic hypercapnia. In most subjects, the translaryngeal pressure-flow relationship appeared linear under normocapnic conditions. During hypercapnia, the pressure-flow relationship on inspiration and expiration was curvilinear with increasing translaryngeal pressure associated with progressively smaller increments in flow. Translaryngeal pressure-flow relationships at different CO2 levels were compared over their common flow ranges by performing a least-squares linear regression on data throughout inspiration and expiration. During normocapnia, the mean slope, i.e., mean Rlar, was 0.50 +/- 0.21 (SD) cmH2O.l-1.s. A moderately significant decrease in Rlar was present at 9% end-tidal CO2 (P = 0.08). In a separate series of experiments, subjects breathed oxygen- and helium-based gas mixtures through a face mask attached to a pneumotachograph. Data analysis over the flow range present during normocapnia revealed no difference in Rlar between nose and mouth breathing and similar decreases in Rlar under hypercapnic conditions with the oxygen- and helium-based gas mixtures. The decrease in Rlar from normocapnic to hypercapnic conditions found over common, but relatively low, ranges of flow predicts that even greater increases in Rlar would occur at high flow rates in the absence of increasing glottic aperture.

Developmental patterns of laryngeal and respiratory function for speech production

Estimates of subglottal air pressure, laryngeal airflow, and laryngeal airway resistance from syllable repetitions of children and adults were used in describing developmental changes in these variables and in hypothesizing corresponding changes in respiratory function. A trend was found for pressure and resistance to decrease with increases in flow from preschool age through adulthood. These patterns could be explained by the smaller size of laryngeal airway structures and increased expiratory muscle forces during speech in the younger subjects. When the subglottal air pressures were combined with published data on air volume expired during speech and recoil pressures of the respiratory system, hypothetical functions were derived for respiratory muscle forces and the work of speech breathing. These functions predict (a) a developmental shift from the use of net expiratory muscle force in the speech of preschool children to the adult patterns of combined inspiratory and expiratory muscle forces, and (b) the expiratory work of speech breathing is greater in preschool children than in older children and adults.