The only "lungless" frog has a glottis and lungs.

Blackburn et al. show using CT-scanning that the only previously reported "lungless" frog retains a glottis and lungs.

Clinical and Anatomical Variation During Assessment of Maximum Glottic Angle.

INTRODUCTION: Quantitative measurement and analysis of glottic abduction is used to assess laryngeal function and success of interventions; however, the consistency of measurement over time has not been established. This study assesses the consistency of glottic abduction measurements across visits in healthy patients and anatomic factors impacting these measurements. METHODS: Review of patients with two sequential flexible stroboscopic exams over seven months from 2019-2022. Images of maximal glottic abduction were captured and uploaded into and measured with ImageJ. Cadaver heads were used to assess the impact of visualization angles on glottic measurements with a monofilament inserted into the supraglottis of each cadaver as a point of reference. Comparisons were done with a paired T-test, T-test, or Mann-Whitney U test as appropriate. RESULTS: Fifty-nine patients and twenty-six cadaveric exams were included. Absolute change in maximum glottic abduction angle (MGAA) was 6.90° (95% CI [5.36°, 8.42°]; p < 0.05). There were no significant differences in change in MGAA by gender or age. Twenty percent of patients had a change of at least 25% in their MGAA between visits. Absolute differences in glottic angle between nasal side for cadaveric measurements was 4.77 ± 4.59° (p < 0.005)-2.22° less than the change in MGAA seen over time (p = 0.185). CONCLUSION: Maximal glottic abduction angles varied significantly between visits. Factors considered to be contributing to the differences include different viewing windows between examinations due to the position and angulation of the laryngoscope and changes in patient positioning, intra- and inter-rater variations in measurement, and patient effort. LEVEL OF EVIDENCE: N/a Laryngoscope, 134:2793-2798, 2024.

Novel and pragmatic exploration of variation in glottic parameters in non-parallel versus parallel vocal cord CT planes with potential reporting pitfalls.

Oblique orientation of vocal cord demands strict compliance, by technicians and clinicians, to the recommended parallel plane CT scan of larynx. Repercussions of non-compliance has never been investigated before. We aimed to observe influence of non-parallel vocal cord plane CT scan on qualitative and quantitative glottic parameters, keeping parallel plane CT as a standard for comparison. Simultaneous identification of potential suboptimal imaging sequelae as a result of unformatted CT plane was also identified. In this study we included 95 normal adult glottides and retrospectively analyzed their anatomy in two axial planes, non-parallel plane ① and parallel to vocal cord plane ②. Qualitative (shape, structures at glottic level) and quantitative (anterior commissure ACom, vocal cord width VCw, anteroposterior AP, transverse Tr, cross-sectional area CSA) glottic variables were recorded. Multivariate statistical analysis was used to predict pattern and their impact on glottic anatomy. Plane ① displayed supraglottic features in glottis; adipose (90.5%) and split thyroid laminae (70.6%). Other categorical variables: atypical shape, submental structures and multilevel vertebral crossing were also in majority. All glottic dimensions varied significantly between two planes with most in ACom (-5.8mm) and CSA (-15.0 mm2). In contrast, plane ② manifested higher VCw (>73%), Tr (66.3%), CSA (64.2%) and AP (44.2%) measurements. On correlation analysis, variation in ACom, CSA, Tr was positively associated with VC or plane obliquity (p<0.05). This variability was more in obese and short necked subjects. Change in one parameter also modified other significantly i.e., ACom versus AP and CSA versus Tr. Results indicated statistically significant change in subjective and objective anatomical parameters of glottis on non-application of appropriate CT larynx protocol for image analysis hence highlighting importance of image reformation.

Numerical study of the impact of glottis properties on the airflow field in the human trachea using V-LES.

The influences of the profiles and cross-sectional areas of glottal aperture on the upper respiratory airway are investigated using an idealized cast-based mouth-throat model and three dimensional computational fluid dynamics (CFD). The open source CFD code OpenFOAM is employed. The transient flows are modeled using the very-large eddy simulation with the Smagorinsky sub-grid scale (SGS) model. Five different shapes of glottis are considered, including circular glottis with 100 %, 75 % and 50 % cross-sectional area and elliptic glottis with 75 % and 50 % cross-sectional area. Both instantaneous and averaged flow fields are analyzed. It is found that the variations of glottis have great impacts on the properties of downstream flow fields such as the secondary flow, laryngeal jet, recirculation zone, turbulent kinetic energy, and vortex. Evident impacts are observed in the region within 6 tracheal diameters downstream of the glottis. The profile of the glottis has more impacts on the laryngeal shape, while the cross-sectional area has more impacts on velocity of the laryngeal jet and turbulent intensity. It is concluded that both the glottal areas and profiles are critical for an idealized geometrical mouth-throat model.

Endoscopic and Computed Tomography Evaluation of Posterior Glottic Closure During Phonation.

OBJECTIVES/HYPOTHESIS: The anatomy of the posterior glottis, specifically the states of the posterior glottis during phonation, has not been thoroughly explored in laryngology. Conventional wisdom about the posterior glottis indicates that it tends to be completely closed in men but may be open in women. Furthermore, professional singers are expected to have a completely closed posterior glottis. The aim of this study was to investigate whether these generalizations are true by comparing rigid videolaryngostroboscopy results with high-resolution computed tomography (HRCT) and three-dimensional (3D) reconstruction findings. STUDY DESIGN: Prospective study. METHODS: Of the 90 volunteers (58 women, 32 men) examined, 48 were female professional singers, 10 were female nonsingers, 22 were male professional singers, and 10 were male nonsingers. Rigid videolaryngostroboscopy as well as HRCT scans were performed during singing at the average singing fundamental frequency. HRCT images of the larynx and air-column were 3D visualized using the software MIMICS®. The states of the posterior glottis were assessed in both examinations and compared among participants. RESULTS: The sensitivity of endoscopy was 67.5%. Complete closure of the posterior glottis was observed in 62.5% men and 52% women (P = .33). Complete closure of the posterior glottis was observed in 35% nonsingers and 61% professional singers (P = .036). CONCLUSIONS: The closure of the posterior glottis seen on videolaryngostroboscopy does not always correlate with actual closure. There seems to be no link between sex and complete closure of the glottis. However, there is strong evidence that posterior glottis closure can be influenced, to some degree, by vocal training. LEVEL OF EVIDENCE: 4 Laryngoscope, 132:124-129, 2022.

Proposing an Endotracheal Tube Selection Tool Based on Multivariate Analysis of Airway Imaging.

OBJECTIVES: We aimed to comprehensively investigate different upper airway segments in adults, determine the predictors of the size of each segment, and identify an appropriate endotracheal tube (ETT) size chart. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary care center. MATERIALS AND METHODS: The data for patients aged >18 years who underwent neck computed tomography were screened. Patients with existing tumors, trauma, or any pathology that can alter the normal airway anatomy and those with intubation, tracheostomy, or nasogastric tubes were excluded. Computed tomography software was used to measure the anteroposterior diameter (APD), transverse diameter (TD), and cross-sectional area (CSA) at the glottic, proximal subglottic, distal subglottic, and tracheal levels. Multiple regression analysis was used to identify the predictors of the airway size. RESULTS: One hundred patients were reviewed. The TD was consistently smaller than or equal to the APD at each level in all but 3 patients. The mean CSA and TD (170 mm2 and 11.3 mm, respectively) of the glottis indicated that the glottis was most often the narrowest level, followed by the proximal subglottis where the mean CSA and TD were 192.1 mm2 and 12.7 mm, respectively. Moreover, the mean APD was the smallest at the level of the trachea (20.1 mm). Multiple regression analysis confirmed that height and sex were the predominant predictors of measurements for the 4 airway segments. In addition, age was associated with the TD and CSA of the distal subglottic and tracheal segments, respectively. CONCLUSION: One-third of our participants exhibited a proximal subglottic diameter that was equal to or smaller than the glottic diameter. Our findings also suggested that the height and sex of the patients are important variables for the selection of an appropriate ETT size.

Hidden Anatomy of Opera Singers.

The history of research on the voice of opera soloists shows that there are certain functional features of the cranial nerves and cortical nerve centers. In this chapter, we review the most important findings in the field of canto voice neuroanatomy, which we corroborate with the results of our team research and experience. Our study focuses on the nerve structures involved in phonation at each level of the vocal formants: infraglottic, glottic, and oropharyngeal. We consider this research to have direct applicability in the fields of neurolaryngology, neuroscience, phoniatry, but also in the academic teaching. At the same time, the present study is a starting point for future research works on the anatomical and functional particularities of the structures involved during the act of phonation in canto soloists.

The Effects of a Shoulder Roll During Laryngoscopy in Infants: A Randomized, Single-Blinded, Crossover Study.

BACKGROUND: The use of a shoulder roll to view the glottic opening during direct laryngoscopy in infants has been recommended but is not evidence based. METHODS: Twenty infants with normal airways, <6 months of age undergoing elective surgery under general anesthesia were randomized to undergo direct laryngoscopy first with a 2-inch vertical shoulder roll and then without, or vice versa. The primary outcome was the difference in the vertical distance between the angle of the laryngoscopist's eye and the operating room table in the 2 positions. Also, the views of the glottic opening in both positions were recorded for each infant and analyzed by a blinded investigator using the percent of glottic opening (POGO). RESULTS: Twenty infants completed the study without complications. The vertical distance did not differ significantly whether the shoulder roll was placed first or second, and there was no evidence of a differential carryover effect in the crossover design (P = .268). The main effect of the shoulder roll on the mean (95% confidence interval [CI]) vertical distances without 47.8 cm (43.5-52.1) and with the shoulder roll 37.2 cm (33.3-41) yielded a mean (95% CI) vertical difference of 10.6 cm (9.3-11.79; P = .0001). The median (interquartile range [IQR]) POGO scores without 100 [86.2, 100] and with the shoulder roll 97.5 [80, 100] did not differ (median difference [95% CI]: 0 [-20 to 0]; P = .39). CONCLUSIONS: A 2-inch shoulder roll lowers the line of sight of the glottic opening compared with no shoulder roll, without affecting the view of the glottic opening during laryngoscopy in infants.

Comparison of the MultiViewScope Stylet Scope and the direct laryngoscope with the Miller blade for the intubation in normal and difficult pediatric airways: A randomized, crossover, manikin study.

BACKGROUND: Managing difficult pediatric airway is challenging. The MultiViewScope (MVS) Stylet Scope is reported to be useful in difficult pediatric airway. In this randomized crossover study, we compared the effectiveness of the MVS Stylet Scope to a standard direct laryngoscope with Miller #1 blade in simulated normal and difficult airways. METHODS: Fifteen expert anesthesiologists and Fifteen anesthesiology residents participated in the study. Participants were asked to perform intubation with the Airsim Baby manikin first, and then with the Airsim Pierre Robin manikin. Participants in each group used the intubation devices in a randomized order. The primary outcome was the time of successful intubation. The secondary outcomes were the force exerted on the incisors during intubation, Cormack-Lehane scale, the difficulty of intubation. RESULTS: There were no differences between MVS Stylet Scope and Direct laryngoscope in the time of successful intubation by the expert anesthesiologists or the anesthesiology residents in a normal or difficult pediatric airway. MVS Stylet Scope significantly improved the force exerted on the incisors during intubation in the expert anesthesiologists or the anesthesiology residents in a normal or difficult pediatric airway. MVS Stylet Scope significantly improved Cormack-Lehane scale, and the difficulty of intubation with difficult pediatric airway situation in both expert anesthesiologists and anesthesiology residents. CONCLUSIONS: Although less forces on the incisors and improved view of glottis were observed with the MVS Stylet Scope, MVS Stylet Scope did not shorten the time of intubation. The results of this study mean that the MVS Stylet Scope may be a less invasive airway devise than the direct laryngoscope with the Miller blade in the pediatric airway management. For the next step, we need to evaluate the MVS Stylet Scope in the real patients as an observational study.

Effect of an aerosol box on tracheal intubation difficulty.

The aim of this study was to determine the effect of an aerosol box on tracheal intubation difficulty. Eighteen experienced anesthetists intubated the trachea of a manikin with a normal airway 6 times using a direct laryngoscope, a McGRATH™ MAC videolaryngoscope, or an airway scope AWS-S200NK videolaryngoscope with or without an aerosol box. Although the aerosol box prolonged the time to successful intubation and decreased the percentage of glottic opening (POGO) score when using a direct laryngoscope, the statistically significant differences were clinically irrelevant. When a McGRATH™ MAC and an AWS-S200NK were used, the times to successful intubation and POGO scores were comparable with and without the aerosol box. When using any of the laryngoscopes, there were no statistically significant differences in the Cormack-Lehane grade and peak force to maxillary incisors with and without the aerosol box. In summary, the effect of an aerosol box on tracheal intubation difficulty is not clinically relevant when an experienced anesthetist intubates the trachea in a normal airway condition.

Measurement of subglottic diameter and distance to pre-epiglottic space among Chinese adults.

Proper endotracheal tube (ETT) size selection and identification of potentially difficult airways are important to reduce laryngeal injury during intubation. However, controversies exist concerning transverse subglottic diameter-the narrowest part of the airway-and the distance to pre-epiglottic space. Because few studies have reported the distance from skin to the midpoint of the epiglottis (DSE) among normal individuals, whether the DSE varies between individuals and by ethnicity remains uncertain. The present study aims to investigate the sonographic subglottic diameter and DSE among healthy Chinese adults. Healthy volunteers were recruited at National Taiwan University Hospital between October and November 2019. Exclusion criteria included pre-existing airway or respiratory diseases, neck tumors, and a history of neck operation. Age, sex, height, weight, body mass index (BMI), sonographic DSE, and transverse subglottic diameter were recorded. A total of 124 participants were enrolled. The average age was 32.5 ± 10.4 years and 63 participants (51%) were males. The subglottic diameter was positively associated with sex (males, 14.40 mm; females, 11.10 mm, p < 0.001) and BMI (underweight, 12.13 mm; normal weight, 12.47 mm; overweight, 13.80 mm; obese, 13.67 mm, p = 0.007). Moreover, the DSE was shorter in males (male, 16.18 mm; females, 14.54 mm, p < 0.001) and participants with increased BMI (underweight, 13.70 mm; normal weight, 15.06 mm; overweight, 16.58 mm; obese, 18.18 mm, p < 0.001). As compared with other ethnicity, a smaller size of subglottic diameter and a shorter DSE were noted among Chinese participants, and we suggest that a relatively smaller size of endotracheal tube selection should be considered in tracheal intubations.

Comparison of Endoscopic and Ultrasonographic Measurements of the Subglottic Airway in Children.

OBJECTIVE: To compare measurements of the pediatric subglottis obtained by surgeon-performed ultrasound and endoscopy. STUDY DESIGN: Prospective observational comparison-of-methods study. SETTING: Tertiary care pediatric hospital. SUBJECTS AND METHODS: Thirty-one patients who underwent direct laryngoscopy from May 2017 to July 2018 were recruited. Transcervical ultrasound was used to visualize the vocal folds, subglottis, and cervical trachea. The anterior-posterior (AP) and transverse (TV) diameter of the subglottic space were measured endoscopically and via ultrasound by 2 independent evaluators. Measurements were compared for correlation, bias, and agreement. A clinically acceptable bias for subglottic diameter was assumed to be 0.5 mm or less. RESULTS: The median age of enrolled patients was 2.6 years (range, 4 months-13.3 years). Endoscopic subglottic AP and TV measurements ranged from 3.33 mm to 14.81 mm and from 4.44 mm to 11.65 mm, respectively, while ultrasonographic AP and TV measurements ranged from 4.57 mm to 9.85 mm and from 3.77 mm to 8.96 mm. Pearson coefficient showed strong a correlation for both endoscopic and ultrasound AP (R = 0.8081, P < .0001) and TV (R = 0.8796, P < .001) measurements of the subglottis. Bland-Altman plots revealed a bias (average discrepancy) for AP measurements of 0.22 mm and 0.11 mm for TV measurements. CONCLUSION: Endoscopic and ultrasonography measurements of the pediatric subglottic airway were strongly correlated. The discrepancy between AP and TV measurements was less than 0.5 mm. Ultrasound of the subglottis may be an alternative to endoscopic assessment of the airway for measurement of the subglottic airway in children in select cases.

Automatic vocal tract landmark localization from midsagittal MRI data.

The various speech sounds of a language are obtained by varying the shape and position of the articulators surrounding the vocal tract. Analyzing their variations is crucial for understanding speech production, diagnosing speech disorders and planning therapy. Identifying key anatomical landmarks of these structures on medical images is a pre-requisite for any quantitative analysis and the rising amount of data generated in the field calls for an automatic solution. The challenge lies in the high inter- and intra-speaker variability, the mutual interaction between the articulators and the moderate quality of the images. This study addresses this issue for the first time and tackles it by means of Deep Learning. It proposes a dedicated network architecture named Flat-net and its performance are evaluated and compared with eleven state-of-the-art methods from the literature. The dataset contains midsagittal anatomical Magnetic Resonance Images for 9 speakers sustaining 62 articulations with 21 annotated anatomical landmarks per image. Results show that the Flat-net approach outperforms the former methods, leading to an overall Root Mean Square Error of 3.6 pixels/0.36 cm obtained in a leave-one-out procedure over the speakers. The implementation codes are also shared publicly on GitHub.

Intubation in the Intensive Care Unit: C-MAC video laryngoscope versus Macintosh laryngoscope.

PURPOSE: Various modifications of the Macintosh blade and direct laryngoscopy have been incorporated into practice to improve the intubation success rate and avoid complications while ensuring patient safety. This study evaluates the usefulness of two different direct laryngoscopy methods used by operators with various level of experience in the Intensive Care Unit. MATERIAL AND METHODS: In a single centre prospective study, C-MAC and Macintosh laryngoscopes were compared in terms of laryngoscopy and intubation outcomes such as glottic visualization, number of intubation attempts, intubation success and satisfaction score. RESULTS: During the one-year study period, 263 patients were evaluated and data of 218 patients were analyzed. The rate of successful first attempt intubation was higher in the video laryngoscope group (VL) (84% vs 57%; P<0.001). A significantly greater number of patients in the Macintosh laryngoscopy group had difficult visualization of the glottis in terms of the modified Cormack and Lehane classification and Percentage of Glottic Opening scale. CONCLUSION: The use of video laryngoscope for intubation in ICU settings results in better visualization of the glottis and a higher incidence of successful intubation attempts.

Analysis of the aerodynamic sound of speech through static vocal tract models of various glottal shapes.

The acoustic spectrum of our voice can be divided into harmonic and inharmonic sound components. While the harmonic components, generated by the oscillatory motion of the vocal folds, are well described by reduced-order speech models, the accurate computation of the inharmonic components requires high-order flow simulations, which predict the vortex shedding and turbulent structures present in the shear layers of the glottal jet. This study characterizes the dominant frequencies in the unsteady flow of the intra- and supraglottal region. A realistic vocal tract geometry obtained through magnetic resonance imaging (MRI) is applied for the numerical domain, which is locally modified to account for different convergent and divergent glottal angles. Both time-averaged and fluctuating values of the flow variables are computed and their distribution at various glottal shapes is compared. The impact of the registered modes in the unsteady flow on the acoustic far field is computed through direct compressible flow simulations. Furthermore, acoustic analogies are applied to localize the sources of the aerodynamically generated sound.

Effect of changes in medial surface shape on voice production in excised human larynges.

Clinical intervention of glottal insufficiency often focuses on correcting glottal gap as visualized from above. In contrast, changes in medial surface shape due to intervention have received less attention. This study investigated how changes in medial surface shape affect voice production in excised human larynges, by locally medializing the medial surface at different longitudinal and vertical locations. The results showed that localized medialization at a more inferior location yielded better improvement in glottal closure and higher-order harmonic excitation in the produced voice. This study shows that surgical intervention of glottal insufficiency should also aim at restoring desirable medial surface shape.

The phylogenetic significance of the morphology of the syrinx, hyoid and larynx, of the southern cassowary, Casuarius casuarius (Aves, Palaeognathae).

BACKGROUND: Palaeognathae is a basal clade within Aves and include the large and flightless ratites and the smaller, volant tinamous. Although much research has been conducted on various aspects of palaeognath morphology, ecology, and evolutionary history, there are still areas which require investigation. This study aimed to fill gaps in our knowledge of the Southern Cassowary, Casuarius casuarius, for which information on the skeletal systems of the syrinx, hyoid and larynx is lacking - despite these structures having been recognised as performing key functional roles associated with vocalisation, respiration and feeding. Previous research into the syrinx and hyoid have also indicated these structures to be valuable for determining evolutionary relationships among neognath taxa, and thus suggest they would also be informative for palaeognath phylogenetic analyses, which still exhibits strong conflict between morphological and molecular trees. RESULTS: The morphology of the syrinx, hyoid and larynx of C. casuarius is described from CT scans. The syrinx is of the simple tracheo-bronchial syrinx type, lacking specialised elements such as the pessulus; the hyoid is relatively short with longer ceratobranchials compared to epibranchials; and the larynx is comprised of entirely cartilaginous, standard avian anatomical elements including a concave, basin-like cricoid and fused cricoid wings. As in the larynx, both the syrinx and hyoid lack ossification and all three structures were most similar to Dromaius. We documented substantial variation across palaeognaths in the skeletal character states of the syrinx, hyoid, and larynx, using both the literature and novel observations (e.g. of C. casuarius). Notably, new synapomorphies linking Dinornithiformes and Tinamidae are identified, consistent with the molecular evidence for this clade. These shared morphological character traits include the ossification of the cricoid and arytenoid cartilages, and an additional cranial character, the articulation between the maxillary process of the nasal and the maxilla. CONCLUSION: Syrinx, hyoid and larynx characters of palaeognaths display greater concordance with molecular trees than do other morphological traits. These structures might therefore be less prone to homoplasy related to flightlessness and gigantism, compared to typical morphological traits emphasised in previous phylogenetic studies.

The distance between the glottis and the cuff of a tracheal tube placed through three supraglottic airway devices in children: A randomised controlled trial.

BACKGROUND: After tracheal tube insertion via various types of supraglottic airway devices, the distance from the tube cuff to the vocal cords has not been evaluated in children. OBJECTIVES: The aim of this study was to evaluate the position of a tracheal tube cuff relative to the glottis in children when one of three supraglottic airway devices (I-gel, AuraGain and air-Q laryngeal airway) are used as intubation conduits. DESIGN: A randomised controlled trial. SETTING: Tertiary children's hospital. PATIENTS: Children aged less than 7 years. INTERVENTION: In vivo fibre-optic assessment and in vitro measurement. MAIN OUTCOME MEASURES: The main outcome was the safety margin: the distance between the ventilation outlet of the supraglottic airway device and the beginning of the proximal cuff minus that from the ventilation outlet to the glottis. The maximum inner diameter of the cuffed tracheal tube that could be inserted, the fibre-optic view score and the oropharyngeal leak pressure were also evaluated. RESULTS: The three devices exhibited significant differences in the distance from the ventilation outlet to the glottis (mean ±â€ŠSD): I-gel 3.6 ±â€Š0.6 cm, AuraGain 3.8 ±â€Š0.7 cm, air-Q 2.8 ±â€Š1.0 cm (P < 0.001). The safety margin was greatest with the air-Q and narrowest with the I-gel: I gel 1.9 ±â€Š1.1 cm, AuraGain 4.4 ±â€Š0.7 cm and air-Q 7.9 ±â€Š1.1 cm. Using the AuraGain and air-Q, the cuffs of the tracheal tubes were predicted to be located below the glottis with one-size and two-size smaller tracheal tubes in all patients. However, using I-gel, the cuffs would be below the glottis in 69% (95% CI 49.6 to 84.5) and 29% (95% CI 14.0 to 48.4) of the patients with a one-size and two-size smaller tube, respectively. CONCLUSION: The AuraGain and air-Q are well tolerated intubating conduits. The possibility of vocal cord damage is higher when the I-gel is used. TRIAL REGISTRATION: www.clinicaltrials.gov (number: NCT03156166).

Sulcus Vocalis.

Sulcus vocalis, defined as a type of groove along the free edge of the vocal fold, disrupts the normal, pliable vocal fold cover, causing alterations in the intrinsic mucosal wave. The primary symptom is breathy, effortful dysphonia. Diagnosis may be challenging, and this classically has led to difficulties with identification and management. Treatment options, although often promising, have been notoriously unreliable. Current understanding, considerations for management, and future treatment options are explored.

Estimation of Source-Filter Interaction Regions Based on Electroglottography.

Source-filter interaction is a phenomenon in which acoustic airway pressures influence the glottal airflow at the source (level 1) and the vibration pattern of the vocal folds (level 2). This interaction is most significant when dominant source harmonics are near airway resonances. The influence of acoustic airway pressures on vocal fold vibration (level 2) was studied systematically by changing the supraglottal vocal tract length in human subjects with tube extensions. The subjects were asked to perform fundamental frequency (fo) glides while phonating through tubes of various lengths. An algorithm was developed using the quasi-open quotient extracted from the electroglottograph. Regions of sudden vocal fold vibration pattern change due to source-filter interaction were inferred from contact area changes. The algorithm correctly identified 89% of male and 84.8% of female quantal changes in contact pattern associated with interactions between source harmonics and formants during ascending glides. During the descending glides, the algorithm correctly identified 84% of male and 81.1% of female quantal changes in contact pattern. These results are in comparison with those obtained from the fo-based algorithm (Maxfield et al).