Biomedical subjects

Stellan Hertegård

Publications and source records attributed to Stellan Hertegård.

9 recordsLinked to original sources

PubMed2005

What have we learned about laryngeal physiology from high-speed digital videoendoscopy?

PURPOSE OF REVIEW: The purpose of this review is to describe recent developments in high-speed videoendoscopy. The applications of this technique are highlighted and important findings regarding vocal fold physiology and voice pathology are discussed. RECENT FINDINGS: The number of applications for digital high-speed imaging has increased during recent years because of the development of camera image sensor systems with increased image resolution of video and television quality. Other improvements are related to computer processing speed and storage capacity and the development of automatic algorithms for quantification and measurements both in time and room dimensions. This is enhanced by combining high-speed videoendoscopy with laser-based measurement systems, acoustic analyses or other glottographic methods, such as flow glottography or electroglottography. High-speed videoendoscopy is currently used in studies of voice mechanisms of phonation (e.g., the voice source can be examined with a high sampling rate, from 1000 to over 8000 frames per second), and in phonation onset or offset. High-speed imaging is also useful in linguistic studies and in the examination of different artistic singing styles, such as extremely high-pitched singing, throat singing, or different pop and rock styles. High-speed videoendoscopy is also used in the examination of patients with voice disorders, particularly with irregular vocal fold vibrations, ventricular phonation, or the phonation of individuals who have had a laryngectomy. SUMMARY: Findings from studies of normal voice physiology and of voice disorders using high-speed imaging are presented and their relevance is discussed.

Electrokymography↗

PubMed2004

Cross-linked hyaluronan versus collagen for injection treatment of glottal insufficiency: 2-year follow-up.

OBJECTIVES: To evaluate the long-term (24 months) clinical performance (vocal fold function) and safety of hylan B gel as compared with bovine cross-linked collagen in the treatment of patients with glottal insufficiency. MATERIAL AND METHODS: In a prospective trial, 70 patients with glottal insufficiency due to unilateral vocal fold paresis (n =35) or atrophy (n =35) were randomized to received either hylan B gel (n =47) or collagen (n =23) injections into 1 vocal fold. Forty-two of the patients were examined 24 months after treatment. Evaluations were made based on patients' subjective ratings, digitized videostroboscopic measurements, maximum phonation time and phonation quotient. RESULTS: The patients' self-ratings were significantly improved in both the hylan B gel and collagen groups. Videostroboscopic measurements of glottal closure were significantly improved for both groups. The hylan B gel group showed a trend towards less resorption at the injected vocal fold edge in comparison with the collagen group (p =0.05). No serious adverse events were observed. Twenty-eight patients dropped out of the study after 12 months: 18 had been re-injected or operated on with medialization laryngoplasty due to insufficient voice and 10 had either died of causes unrelated to the study or refused to attend follow-up. CONCLUSIONS: No long-term side-effects were found for either the hylan B gel or collagen groups after injection treatment. Both treatments resulted in significantly improved voice as rated by the patients and significantly improved glottal closure. Some resorption was noted for both substances, and approximately 25%, of the patients chose re-treatment 2 years after the initial treatment.

Adult↗

PubMed2004

Laryngeal adduction asymmetries in normal speaking subjects.

To investigate the prevalence of asymmetries at vocal fold adduction, 109 vocally healthy subjects between 22 and 80 years of age were examined. All subjects were examined with a rigid endoscope and video recorded. The recordings were analysed off line by two laryngologists. Seventy percent of the subjects displayed some kind of asymmetry. There was no difference between the sexes. Side differences in antero-posterior position of the corniculate or cuneiform tubercles were the most frequent asymmetries, occurring in 66% of the total material and in 92% of the asymmetrical cases. Asymmetries appeared more common and more marked in older subjects and possibly more frequent in singers than in non-singers. Laryngeal adduction asymmetries are probably of little importance for voice function.

Adult↗

PubMed2004

Calibration of high-speed imaging by laser triangulation.

A method was developed for absolute calibration of endoscopic vocal fold images using laser triangulation. The laser is attached to a rigid endoscope with 8-degrees angle in relation to the optical axis of the endoscope. A special software is used for calibration and measurements from high-speed images. The equipment can provide measurements both in horizontal and vertical planes, and can be used for calibrated measurements of vocal fold length, amplitude of vocal fold vibrations and vertical movements.

Calibration↗

PubMed2004

Viscoelasticity of rabbit vocal folds after injection augmentation.

OBJECTIVES/HYPOTHESIS: Vocal fold function is related to the viscoelasticity of the vocal fold tissue. Augmentation substances used for injection treatment of voice insufficiency may alter the viscoelastic properties of vocal folds and their vibratory capacity. The objective was to compare the mechanical properties (viscoelasticity) of various injectable substances and the viscoelasticity of rabbit vocal folds, 6 months after injection with one of these substances. STUDY DESIGN: Animal model. METHODS: Cross-linked collagen (Zyplast), double cross-linked hyaluronan (hylan B gel), dextranomers in hyaluronan (DHIA), and polytetrafluoroethylene (Teflon) were injected into rabbit vocal folds. Six months after the injection, the animals were killed and the right- and left-side vocal folds were removed. Dynamic viscosity of the injected substances and the vocal folds was measured with a Bohlin parallel-plate rheometer during small-amplitude oscillation. RESULTS: All injected vocal folds showed a decreasing dynamic viscosity with increasing frequency. Hylan B gel and DiHA showed the lowest dynamic viscosity values, and vocal folds injected with these substances also showed the lowest dynamic viscosity (similar to noninjected control samples). Teflon (and vocal folds injected with Teflon) showed the highest dynamic viscosity values, followed by the collagen samples. CONCLUSION: Substances with low viscoelasticity alter the mechanical properties of the vocal fold to a lesser degree than substances with a high viscoelasticity. The data indicated that hylan B gel and DiHA render the most natural viscoelastic properties to the vocal folds. These substances seem to be appropriate for preserving or restoring the vibratory capacity of the vocal folds when glottal insufficiency is treated with augmentative injections.

Animals↗

PubMed2003

Viscoelastic properties of rabbit vocal folds after augmentation.

BACKGROUND: Vocal fold function is closely related to tissue viscoelasticity. Augmentation substances may alter the viscoelastic properties of vocal fold tissues and hence their vibratory capacity. OBJECTIVES: We sought to investigate the viscoelastic properties of rabbit vocal folds in vitro after injections of various augmentation substances. STUDY DESIGN AND SETTING: Polytetrafluoroethylene (Teflon), cross-linked collagen (Zyplast), and cross-linked hyaluronan, hylan b gel (Hylaform) were injected into the lamina propria and the thyroarytenoid muscle of rabbit vocal folds. Dynamic viscosity of the injected vocal fold as a function of frequency was measured with a Bohlin parallel-plate rheometer during small-amplitude oscillation. RESULTS: All injected vocal folds showed a decreasing dynamic viscosity with increasing frequency. Vocal fold samples injected with hylan b gel showed the lowest dynamic viscosity, quite close to noninjected control samples. Vocal folds injected with polytetrafluoroethylene showed the highest dynamic viscosity followed by the collagen samples. CONCLUSIONS: The data indicated that hylan b gel in short-term renders the most natural viscoelastic properties to the vocal fold among the substances tested. This is of importance to restore/preserve the vibratory capacity of the vocal folds when glottal insufficiency is treated with injections.

Animals↗

PubMed2003

Simultaneous analysis of vocal fold vibration and transglottal airflow: exploring a new experimental setup.

The purpose of this study was to develop an analysis system for studying the relationship between vocal fold vibration and the associated transglottal airflow. Recordings of airflow, electroglottography (EGG), oral air pressure, and acoustic signals were performed simultaneously with high-speed imaging at a rate of approximately 1900 frames/s. Inverse filtered airflow is compared with the simultaneous glottal area extracted from the high-speed image sequence. The accuracy of the synchronization between the camera images and the foot pedal synchronization pulse was examined, showing that potential synchronization errors increase with time distance to the synchronization pulse. Therefore, analysis was limited to material near the synchronization pulse. Results corroborate previous predictions that air flow lags behind area, but also they reveal that relationships between these two entities may be complex and apparently varying with phonation mode.

Acoustics↗

PubMed2003

High-speed imaging: applications and development.

This article shows some examples of applications of digital high-speed imaging in phoniatrics. Advantages and disadvantages of digital high-speed imaging as compared to the current world-wide standard, videostroboscopy, are discussed as well as possible future developments in this area. Parts of this paper were presented by the authors at the Pan European Voice Conference in Stockholm in 2001 (Pevoc IV).

Biophysical Phenomena↗

PubMed2002

Cross-linked hyaluronan used as augmentation substance for treatment of glottal insufficiency: safety aspects and vocal fold function.

OBJECTIVE: To examine safety aspects and vocal fold function after vocal fold augmentation with a cross-linked hyaluronan derivative (hylan B gel) as compared with bovine collagen. STUDY DESIGN; A prospective, randomized trial. METHODS: Eighty-three patients with glottal insufficiency were treated with injection augmentation with hylan B gel and bovine collagen and were examined at 1, 6, and 12 months after treatment. Seventy patients with unilateral vocal fold paresis (n = 35) or atrophy (n = 35) were randomly assigned to receive either hylan B gel (n = 47) or collagen (n = 23) injections into one vocal fold. Thirteen patients with glottal insufficiency caused by scar defects or paresis resulting from malignant disease were included in a nonrandomized group and were treated only with hylan B gel. Evaluations were made from patients' subjective ratings (visual analogue scales), digitized videostroboscopic measurements, phonetograms, maximum phonation time, and phonation quotients. RESULTS: Twelve months after injections, the patients' self-ratings were significantly improved for both the hylan B gel and the collagen groups. In addition, the videostroboscopic measurements showed significantly improved glottal closure for both groups. However, for the hylan B gel group, vibration amplitude and glottal area variations were preserved, and this group showed significantly less resorption at the injected vocal fold edge. Furthermore, maximum phonation time had increased significantly for the hylan B gel patients (collagen, nonsignificant). No serious adverse events were observed; three patients injected with hylan B gel had temporary inflammation at the injection site, which resolved without sequelae. CONCLUSIONS: The results showed that both hylan B gel and collagen can be safely used for injection treatment of glottal insufficiency. Both treatments resulted in significantly improved voice as rated by the patients. However, the patients treated with hylan B gel showed better vocal fold status and longer maximum phonation time at 12 months after treatment as compared with patients treated with collagen.

Aged↗