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At least 433 records · Page 24Linked to original sources
PubMed2004

Real-time PCR assay using molecular beacon for quantitation of hepatitis B virus DNA.

Levels of hepatitis B virus (HBV) DNA in the blood serve as an important marker in monitoring the disease progression and treatment efficacy of chronic HBV infection. Several commercial assays are available for accurate measurement of HBV genomic DNA, but many of them are hampered by relatively low sensitivity and limited dynamic range. The aim of this study was to develop a sensitive and accurate assay for measuring HBV genomic DNA using real-time PCR with a molecular beacon (HBV beacon assay). The performance of this assay was validated by testing serial dilutions of the two EUROHEP HBV DNA standards (ad and ay subtypes) of known concentrations. The assay showed low intra-assay (<7%) and interassay (<5%) variations for both subtypes. Its dynamic range was found to be 10(1) to 10(7) copies per reaction (1.0 x 10(2) to 1.0 x 10(9) copies ml(-1)). The assay was further evaluated clinically using serum samples from 175 individuals with chronic hepatitis B. The HBV DNA level measured by this assay showed good correlation with that measured by the commercially available COBAS AMPLICOR HBV Monitor test (r = 0.901; P < 0.001). The higher sensitivity and broader dynamic range of this assay compared to the existing commercial assays will provide an ideal tool for monitoring disease progression and treatment efficacy in HBV-infected patients, in particular for those with low levels of HBV viremia.

Bacteriophage M13↗
PubMed1997

Digitizing of radiographs with a roller-type CCD scanner.

OBJECTIVES: Roller-type scanners can be used to digitize radiographs. This study evaluated the physical performance of a roller-type scanner with regard to dynamic range, scan reproducibility, and homogeneity. METHODS: A VXR-12 (Vidar System Corp., Herndon, Va.) roller-type scanner with imaging editing software Paint Shop Pro (JASC Inc., Minnetonka, Minn.) was used to digitize a step tablet image on Kodak T-MAT G films (Kodak, Rochester, N.Y.). The step tablet image was scanned at various locations and with different scanning settings. The pixel values of the resulting image were analyzed. The step tablet image was also scanned by a Wellhofer WD 102 Filmdensitometer (Wellhofer Dosimetrie, Schwarzenbruck, Germany) to measure the optical densities of the steps on the film for comparison. RESULTS: With the use of the default scanning settings the digitized images had pixel values distributed in a similar dynamic range to that of the film densitometer. This scanner produced consistent images with different scanning positions, different orientation of the images, and different power states of the scanner. CONCLUSIONS: This roller-type scanner has a similar dynamic range to that of the film densitometer. The operating condition of the scanner is stable, and the resulting image is not significantly affected by the scanning positions. This type of scanner should be suitable for digitizing dental x-ray films, although the limiting scanning resolution might not be sufficient for some diagnostic purposes.

Absorptiometry, Photon↗
PubMed1999

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1990

[Changes of the threshold level in patients with 22-channel cochlear implant].

Psychophysical responses of the patients to electrical stimulation were examined in order to clarify long-term effects of the cochlear implant in 9 patients who had received a 22-channel cochlear implant. Measured items were the minimal threshold level (T-level), the maximum comfortable level (C-level), and the dynamic range between T- and C-level. Measurements were repeated for each electrode every three months over more than 6 months. Following results were obtained. 1) The changes of the T-level were classified into four types as follows, a type with no change, a type with gradual decrease, a type with decrease in two to three months followed by gradual increasing threshold and a type with gradual increasing just after surgery. Even in a last type, the maximum increase in the T-level did not exceed 200 microA and, in most cases, these changes were stabilized within a few months after implantation. 2) The dynamic range gradually increased. It was obvious in both in the middle and apical electrodes, while such increased threshold was not observed in the basal electrodes. 3) In some cases, a few basal electrodes could not been used since they caused uncomfortable sensation or those dynamic ranges became below a certain extent. As a result, it was suggested that the electrical stimulation had not induced serious degeneration of the ganglion cells and the auditory nerve fibers. The reduction in the number of usable electrodes might be due to the surgical trauma to the intracochlear tissue. Therefore, exposing of the scala tympani should be minimal in order to avoid the damage of the cochlea.

Adult↗
PubMed2004

Comparison of a multiplexed fluorescent covalent microsphere immunoassay and an enzyme-linked immunosorbent assay for measurement of human immunoglobulin G antibodies to anthrax toxins.

Recently, the Centers for Disease Control and Prevention reported an accurate, sensitive, specific, reproducible, and quantitative enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G (IgG) antibodies to Bacillus anthracis protective antigen (PA) in human serum (C. P. Quinn, V. A. Semenova, C. M. Elie et al., Emerg. Infect. Dis. 8:1103-1110, 2002). The ELISA had a minimum detectable concentration (MDC) of 0.06 microgram/ml, which, when dilution adjusted, yielded a whole-serum MDC of 3.0 micro g of anti-PA IgG per ml. The reliable detection limit (RDL) was 0.09 microgram/ml, while the dynamic range was 0.06 to 1.7 microgram/ml. The diagnostic sensitivity of the assay was 97.6% and the diagnostic specificity was 94.2% for clinically verified cases of anthrax. A competitive inhibition anti-PA IgG ELISA was also developed to enhance the diagnostic specificity to 100%. We report a newly developed fluorescence covalent microbead immunosorbent assay (FCMIA) for B. anthracis PA which was Luminex xMap technology. The FCMIA MDC was 0.006 microgram of anti-PA IgG per ml, the RDL was 0.016 microgram/ml, and the whole-serum equivalent MDC was 1.5 micrograms/ml. The dynamic range was 0.006 to 6.8 microgram/ml. Using this system, we analyzed 20 serum samples for anti-PA IgG and compared our results to those measured by ELISA in a double-masked analysis. The two methods had a high positive correlation (r2 = 0.852; P < 0.001). The FCMIA appears to have benefits over the ELISA for the measurement of anti-PA IgG, including greater sensitivity and speed, enhanced dynamic range and reagent stability, the use of smaller sample volumes, and the ability to be multiplexed (measurement of more than one analyte simultaneously), as evidenced by the multiplexed measurement in the present report of anti-PA and anti-lethal factor IgG in serum from a confirmed clinical anthrax infection.

Adult↗
PubMed2005

Determination of tannin in green tea infusion by flow-injection analysis based on quenching the fluorescence of 3-aminophthalate.

A flow-injection analytical system was developed to determine tannin content in green tea infusions. The flow-injection system is based on measuring the quenching effect of tannin on the fluorescence of 3-aminophthalate. Fluorophore was obtained by auto-oxidation of luminol during solution preparation. System performance was satisfactory for routine analysis (sample throughput >20 h(-1); linear dynamic range for tannic acid, 0.005-0.3 mg/mL; linear dynamic range for green tea tannin, 0.02-1.0 mg/mL; CV < 3%). The flow-injection method is immune from interference by coexisting ascorbate in green tea infusion. Analytical results were verified by the ferrous tartrate method, the Japanese official analytical method.

Ascorbic Acid↗
PubMed2003

Effects of presentation level on phoneme and sentence recognition in quiet by cochlear implant listeners.

OBJECTIVE: The objectives of this study were to characterize the effects of presentation level on speech recognition in quiet by cochlear implant users with the Nucleus 22 SPEAK and Clarion v1.2 CIS speech-processing strategies, and to relate speech recognition at low presentation levels to stimulus audibility as measured by sound field thresholds. It was hypothesized that speech recognition performance in both Nucleus SPEAK and Clarion CIS participants would decrease as presentation level was decreased below 50 to 60 dBA, due to audibility limitations. However, it was expected that such level effects would be less severe in CIS participants than in SPEAK participants because the Clarion v1.2 device encodes a wider acoustic dynamic range (up to 60 dB) than the Nucleus 22 device (30 dB). DESIGN: Performance-intensity (P-I) functions for vowels, consonants and sentences in quiet were obtained from each participant. P-I functions incorporated speech levels of 70, 60, 50, 40 and 30 dBA. Subjects used their clinical speech processor maps and adjusted the loudness (volume/sensitivity) controls on their processors so that speech presented at 60 dBA was comfortably loud. Maps were created using default clinical procedures and were not adjusted to optimize sound field thresholds. Sound field thresholds and dynamic ranges were measured for warbled pure tones with frequencies of 250 to 6000 Hz. RESULTS: Consonant and sentence recognition showed strong level effects for both SPEAK and CIS participants, with performance decreasing substantially at levels below 50 dBA in most individuals. Vowel recognition showed weaker level effects. For all three speech materials, SPEAK and CIS participants demonstrated similar mean performance at 70 dBA; however, SPEAK participants showed larger reductions in performance than CIS participants with decreasing level. Sound field thresholds were more sensitive for CIS participants than for SPEAK participants, supporting the hypothesis that performance differences were related to audibility. CONCLUSIONS: Cochlear implant listeners are unable to maintain good speech recognition at low presentation levels due to reduced stimulus audibility, and this may significantly limit their ability to communicate in daily life. It is likely that audibility differences between SPEAK and CIS participants in the present study can be attributed at least partly to differences in the acoustic dynamic range used by the respective processors. However, several additional factors may have contributed to differences in audibility and perception of soft speech among individual listeners with both devices. These include the minimum and maximum electrical stimulation levels specified in participants' maps and the speech processor sensitivity setting used for testing.

Adult↗
PubMed2002

Investigation of an enhanced resolution triple quadrupole mass spectrometer for high-throughput liquid chromatography/tandem mass spectrometry assays.

Triple quadrupole mass spectrometers, when operated in multiple reaction monitoring (MRM) mode, offer a unique combination of sensitivity, specificity, and dynamic range. Consequently, the triple quadrupole is the workhorse for high-throughput quantitation within the pharmaceutical industry. However, in the past, the unit mass resolution of quadrupole instruments has been a limitation when interference from matrix or metabolites cannot be eliminated. With recent advances in instrument design, triple quadrupole instruments now afford mass resolution of less than 0.1 Dalton (Da) full width at half maximum (FWHM). This paper describes the evaluation of an enhanced resolution triple quadrupole mass spectrometer for high-throughput bioanalysis with emphasis on comparison of selectivity, sensitivity, dynamic range, precision, accuracy, and stability under both unit mass (1 Da FWHM) and enhanced (<or=0.1 Da FWHM) resolution. The advantage of enhanced resolution was demonstrated in the case of mometasone with polypropylene glycol (PPG) interference. At unit mass resolution, the transmitted precursor ion from the first quadrupole contained not only protonated molecules from mometasone, but also PPG interference. At enhanced resolution only selected mometasone peaks were transmitted, and no interference from PPG was detected. Sensitivity of the instrument was demonstrated with 10 femtograms of descarboethoxyloratadine injected on-column, for which a signal-to-noise (S/N) ratio of 24 was obtained for MRM chromatograms at both unit and enhanced resolution. Absolute signals obtained at enhanced resolution were about one-third those obtained at unit mass resolution. However, S/N was maintained at enhanced resolution due to the proportional decrease in noise level. Finally, the stability of the instrument operating at enhanced resolution was demonstrated during an overnight 17 h period that was used to validate a liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for the quantitation of loratadine and descarboethoxyloratadine in human plasma. Assay performances (dynamic range, correlation coefficients for standard curves, precision and accuracy for QC samples) under unit and enhanced resolution were both within current pharmaceutical and regulatory guidelines demonstrating the stability of the mass spectrometer operating at enhanced resolution for typical bioanalytical high-throughput applications.

Calibration↗
PubMed2002

Measuring the electrical stapedius reflex with stapedius muscle electromyogram recordings.

Previous studies have demonstrated a correlation between cochlear implant recipients' comfort levels (C level, upper limit of dynamic range of stimulation) and the contralateral electrical stapedius reflex (ESR) threshold, detected by acoustic impedance change. However, the utility of the approach is limited because many recipients have no detectable impedance change. The goals of this study were to investigate the utility of the stapedial electromyogram (EMG) for estimating onset and strength of the ESR. Ketamine-anesthetized guinea pigs were implanted with Nucleus electrode arrays and stimulated with biphasic current pulse trains (250 pps) via a Cochlear Corporation CI24M stimulator. Typical EMG recordings (obtained with bipolar microwire electrodes) contained easily detectable unit potentials up to 300 microV in amplitude. Growth response curves (obtained from threshold-crossing counts or rms of the EMG signal) were typically monotonic with dynamic ranges spanning 700 microA or 8 dB. Based on adaptation and temporal properties, the stimulus protocol (500 ms duration with 4-5 s interstimulus intervals) was adequate for producing independent responses. The data presented are consistent with ESR characteristics (acoustic impedance technique) of cochlear implant recipients and with EMG properties of acoustically stimulated guinea pigs. Use of the EMG for characterizing the ESR may eventually be applied to human cochlear implant recipients as a guide in setting the upper limit of the dynamic range.

Action Potentials↗
PubMed2001

Comparison of three procedures for initial fitting of compression hearing aids. I. Experienced users, fitted bilaterally.

We compared the effectiveness of three procedures for the initial fitting of hearing aids with multi-band compression: (1) CAMEQ, which aims to amplify speech so as to give equal loudness per critical band over the frequency range important for speech intelligibility, and to give similar overall loudness to 'normal': (2) CAMREST, which aims to amplify speech so as to restore 'normal' specific loudness patterns, over a wide range of speech levels; (3) DSL I/O, which aims to map the dynamic range of normally hearing people into the reduced dynamic range of hearing-impaired people, with 'full' restoration of audibility. Ten experienced hearing aid users with moderate sensorineural loss were fitted bilaterally with Danalogic 163D digital hearing aids, using each procedure in turn; the order was counterbalanced across subjects. The fitting required specification of gains for input levels of 55 and 80 dB SPL at six centre frequencies. Real-ear measurements were made to ensure that target gains were reached (+/-3 dB). Immediately after fitting with a given procedure, and one week after fitting, the gains were adjusted when required by the minimum amount necessary to achieve acceptable fittings. The amount of adjustment required provides one measure of the adequacy of the initial fitting. On average, the adjustments were smallest for the CAMEQ procedure. The gain changes were slightly larger for the CAMREST procedure and were largest of all for DSL I/O. For the latter, the gain changes were mostly negative, especially for high frequencies and the higher input level. This indicates that the DSL I/O procedure prescribes more high-frequency gain than is preferred by adult users. After these gain adjustments, users wore the aids for at least three weeks before filling out the APHAB questionnaire and taking part in laboratory measurements of the speech reception threshold (SRT) for sentences in quiet and in steady and fluctuating background noise at levels of 60 and 75 dB SPL. Following these tests, the hearing aids were re-fitted with the next procedure. The scores on the APHAB test and the SRTs did not differ significantly for the three procedures. We conclude that the CAMEQ and CAMREST procedures provide more appropriate initial fittings than DSL I/O.

Acoustic Stimulation↗
PubMed2002

Clinical and dynamic range-of-motion techniques in subjects with and without diabetes mellitus.

Thirty subjects with type 1 diabetes, 30 subjects with type 2 diabetes, and 30 age- and sex-matched controls were evaluated through clinical goniometry and two-dimensional motion analysis systems to determine the dynamic and static range of motion of the knee, ankle, and hallux joints. The purpose of this study was to determine if the knee and ankle joints of patients with diabetes mellitus are affected by limited joint mobility syndrome. The study results support previous medical literature showing significant reduction of range of motion of the hallux in subjects with type 1 diabetes. Significant differences were found between the range of motion of male and female subjects in all lower-limb joints for both subject groups with diabetes compared to the control group, and male subjects in all groups recorded less range of motion than female subjects.

Adult↗
PubMed2001

Rate and timing cues associated with the cochlear amplifier: level discrimination based on monaural cross-frequency coincidence detection.

The perceptual significance of the cochlear amplifier was evaluated by predicting level-discrimination performance based on stochastic auditory-nerve (AN) activity. Performance was calculated for three models of processing: the optimal all-information processor (based on discharge times), the optimal rate-place processor (based on discharge counts), and a monaural coincidence-based processor that uses a non-optimal combination of rate and temporal information. An analytical AN model included compressive magnitude and level-dependent-phase responses associated with the cochlear amplifier, and high-, medium-, and low-spontaneous-rate (SR) fibers with characteristic frequencies (CFs) spanning the AN population. The relative contributions of nonlinear magnitude and nonlinear phase responses to level encoding were compared by using four versions of the model, which included and excluded the nonlinear gain and phase responses in all possible combinations. Nonlinear basilar-membrane (BM) phase responses are robustly encoded in near-CF AN fibers at low frequencies. Strongly compressive BM responses at high frequencies near CF interact with the high thresholds of low-SR AN fibers to produce large dynamic ranges. Coincidence performance based on a narrow range of AN CFs was robust across a wide dynamic range at both low and high frequencies, and matched human performance levels. Coincidence performance based on all CFs demonstrated the "near-miss" to Weber's law at low frequencies and the high-frequency "mid-level bump." Monaural coincidence detection is a physiologically realistic mechanism that is extremely general in that it can utilize AN information (average-rate, synchrony, and nonlinear-phase cues) from all SR groups.

Audiometry, Pure-Tone↗
PubMed2001

On-line monitoring of electroosmotic flow for capillary electrophoretic separations.

A recently developed technique for monitoring electroosmotic flow (EOF) in capillary electrophoresis by periodic photobleaching of a neutral fluorophore added to the running buffer has been further characterized and optimized and then applied to monitoring EOF during a typical capillary electrophoresis separation. The concentration of neutral fluorophore (rhodamine B) added to the running buffer for monitoring EOF has been decreased by one order of magnitude. The rate at which EOF can be measured has been increased from 0.2 to 1.0 Hz by decreasing the distance between the bleaching beam and the laser-induced fluorescence detector from 6.13 to 0.635 mm. The precision of the measured EOF ranges from 0.2 to 1.8%. Under typical experimental conditions, the dynamic range for flow measurements is 0.066 to 0.73 cm s(-1). Experimental factors affecting precision, signal-to-noise (S/N) ratio and dynamic range for EOF monitoring have been examined. This technique has been applied to measure EOF during a separation of phenolic acids with analyte detection by UV/VIS absorbance. The EOF monitoring method has been shown not to interfere with UV/VIS absorbance detection of analytes.

Journal Article↗
PubMed2003

Carrier ampholyte-free solution isoelectric focusing as a prefractionation method for the proteomic analysis of complex protein mixtures.

The field of proteomics requires methods that offer high sensitivity and wide dynamic range. One of the strategies used to improve the dynamic range is sample prefractionation, such as microsolution isoelectric focusing (IEF). We have modified a commercial solution IEF instrument, the Rotofor, to prefractionate protein mixtures by carrier ampholyte-free solution IEF. The focusing chamber of the Rotofor was divided into several compartments by polyacrylamide membranes with imbedded Immobiline mixtures of specific pH values. When an electric field is applied, each protein migrates to the compartment confined by membranes with pH values flanking its isoelectric point. The approach was demonstrated for the focusing of myoglobin into a predicted compartment, as well as the separation of a complex soluble yeast protein mixture into several distinct fractions. The proteins were dissolved in water or 30% isopropanol. The method is applicable to both gel-based and solution-phase protein identification methods, without the need for further sample preparation.

Animals↗
PubMed2000

Regulated gene expression in Staphylococcus aureus for identifying conditional lethal phenotypes and antibiotic mode of action.

Selectively regulating gene expression in bacteria has provided an important tool for studying gene function. However, well-regulated gene control systems have been restricted primarily for use in laboratory non-pathogenic strains of bacteria (e.g. Escherichia coli, Bacillus subtilis). The development of analogous systems for use in bacterial pathogens such as Staphylococcus aureus would significantly enhance our ability to examine the contribution of any given gene product to pathogen growth and viability. In this report, we adapt, examine and compare three regulated gene expression systems in S. aureus, which had previously been used in B. subtilis. We demonstrate that all three systems function and exhibit titratable induction, together covering a dynamic range of gene expression of approximately 3000-fold. This dynamic range correlates well with the physiological expression levels of cellular proteins. Importantly, we show that one of these systems, the Spac system, is particularly useful for examining gene essentiality and creating specific conditional lethal phenotypes. Moreover, we find that titration of selective target gene products using this system allows direct demonstration of antibiotic mode of action.

Anti-Bacterial Agents↗
PubMed1992

On the capability of the vestibular apparatus to perceive sound stimuli.

This paper discusses the capacity of sound perception in 5 profoundly deaf subjects in whom a "fenestra" was previously formated on the lateral semicircular canal. The ability of sound and vibration perception after fenestra formation in profoundly deaf subjects with normal function of the vestibular apparatus has been described previously. The experiments for this procedure were done on pigeons by Wit & Bleeker. The subjects aged from 22 to 34 years. Causes of deafness varied. Their hearing threshold was bilaterally higher than 95 dB HL and their vestibular apparatus was of normal excitability bilaterally when tested with a caloric test. In all 5 patients the ear conduction hearing threshold remained the same, but the ability of vibration perception improved significantly, and ranged postoperatively between 30 and 45 dB HL. The frequency dynamic range was from 125 to 2,000 Hz in 4 subjects, and from 125 to 4,000 Hz in 1 subject. The patients claimed to have perceived higher intensities, but with a variable dynamic range from frequency to frequency. The intensity range amounted to between 15 and 40 dB. The obtained data of vibration perception ability are discussed.

Adult↗
PubMed2004

Comparison of three procedures for initial fitting of compression hearing aids. II. Experienced users, fitted unilaterally.

This paper is the second in a series comparing three procedures for the initial fitting of multichannel compression hearing aids. The first paper reported the results for a group of 10 experienced hearing aid users fitted bilaterally. This paper reports the results for a different group of 10 experienced hearing aid users fitted unilaterally. The three procedures were: (1) CAMEQ, which aims to amplify speech so as to give equal loudness per critical band over the frequency range 500-5000 Hz, and to give similar overall loudness to normal over a wide range of speech levels; (2) CAMREST, which aims to amplify speech so as to restore normal specific loudness patterns, over a wide range of speech levels; and (3) DSL [i/o], which aims to map the dynamic range of normal-hearing people into the reduced dynamic range of hearing-impaired people, with full restoration of audibility. Each subject was fitted with one Danalogic 163D digital hearing aid, using each of the three fitting procedures in turn; the order was counter-balanced across subjects. Prescribed insertion gains for 55 and 80 dB SPL input levels were verified using real-ear measurements. Immediately after fitting with a given procedure, and 1 week after fitting. the gains were adjusted, when required, by the minimum amount necessary to achieve acceptable fittings. On average, the adjustments were smallest for the CAMREST procedure, slightly larger for the CAMEQ procedure, and largest of all for DSL [i/o]. For the DSL [i/o] the gain changes were mostly negative, especially for high frequencies and the higher input level. After these gain adjustments, users wore the aids for at least 3 weeks before speech reception thresholds (SRTs) for sentences in quiet and in steady and fluctuating background noise were measured. The APHAB questionnaire was also administered. The hearing aids were then refitted with the next procedure. SRTs and APHAB scores did not differ significantly between the three procedures. We conclude that the CAMEQ and CAMREST procedures provide a more appropriate initial fitting than DSL [i/o] for unilaterally experienced hearing aid wearers. Comparison with our earlier study based on bilateral fittings suggests that the preferred gains are similar for unilateral and bilateral fittings.

Acoustic Stimulation↗
PubMed1998

The influence of stoma occlusion on aspects of tracheoesophageal voice.

In this study, speech of 21 laryngectomized patients is investigated under 2 different stoma occlusion conditions, i.e. direct digital occlusion of the stoma (by thumb or finger), and digital occlusion (by finger) via a special heat and moisture exchanger with speech valve (Provox Stomafilter). For both conditions, acoustical analyses of voice quality (various pitch, amplitude, tremor and harmonicity measures) were performed on a sustained /a/, the mean maximum phonation time was calculated, and a phonetogram was made. Acoustical analysis was possible in 13 of the 21 voices (for the other voices, the pitch was too low or the voice was too aperiodic), but no statistical significant differences were found for any of the acoustical parameters studied. However, the maximum phonation time was significantly longer, and the dynamic range significantly larger, under the Stomafilter occlusion condition. The maximum phonation time showed a relevant improvement in 57% of the patients, while the dynamic range showed a relevant improvement in 35% of the patients. In total, 75% of the patients experience an improvement in one or both of these speech characteristics when using the Stomafilter occlusion. It can be concluded that optimal stoma occlusion by means of a specialized device has a positive influence on two relevant parameters of prosthetic voice production: maximum phonation time and dynamic loudness range.

Aged↗