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At least 1,099 records · Page 61Linked to original sources
PubMed1990

Evoked potential tone-on-tone masking patterns in the chinchilla.

Tone-on-tone masking patterns were measured in the chinchilla using the auditory evoked response from the inferior colliculus. The masker was a 2 kHz continuous tone presented at one of five levels from 20 to 70 dB SPL. The evoked response was elicited with tone bursts presented over a wide range of frequencies. Masking was defined as the difference between evoked response thresholds measured in the presence of the masker versus quiet. At low masker levels, the masking profile was symmetrical and centered around 2 kHz. However, as masker level increased, masking spread toward the high frequencies. Furthermore, at masker levels above 50 dB SPL, a low-threshold notch occurred above the masker. The masking profiles obtained with the evoked response are in good agreement with those obtained psychophysically.

Acoustics↗
PubMed1986

Auditory backward recognition masking with well-practiced listeners.

Five adult listeners who had extensive previous practice on a pitch discrimination task participated in an auditory backward recognition masking (ABRM) experiment. S identified the relative pitch "higher"-"lower" of a test tone. A standard tone of 20 msec duration at 800 c/s was followed after 500 msec by a similar 20-msec test tone at 800 +/- delta f. delta f varied from 3.3-11.4 c/s across Ss, adjusted for each S to yield approximately 75%-correct performance. The test tone was followed, after a silent interval of 20-250 msec, by a 100-msec mask, either a tone of 800 c/s or white noise. All stimuli were approximately equal to 77 dbA. All Ss exhibited substantial ABRM when the backward mask was a tone but substantially less when it was white noise. Evidently it is not necessary to use relatively naive listeners to demonstrate ABRM. The performance of most Ss was reduced by the tone masker (i.e., ABRM was in evidence) to chance or nearly chance levels (i.e., little or no ABRM) until the ISI exceeded 80 msec, and for 3 of the Ss ABRM with the tone masker was still evident after 250 msec. It was concluded that a backward mask interferes with test-tone information held in a multichannel preperceptual store and that such interference depends, in part, on the degree to which the properties of the test tone and mask overlap.

Acoustic Stimulation↗
PubMedDate not supplied

Positive expiratory pressure (PEP-mask) physiotherapy improves ventilation and reduces volume of trapped gas in cystic fibrosis.

To investigate the lung function during positive expiratory pressure (PEP) physiotherapy in cystic fibrosis, the resistance tube of the PEP-mask was inserted into the expiratory outlet of our lung function equipment. This enabled us to measure a variety of lung function variables, while the lung function equipment functioned as a PEP-mask. We studied 12 patients and found that during PEP-mask physiotherapy functional residual capacity (FRC) increased significantly (p less than 0.02). There was a decrease of washout volume (WOV) (p less than 0.05), lung clearance index (WOV/FRC) (p less than 0.001) and volume of trapped gas (p less than 0.05), whereas total lung capacity, vital capacity, tidal volume and residual volume did not change significantly. It is concluded that in cystic fibrosis PEP-mask physiotherapy evens the intrapulmonary distribution of the ventilation and opens up regions, that are otherwise closed off. The results support the clinical observation that PEP-mask physiotherapy increases the transcutaneous tension of oxygen and the expectoration of sputum.

Adolescent↗
PubMed1985

[Upward spread of masking in normal and abnormal ears].

Upward spread of masking was studied for normals and sensorineurally hearing-impaired subjects with high-frequency hearing loss. Hearing-impaired listeners were recruited in such a way as to present normal hearing on the frequency of the masker, that is a narrow band of noise centered at 1 000 Hz. Levels of the masker were set at 70, 80 and 90 dB, respectively. Results first indicated the presence of a relationship between masked and elevated absolute thresholds for a masker level of 70 dB. At masker levels of 80 and 90 dB, hearing-impaired listeners showed excessive upward spread of masking in spite of normal hearing sensitivity at the masker frequency: with 80 and 90 dB of noise, upward spread of masking grew, respectively, 2.6 and 1.6 times faster than in normals. Furthermore, excessive upward spread of masking was shown to progress as a function of hearing loss. Results were interpreted as additional evidence of abnormal frequency selectivity in sensorineurally hearing-impaired listeners.

Adult↗
PubMed1980

The efficacy of standard surgical face masks: an investigation using "tracer particles".

To examine the efficacy of currently used synthetic-fiber disposable face masks in protecting wounds from contamination, human albumin microspheres were employed as "tracer particles," and applied to the interior of the fact mask during 20 operations. At the termination of each operation, wound irrigates were examined under the microscope. Particle contamination of the wound was demonstrated in all experients. Since the microspheres were not identified on the exterior of these face masks, they must have escaped around the mask edges and found their way into the wound. The wearing of the mask beneath the headgear curtails this route of contamination.

Humans↗
PubMed1995

Laryngeal mask airway: an alternative for the difficult airway.

The laryngeal mask airway (LMA) was invented by Dr. Archie Brain at the London Hospital, Whitechapel, in 1981. Dr. Brain's main objective for the LMA was that it would provide a better method of maintaining a patient's airway than by face mask. Also, the LMA would be less hemodynamically stressful than with insertion of an endotracheal tube. The LMA consists of a silicone rubber tube connected to a miniature silicone mask. The perimeter of the mask consists of an inflatable elliptical cuff, which forms a tip at the distal aspect of the LMA. The aperture bars in the dome of the mask lift the epiglottis away, so the lumen remains unobstructive. The LMA forms a low pressure seal around the larynx. The LMA is contraindicated in any situation where the patient is at risk for pulmonary aspiration. The LMA is not a substitute for a properly placed endotracheal tube in this situation. The American Society of Anesthesiologists' difficult airway algorithm recommends the insertion of an LMA when ventilation and/or intubation are difficult. The distal aperture of the LMA is in close approximation to the vocal cords, so a 6.0-mm internal diameter endotracheal tube can be passed over an intubating stylet or a pediatric fiberoptic bronchoscope to secure a patient's airway.

Contraindications↗
PubMed1994

[The mapping of the masking effect of noise in relation to the adaptive potentials of the auditory analyzer for speech communication].

The work considers the problem of ergonomic evaluation on the abilities of the auditory analyzer for speech information processing, depending on the zones of masking effect of noise and the rate of speech communication. Significant increase the loss of speech communication with increase in the intensity of the masking effect of noise (from 21.33% at L eq. 40 dB to 96% at L eq. 90 and above 90 dB/A). The speech communication is determined on scale in 4 zones, depending on the qualitative-quantitative criteria of the speech communication processing [I, II, III and IV zones]. Of point of view of ensuring the necessary conditions for perception of the speech communication is confirmed the correctness of the norm for masking noise L eq. 65 dB/A/, which guarantees a good speech communication. Equivalent levels of the masking noise about or equal to L eq. dB/A/ guarantee a satisfactory speech communication in the command desks. When the intensities of the masking noise are above the norms they are of specific importance, as they fall into the unaccepted (bad) zone, of the auditory perception of speech communication.

Adaptation, Physiological↗
PubMed1994

[Physiotherapy in chronic obstructive pulmonary disease with and without mask training].

16 patients with chronic obstructive lung disease were randomized into two groups which were treated with physiotherapy for six weeks. In one group the treatment also involved using a respiratory training mask. Six patients in both groups completed the study. Both groups experienced an improvement for most parameters. The study showed that physiotherapeutic treatment with physical training improved the patients working capacity. However, the treatment with a mask gave no significant additional effect. 46 outpatients who were treated with a mask were asked later if they still used the mask. Only 28% used it regularly and 35% had stopped using the mask because they did not feel any effect.

Adult↗
PubMed1995

[Anesthetic management of Nd-YAG laser surgery in the airway using a larengeal mask].

We used a laryngeal mask for Nd-YAG laser operations of airway stenosis due to tracheal granulation, broncheal granulation and subglottic tumor. Anesthesia was induced with inhalation of N2O-O2-sevoflurane in two cases and intravenous thiopental in one case. The laryngeal mask was inserted with intravenous injection of vecuronium. Anesthesia was maintained with N2O-O2-sevoflurane with intermittent positive pressure ventilation. Laryngeal mask airway was stable with respect to circulation and respiration during Nd-YAG laser irradiation. Ignition of a laryngeal mask caused by Nd-YAG laser is much less common compared to that of a tracheal tube with cuff. Therefore, we recommend to use laryngeal mask airway for Nd-YAG laser operation of airway stenosis because of much less danger of ignition and because it keeps good cardiovascular and respiratory conditions.

Adult↗
PubMed1998

Biological significance of the zoning of the masking effect of noise, related to the adaptive capacities of the auditory analyzer for speech communication.

The paper discusses the problem about the ergonomic assessment of the abilities of the auditory analyzer for processing of speech information, depending on the zoning of the masking effect of noise and the degree of speech communication. A significant increase of the loss of speech information with rise of the intensities of the masking effect of noise (from 21.33% at L eq. 40 dB up to 96% at L eq. 90 and less than 90 dB/A/) is found. The speech communication is graded into 4 bands, depending on the qualitative-quantitative criteria of the processed speech communication. The regularity of the standard for masking noise (L eq. 65 dB/A), which guarantees good comprehensibility is proved from the aspect of ensuring the necessary conditions for speech information perception. Equivalent levels of masking noise near or equal to L eq. 85 dB/A/ ensure satisfactory comprehensibility at the control boards. The abnormal intensities of the masking noise effect are of particular importance as they belong to the inadmissible (bad) zone of auditory perception of speech information.

Audiometry, Speech↗
PubMed2001

Inappropriate use of antibiotics and the risk for delayed admission and masked diagnosis of infectious diseases: a lesson from Taiwan.

BACKGROUND: Antibiotic resistance is a serious problem worldwide. It is particularly alarming in Taiwan and other countries of the Pacific Rim, where antimicrobial drugs are used excessively. OBJECTIVE: To determine whether use of antimicrobial drugs before coming to an emergency department was associated with delayed admission or masked or missed diagnoses at a large general hospital in Taiwan. METHODS: Antimicrobial activity in urine (AAU) was determined in all patients seen in the emergency department during a 3-month study. A physician, unaware of the results of the urine tests, reviewed the medical charts of patients who were admitted to the hospital to determine whether admission was delayed for at least 7 days or the diagnosis was masked or missed. RESULTS: Of the 1182 patients, 444 were admitted to the hospital. In 220 patients (49.5%), AAU was detected. There was no significant difference in AAU between patients with or without an infectious disease (53.0% vs 46.3%, respectively; P =.41). For patients with infection, 34.8% of those with AAU had a delayed admission, compared with only 21.6% without AAU (relative risk [RR], 1.61; 95% confidence interval [CI], 1.03-2.52; P =.03). For patients without infection, 36.2% of those with AAU had a delayed admission compared with 31.1% without AAU (RR, 1.16; 95% CI, 0.81-1.68; P =.64). For patients with infection, 48.7% of those with AAU had a masked or missed diagnosis, compared with 25.5% without AAU (RR, 1.91; 95% CI, 1.30-2.80; P<.001). For patients without infection, 27.6% of those with AAU had a masked or missed diagnosis compared with 14.8% without AAU (RR, 1.87; 95% CI, 1.11-3.17; P =.02). CONCLUSION: Use of antimicrobial drugs before coming to an emergency department was associated with a significantly increased risk for delayed and masked or missed diagnoses of infectious diseases and missed diagnosis of noninfectious diseases.

Adolescent↗
PubMed1986

Solving audiometric masking dilemmas with an insert masker.

For some bilateral hearing losses, standard audiometric techniques cannot provide sufficient data for correct otologic diagnosis. These hearing losses are termed "masking dilemmas" because sound attenuation across the head is inadequate to prevent unwanted masking of the test cochlea. In most cases, the masking dilemma can be eliminated by presenting masking through an insert phone in the ear canal, rather than through a standard earphone and cushion. Insert earphones are not standard on most audiometers, but the minimal necessary equipment and alterations are inexpensive, readily available, and require little time to implement. Test time is not increased significantly. Some masking dilemmas will not be solved by the insert masker, but, when properly constructed and used, an insert masker will provide an accurate measurement of cochlear reserve not otherwise obtainable for most cases.

Acoustic Impedance Tests↗
PubMed2006

Influence of fluorescent and opalescent properties of resin composites on the masking effect.

The objective of this study was to determine the influence of fluorescent properties in the reflectance and transmittance modes and opalescent properties and translucency under ultraviolet (UV)-included and -excluded conditions on the masking effect of commercial resin composites quantitatively. Color and spectral distribution of seven resin composites (14 shades) of 1-mm thick were measured in the reflectance and transmittance modes under UV-included and -excluded conditions. For the fluorescence evaluation, subtraction spectra by the inclusion and exclusion of the UV component of the illumination in the reflectance and transmittance modes were calculated. Opalescence parameter (DeltaO*(ab)) was calculated as the difference in yellow-blue (Deltab*) and red-green (Deltaa*) coordinates between the reflected and transmitted colors under UV-included and -excluded conditions. Under UV-included and -excluded conditions, translucency parameter (TP) was calculated and masking effect was calculated as the color difference between a specimen over a black tile and black tile itself. Fluorescent and opalescent properties varied by the brand and shade of composites and measurement protocols. Masking effect was correlated with TP values when TP values of materials were obviously different. But when TP values were in the similar range, the opalescent property influenced the masking effect of resin composites. The influence of fluorescent property on masking effect was also confirmed, although the degree of correlation was very low.

Biocompatible Materials↗
PubMed1995

Dependent masking and system life data analysis: Bayesian inference for two-component systems.

Data from field operations of a system is often used to estimate the reliability of components. Under ideal circumstances, this system field data contains the time to failure along with information on the exact component responsible for the system failure. However, in many cases, the exact component causing the failure of the system cannot be identified, and is considered to be masked. Previously developed models for estimation of component reliability from masked system life data have been based upon the assumption that masking occurs independently of the true cause of system failure. In this paper we develop a Bayesian methodology for estimating component reliabilities from masked system life data when the probability of masking is dependent upon the true cause of system failure. The Bayesian approach is illustrated for the case of a two-component system of exponentially distributed components.

Bayes Theorem↗
PubMed1993

Decentered ablation zones resulting from photorefractive keratectomy with an erodible mask.

Four patients underwent photorefractive keratectomy for compound myopic astigmatism using the erodible mask. All achieved improvements in unaided visual acuities despite manifesting varying levels of decentration of the ablated zones. However, one patient had significant monocular diplopia because of the severity of the decentration. The problems with the present system include the use of a NON coaxial microscope; difficulty with obtaining and maintaining proper alignment of the excimer laser beam to the erodible mask and the central corneal zone; the inability to interrupt and restart the procedure due to the ablation of the reference marks on the mask; and patient discomfort. We suggest installation of the PMMA mask at the laser aperture in order to alleviate the above difficulties. In the meantime, use of a coaxial microscope, a limbal suction device for fixation, permanent reference marks on the mask and peribulbar anaesthesia may be helpful.

Adult↗
PubMed1991

The use of the laryngeal mask airway in pediatric anesthesia.

Laryngeal mask airway (LMA) insertion was tried in 120 pediatric cases, from 2 months to 12 years of age. Initial indications for LMA were the same as for a face mask, except for two additional conditions; anticipation of difficulty with intubation and difficulty in management by a face mask. Size 2 LMA was used in the vast majority of cases. The insertion was successful on the first trial in 108 cases. More than one trial was necessary in 9 cases but only 3 cases required more than 3 trials. Insertion could not be completed in 3 cases. The relationship between the depth of LMA at the front teeth and age could be roughly described by "depth = 10 cm + 0.3 x Age". LMA was found to provide a better and more secure airway than the face mask without direct tracheal intervention. Heart rate did not increase with LMA insertion. It is easy to use and can be used in place of the face mask, but complications such as stomach air inflation due to too vigorous manual ventilation, slight pharyngeal injury, and airway obstruction due to kinking of LMA can occur. These complications can be avoided and must be kept in mind during it's use. LMA itself can be used to obtain a patent airway where an endotracheal airway is difficult to obtain. LMA-aided tracheal intubation can be extremely useful in obtaining endotracheal airways. Non-blind techniques can be used with LMA to increase safety. LMA is a very useful addition to pediatric anesthesia practice.

Journal Article↗
PubMed2003

Fast adaptive unsharp masking with programmable mediaprocessors.

Unsharp masking is a widely used image-enhancement method in medical imaging. Hardware-based solutions can be developed to support high computational demand for unsharp masking, but they suffer from limited flexibility. Software solutions can easily incorporate new features and modify key parameters, such as filtering kernel size, but they have not been able to meet the fast computing requirement. Modern programmable mediaprocessors can meet both fast computing and flexibility requirements, which will benefit medical image computing. In this article, we present fast adaptive unsharp masking on two leading mediaprocessors or high-end digital signal processors, Hitachi/Equator Technologies MAP-CA and Texas Instruments TMS320C64x. For a 2k x 2k 16-bit image, our adaptive unsharp masking with a 201 x 201 boxcar kernel takes 225 ms on a 300-MHz MAP-CA and 74 ms on a 600-MHz TMS320C64x. This fast unsharp masking enables technologists and/or physicians to adjust parameters interactively for optimal quality assurance and image viewing.

Algorithms↗
PubMed1992

Single photon emission computed tomographic teboroxime imaging with a preprocessing masking technique.

We previously reported that single-head SPECT imaging with teboroxime is feasible. However, excessive hepatic uptake in some patients may interfere with image interpretation. This study examined the feasibility of improving image quality by use of a preprocessing masking technique to subtract hepatic activity. A band of 10 pixels in width adjacent to the inferior cardiac silhouette was marked on the raw planar images, and then SPECT reconstruction was done with the Butterworth filter with a frequency cutoff of 0.3 cycles/cm and the power of 10. The stress and rest images were compared before and after masking in 10 patients who underwent SPECT teboroxime imaging during adenosine-induced coronary hyperemia (140 micrograms/kg/min for 6 minutes). SPECT imaging with a single-head detector was performed with the use of a 180-degree anterior arc (from the 45-degree left posterior oblique projection to the 45-degree right anterior oblique projection); 32 images at 8 seconds per stop were obtained (total imaging time = 6.8 minutes). All images were considered subjectively better after the masking technique was used, especially for assessment of inferior wall perfusion pattern. The maximum count in any pixel was in the hepatic region of interest before masking and in the cardiac region of interest after masking (303 +/- 110 counts vs 166 +/- 55 counts; p < 0.001). The difference was especially pronounced in the images that were obtained when patients were at rest (366 +/- 102 counts vs 184 +/- 64 counts; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗