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PubMed1980

[Bacteriological evaluation of surgical masks (author's transl)].

An experimental set-up is described permitting the evaluation and quantification under controlled conditions of retention efficiencies of surgical mask materials and different types of masks, using bacterial aerosols standardized both quantitatively and qualitatively. Screening of various materials used in one-way surgical paper masks has shown that, apart from the one-layered thin models, present paper masks with bacterial transmittance under 1% are far superior to the muslin masks of the past. For meeting the aseptical requirements in hospital operating rooms, adaptable masks (green exterior) provided with multi-layered polyester filter pads have proven most suitable by their virtual impenetrability for bacteria. After several hours use and heavy wetting of the filters layers, no increase of bacterial transmittance was observed.

Bacteria↗
PubMed1994

Noninvasive mechanical ventilation via face mask in patients with acute respiratory failure who refused endotracheal intubation.

OBJECTIVE: To evaluate the response to noninvasive ventilation in a group of terminally ill patients with acute respiratory failure who refused endotracheal intubation. DESIGN: Case series. SETTING: Medical intensive care units (ICUs) in a university health science center. PATIENTS: Eleven patients, nine with hypercapnic and two with hypoxemic acute respiratory failure. Mean age of patients was 64 yrs. INTERVENTION: Mechanical ventilation was delivered via a face mask. The initial ventilatory setting was continuous positive airway pressure mode, with pressure-support ventilation of 10 to 20 cm H2O, titrated to achieve a respiratory rate of < 25 breaths/min and a tidal volume of 5 to 7 mL/kg. Ventilatory settings were adjusted based on results of arterial blood gases. Mean duration of mechanical ventilation was 44 hrs. MEASUREMENTS AND MAIN RESULTS: Mechanical ventilation via face mask was effective in correcting gas exchange abnormalities in seven of 11 patients, all of whom survived and were discharged from the ICU. Four patients with hypercapnic acute respiratory failure died. Mechanical ventilation via face mask was effective in improving respiratory acidosis in three patients and had no effect in one patient. Two of the four patients could not be weaned from mechanical ventilation and opted for discontinuation of this method. Removal of the ventilator while retaining the mask for oxygen supplementation was a nontraumatic experience to the patient and family. Even when respiratory failure did not resolve, mechanical ventilation via face mask was effective in lessening dyspnea and allowed the patient to maintain autonomy and continuous verbal communication. CONCLUSIONS: We conclude that mechanical ventilation via face mask offers an effective, comfortable, and dignified method of supporting patients with end-stage disease and acute respiratory failure.

Acute Disease↗
PubMed1998

Informativeness of critical ratios "useful signal-masking noise" in speech communication.

In experimental conditions the influence of 8 ratios "useful signal-masking noise" of 3 types of production noise (impulse, continuous and interrupted) is studied as well as continuous (white) noise as control on the perception of an audiometric test by 60 individuals with normal hearing. The test is understandable phonetically with difficulties and balanced at speech. The test intensity is L(equiv).70-75 dB/A/. The most expressed masking effect of continuous (white) noise, followed by the impulse and constant production noise is found. The lowest masking effect is found out at interrupted noise. This is explained by the acoustic characteristics of exposed types of noise. The masking effect of noise is limited to a high degree by the parameter "signal-noise" ratio, which is confirmed by the found negative correlation relationship with percentage speech intelligibility. The critical ratios "signal-noise", characterized with sharp decline of the level of discrimination of speaking signal and deterioration of the effectiveness of speech communication are established. In this paper the problem for conforming the speech communication both with the intensity and acoustic characteristics of masking noise and with the "signal-noise" ratio is discussed. Besides this in the critical "useful signal-masking noise" ratios better individual achievements could be a criterion for professional selection of candidates for operators.

Adult↗
PubMed1999

Geographically masking health data to preserve confidentiality.

The conventional approach to preserving the confidentiality of health records aggregates all records within a geographical area that has a population large enough to ensure prevention of disclosure. Though this approach normally protects the privacy of individuals, the use of such aggregated data limits the types of research one can conduct and makes it impossible to address many important health problems. In this paper we discuss the design and implementation of geographical masks that not only preserve the security of individual health records, but also support the investigation of questions that can be answered only with some knowledge about the location of health events. We describe several alternative methods of masking individual-level data, evaluate their performance, and discuss both the degree to which we can analyse masked data validly as well as the relative security of each approach, should anyone attempt to recover the identity of an individual from the masked data. We conclude that the geographical masks we describe, when appropriately used, protect the confidentiality of health records while permitting many important geographically-based analyses, but that further research is needed to determine how the power of tests for clustering or the strength of other associative relationships are adversely affected by the characteristics of different masks.

Confidentiality↗
PubMed1994

Storage of messenger RNA in eukaryotes: envelopment with protein, translational barrier at 5' side, or conformational masking by 3' side?

Messenger RNA can be stored in the cytoplasm of higher Eukaryotes in the form of masked messenger ribonucleoprotein particles (masked mRNPs, or informosomes). The typical example is the storage of mRNPs in germ cells (oocytes and spermatocytes). The masked mRNPs are inactive in translation, stable, i.e., protected against degradation, and unavailable for poly(A) tail processing, such as cytoplasmic polyadenylation and deadenylation. The major nonspecific mRNA-binding protein forming mRNPs and belonging to a special p50 family of basic, glycine-rich, phosphorylatable proteins seems to be necessary, but not sufficient for the masking. In some cases, mRNA-specific repressor proteins bound to the 5'-untranslated regions (5'-UTR) of mRNAs may be involved. Interactions of the 3'-untranslated regions (3'-UTR) with sequence-specific proteins seem to be of decisive importance for the masking of mRNPs. The hypothesis is proposed that the masking is achieved through a 3'-UTR-induced conformational rearrangement of mRNP; closing into a circle and condensation of mRNP are considered plausible.

Animals↗
PubMed1983

Effect of contralateral and ipsilateral masking of acoustic stimulation on the latencies of auditory evoked potentials from cochlea and brain stem.

Masking techniques were applied to a group of 10 subjects with normal hearing, to investigate the influence of masking on the latencies of brain stem auditory evoked potentials. The levels of sufficient masking and overmasking were determined. Central masking, as established in a psychophysiological manner, cannot be clearly demonstrated by auditory brain stem evoked potentials. When masking the untested ear, the alterations in the response are small and this can be ignored in clinical practice if masking of the untested ear is necessary.

Acoustic Stimulation↗
PubMed1988

Effects of acoustic and sensory variables on masking tuning curves of the offset auditory brain-stem response in the rodent.

Simultaneous sinusoidal masking of the auditory brain-stem response (ABR) which is generated by the offset of a tone produces a W-shaped masking tuning curve (TC) in the gerbil, rat, mouse, and guinea pig. The probe stimulus offset must be very rapid in most animals. Lesions of the contralateral ear, strychnine blockage of the olivocochlear bundle, or removal of the ipsilateral outer ear do not alter the basic properties of the offset masking TC. Increasing the simultaneous masker duration selectively increases the tuning of the offset masking TC peak. Masking only the latter portions of the probe stimulus does not alter the shape of the offset masking TC.

Animals↗
PubMedDate not supplied

Flicker masking depends on the method of measurement.

Luminance flicker masks sinusoidal gratings of low spatial frequency (SF), the effect being attributed to the transiency of response within this SF range. An alternative point of view is that the lower number of cycles of such gratings makes them more susceptible to flicker masking. To verify this possibility, flicker masking of low-SF gratings (1 c/deg) of varying size was studied by the methods of human visually evoked potentials (VEP), reaction time (RT) and contrast threshold. Difference between the effects of flicker masking on contrast threshold, RT and VEP was found: RT was delayed and VEP was reduced in amplitude by flicker with both small and large gratings while contrast threshold was only increased with the small gratings. The decrease of grating duration increased the masking effect on contrast threshold. Moreover, contrast threshold was a unimodal function of flicker frequency with brief test gratings and a bimodal one with long-lasting gratings. It is concluded that: (1) the previously reported effects of luminance flicker masking on RT and VEP are not an artefact of the reduced number of cycles; (2) at the SF tested, both RT and VEP depend on the transient components of the response, while contrast sensitivity depends on both transient and sustained components of the response.

Adult↗
PubMed1987

Evoked response 'forward masking' functions in chinchillas.

Evoked potentials were obtained from the inferior colliculus of awake chinchillas using a 'forward masking' stimulus paradigm. The response was elicited using a brief probe tone presented 10 dB above threshold. Forward masking functions were then measured by determining the intensity of the masker needed to produce a 50% reduction in evoked response amplitude over a range of time intervals between masker offset and probe onset. The time course of forward masking was evaluated by fitting an exponential function to the results. The average time constant values of forward masking functions ranged from 50 to 90 ms. Although the constants at 0.5 and 8.0 kHz were somewhat longer than those at the midfrequencies, the differences were not statistically significant. The evoked response forward masking functions were quite similar to those obtained psychophysically; this suggests that it may be an efficient method of estimating the time course of forward masking in difficult to test subjects.

Acoustic Stimulation↗
PubMed1989

Changes in the masked thresholds of brief tones produced by prior bursts of noise.

Thresholds were measured for 5-ms 1-kHz tones masked by synchronous bursts of noise containing a spectral notch centered on the signal frequency. Thresholds were reduced by prior exposure to a 200-ms burst of a 'priming stimulus' which had the same spectral shape as the masker. The masking release was greatest for notch widths extending between 20-30% above and below the signal frequency. It did not occur when the masker and primer were bandpass noises extending from 200-1800 Hz. A smaller masking release could be obtained with a primer consisting of only the lower band of a notched noise masker. This was also true, but to a lesser extent, for a primer consisting of the higher band alone. A primer that was a narrow band of noise centered on the signal frequency produced an increase in masking, which could not be attributed to forward masking of the tone by the primer. The effects of all primers were independent of primer level over the 30-dB range studied, ruling out explanations in terms of peripheral adaptation or of adaptation of suppression. A significant masking release occurred when the silent interval between primer offset and masker onset was as long as 320 ms, but increasing the duration of the masker and signal beyond 80 ms eliminated the effect in two out of three subjects. The results are consistent with a form of processing which groups together energy in frequency regions containing common amplitude envelopes, and which enhances the internal representation of newly-arriving energy in previously unstimulated frequency regions.

Acoustic Stimulation↗
PubMed1992

Derived and enhanced compound action potentials at near-threshold levels: forward masking increases sensitivity of audiograms and tuning curves.

The amplitude of a cochlear nerve compound action potential (CAP) can be increased by forward maskers having levels close to the visual detection threshold of the CAP. This effect, termed enhancement, varies as a function of the frequency of the masker and probe stimulus, and is nonmonotonic with respect to the level of the masker. Other studies using the derived CAP have used a subtraction technique to evaluate the ability of simultaneous maskers having levels near the CAP visual detection threshold to influence the CAP produced by an above threshold tone. The present paper compares audiograms produced by the conventional nonmasked CAP visual detection threshold technique with audiograms produced by both forward masked derived CAPs and forward masked enhanced CAPs. In response to low and middle frequency stimuli, both masked CAP measures produce more sensitive audiograms than does the conventional nonmasking method. Forward masked amplitude tuning curves (TCs) were also produced, comparing the conventional 50% amplitude reduction and 20 microV amplitude reduction methods with TCs obtained with derived and enhanced CAPs. When the same criteria are used, both masked CAP measures result in sharply tuned amplitude TCs that are approximately 60 dB more sensitive than the conventional CAP technique. At near-threshold levels, the properties of forward masked enhanced and derived CAPs appear to be similar.

Acoustic Stimulation↗
PubMed2005

Cardiovascular outcome in treated hypertensive patients with responder, masked, false resistant, and true resistant hypertension.

BACKGROUND: The aim of this study was to evaluate the cardiovascular outcome in apparently responder hypertensive patients with responder and masked hypertension, and in apparently resistant hypertensive patients with false and true resistant hypertension. METHODS: The occurrence of fatal and nonfatal cardiovascular events was evaluated in 340 patients with responder hypertension (clinic blood pressure [BP] <140/90 mm Hg and daytime BP <135/85 mm Hg), 126 with masked hypertension (clinic BP <140/90 mm Hg and daytime BP >135 or 85 mm Hg), 146 with false resistant hypertension (clinic BP >or=140 or 90 mm Hg and daytime BP <135/85 mm Hg), and 130 with true resistant hypertension (clinic BP >or=140 or 90 mm Hg and daytime BP >135 or 85 mm Hg). RESULTS: During follow-up period (4.98 +/- 2.9 years), the event-rate per 100 patient-years was 0.87, 2.42, 1.2, and 4.1 in patients with responder, masked, false resistant, and true resistant hypertension, respectively. After adjustment for several covariates, including clinic BP (forced into the model), Cox regression analysis showed that cardiovascular risk was significantly higher in masked hypertension (masked versus responder hypertension, relative risk [RR] 2.28, 95% confidence interval [CI] 1.1-4.7, P < .05) and in true resistant hypertension (true resistant versus responder hypertension, RR 2.94, 95% CI 1.02-8.41, P < .05), whereas there was no significant difference between false resistant and responder hypertension. CONCLUSIONS: This study shows that patients with masked hypertension are at higher risk than those with responder hypertension, and that those with false resistant hypertension are at lower risk than those with true resistant hypertension. Ambulatory BP monitoring should be performed in treated hypertensive patients to obtain a better prognostic stratification.

Aged↗
PubMed2006

Taste masking analysis in pharmaceutical formulation development using an electronic tongue.

The purpose of this study is to assess the feasibility for taste masking and comparison of taste intensity during formulation development using a multichannel taste sensor system (e-Tongue). Seven taste sensors used in the e-Tongue were cross-selective for five basic tastes while having different sensitivity or responsibility for different tastes. Each of the individual sensors concurrently contributes to the detection of most substances in a complicated sample through the different electronic output. Taste-masking efficiency was evaluated using quinine as a bitter model compound and a sweetener, acesulfame K, as a bitterness inhibitor. In a 0.2 mM quinine solution, the group distance obtained from e-Tongue analysis was reduced with increasing concentration of acesulfame K. This result suggests that the sensors could detect the inhibition of bitterness by a sweetener and could be used for optimization of the sweetener level in a liquid formulation. In addition, the bitterness inhibition of quinine by using other known taste-masking excipients including sodium acetate, NaCl, Prosweet flavor, and Debittering powder or soft drinks could be detected by the e-Tongue. These results further suggest that the e-Tongue should be useful in a taste-masking evaluation study on selecting appropriate taste-masking excipients for a solution formulation or a reconstitution vehicle for a drug-in-bottle formulation. In another study, the intensity of the taste for several drug substances known to be bitter was compared using the e-Tongue. It was found that the group distance was 695 for prednisolone and 686 for quinine, which is much higher than that of caffeine (102). These results indicate that the taste of prednisolone and quinine is stronger or more bitter than that of caffeine as expected. Based on the group distance, the relative intensity of bitterness for these compounds could be ranked in the following order: ranitidine HCl>prednisolone Na>quinine HCl approximately phenylthiourea>paracetamol>>sucrose octaacetate>caffeine. In conclusion, the multichannel taste sensor or e-Tongue may be a useful tool to evaluate taste-masking efficiency for solution formulations and to compare bitterness intensity of formulations and drug substances during pharmaceutical product development.

Biosensing Techniques↗
PubMed2003

Visual masking as a probe for abnormal gamma range activity in schizophrenia.

BACKGROUND: Visual masking procedures assess very early stages of visual perception. Patients with schizophrenia consistently show deficits on visual masking tasks, and these deficits likely reflect vulnerability to schizophrenia. We conducted two experiments to determine whether visual masking procedures can reveal underlying abnormalities in gamma range oscillations in schizophrenia. METHODS: In the first experiment, we conducted nonlinear modeling of visual masking performance data from 89 male schizophrenic patients and 20 male comparison subjects. In the second experiment, electrophysiological recordings of event-related gamma activity were taken during a visual masking task in a subset of eight patients and seven control subjects. RESULTS: In the first experiment, nonlinear modeling of the performance data revealed evidence of oscillations in the gamma range (30 and 35 Hz) for the comparison group but not patients. In the second experiment, the comparison group, but not the patients, showed a burst of gamma range activity 200-400 msec following target presentation. The difference between patients and comparison subjects in this time period was significant (p <.05). CONCLUSIONS: Visual masking procedures can serve as a probe for underlying gamma range activity, which appears to be aberrant in schizophrenia. Perceptual problems in schizophrenia may, at least in part, be due to a failure to establish and/or maintain gamma range oscillations.

Case-Control Studies↗
PubMed1982

Mouth-to-mask ventilation: a superior method of rescue breathing.

Tidal volumes achieved using endotracheal intubation with a self-inflating bag were compared to those achieved with the esophageal obturator airway, a bag-valve mask system, and mouth-to-mask ventilation in an experimental model employing 18 unskilled and 4 partially skilled rescuers. When compared to mean tidal volumes achieved with endotracheal intubation (1,193 ml with unskilled, 942 ml with semi-skilled rescuers), ventilation with the bag-valve-mask system was significantly less (509 and 495 ml tidal volumes) and was, in fact, well below the value of 800 ml recommended for rescue breathing. Mouth-to-mask ventilation produced tidal volumes (1,093 ml and 1,200 ml) not significantly different from those seen with endotracheal intubation. If clinical findings confirm these experimental results, mouth-to-mask ventilation should replace the bag-valve-mask system in the initial management of respiratory arrest.

Humans↗
PubMed2003

Combining backward masking and transcranial magnetic stimulation in human observers.

Both backward masking and transcranial magnetic stimulation (TMS) are capable of hindering perception of a visual target. To study the relationship between these two methods we applied TMS over the occipital pole in combination with the visual backward masking technique shine-through. The recently discovered weak shine-through mask consists of a horizontal grating with 25 vernier elements. In three subjects we determined discrimination thresholds for vernier acuity without and with the shine-through mask. Modulation of the vernier discrimination threshold was determined in both conditions with TMS at various stimulus onset asynchronies (SOAs). In the unmasked condition TMS deteriorates discrimination moderately around 120 ms TMS SOA from 25" (arc seconds) to about 130". If in addition to TMS the vernier is backward-masked, discrimination of the vernier offset is completely abolished (>300"). Therefore, TMS and backward masking can interact in a non-linear manner, strongly interfering with early visual processing.

Adult↗
PubMed1998

Repositioning accuracy: comparison of a noninvasive head holder with thermoplastic mask for fractionated radiotherapy and a case report.

PURPOSE: To compare accuracy, clinical feasibility, and subjective patient impression between a noninvasive head holder (Vogele Bale Hohner [VBH]; Wellhoefer Dosimetry, Schwarzenbruck, Germany) developed at the University of Innsbruck and the thermoplastic mask fixation system for use in fractionated external radiotherapy. We present a case report of an actual patient fixated in the VBH head holder during radiation therapy. MATERIALS AND METHODS: The VBH head holder consists of an individualized vacuum dental cast connected to a head plate via two hydraulic arms allowing noninvasive, reproducible head fixation of even uncooperative patients. Accuracy was tested and compared with that of the thermoplastic mask using the Phillips EasyGuide navigation system on five volunteers. Specific external registration points served as landmarks and their positions were compared after each repositioning. System and operator inaccuracy were also taken into account. The times taken for production and repositioning of the respective fixation devices were compared, and subjective impressions were noted. RESULTS: Mean VBH head holder repositioning accuracy was 1.02 mm while that of the thermoplastic mask was 3.05 mm. 69% of mask repositionings showed a deviation > 2 mm and 41% > 3 mm (as opposed to 8% and 1% respectively for the VBH head holder) Those points located farthest away from the respective plane of fixation showed the largest deviations. Both production and repositioning times were similar between the systems; depending upon the patient, the VBH head holder was generally better tolerated than the mask system. CONCLUSION: Due to its significantly better repositioning accuracy compared to that of the thermoplastic mask, the VBH head holder is especially suited for external radiation requiring precise repositioning due to critical tissues in immediate surrounding of the area to be irradiated.

Adult↗
PubMed1975

Masking of the non-test ear in tone decay, Békésy audiometry, and SISI tests.

Masking of the non-test ear is frequently required in tone decay, Békésy audiometry and SISI tests; without it, serious misdiagnoses can result. Methods are given for calculating the dial levels of masking noises to be delivered and the extent of possible cross-masking. The methods are subdivided according to whether the tests to be employed are fixed-frequency or sweep-frequency, and to whether masking function data are available from previous use of shadow masking. In difficult cases, careful preliminary shadow-masking procedures and subsequent use of fixed-frequency tests is recommended.

Acoustic Stimulation↗