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At least 19 recordsLinked to original sources
PubMed1975

Efficiency of constant-flow oxygen masks for general aviation: a new method of mask evaluation.

Three commercially popular oxygen masks for general aviation were tested by measuring arterial blood gases at altitude and alveolar gases at ground level with a respiratory mass spectrometer. At 4,575 m (15,000 ft) and 3.65 1/min oxygen flow, calculated fractional inspired oxygen (F102) averaged 38.1% for the Hudson-type mask; 49.6% for the Scott Sky Mask; and 52.4% for the Scott Duo Seal Mask. At ground level, 1280 m (4,200 ft) 2.6 1/min oxygen flow, F102 calculated from alveolar gases averaged 41.5% plus or minus S.D. 5.3 for the Hudson Mask; 48.0% plus or minus 5.2 for the Scott Sky Mask; and 54.9% plus or minus S.D. 6.2 for the Scott Duo Seal Mask. The asymptomatic hyperventilation observed in all subjects at altitude degraded the performance of all three masks to a sufficient degree to offset the benefits of increased oxygen flow achieved through the regulator at higher altitudes. The respiratory mass spectrometer provides a new technique for analyzing efficiency of oxygen masks and the effect of changes in mask design.

Aerospace Medicine↗
PubMed1991

[Study on tinnitus masking--an evaluation of ipsilateral and contralateral masking for tinnitus].

In this study, the tinnitus masking curves measured by the ipsilateral and contralateral masking test were evaluated for the unilateral tinnitus cases of following 4 groups; 40 cases without hearing loss, 22 cases with symmetrical sensorineural hearing loss, 12 cases with unilateral deafness, and 70 cases with unilateral sensorineural hearing loss. Then the characteristics of tinnitus masking curves and central masking phenomenon for tinnitus masking were investigated. Consequently, tinnitus was masked by a masking tone given from nontinnitus ear when it reached at some definite loudness level, in spite of the presence of hearing loss or the degree of hearing loss in tinnitus ear. Then it was suggested to be a influence of central masking phenomenon in the contralateral tinnitus masking.

Auditory Perception↗
PubMed1992

Use of the laryngeal mask airway as an alternative to a face mask during outpatient arthroscopy.

The laryngeal mask airway (LMA) has recently become available in the United States, and several authors have suggested that it is superior to an anesthesia mask. To test this hypothesis, 64 patients undergoing outpatient arthroscopic knee surgery were randomly assigned to have anesthesia maintained via either a laryngeal mask airway (LMA) (n = 31) or a standard face mask (n = 33). Anesthesia was induced with fentanyl 1 microgram.kg-1 and propofol 2 mg.kg-1 and maintained with a variable-rate propofol infusion (50-180 micrograms.kg-1 x min) and nitrous oxide 67% in oxygen. The LMA was inserted without difficulty by inexperienced anesthesiologists in 90% of the patients. Problems associated with airway management were more common in patients in the face mask (control) group. Episodes of hemoglobin oxygen desaturation (< 95%) occurred in 52% of patients in the face mask group compared to only 13% in the LMA group (P < 0.05). Intraoperative airway manipulations were required in 15% of face mask patients (vs. 3% of the LMA group), and difficulties in maintaining an airway were reported by 24% of the resident anesthesiologists caring for patients in the face mask group (vs. none in the LMA group) (P < 0.05). Insertion of the LMA was not associated with any acute changes in hemodynamic values. Intraoperative hemodynamic values and anesthetic requirements did not differ significantly between the two treatment groups. There were no significant differences in the emergence and recovery times or in the incidence of postoperative sore throats between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Comparison of the use of the laryngeal mask and face mask by inexperienced personnel.

Ten junior doctors with no postgraduate anaesthetic experience attempted to ventilate the lungs of 50 anaesthetized patients, using either a laryngeal mask or a Guedel airway and face mask. Success was defined as the production of two successive tidal volumes exceeding 800 ml within 40 s. The failure rate was significantly greater using the laryngeal mask compared with the face mask (P < 0.05) and the average time was significantly longer with the laryngeal mask than with the face mask (P < 0.01). The results from this investigation suggest the laryngeal mask airway cannot be recommended as a resuscitation device for use by inexperienced operators.

Cardiopulmonary Resuscitation↗
PubMed1992

Temporal decline of masking and comodulation masking release.

Masking sounds can be continuously present, gated simultaneously with the signal, or gated somewhat prior to the signal. This continuum of relative onset times was explored using waveforms of the sort commonly employed in studies of comodulation masking release (CMR). There was a 50-Hz masker band centered on the 1250-Hz tonal signal, and four 50-Hz flanker bands centered at 850, 1050, 1450, and 1650 Hz. In some conditions, all four flanker bands had the same temporal envelope, and the masker band either had that same envelope (correlated presentations) or a different envelope (uncorrelated presentations). In other conditions, all five bands had different temporal envelopes (all-uncorrelated presentations). The masker band and/or the four flanker bands were either gated nearly simultaneously with the signal (burst conditions) or were gated prior to the signal by a duration that was systematically varied (fringed conditions). The eight listeners could be partitioned into three groups on the basis of their response to these fringing manipulations. Two listeners (the large fringers) showed a gradual improvement in detectability with increasing fringe duration (called a temporal decline of masking), while three others (the small fringers) showed little improvement in detectability. For the remaining three subjects, there was evidence of a "learning" effect that changed them from large fringers to small fringers over a 10-week period of listening. When present, the temporal decline of masking was greater for the correlated than for the uncorrelated comodulation condition; as a consequence, the difference in detectability between them (the comodulation masking release or CMR) increased with fringe duration. By fringing the masker and flanker bands separately and in combination, it was revealed that the temporal declines of masking were primarily attributable to the fringing of the flanker bands. In contrast, large CMRs required long fringes on both the masker and flanker bands. The above results were obtained with 50-ms signals, but generally similar data were obtained with a signal duration of 240 ms. The difficulties raised for experimentalists and theorists by such long-term practice effects are discussed.

Adult↗
PubMed1978

A study on the microbial filtration efficiency of surgical face masks--with special reference to the non-woven fabric mask.

With the experimental apparatus designed and made available by Nicholes, we evaluated the bacterial filtration efficienty (B.F.E.) of the non-woven fabric and cotton cloth masks. The apparatus was supplied by Nicholes (U.S. Military Specification 36954 C mask, surgical, disposable). The study presented here was performed as a round robin test with Nicholes. By using this apparatus, comparison was made as to the B.F.E. of the six different kinds of surgical face mask before and after prolonged use. The result was obtained that the disposable mask made of glass fiber mat combined with non-woven fabric proved to be the highest in performance with a B.F.E. of 98.1-99.4%. It is useful both in preventing hospital infection and in general clinical practice. The B.F.E. of the conventional cotton cloth masks is not only lower but variable over a wide range of 43.1-93.6%.

Aerosols↗
PubMed1991

The Brain laryngeal mask. A comparative study with the nasal mask in paediatric dental outpatient anaesthesia.

Fifty ASA grade 1 children, who presented for dental outpatient extraction were studied. They were randomly allocated to two groups after induction: group 1 had conventional nasal mask anaesthesia and group 2 anaesthesia with a laryngeal mask. Group 2 had fewer hypoxic episodes and significantly better arterial oxygen saturations (p less than 0.01). There was no difference between the groups as regards surgical access, difficulty of extraction or bleeding. The laryngeal mask appears to provide an alternative to conventional nasal mask anaesthesia, with better overall oxygenation and would seem particularly suitable for prolonged or difficult extractions.

Airway Obstruction↗
PubMed1978

Simultaneous pure-tone masking: the dependence of masking asymmetries on intensity.

Phase locking between probe and masker was used in a series of pure-tone masking experiments. The masker was a stationary sine wave of variable frequency; the probe a fixed-frequency tone burst. We have observed that for small frequency separation the masking behaves asymmetrically around the probe frequency. This asymmetry depends on intensity. For a 1-kHz probe at low stimulus levels there is a maximum masking effect at about 60 Hz above the probe frequency, whereas at high levels maximum masking is produced at a frequency definitely below the probe frequency. These results are discussed in relation to current neurophysiological and psychophysical data. For the high-level assymetry possible interpretations are suggested in terms of two changes in the excitation pattern of the basilar membrane, (a) a shift of the top and/or (b) a slope asymmetry, both increasing with level. The low-level asymmetry will be treated in a second paper [Vogten, J. Acoust. Soc. Am. 63, 1521-1528 (1978)].

Auditory Perception↗
PubMed1991

Comodulation masking release and the masking-level difference.

An experiment was performed to determine if the mechanism that mediates comodulation masking release (CMR) is associated with that used to improve detection by the masking-level difference (MLD). The experiment consisted of first improving detectability of a masked diotic tone burst by adding a synchronous noise band at another frequency region (CMR), and then measuring an MLD in the usual manner, by inverting the tone-burst signal to one ear. Results indicate that a substantial MLD can be measured for a signal whose detectability has already been improved by CMR. However, that MLD (9 dB) is smaller than that measured in random noise (14 dB). Put another way, a small CMR (4 dB) can be produced even when the detectability of a stimulus has already been improved due to the MLD. These data are in general agreement with those of Hall et al. [J. Acoust. Soc. Am. 83, 1839-1845 (1988)] and Schooneveldt and Moore [J. Acoust. Soc. Am. 85, 262-272 (1989)].

Adolescent↗
PubMed1991

Modification of an aerosol mask to provide high concentrations of oxygen in the inspired air. Comparison to a nonrebreathing mask.

With a few simple modifications, an aerosol mask was adapted to deliver high concentrations of oxygen. We compared the delivery of high concentrations of oxygen by this modified aerosol mask (MAM) with that of a nonrebreathing mask (NRM) in five normal volunteers and six patients with respiratory failure. Besides improved oxygenation, the MAM also permitted the following: humidification of the inspired oxygen, nebulization of bronchodilators, oropharyngeal suctioning, and performance of fiberoptic bronchoscopy. In lieu of intubation and mechanical ventilation, MAM may be a better alternative to a NRM for maintaining adequate oxygenation until the clinical situation improves.

Adult↗
PubMed1992

Life masks and death masks.

The death of a relative or anyone in a small, tightly knit community with closely shared cultural and religious values has great social impact. As part of the grieving process, people wish to preserve the memory of a loved one or a community leader. Life masks and death masks have been used as art forms to mark life passages, offering permanent reminders of family and continuity with the past. This article discusses the history and technique of life and death masks and their role in 19th-century American culture.

Funeral Rites↗
PubMed1990

Masking of tone bursts by modulated noise in normal, noise-masked normal, and hearing-impaired listeners.

Threshold of 4.6-ms tone bursts was measured in quiet and in the presence of a 100% sinusoidally amplitude-modulated speech-shaped noise. For the modulated-noise conditions, the onset of the tone burst coincided either with the maximum or the minimum modulator amplitude. The difference in these two masked thresholds provided an indication of the psychoacoustic modulation depth, or the modulation depth preserved within the auditory system. Modulation frequencies spanning the modulation spectrum of speech (2.5 to 20 Hz) were examined. Tone bursts were 500, 1400, and 4000 Hz. Subjects included normal listeners, normal listeners with a hearing loss simulated by high-pass noise, and hearing-impaired listeners having high-frequency sensorineural hearing loss. Normal listeners revealed a psychoacoustic modulation depth of 30-40 dB for the lowest modulation frequencies which decreased to about 15 dB at 20 Hz. The psychoacoustic modulation depth was decreased in the normal listeners with simulated hearing loss and in the hearing-impaired listeners. There was general agreement in the data, however, for the latter two groups of listeners suggesting that the normal listeners with hearing loss simulated by an additional masking noise provided a good representation of the performance of hearing-impaired listeners on this task.

Adult↗
PubMed1991

The development of the Laryngeal Mask--a brief history of the invention, early clinical studies and experimental work from which the Laryngeal Mask evolved.

The history of the invention and development of the Laryngeal Mask in the East End of London during the years 1981-88 is briefly described. The concept evolved from home-made prototypes built from the Goldman Dental Mask through a complex series of one-off latex models culminating in a primitive factory-made silicone cuff in 1986. This work defined the design parameters necessary to reconcile the needs for safety, reliability and ease of insertion while at the same time exploring the limits to possible use. In early 1988 the final version was tested by the inventor who had by this time used the device in more than 7500 patients undergoing routine surgery. From this experience a number of important lessons were learned relating to safe and effective use, which are summarized in the inventor's Instruction Manual. The importance of referring to this volume before use is stressed.

Anesthesiology↗
PubMed1991

[The laryngeal mask: a new alternative to the facial mask and the endotracheal tube].

The laryngeal mask is a new airway system for use under anaesthesia which assumes a position between the face mask and the endotracheal tube. Employment of this system achieves several of the advantages of intubation while the disadvantages are avoided. The possibilities which this system offers in cases of difficult intubation are particularly interesting, especially in unexpected.

Anesthesia, Endotracheal↗
PubMed1992

Physiological studies of central masking in man. II: Tonepip SSRs and the masking level difference.

The auditory steady-state response (SSR), an evoked response generated in the auditory cortex, was initiated by monaural trains of 500-Hz tonepips repeated at rates near 40 Hz while wideband noise was being delivered to the same or opposite ear. Contralateral noise reduced SSR amplitudes in an intensity-dependent manner, whereas ipsilateral noise enhanced the SSR amplitudes at low levels and depressed them at high levels. Systematic phase changes accompanied the amplitude changes. These results, obtained with tonepips, closely resemble those previously reported for clicks. A third experiment, a masking level difference (MLD) experiment, examined changes in the SSR measures during four successive tonepip-plus-noise conditions: (1) monaural tonepips alone; (2) adding ipsilateral noise; (3) then adding contralateral noise; (4) finally, adding contralateral tonepips. The SSR amplitude changes measured in the experiment did not always correspond with the changes in perception reported by the subject.

Acoustic Stimulation↗
PubMed1991

[Psychological disorders masked as physical symptoms. Problems in the diagnosis of masked depression].

In unclear clinical pictures, the diagnosis "masked depression" is often made, and forms the basis for anxiolytic and antidepressive drug treatment. What is required, however, is a positive diagnosis of a functional syndrome with predominance of a depressive symptomatology. This diagnosis is not simply based on vegetative symptoms, but also has to include psychological and psychodynamic criteria. This consideration of the patient's subjective reality is necessary for a stable therapeutic alliance, especially since therapy is a long-term undertaking.

Affect↗
PubMedDate not supplied

[Psychotic masked depression or black mask for depression].

We have used as depression criteria those of Pichot and Hassan, described during the Sint-Moritz Symposium in 1973 on masked depression. According to their clinical experience in Zaïre and Senegal, the authors consider the possibility that the "bouffée délirante" (acute psychotic reaction), frequent in black Africa, is in fact a manifestation of depression. They remind the five criterias of Pichot and Hassan, i.e.: 1 degree evidence of depression symptoms; 2 degrees a background and a particular underlying personality; 3 degrees evolutional characteristics; 4 degrees familial antecedents and hereditary factors; 5 degrees the response to antidepressive treatment. They present ten cases of acute psychosis: five from Zaïre and five from Senegal. These ten patients have been successfully treated with antidepressive drugs imipramine type, without any neuroleptic drugs; the outcome has always been a rapid remission. Some socio-cultural references are described; it permits to better comprehend the psychological frame of African people. An attempt to psychodynamically interpret the results ends the article.

Adolescent↗