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At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

The masked threshold to noise ratio in brainstem electric response audiometry: assessment of the conductive loss component by bone-conducted masking.

The aim of this study was to assess the conductive loss component (CLC) by brainstem electric response audiometry. A bone-conducted noise was used to mask out the response to a conventional air-conducted click stimulus. The difference between the levels of the click and the noise is defined as the masked threshold to noise ratio (MTNR). This MTNR was determined for 21 normal ears (MTNR = -13 +/- 5 dB). The increase in MTNR compared to this normative value is a measure of the CLC. For 10 ears with an artificially induced purely conductive loss, the increase in MTNR is in good agreement with the results of conventional pure-tone and brainstem electric response audiometry.

Acoustic Stimulation↗
PubMed1999

[Laryngeal mask as alternative to facial mask in the newborn].

OBJECTIVE: The present study demonstrates that the use of laryngeal mask airway (LMA) is an alternative to face-mask (FM) during induction of general anesthesia with halothane. In all patient the induction of general anesthesia is carried out by halotane and N2O/O2 50%, using only the LMA, preceding topical anesthesia of pharynx. METHODS EXPERIMENTAL DESIGN: prospective study. SETTING: this study was carried out at the surgical-division of the Pediatric Clinic, of University "La Sapienza", Rome. PATIENTS: a total of 80 newborns, average age 14.8 +/- 2.4 days and average body weight 2280 +/- 110 g were examined. INTERVENTIONS: newborns were submitted to surgery for congenital malformations, diagnostic research and positioning of a central venous catheter (CVC). MEASUREMENTS: Heart rate, non-invasive arterial pressure through cardiomonitor Hewlett Packard 78352A, oxygen saturation through Nellcor N3000, time of induction of general anesthesia and respiratory rate were assessed. RESULTS: Blood pressure and heart rate were increased during the positioning of LMA; oxygen saturation remained > or = 94% and respiratory rate was constant during the whole observation. Muscular relaxing, as an index of anesthesia, was observed after 33 +/- 1.5 sec after positioning of LMA. CONCLUSIONS: In the light of the results obtained, the use of the LMA for airway ventilation during the induction period of pediatric anesthesia is suggested.

Anesthesia, General↗
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↗
PubMedDate not supplied

A nasal mask for the Chinese (Rodrigo-Leung mask).

For people of Chinese descent, facial configuration differs from that of other Asians as well as Caucasians, and the standard nasal masks used in dentistry do not fit their faces well. A simple, easily sterilizable nasal mask has been developed for this purpose and is adaptable to existing nitrous oxide machines.

Anesthesia, Dental↗
PubMed1989

Binocular rivalry and dichoptic masking: suppressed stimuli do not mask stimuli in a dominating eye.

Reaction time was used to gauge the sensitivity of an eye during its dominant and suppressed phases of binocular rivalry. During dominance, performance was uniformly good in detecting both stimuli that were spatially identical to the suppressed stimulus and those that were different in spatial frequency. When suppressed eyes were tested, performance was poor when the stimulus was different from the dominating stimulus, but even worse when the test stimulus and the dominating stimulus were spatially identical. The results favor the view that suppression operates nonselectively on a monocular visual channel, prior to the point at which dichoptic pattern masking occurs.

Attention↗
PubMed2004

Size 2 ProSeal laryngeal mask airway: a randomized, crossover investigation with the standard laryngeal mask airway in paediatric patients.

BACKGROUND: One of the main concerns with the use of the standard laryngeal mask airway (SLMA) in small infants is that its low-pressure seal might be inadequate for positive pressure ventilation so that there is a risk of gas leakage into the stomach with the subsequent risk of regurgitation. The new ProSeal LMA (PLMA) has been shown to form a more effective seal than the SLMA and to facilitate gastric tube placement in adults. The first paediatric size PLMA became available recently. METHODS: Thirty anaesthetized, non-paralysed children aged 46 (19) months, weighing 16 (10-21) kg, were studied. The SLMA and PLMA were inserted in random order into each patient. Airway leak pressure and maximum tidal volume were measured. Ease of insertion, quality of initial airway and fibreoptic position were also determined. Gastric tube placement was assessed for the PLMA. RESULTS: The airway leak pressure and maximum tidal volume were significantly higher for the PLMA (P=0.001). Ease of insertion and quality of initial airway were similar for both devices. Air entry into the stomach occurred more frequently with the SLMA (P=0.005). Gastric tube placement was possible in all patients. CONCLUSIONS: The size 2 PLMA offered some advantages over the same size of SLMA in this crossover investigation. The high reliability of gastric tube placement and the significantly increased airway leak pressure might have important implications for use of this device for positive pressure ventilation in infants.

Air Pressure↗
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↗
PubMed1993

Comodulation masking release as a function of type of signal, gated or continuous masking, monaural or dichotic presentation of flanking bands, and center frequency.

Thresholds were measured for detecting a signal centered in a narrow-band noise (NBN) masker (on-frequency band, OFB), for the OFB alone, and with two flanking bands (FBs) added to the OFB, one centered above and one below the OFB. The FBs were either correlated with the OFB or were independent and were presented either to the same ear as the signal plus OFB (monaural condition) or to the opposite ear (dichotic condition). The OFB and FBs were either gated with the signal, or were presented continuously. Three signal types were used: a pure tone; an NBN uncorrelated with the OFB; and an NBN correlated with the OFB. The signal was centered at 0.5, 2, or 6 kHz. Comodulation masking release was estimated either as the difference between threshold with the OFB alone and with the OFB plus correlated FBs [CMR(R-C)], or as the difference between thresholds using correlated and uncorrelated FBs [CMR(U-C)]. Although there were marked individual differences, positive CMR(R-C) values were found in all conditions for all three signal types. CMR(U-C) values were often larger than those for CMR(R-C), reflecting the fact that the uncorrelated FBs tended to produce interference effects, especially for the gated maskers, and at 6 kHz. Values of CMR were larger and more consistent across subjects for continuous than for gated maskers. For continuous maskers, the values of CMR tended to be smallest for the correlated-NBN signal. Results are discussed in terms of available cues and in terms of perceptual grouping mechanisms.

Acoustic Stimulation↗
PubMed1995

Phase effects in masking related to dispersion in the inner ear. II. Masking period patterns of short targets.

This article investigates how the amplitude and phase characteristics of the inner ear influence the spectrotemporal representation of harmonic complex sounds. Five experiments are reported, in each of which three sets of maskers are compared that differ only in their phase spectra. The amplitude spectra of the complexes were flat and the phase choices were (a) zero phase, (b) Schroeder phases with a positive sign, and (c) Schroeder phases with a negative sign. In the first four experiments, the spectra contained all harmonics between 200 and 2000 Hz. In experiments 1 and 2, the signal frequency was fixed at 1100 Hz and the fundamental frequency of the maskers was varied. In experiments 3 and 4, the fundamental frequency of the maskers was fixed and the signal frequency varied between 200 and 2000 Hz. In experiments 1 and 3, the signal duration was long compared to the period of the maskers. In experiments 2 and 4, the signal duration was only 5 ms and thresholds were determined for different time points within the masker's period. The results show a strong correlation between the minima of the short signal's thresholds and the threshold of the long signal. In experiment 5, the spectral extent of the masker was shifted to values one octave lower (100 to 1000 Hz) or one or two octaves higher (400 to 4000 Hz and 800 to 8000 Hz, respectively). For each spectral region, masked thresholds of a long signal were obtained for three values of the fundamental frequency. In all five experiments the thresholds depended very much on the specific phase choices with differences of up to 25 dB. The masker with a negative Schroeder phase always led to the highest thresholds. The thresholds of the masker with a positive Schroeder phase, on the other hand, were for a wide range of parameters lower than the thresholds for the zero-phase masker. These phase effects are most likely caused by the phase characteristic of the basilar-membrane filter, which affects the flat envelopes of the two Schroeder-phase maskers in a very different way. For an appropriate choice of parameters, one of the two becomes even more strongly modulated than the zero-phase complex. This latter observation imposes some restrictions on the second derivative (curvature) of the phase-versus-frequency relation for the auditory filters.

Adult↗
PubMed2005

A randomized crossover comparison of the size 2 1/2 laryngeal mask airway ProSeal versus laryngeal mask airway-Classic in pediatric patients.

The laryngeal mask airway (LMA)-ProSeal (P-LMA) forms a more effective seal than the LMA-Classic (C-LMA) and facilitates gastric tube (g-tube) placement in adults. The first pediatric sizes of P-LMA recently became available. In 30 anesthetized, nonparalyzed children, aged 7.7 +/- 2 yr and weighing 27 (20-35) kg, we inserted the size (1/2) P-LMA and C-LMA in random order. Ease of insertion, quality of initial airway, fiberoptic position, airway leak pressure, and maximum tidal volume were determined. G-tube placement was assessed for the P-LMA. Ease of insertion was similar for both devices. The quality of the initial airway was better for the P-LMA (P = 0.01). Airway leak pressure in neutral head position (22.6 versus 18.5 mbar; P = 0.003), maximum flexion (37 versus 26.3 mbar; P < 0.001), maximum extension (15.2 versus 13 mbar; P = 0.045), and maximum tidal volume (1088 versus 949 mL; P = 0.002) were significantly better for the P-LMA. Air entry into the stomach occurred with the C-LMA but not with the P-LMA (P = 0.014). G-tube placement was possible in all patients. The reliability of g-tube placement and the significantly increased airway leak pressure found in this investigation might have important implications for use of the size (1/2) P-LMA for positive pressure ventilation in children.

Anesthesia, General↗
PubMed1985

The binaural masking level difference as a function of frequency, masker level and masking bandwidth in normal-hearing and hearing-impaired listeners.

Binaural masking level differences (MLDs) were measured for 10 normal-hearing and 10 cochlear-impaired listeners, at 500 and 2 000 Hz. Maskers were either wide-band (approximately 2 000 Hz), or narrow-band (50 Hz). For wide-band maskers the noise pressure spectrum level was 50 dB/Hz, and for the narrow-band maskers the noise levels were 50 and 60 dB/Hz. At 500 Hz the hearing-impaired listeners show abnormally low MLDs in wide-band noise, but not in narrow-band noise. At 2 000 Hz, the hearing-impaired subjects show abnormally low MLDs only in narrow-band noise at the 50 dB/Hz level. The clinical implications of the results are considered.

Auditory Perception↗
PubMed1998

Masking-level differences in older adults: the effect of the level of the masking noise.

In Experiment 1, masking-level differences (MLDs) for a 500-Hz tone at five masker levels were obtained from younger and older adults. For both age groups, there were no reliable increases in MLD once the spectrum level of the masker exceeded 27 dB SPL. MLDs were larger for younger than for older adults over the range of masker levels tested. In Experiment 2, the levels of both the signal and the masker in one ear were attenuated by either 15 or 30 dB relative to their level in the other ear, which was fixed at a spectrum level of 47 dB SPL. MLDs for both age groups declined with increasing IAA and age-related differences were observed in all conditions. The findings of these experiments indicate that (1) age-related differences in MLDs exist even when the level of the masker is sufficiently high that older adults achieve their plateau performance, and (2) older listeners are not disadvantaged more than younger listeners by interaural differences in the level of the input.

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↗