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At least 1,279 records · Page 71Linked to original sources
PubMed2000

The submental route revisited using the laryngeal mask airway: a technical note.

The submental route for endotracheal intubation is well known and this paper reports the use of the same route for the laryngeal mask airway. This technique can be used whenever it is considered too awkward to perform submental, transoral or transnasal endotracheal intubations. When the surgery has been completed, the mouth is left open to allow the laryngeal mask to be removed; it cannot be left in place in cases of intermaxillary fixation. It is necessary to detach the laryngeal mask orally, never submentally, as it is impossible to remove the mask via the submental route.

Dissection↗
PubMed2004

[The positioning of reinforced laryngeal masks (LMA) with the "Zerer-introducer"].

OBJECTIVE: Correct and rapid positioning of reinforced laryngeal masks (LMA) is often a problem in anaesthetics. Although different techniques have been developed, none of them are satisfactory. A newly designed introduction device was used to place reinforced laryngeal masks. These are first results of a clinical observational study. METHODS: A special fork fixed on a handhold was constructed. The introduction of the LMA was possible in an arched movement down to the hypopharynx using appropriate sizes for different sizes of LMA's. RESULTS: The intubation in 500 surgical cases (30 % adult, 70 % children, mostly in ENT-surgery) was easy and rapidly performed. A leading finger for placement was not necessary. There were neither cases of rotation nor retrograde flexion of the top of the mask. Direct vision by the ENT-specialist revealed no evidence of any injuries of the palate or throat. CONCLUSION: A newly designed introduction device allows a fast and efficient placement of reinforced laryngeal masks and contributes to the safety of this mode of application.

Adult↗
PubMed1997

[Experiences with use of the laryngeal mask with flexible, wire reinforced tube for ENT interventions in childhood].

UNLABELLED: This is a report on experiences regarding the use of the reinforced laryngeal mask airway for 121 minor operations in paediatric otolaryngology. By far the most interventions were adeno-tonsillectomies (104), which until now were performed under general anaesthesia with tracheal intubation. RESULTS: The rate of observed complications was surprisingly low. 117 children were able to undergo their operation using the laryngeal mask airway. Tracheal intubation became necessary four times (failure to bring laryngeal mask into position occurred twice, laryngospasm occurred once, cough/pressing caused by lack of adequate depth of anaesthesia in two cases). In five cases there were problems of ventilation (4.1%), provoked by the Boyle-Davis gag. Seven children complained of postoperative sore throat, a complication that could be avoided later by measuring the cuff pressure (25-70 cm H2O). Aspiration was not observed in any of the cases. The complete absence of choking or pressing was regarded as particularly favourable by both the anesthetist and the surgeon. CONCLUSION: The use of the reinforced laryngeal mask airway during paediatric otolaryngological operations in the hand of an experienced anaesthetist appears to be a promising alternative to tracheal intubation and merits more widespread use.

Adenoidectomy↗
PubMed1996

[Ventilation via a transnasally placed pharyngeal tube. Comparison with mask ventilation].

OBJECTIVE: The present prospective study was designed to investigate the respiratory function during ventilation via a tube inserted through the nose into the pharynx. Results were compared with respiratory parameters measured during conventional mask ventilation in the same patients. METHODS: 20 ASA physical status I-II patients were studied after approval by the local Ethics Committee. Anaesthesia was induced with alfentanil 15 micrograms/kg and propofol 2.5-3.0 mg/kg and maintained with propofol, 12-15 mg/kg/h. Patients were ventilated via a facemask with oxygen and a tidal volume of approximately 8ml/kg (measurement A). After insertion of a tube (I.D. 7.0-7.5 mm) through the nostril into the pharynx ventilation was repeated in the same manner (measurement B). To secure airway seal a second person closed the patient's mouth and exerted cricoid pressure. Following neuromuscular blockade with suxamethonium (1.5 mg/kg) respiratory parameters were measured again (C). Measurements included pulse oximetry and side stream spirometry with continuous collection of the following data: airway pressure, inspired and expired tidal volume, dynamic compliance, expired volume in one second, inspiratory and expiratory oxygen and carbon dioxide concentration. Pressure-volume and flow-volume loops were displayed continuously. RESULTS: Ventilation via facial mask or via pharyngeal tube with and without relaxation showed normal endtidal FECO2. The mean values were 4.5 +/- 0.7%, 4.8 +/- 0.4% and 4.6 +/- 0.7%, respectively. Mean oxygen saturation exceeded 98% in each period. Leakage during mask ventilation was 59.3 +/- 65.5 mL and decreased to 40.5 +/- 62.1 mL with the pharyngeal tube, whereas relaxation resulted in a significant increase to 92.3 75.0 mL. Compliance (Cdyn) and expired volume in one second (V 1.0) did not change significantly during the entire period of measurement. CONCLUSION: The use of a pharyngeally placed tube proved adequate compared to conventional mask ventilation in 20 patients without underlying airway disease.

Adolescent↗
PubMed1995

[Diagnosis of endolymphatic hydrops with low tone masked otoacoustic emissions].

BACKGROUND: A new method of diagnosis of endolymphatic hydrops by recording low-tone masked evoked otoacoustic emissions (TEOAE) is presented. METHODS: A short acoustic stimulus and a masker tone of 30 Hz are applied in an adjustable phase relation simultaneously to the same ear. In the normal hearing ear the masker shows little influence on the TEOAE at 0 degrees, whereas the suppression at phase 270 degrees (maximal rarefaction at the eardrum) is nearly complete. However, in cases of endolymphatic hydrops this masking effect is reduced or absent, indicating impaired mobility of the basilar membrane. RESULTS: The masked TEOAE were recorded of patients with normal hearing, Menière's disease, and sudden hearing loss without vertigo. In Menière cases with supposed endolymphatic hydrops, the amplitude modulation of the emissions was found to be much less than in the other groups. CONCLUSIONS: Where TEOAE can be recorded, low-tone masking is a quick, objective, and noninvasive method for the diagnosis of endolymphatic hydrops.

Acoustic Stimulation↗
PubMed1993

[The laryngeal mask versus intubation in difficult intubation conditions in the Franceschetti-Zwahlen-Klein syndrome (Treacher-Collins syndrome)].

A twenty-nine-year-old man suffering from Franceschetti syndrome requiring a retinal detachment operation was successfully anaesthetised using the laryngeal mask airway. The laryngeal mask has many advantages compared to endotracheal intubation in patients suffering from craniofacial abnormalities i.e. hypoplasia of the mandibular bone and ventral position of the larynx. In these cases the laryngeal mask is easily placed. However, the facilities of fibreoptic bronchoscopy should be readily available. The physician should have gained confidence in using a laryngeal mask before employing this device in cases of difficult intubation.

Adult↗
PubMed1980

Evidence for the role of attentive fields in masking.

A masking task was employed to determine whether predictions derived from the attentive-field postulate of assimilation theory could be verified. The distance between masking and test lines was varied both towards and away from the center of the attentive field. As predicted, masking was greater when the mask was near the center of attention than when it was located at the periphery of the field. A variation of the mathematical formula developed previously to predict visual illusions was employed to fit the individual and group functions found in this study.

Attention↗
PubMed1984

Summation of target and mask metacontrast stimuli.

Three experiments are reported; they show the following: (i) Metacontrast occurs at high photopic conditions (250 cd m-2); at this luminance the function peaks at stimulus asynchronies of approximately 40 ms (compared with 100 ms at lower luminances). (ii) The strength of metacontrast is contrast-independent, down to contrast very near detection threshold. (iii) Detection thresholds for the combined target and mask presentation are lower than those for the mask alone, implying summation between target and mask. Summation is greatest at the same asynchronies which yield maximum metacontrast masking. The experiments are taken as evidence in favour of a fusion explanation for metacontrast. An argument is made which implicates temporally units of the motion detection system as being instrumental in the fusion process.

Humans↗
PubMed1987

Masking by uniform field flicker: some practical problems.

The technique of uniform field flicker (UFF) masking has frequently been used to address issues concerning the relative performance of sustained and transient neural channels in the human visual system. Unfortunately there has been an artifact in the implementation of this method in most published experiments which has meant that the contrast of the target has been flickered in synchrony with the mean luminance. A study is reported in which the artifact was corrected and the effects of UFF masking on the contrast sensitivity function then examined. With this correction, masking was still restricted to low spatial frequencies but it was much weaker than reported originally. It is argued that the original evidence suggesting that UFF masking can be used to examine the functioning of transient and sustained channels has not been interpreted correctly and that the basis for such a claim is weak.

Adult↗
PubMed2005

Chromatic masking revealed by the standing wave of invisibility illusion.

We have used the standing wave of invisibility illusion (Macknik and Livingstone, 1998 Nature Neuroscience 1 144-149) to examine the masking effects produced by a range of stimuli of varying chromatic and luminance contrast content. The pattern of masking was highly selective. Maximum effects were always obtained when the target and mask were identical in terms of their chromatic and/or luminance contrast composition, but were reduced as the angular separation in colour space between them was increased. Masking was of a monopolar nature, indicating the operation of rectified mechanisms selective for different combinations of colour and luminance contrast.

Color Perception↗
PubMed2001

The vestibular evoked response to linear, alternating, acceleration pulses without acoustic masking as a parameter of vestibular function.

In this study, short latency vestibular evoked potentials (VsEPs) were recorded in five guinea pigs in response to alternating linear acceleration pulses with and without acoustic masking. A steel bolt was implanted in the skull and coupled to a shaker. Linear acceleration pulses (n = 400) in upward, downward or alternating directions were given, with a peak acceleration of 4g after 0.5 msec. Tests were repeated with acoustic masking, after modiolus destruction and after application of KCl in the vestibule. Stimuli of the vestibular nerve were recorded with a platinum electrode in the bony facial nerve canal in the bulla. Unilateral linear acceleration showed a shallow plateau at 0.5 msec, which disappeared with alternating acceleration impulses and after modiolus destruction. Therefore all further tests were done with alternating impulses. After a latency time of 0.8 msec a multiwave response was seen, with a first positive peak P1 at 1.16 ms. These were followed by other positive and negative peaks (N1, P2, N2, P3, N3). With the elimination of cochlear influences by using acoustic masking, P1 remained stable, while subsequent peaks were altered or eliminated. After modiolus destruction, the P1 peak remained, although with a smaller amplitude due to vestibular damage. After application of a saturated KCl solution in the vestibule all responses, including P1, disappeared, thus confirming the vestibular origin of these responses. We conclude that the onset latency of the VsEP and the peak latency and level of the first positive peak P1 in response to alternating linear acceleration pulses without acoustic masking, measured in the facial canal, are good and stable parameters of vestibular function in guinea pigs.

Animals↗
PubMed1999

Effect of white noise "masking" on vestibular evoked potentials recorded using different stimulus modalities.

Short latency vestibular evoked potentials (VsEPs) to linear acceleration impulses (L-VsEPs) are initiated in the otolith organs (saccule and utricle). Some of the saccule afferents have been reported to respond not only to linear acceleration, but also to high intensity acoustic stimuli. If so, the L-VsEP recorded from the saccule (elicited with the stimulus orientated relative to the head so as to optimally activate the saccule, i.e. stimulus in the vertical plane, Z-VsEP) should be reduced during high intensity broad band noise (BBN) "masking". Conversely, the utricular afferents have been reported to be less auditory-sensitive. Therefore, an L-VsEP which is mainly utricular in origin (stimulus in the horizontal plane, X-VsEP) should be less affected by this noise "masking". This was investigated in rats by recording X-VsEPs and Z-VsEPs and angular VsEPs (A-VsEPs), originating in the lateral semi-circular canals, before, during and after exposure to short duration, high intensity (113 dB SPL) BBN. This intensity completely masked auditory nerve evoked responses. The Z-VsEP did appear to be slightly more affected by the noise "masking" than the X-VsEP, implying the presence of more auditory-sensitive elements in the saccule. The A-VsEP was also affected by the BBN. The overall effect was relatively small (on average, 10-25% depression of the first wave of the different VsEPs). The responses showed recovery 5 min later.

Animals↗
PubMed2002

Locus of inhibition in the masked priming of response alternatives.

Masked prime stimuli presented immediately before target stimuli in a choice reaction task give rise to behavioral costs when the primes and the target stimuli are mapped to the same response and result in benefits when they are mapped to opposite responses. Researchers assume that this negative compatibility effect reflects inhibitory processes in the control of perceptuomotor links. The authors investigated whether the inhibition operates at the level of abstract central codes or at effector-specific motor stages. In 2 experiments (N = 8 participants in each), left or right hand or foot responses were required to target stimuli that were preceded by masked arrow primes mapped to the same response side as the target stimuli in compatible trials and to the opposite response side in incompatible trials; the primes were irrelevant in neutral trials. In Experiment 1, when the masked primes determined both response side and modality, there was no transfer of negative compatibility effects across response modalities. That finding is inconsistent with a central abstract locus of inhibition and suggests that inhibition operates at effector-specific motor stages. In Experiment 2, primes conveyed only response side information but left response modality uncertain, and negative compatibility effects were elicited for both hand and foot responses, suggesting that partially informative masked primes can trigger a parallel activation and subsequent inhibition of response processes within separate effector systems.

Adult↗
PubMed1998

Masking effects and tinnitus as explanatory variables in hearing disability.

In cases of substantial auditory handicap, the degree of pure-tone hearing loss or hearing loss for speech is seen as the primary determining factor. Sometimes the presence of tinnitus complaints and disproportionate masking effects of noise on speech reception are seen as aggravating factors. To investigate the relevance of tinnitus and masking effects in the context of hearing disability, four factorial designs with self-perceived hearing disability as the dependent variable were submitted to an analysis of variance. Impact of masking and tinnitus complaints were treated as independent variables with two levels and were each combined with a second independent variable to form a 2 x 2 fixed factor statistical model. This second independent variable was either hearing loss for pure tones (first and second model) or speech reception ability (third and fourth model). Both hearing loss for pure tones and speech reception capability were found to be significant explanatory factors for hearing disability. Impact of masking, if juxtaposed to average pure-tone hearing loss (first model), also came out of the analysis as a significant factor in hearing disability, whereas the tinnitus factor did not reach significance levels. No significant interactions between factors were found. The results support the idea of the differentiating audiogram-based disability estimates by taking noise susceptibility into account. The findings also suggest in an equivocal relation of tinnitus with hearing disability, which prevents it from being a straightforward disability predictor.

Aged↗
PubMed2001

The attentional blink is immune to masking-induced data limits.

The attentional blink is the robust finding that processing a masked item (T1) hinders the subsequent identification of a backwards masked second item (T2), which follows soon after the first one. There has been some debate about the theoretically important relation between the difficulty of T1 processing and the ensuing blink. In Experiment 1 we manipulated the difficulty of T1 in such a way as to affect the quality of data without altering the amount of resources allocated to its identification. We found no relation between the accuracy of T1 identification and the blink. In Experiment 2, the same difficulty manipulation was applied to T2, and we observed an additive pattern with the blink. Together, this pattern of results indicates that a data-limited difficulty manipulation does not affect the blink, whether applied to T1 or T2. In Experiment 3 we used an individual differences methodology to show that performance in the traditional "stream"-like presentation (rapid serial visual presentation) was highly correlated with performance in our modified "target mask, target mask" paradigm, thus allowing for comparisons beyond the present methodology to much of the previous literature that has used the stream paradigm.

Adult↗
PubMed2000

Feasibility study of prolonged ozone inhalation exposure via face mask.

Because of the interest attendant to establishing an 8-h ozone (O(3)) federal air quality standard, acute pulmonary function responses to prolonged (6.6 to 8 h) O(3) exposure between 0.08 and 0. 24 ppm have been examined in chamber studies. Given time constraints for O(3) concentration changes in room-sized chambers and the need to simulate rapid fluctuations in O(3) levels, such as occurs when one goes from indoors to outdoors during an air pollution episode, mouthpiece or face-mask exposure systems offer potential advantages over chamber exposure systems. In a recent study in this laboratory, subjects indicated that over 2 h of continuous exposure via an obligatory mouthpiece inhalation system (with noseclip) was more than they could tolerate with this type of exposure system. The purpose of this study was to compare O(3)-induced responses observed following 2-h exposures via an obligatory mouthpiece inhalation system and a newly devised face-mask exposure system, and to determine whether the latter could be tolerated during 4-h exposures. Six young adults completed 5 experimental protocols (three 2-h and two 4-h) while exposed to O(3) concentrations ranging from 0.00 ppm (filtered air) to 0.24 ppm. Exercise and resting minute ventilation (V(E)) were measured continuously. Pulmonary function, subjective symptoms (SS) of breathing discomfort, and exercise ventilatory pattern responses were obtained. Exposure to 0.24 ppm O(3) with intermittent exercise (IE) for 2 h via a newly devised inhalation system, consisting of a nylon plastic non-rebreathing respiratory valve and a silicone rubber face mask with Teflon overlay on the inner surface, yielded pulmonary function, SS, and exercise ventilatory pattern responses nearly identical to those obtained in the same O(3) exposure effected via a Teflon-coated Hans-Rudolph respiratory valve obligatory mouthpiece inhalation system. It was concluded that the newly devised face-mask inhalation system was well tolerated by all subjects during the 4-h exposure protocols, with each subject indicating that longer 6.6-h exposures with this system would be tolerable.

Administration, Inhalation↗
PubMed2003

Comparison of chamber and face mask 6.6-hour exposure to 0.08 ppm ozone via square-wave and triangular profiles on pulmonary responses.

Recently, a stainless-steel air pollution chamber was acquired in this laboratory, and data were obtained in a study that convincingly demonstrated that chamber and face-mask inhalation methods of exposing young adult subjects for 6.6 h to nearly identical total inhaled O(3) doses at 0.12 ppm produced very similar pulmonary function, symptoms, and exercise ventilatory pattern responses. However, the results of a 6.6-h face-mask exposure to 0.08 ppm O(3), compared to some previous chamber exposure study results, revealed several small incongruities that may be due primarily to high individual subject "noise" in responses to a relatively low O(3) exposure. To resolve these differences, it was the primary purpose of this study to compare chamber exposure responses to those elicited via face-mask exposure to 0.08 ppm O(3) for 6.6 h with subjects serving as their own controls. Two types of O(3) exposure patterns were used: (1) the usual square-wave profile, and (2) an acute triangular profile, in which O(3) concentration was increased each hour from 0.03 ppm to 0.15 ppm during h 4 and then decreased each hour to 0.05 ppm (mean = 0.08 ppm). Thirty young adults (15 of each gender) served as subjects. The two exposure methods (i.e., face mask and chamber) yielded near identical total inhaled O(3) doses in both the square-wave and triangular exposure profiles, and produced very similar postexposure pulmonary function, symptoms, and exercise ventilatory pattern responses. However, pulmonary function and symptoms responses became statistically significant from preexposure at the end of h 4 (when [O(3)] = 0.15 ppm) in the triangular protocols, but not until h 6 in the square-wave protocols. These results support previous evidence that O(3) concentration has a greater singular effect in the total inhaled O(3) dose than do V(E) and exposure duration.

Adult↗
PubMed2005

Evaluation of phoneme compression schemes designed to compensate for temporal and spectral masking in background noise.

The effect of phonemic compression has been studied on speech intelligibility in background noise in hearing-impaired listeners with moderate-to-severe high-frequency losses. One configuration, anti-upward-spread-of-masking (anti-USOM) focuses on a release from spectral masking of high-frequency speech cues by selective spectral tilting. Release from temporal masking is the main goal of a second configuration, high-pass filtered compression (HFC), which reduces the speech modulations within a high-pass filtered compression channel. Speech intelligibility was measured with consonant-vowel-consonant (CVC) words in a multi-talker babble and a single-talker background noise. Anti-USOM has a significant negative effect on the phoneme scores in background noise. HFC compression tends to improve vowel intelligibility in a single-talker background noise, especially for the listeners with a relatively poor speech score. In a multi-talker babble noise the effects of HFC compression tend to be negative. It can be concluded that no significant release from spectral or temporal masking is obtained by the applied processing.

Adult↗