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At least 811 records · Page 45Linked to original sources
PubMed2000

Breath-synchronized nebulization diminishes the impact of patient-device interfaces (face mask or mouthpiece) on the inhaled mass of nebulized budesonide.

The choice of patient-device interface (face mask or mouthpiece) influences the inhaled mass and the lung deposition of nebulized drugs. The use of a mouthpiece has been shown to double the lung deposition compared with use of a face mask. We have determined the inhaled mass of budesonide using a jet nebulizer with mouthpiece in either a constant output or breath-synchronized mode in children. We have also determined the inhaled mass when the jet nebulizer is used with a nonsealing face mask in a constant output mode. The study was a 1-day, randomized, crossover, single-center study involving 158 asthmatic children (age range 5.1-15.7 years). Nebulized budesonide was administered in three single nominal doses of 1.0 mg by means of a jet nebulizer. The inhaled mass of budesonide was defined as the amount of drug deposited on filters positioned between the nebulizer and the mouthpiece or face mask. The mean inhaled mass of budesonide from different age groups ranged from 1 7.1% to 21.6% of the nominal dose with breath-synchronized nebulization with a mouthpiece. With constant output nebulization with a mouthpiece, the mean inhaled mass ranged from 8.9% to 12.2%, and with a nonsealed face mask the mean inhaled mass ranged from 5.0% to 6.9%. For children using jet nebulizers with mouthpiece, breath-synchronized nebulization appears to be superior to conventional constant output nebulization. The use of jet nebulizers with nonsealing face masks should be avoided.

Administration, Inhalation↗
PubMed2005

Temporal properties in masking biological motion.

The perception of biological motion using point light animation techniques was investigated in several experiments. Animations simulating walking were presented with additional masking dots. The temporal properties of the walking motion or the temporal relationship between the walking and masking motions were systematically manipulated. Results showed that (1) perception of biological motion was sensitive to even small temporal perturbation within the walker, (2) the effectiveness of a mask depended upon the temporal phase difference between the mask and point light walker, (3) relatively small temporal differences between the mask and point light walker decreased the effectiveness of the mask, and (4) these effects were not due simply to observers detecting the phase offsets in the display. Temporal properties of the motion are important in perceiving the human form in action, just as in other types of figure-ground segregation. This information may be processed by both motion and form pathways for processing biological motion.

Humans↗
PubMed2004

On the relations between crowding and visual masking.

To study the question of which processes contribute to crowding and whether these are comparable to those of visual temporal masking, we varied the stimulus onset asynchrony (SOA) between target and flankers in a crowding setting. Monotonically increasing Type A masking functions observedfor small spacings and large eccentricities indicate that the integration of information from target and flankers underlies crowding. Decreasing masking functions obtained for large spacings and small eccentricities relate processes of crowding to those contributing to Type B masking. In addition, Type B masking was more frequent with letter-like nonletter flankers than with letter flankers, suggesting that Type B masking, just like crowding over large areas, is due to higher level interactions. The rapid decrease of the effects of interletter spacing and eccentricity with increasing SOA indicates that positional information is transient.

Fixation, Ocular↗
PubMed1999

Nonstrategic subjective threshold effects in phonemic masking.

Three backward-masking experiments demonstrated that the magnitude of the phonemic mask reduction effect (MRE) is a function of subjective threshold and that the magnitude is also independent of stimulus-based response strategies. In all three experiments, a target word (e.g., bake) was backward masked by a graphemically similar nonword (e.g., BAWK), a phonemically similar nonword (e.g., BAIK), or an unrelated control (e.g., CRUG). Experiments 1 and 2 had a low percentage (9%) of trials with phonemic masks and differed only in baseline identification rate. Experiment 3 controlled baseline identification rate at below and above subjective threshold levels, with 9% phonemic trials. The results were that identification rates were higher with phonemic masks than with graphemic masks, irrespective of the low percentage of phonemic trials. However, the magnitude of the phonemic MRE became large only when the baseline identification rate was below subjective threshold. The pattern of the phonemic MRE was interpreted as a result of rapid automatic phonological activation, independent of stimulus-based processing strategies.

Adult↗
PubMed1992

[Masking in bone-conduction testing--proposal of ABC method].

A new strategic masking technique, namely the ABC method, has been developed. In performing this method of measuring thresholds of bone-conduction, the vibrator is placed at the forehead with both ears occluded by air-conduction earphones. One of the earphones is for masking noise and the other is a dummy which balances out the occlusive effect of the test ear against the nontest ear. The ABC method is based on the ABC rule that, in bone-conduction testing, the effective masking noise level necessary to block out the nontest ear can be calculated by a simple equation: right AC (A) + left AC (B)--unmasked BCu (C) under the assumption that the BCu belongs to the nontest ear. In some cases of hearing loss, the above noise level might produce overmasking, then an additive safety noise level, BCu + Interaural Attenuation, is employed. This method offers testers step by step directions which consist of indications of the noise level and a criterion for determining whether the measured bone-conduction is free from cross hearing and overmasking for the given configuration of air-conduction of both ears, BCu, and the masking noise level. Compared to the well known Plato method, in which measurements of thresholds are repeated at several masking noise levels in order to find a single bone-conduction threshold, the ABC method can essentially find the threshold at only one masking noise level. Therefore the ABC method makes it possible to save a great deal of time in performing bone conduction testing.

Audiometry↗
PubMed1998

Tracheal intubation through the intubating laryngeal mask in a patient with a fixed flexed neck and deviated larynx.

Insertion of the conventional laryngeal mask is more difficult or impossible when the patient's head and neck are in either the neutral or flexed position. The intubating laryngeal mask is best inserted when the patient's head is supported by a pillow, without placing the head and neck into the Magill position; therefore, insertion of this modified mask may be less difficult than the conventional mask in the patient with a flexed neck. We report a case of successful insertion of the intubating laryngeal mask and subsequent tracheal intubation through the mask using a fibre-optic bronchoscope, in a patient with a flexed neck in whom tracheal intubation using several methods had been difficult previously.

Adult↗
PubMed1999

[Patil-Syracuse mask for fiberoptic intubation].

Patil-Syracuse mask, recently introduced in Japan, has a port for fiberscopy. A fiberoptic bronchoscope and an endotracheal tube can be passed through the port with little air leakage. Positive pressure ventilation can be continuously maintained using this mask during fiberoptic intubation. This mask is particularly useful when a patient can be easily ventilated through a face mask but the trachea is unexpectedly difficult to intubate. With a modified endoscopy mask technique, the mean expiratory tidal volume of 10 ml.kg-1 could be obtained during fiberoptic orotracheal intubation. We describe a fiberoptic intubation technique using this mask, and discuss the complications and limitations of this method.

Anesthesia, General↗
PubMed1999

Development of rivalry and dichoptic masking in human infants.

PURPOSE: To examine the development of rivalry, dichoptic masking, and binocular interactions in infants more than 5 months of age using the visual evoked potential (VEP). METHODS: VEPs were recorded in 35 infants between 5 and 15 months of age and 23 adults between 13 and 59 years of age. Counterphasing, sinusoidal, 1 cycle/deg gratings were presented dichoptically. Responses from each eye were isolated by "tagging" each half-image with a different temporal frequency (5 or 7.5 Hz). Observers were presented with fixed 80% contrast gratings in each eye in experiment 1. Rivalry was detected on the basis of a negative correlation between the simultaneously measured response amplitudes at the second harmonics of the two eye-tagging frequencies. In a second analysis of the same data, response amplitudes recorded under dichoptic viewing conditions were compared to those obtained in a monocular control condition (dichoptic masking). In experiment 2, a 40% fixed-contrast grating was presented to one eye, whereas the other eye viewed a grating that was swept in contrast from 1% to 67%. Dichoptic masking was measured as the reduction in the fixed-grating response caused by the variable contrast grating. RESULTS: Experiment 1: although adults showed evidence of VEP amplitude alternations between the eyes for cross-oriented half-images (physiological rivalry), infants did not. This immature response to rivalrous stimuli occurred despite the presence of responses at nonlinear combination frequencies recorded with gratings of the same orientation in each eye, a definitive indication of binocular interaction. In addition, both iso- and cross-oriented half-images produced less dichoptic masking in infants than in adults in this experiment. Experiment 2: dichoptic masking in the infants was equivalent to that seen in adults with parallel gratings in the two eyes; however, masking with cross-oriented configurations was approximately five times weaker in the infants relative to the adults. CONCLUSIONS: The authors have identified a set of stimulus conditions under which infants between 5 and 15 months of age fail to demonstrate physiological rivalry despite the presence of binocular interactions. The observed lack of binocular rivalry may be the result of a specific immaturity in dichoptic, cross-orientation suppression.

Adolescent↗
PubMed2000

[A comparison of bullard laryngoscope and intubating laryngeal mask using fiberoptic guidance for tracheal intubation].

The purpose of this study is to compare the success rate of tracheal intubation, intubation time and laryngoscopic view of the larynx by Bullard laryngoscope or by intubating laryngeal mask using fiberoptic guidance in 50 patients. Following a standardized induction protocol, conventional laryngoscopic view by Macintosh's laryngoscope was obtained and classified by Cormack's grades. We measured the times from incertion of laryngoscopy or laryngeal mask until obtaining the best view of the larynx and until tracheal intubation. A best view by Bullard laryngoscopy or by fiberoscopy through the laryngeal mask was classified by Cormack's grades. The success rate of tracheal intubation was higher by Bullard laryngoscopy than by intubating laryngeal mask. The durations of laryngoscopy and tracheal intubation were significantly shorter and Cormack's grades were significantly lower by Bullard laryngoscopy than by laryngeal mask and fiberscopy. These results demonstrate that tracheal intubation by Bullard laryngoscope is faster and more successful compared with intubating laryngeal mask using fiberoptic guidance.

Adolescent↗
PubMed1993

Fibreoptic bronchoscopy under general anaesthesia using the laryngeal mask airway.

The laryngeal mask airway was used to facilitate fibreoptic bronchoscopy under general anaesthesia in 140 adult patients. Following placement, the position of the mask was observed through the fibreoptic bronchoscope. Three different positions were identified. In 120 patients (86%) the concave surface of the mask faced the larynx directly with or without some unfolding of the epiglottis. In 17 patients (12%) the laryngeal mask appeared to be at an angle facing one pyriform fossa and in two patients the tip of the mask lay anterior to the arytenoids. No problems with ventilation or maintenance of an acceptable airway were encountered. In one patient repositioning of the laryngeal mask was necessary to allow the passage of the bronchoscope. One patient developed laryngospasm and required tracheal intubation.

Adolescent↗
PubMed1975

Anthropometric sizing program for oral-nasal oxygen masks based on 1967 U.S. Air Force survey data.

A new sizing program for oral-nasal masks, based on total facial length, has been developed through an analysis of the 1967 USAF anthropometric survey head and face data. A four-size series of three-dimensional face forms has been sculpted based on this sizing program as a design aid for sizing such masks. This report includes a discussion of the theoretical and practical aspects of the sizing analyses and procedures, and establishes design limits and procurement tariffs for the four sizes of masks. The MBU-12/P oxygen mask, an aoral-nasal pressure-demand type of mask, has been fabricated in accordance with this sizing system using the face forms as sizing guides. The results obtained during fit-tests using 66 USAF personnel as subjects are described. The authors concluded that the dimensional sizing of the oral-nasal oxygen mask facepieces is valid for USAF flight crews.

Aerospace Medicine↗
PubMed2002

[First clinical impressions of ProSeal laryngeal mask].

ProSeal laryngeal mask airway (PLMA, LMA-ProSeal) is a newly developed laryngeal mask airway intended to overcome two major disadvantages of the conventional laryngeal mask airway, i.e., poor protection of the airway from gastric regurgitation and low sealing effect around the laryngeal inlet. The new PLMA can provide air-tight sealing by a second cuff positioned at the back of the mask and a bypass channel for the alimentary tract by a second tube (drain tube) opening at the tip of the mask. However, clinical feature of this new device has been assessed by few authors. Forty adult patients (19 males and 21 females) under general anesthesia immobilized with vecuronium were included in this study. A PLMA size 4 was inserted with (n = 10) or without (n = 30) an introducer at first (n = 37), second (n = 2) or third (n = 1) attempt and clear airway was obtained in all patients. After placing the PLMA in 10 patients (5 males and 5 females) sealing pressure was measured at cuff pressure of 0, 20, 40 and 60 cmH2O and at completely deflated cuff state. Averaged seal pressure at the 60 cm H2O cuff pressure was 22.7 +/- 8.0 cmH2O in the all 40 patients. Averaged seal pressure was higher in female than in male at all cuff pressure. The average seal pressure was 15.1 cmH2O even when the cuff was deflated completely. A lubricated 16-French gastric tube was inserted easily through the drain tube in all patients except one in which the mask was found to be deflected backward. There were no significant complications related to the PLMA. We concluded that the PLMA can provide high sealing pressure and isolate the airway from the alimentary tract. Further study including adverse effect of the high sealing effect should be required.

Adult↗
PubMed2002

The laryngeal tube compared with the laryngeal mask: insertion, gas leak pressure and gastric insufflation.

BACKGROUND: We have compared the laryngeal tube and laryngeal mask in 22 patients for the success rate of insertion, gas leak pressure and the incidence of gastric insufflation. METHOD: In a randomized, crossover design, the laryngeal tube and laryngeal mask were inserted in turn after induction of anaesthesia and neuromuscular block. The cuffs were inflated until the intracuff pressure reached 60 cm H(2)O. We measured adequacy of ventilation and the minimum airway pressure at which gas leaked around the cuff. The presence or absence of gastric insufflation was studied at an inflation pressure of 20 cm H(2)O. RESULTS: It was possible to ventilate through the laryngeal tube in 21 patients and through the laryngeal mask in 21 patients. The mean leak pressure for the laryngeal tube (26 (SD 5) cm H(2)O) was significantly greater than that for the laryngeal mask (19 (4) cm H(2)O) (P<0.01; 95% confidence intervals for mean difference: 5.3-10.2 cm H(2)O). Gastric insufflation did not occur when the laryngeal tube was used and was noted in three patients when the laryngeal mask was used. CONCLUSION: The laryngeal tube provides a better seal in the oropharynx than the laryngeal mask.

Adolescent↗
PubMed2003

[Effect of forward masking on evoked potentials of auditory cortex in guinea pigs].

Thresholds of the event-related potentials (ERPs) appearance were measured for one stationary and four moving auditory images presented in silence or under forward masking conditions. The difference between thresholds in silence and after noise masker was considered as masking level. Under the forward masking, the amplitude of the ERP to the first click in the test series decreased in guinea pig auditory cortex. Masking level decreased with the time lag between signal and masker and didn't depend on the fused auditory image localization that corresponded to the first click in different test signals. This fact can support the hypothesis that for the long test signals the initial part can be masked more than the final one. The ERPs amplitude to next clicks in test series depended on interaction of two factors: forward masking in the "masker-signal" system and interaction of separate ERPs in the series evoked by the test signal.

Acoustic Stimulation↗
PubMed2003

Acute physiologic effects of nasal and full-face masks during noninvasive positive-pressure ventilation in patients with acute exacerbations of chronic obstructive pulmonary disease.

OBJECTIVE: To assess the efficacy of and patient tolerance for nasal and full-face masks during noninvasive positive-pressure ventilation (NPPV) with patients suffering acute exacerbations of chronic obstructive pulmonary disease. SETTING: A respiratory medicine ward of a referral hospital. METHODS: Fourteen patients were randomized to 2 groups. Seven used nasal masks and 7 used full-face masks. We used a portable ventilator and recorded arterial blood gases and indices of respiratory muscle effort before and after 15 min of NPPV. Patient tolerance was scored as follows: no tolerance (mask had to be withdrawn before the study period ended) = 0 points; poor tolerance (patient complained of discomfort from the ventilation devices but nevertheless remained compliant) = 1 point; fair tolerance (patient seemed uncomfortable but did not complain) = 2 points; excellent tolerance (patient felt better than before beginning NPPV) = 3 points. RESULTS: The groups were comparable in clinical and pulmonary function variables at baseline. NPPV improved both arterial blood gases and the indices of respiratory effort, with no significant differences between the groups. During NPPV the group that used full-face mask had a greater decrease in respiratory rate, but no other differences. NPPV was well tolerated in both groups. CONCLUSIONS: In patients suffering acute exacerbations of chronic obstructive pulmonary disease NPPV improves arterial blood gases and respiratory effort indices regardless of the type of mask used.

Acute Disease↗
PubMed2004

The physiological impact of wearing an N95 mask during hemodialysis as a precaution against SARS in patients with end-stage renal disease.

BACKGROUND AND PURPOSE: Most patients with end-stage renal disease (ERSD) visiting our hospital for hemodialysis treatment during the SARS outbreak wore an N95 mask. Data on the physiological stress imposed by the wearing of N95 masks remains limited. This study investigated the physiological impact of wearing an N95 mask during hemodialysis (HD) on patients with ESRD. METHODS: ESRD patients who received regular HD at National Taiwan University Hospital between April to June 2003 were enrolled. Each patient wore a new N95 mask (3M Model 8210) during HD (4 hours). Vital signs, clinical symptoms and arterial blood gas measured before and at the end of HD were compared. RESULTS: Thirty nine patients (23 men; mean age, 57.2 years) were recruited for participation in the study. Seventy percent of the patients showed a reduction in partial pressure of oxygen (PaO2), and 19% developed various degrees of hypoxemia. Wearing an N95 mask significantly reduced the PaO2 level (101.7 +/- 12.6 to 92.7 +/- 15.8 mm Hg, p = 0.006), increased the respiratory rate (16.8 +/- 2.8 to 18.8 +/- 2.7/min, p < 0.001), and increased the occurrence of chest discomfort (3 to 11 patients, p = 0.014) and respiratory distress (1 to 17 patients, p < 0.001). Baseline PaO2 level was the only significant predictor of the magnitude of PaO2 reduction (p < 0.001). CONCLUSION: Wearing an N95 mask for 4 hours during HD significantly reduced PaO2 and increased respiratory adverse effects in ESRD patients.

Adult↗
PubMed1987

The concept of spatial frequency channels cannot explain some visual masking effects.

Visual masking is assumed to be predictable by the degree to which mask and signal spatial frequency amplitudes are similar. In this masking experiment we have clearly shown this not to be the case by studying the effects of factorial combinations of signal-mask amplitude and phase spectra. Results show that the amplitude spectra characteristics do not predict masking, and a better predictor of these results appears to be the correlations between the mask and signal's luminance profiles. These results, therefore, show that the spatial similarity between two images, as may be processed by "spatial frequency channels" cannot be determined by the similarities between these channel outputs as defined by the (output) modulated amplitudes.

Humans↗
PubMed1978

Frequency selectivity in the parakeet (Melopsittacus undulatus) studied with narrow-band noise masking.

Narrow-band noise masking was studied in the parakeet (Melopsittacus undulatus) using a modified method of limits and an instrumental avoidance-conditioning procedure. Masked thresholds were obtained from five subjects at 10 frequencies between 0.5 and 5.0 kHz for each of four sensation levels (26, 46, 66, and 86 db) of a 1/3-octave band noise masker centered at 1.6 kHz. The amount of masking was found to be linearly related to noise level, and the shape of the masking curve was symmetrical on both sides of the center frequency of the masker. In all cases, the greatest threshold shift occurred at the center frequency of the masker. The relative symmetry of the parakeet narrow-band masking curves contrasts with masking results reported in mammals.

Acoustic Stimulation↗