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At least 55 records · Page 3Linked to original sources
PubMed1985

Ventilatory volumes using mouth-to-mouth, mouth-to-mask, and bag-valve-mask techniques.

The volumes delivered to a resuscitation manikin were compared using four ventilatory techniques: mouth-to-mouth, mouth-to-mask, one-person bag-valve-mask, and two-person bag-valve-mask. The effects of experience and sex of the rescuer on the resuscitation volume delivered were also evaluated. The volume delivered using the one-person bag-valve-mask technique was significantly less than that using the other three techniques (P less than 0.001). The experience and sex of the rescuer made no significant difference in the volume delivered using any of the techniques. As compared with the one-person technique, bag-valve-mask ventilatory volume improved significantly when it was performed as a two-person technique. The mean volumes delivered using mouth-to-mouth and mouth-to-mask ventilation were lower than those recommended by the American Heart Association. Emphasis must be placed on ventilation with an adequate volume when these techniques are taught. When mouth-to-mouth and mouth-to-mask ventilation are taught, a spirometer should be used with the manikin so that the rescuer can learn how to estimate an adequate expired volume.

Allied Health Personnel↗
PubMed1967

Recovery of masked visual targets by inhibition of the masking stimulus.

Theories of visual backward masking all assume that a masked target is eliminated from the visual system. Experiments on reaction time to masked signals suggest otherwise, as does a recent demonstration that a masked target can be restored to phenomenal awareness by backward masking of the target's mask. Two experiments are reported here that substantiate the possibility of recovering a masked target, by using different stimulus materials and a more elaborate design than was employed in the first demonstration of this effect.

Humans↗
PubMed1996

Masking Patterns for Partially Masked Tinnitus.

Tinnitus isomasking contours were determined for unmasked tinnitus and for tinnitus partially masked by high-pass noise. The noise was selected so that it masked all but the low frequency components of the tinnitus. As a control, the masking pattern of an external tone in the tinnitus region and in the presence of the high-pass noise was compared with that of the partially masked tinnitus. Frequency-specific masking was obtained for the external tone but not for the partially masked tinnitus. This suggests that even narrowband tinnitus is not masked in the cochlea. Thus, tinnitus maskers need not include the frequency region presumed to contain the tinnitus.

Journal Article↗
PubMed1998

Physiological dead space/tidal volume ratio during face mask, laryngeal mask, and cuffed oropharyngeal airway spontaneous ventilation.

OBJECTIVE: To compare the physiological dead space/tidal volume ratio and arterial to end-tidal carbon dioxide tension (ETCO2) difference during spontaneous ventilation through a face mask, a laryngeal mask (LMA), or a cuffed oropharyngeal airway. DESIGN: Prospective, randomized, cross-over study. SETTING: Inpatient anesthesia at a university department of orthopedic surgery. PATIENTS: 20 ASA physical status I and II patients, without respiratory disease, who underwent ankle and foot surgery. INTERVENTIONS: After a peripheral nerve block was performed, propofol anesthesia was induced and then maintained with a continuous intravenous (i.v.) infusion (4 to 6 mg/kg/h). A face mask, a cuffed oropharyngeal airway, or an LMA were placed in each patient in a random sequence. After 15 minutes of spontaneous breathing through each of the airways, ventilatory variables, as well as arterial, end-tidal, and mixed expired CO2 partial pressure, were measured, and physiological dead space/tidal volume ratio was calculated. MEASUREMENTS AND MAIN RESULTS: Expired minute volume and respiratory rate (RR) were lower with LMA (5.6 +/- 1.2 L/min and 18 +/- 3 breaths/min) and the cuffed oropharyngeal airway (5.7 +/- 1 L/min and 18 +/- 3 breaths/min) than the face mask (7.1 +/- 0.9 L/min and 21 +/- 3 breaths/min) (p = 0.0002 and p = 0.013, respectively). Physiological dead space/tidal volume ratio and arterial to end tidal CO2 tension difference were similar with the cuffed oropharyngeal airway (3 +/- 0.4 mmHg and 4.4 +/- 1.4 mmHg) and LMA (3 +/- 0.6 mmHg and 3.7 +/- 1 mmHg) and lower than with the face mask (4 +/- 0.5 mmHg and 6.7 +/- 2 mmHg) (p = 0.0001 and p = 0.001, respectively). CONCLUSION: Because of the increased dead space/tidal volume ratio, breathing through a face mask required higher RR and expired minute volume than either the cuffed oropharyngeal airway or LMA, which, in contrast, showed similar effects on the quality of ventilation in spontaneously breathing anesthetized patients.

Analysis of Variance↗
PubMed2006

Effects of face mask ventilation in apneic patients with a resuscitation ventilator in comparison with a bag-valve-mask.

Bag-valve-mask ventilation in an unprotected airway is often applied with a high flow rate or a short inflation time and, therefore, a high peak airway pressure, which may increase the risk of stomach inflation and subsequent pulmonary aspiration. Strategies to provide more patient safety may be a reduction in inspiratory flow and, therefore, peak airway pressure. The purpose of this study was to evaluate the effects of bag-valve-mask ventilation vs. a resuscitation ventilator on tidal volume, peak airway pressure, and peak inspiratory flow rate in apneic patients. In a crossover design, 40 adults were ventilated during induction of anesthesia with either a bag-valve-mask device with room air, or an oxygen-powered, flow-limited resuscitation ventilator. The study endpoints of expired tidal volume, minute volume, respiratory rate, peak airway pressure, delta airway pressure, peak inspiratory flow rate and inspiratory time fraction were measured using a pulmonary monitor. When compared with the resuscitation ventilator, the bag-valve-mask resulted in significantly higher (mean+/-SD) peak airway pressure (15.3+/-3 vs. 14.1+/-3 cm H2O, respectively; p=0.001) and delta airway pressure (14+/-3 vs. 12+/-3 cm H2O, respectively; p<0.001), but significantly lower oxygen saturation (95+/-3 vs. 98+/-1%, respectively; p<0.001). No patient in either group had clinically detectable stomach inflation. We conclude that the resuscitation ventilator is at least as effective as traditional bag-valve-mask or face mask resuscitation in this population of very controlled elective surgery patients.

Apnea↗
PubMed2001

Ease of ventilation through the cuffed oropharyngeal airway (COPA), the laryngeal mask airway and the face mask in a cardiopulmonary resuscitation training manikin.

The aim of this study was to compare ease of ventilation of a cardiopulmonary resuscitation manikin using a cuffed oropharyngeal airway (COPA), a laryngeal mask airway (LMA) and a face mask, by two groups of people with different levels of earlier experience in cardiopulmonary resuscitation (CPR). Enrolled were, 108 people identified as experienced (54), or inexperienced (54), in CPR. Training equipment included a manikin, a COPA (n=10), an LMA (n=4), a face mask (n=4) and self-inflating bag-valve device. The same investigator explained the theoretical use and practice of the three techniques with the subjects in groups of three. The variables recorded were the number of attempts needed to achieve correct placement (and a tidal volume of 200 ml, was achieved), the insertion time for the COPA and the LMA, and the average time taken to achieve the first ten correct ventilations. The face mask and LMA required fewer attempts for correct placement than did the COPA. The LMA also took less time to insert than the COPA. The face mask required a significantly shorter total time with all attempts and the mean time of placement and time to achieve ten correct ventilations was shorter than with either the LMA or the COPA (P=0.0001). We conclude that the face mask offers an easier and quicker way to provide ventilation for CPR manikins than does the COPA or the LMA. Earlier experience affects the ease of insertion of the LMA and the total time needed to achieve effective ventilation.

Cardiopulmonary Resuscitation↗
PubMed1984

Masking of tinnitus compared to masking of pure tones.

In 10 subjects with sensorineural tinnitus (associated with a sensorineural hearing loss and no apparent source for a tinnitus originating elsewhere), the minimum level required to mask the tinnitus was determined for tonal maskers at several masker frequencies. This tinnitus masking pattern was compared to a psychoacoustical tuning curve (PTC) in which the signal frequency and level were determined from tinnitus pitch and loudness matching. Different patterns emerged. One subject showed a near-normal PTC but required high-level maskers across the frequency range to mask the tinnitus. Another subject showed some frequency resolution in the PTC but required low-level maskers across the frequency range to mask the tinnitus. For the remaining eight subjects, the masker levels required to mask the tone were generally higher than those levels required to mask the tinnitus. In addition, it was noted that the tinnitus pitch-match frequency was sometimes associated with an increase or a decrease in threshold sensitivity, or it was found at the low-frequency edge of a steep high-frequency threshold loss. In other subjects there was no apparent relationship between the tinnitus pitch and the audiogram shape.

Adult↗
PubMed1987

Masking of tinnitus and central masking.

In the first experiment reported here, for subjects with sensorineural hearing loss and tinnitus, the masking of tinnitus is primarily dependent on the masker intensity; masking is nearly independent of masker frequency. In the second experiment reported here, for subjects with normal hearing, the central masking of a continuous tone (used to stimulate the tinnitus) is primarily dependent on the intensity of a contralateral masker; masking is nearly independent of masker frequency. Implications of the flat tuning curves on the design of tinnitus maskers and one possible interpretation of the similarity of tinnitus masking and central masking are discussed.

Acoustic Stimulation↗
PubMed1998

The effects of hearing loss and noise masking on the masking release for speech in temporally complex backgrounds.

Speech recognition was measured in three groups of listeners: those with sensorineural hearing loss of (presumably) cochlear origin (HL), those with normal hearing (NH), and those with normal hearing who listened in the presence of a spectrally shaped noise that elevated their pure-tone thresholds to match those of individual listeners in the HL group (NM). Performance was measured in four backgrounds that differed only in their temporal envelope: steady-state (SS) speech-shaped noise, speech-shaped noise modulated by the envelope of multi-talker babble (MT), speech-shaped noise modulated by the envelope of single-talker speech (ST), and speech-shaped noise modulated by a 10-Hz square wave (SQ). Threshold signal-to-noise ratios (SNRs) were typically best in the ST and especially the SQ conditions, indicating a masking release in those modulated backgrounds. SNRs in the SS and MT conditions were essentially identical to one another. The masking release was largest in the listeners in the NH group, and it tended to decrease as hearing loss increased. In 5 of the 11 listeners in the HL group, the masking release was nearly identical to that obtained in the NM group matched to those listeners; in the other 6 listeners, the release was smaller than that in the NM group. The reduced masking release was simulated best in those HL listeners for whom the masking release was relatively large. These results suggest that reduced masking release for speech in listeners with sensorineural hearing loss can only sometimes be accounted for entirely by reduced audibility.

Adult↗
PubMed2000

Cricoid pressure applied after placement of laryngeal mask impedes subsequent fibreoptic tracheal intubation through mask.

We studied 70 patients to see if cricoid pressure applied after insertion of the laryngeal mask altered the success rate of tracheal intubation through the mask. After induction of anaesthesia and neuromuscular blockade, patients were randomly allocated to have either cricoid pressure (Group C) or sham pressure (Group S). The view of the glottis through the laryngeal mask was assessed before and after the test pressure, and tracheal intubation through the mask was attempted using a fibreoptic bronchoscope. The test pressure did not alter the view of the glottis in any patient in group S, whereas it narrowed the glottic aperture in 16 out of 35 patients in group C. The fibrescope was inserted into the trachea in all patients in group S and in 25 patients in group C. The success rate of tracheal intubation in group S (31 patients) was significantly higher than in group C (21 patients, P << 0.001; 95% CI for difference: 9-48%). The time for insertion of the fibrescope in group S (median (95% CI): 12 (11-12) s) was significantly faster than in group C (16 (14-17) s, P << 0.001; 95% CI for difference: 3-6 s), and the time for tracheal intubation in group S (16 (15-18) s) was significantly faster than in group C (22 (19-24) s, P < 0.0005; 95% CI for difference: 3-7 s). Cricoid pressure after insertion of the laryngeal mask makes tracheal intubation through the mask significantly more difficult.

Adolescent↗
PubMed1981

Direct vs. indirect tests of the information available from masked displays: what visual masking does and does not prevent.

A comparison was made between two procedures for testing whether an alpha-numeric character, which was patter masked to prevent awareness, could access higher-order information concerning its category. In the indirect test, subjects made categorization responses to a letter or digit target which was immediately preceded by a masked letter or digit stimulus. In the direct test, the target stimulus was not presented; nevertheless, categorization responses were required, and it was assumed that any higher-order information available from the masked stimulus would be evident in these responses. Using the indirect procedure, category information was shown to be accessed by the masked stimulus, since target discrimination was affected by the category relationship between the stimuli. In contrast, categorization responses when the target was absent (in the direct test) were uninfluenced by the category of the masked stimulus. It was suggested that pattern masking disrupts the information necessary for (direct) report. However, it does not prevent the processing of stimuli to semantic levels, or the (indirect) effect the information accessed on the analysis of subsequent stimuli.

Adult↗
PubMed2004

Effect of number of masking talkers and auditory priming on informational masking in speech recognition.

Three experiments investigated factors that influence the creation of and release from informational masking in speech recognition. The target stimuli were nonsense sentences spoken by a female talker. In experiment 1 the masker was a mixture of three, four, six, or ten female talkers, all reciting similar nonsense sentences. Listeners' recognition performance was measured with both target and masker presented from a front loudspeaker (F-F) or with a masker presented from two loudspeakers, with the right leading the front by 4 ms (F-RF). In the latter condition the target and masker appear to be from different locations. This aids recognition performance for one- and two-talker maskers, but not for noise. As the number of masking talkers increased to ten, the improvement in the F-RF condition diminished, but did not disappear. The second experiment investigated whether hearing a preview (prime) of the target sentence before it was presented in masking improved recognition for the last key word, which was not included in the prime. Marked improvements occurred only for the F-F condition with two-talker masking, not for continuous noise or F-RF two-talker masking. The third experiment found that the benefit of priming in the F-F condition was maintained if the prime sentence was spoken by a different talker or even if it was printed and read silently. These results suggest that informational masking can be overcome by factors that improve listeners' auditory attention toward the target.

Adult↗
PubMed1984

Predicting frequency selectivity in forward masking from simultaneous masking.

Measures of frequency selectivity from forward masking suggest sharper tuning than those from simultaneous masking. To account for this result, various interpretations involving additional tuning mechanisms have been proposed. In the present study, it is shown that a simple multiplicative relation between on-frequency forward and off-frequency simultaneous masking predicts this result quite well. The relation assumes that changes in masking produced by separating the masker from the signal in frequency, in time, and in both frequency and time are related to one another by Weber's law. The accuracy of the predictions suggests that the limits of auditory frequency selectivity are already established in simultaneous masking and that special interpretations involving additional tuning mechanisms are not required to account for the difference between simultaneous and forward measures. Implications for a dB scale of masking are discussed.

Adolescent↗
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↗
PubMed1982

Visual masking with presentations in same and opposite visual fields: evidence for contralateral masking.

Three experiments were conducted in a preliminary attempt to study the effects of presentations of an informational target stimulus to the right or left visual fields when the target was either preceded or followed by a noninformational masking stimulus and when the mask was presented to the same or opposite visual field of the target. Results indicated that masking was more effective in the same than in the opposite visual field but that masking of the opposite visual field was feasible for both forward and backward masking. Laterality effects were also found for forward and backward masking, with a modest advantage of the right visual field (left hemisphere) in both cases. Limitations of the data and directions for future research were discussed.

Discrimination Learning↗
PubMed1990

Visual masking and unconscious processing: differences between backward and simultaneous masking?

Visual masking procedures are considered to have great potential for studying information processing that occurs outside of consciousness. Unfortunately, effects that indicate processing of masked word stimuli have been both difficult to obtain and, once obtained, difficult to replicate. The present seven experiments failed to obtain an effect of lexicality (word vs. nonword targets) on detection that was recently reported by Doyle and Leach (1988). Whereas Doyle and Leach had used backward binocular masking, most of the present experiments used simultaneous dichoptic masking. Doyle (1990) recently suggested that the effect of lexicality on detection (coupled with an effect of knowledge of results, which was also not obtained in the present research) could explain why Greenwald, Klinger, and Liu (1989) found no evidence for detectability of masked words that were nevertheless analyzed semantically. The differences of the present findings from those of Doyle and Leach (1988) not only confirm the uncertainty of generalizing across masking procedures, but also indicate that Greenwald et al.'s "detectionless processing" interpretation remains viable.

Adult↗
PubMed2002

Intraocular pressure changes during general anesthesia in children, comparing no mask, undermask and laryngeal mask airway.

In a before and after study of 35 children's eyes, we compared the intraocular pressure (IOP) during general anesthesia consisting of 6-8 per cent sevoflurane in 100 per centoxygen at induction. IOP measurement, blood pressure, oxygen saturation, and heart rate were recorded in patients with an applied face mask while the patient became unconscious and proceeded to surgery. These measurements were compared with those using no face-mask and after insertion of a laryngeal mask airway (LMA). The IOP with an applied face-mask was significantly statistically different from that after insertion of a LMA (12.8 +/- 3.1 and 12.0 +/- 3.3, p < 0.05) but not significantly different cilnically. We concluded that clinically, the IOP does not change in children given general anesthesia with a correct size of face mask when compared with insertion of an LMA or no face mask.

Analysis of Variance↗