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At least 109 records · Page 6Linked to original sources
PubMed2003

Eliminating protein from reusable laryngeal mask airways. A study comparing routinely cleaned masks with three alternative cleaning methods.

Laryngeal mask airways (LMAs) have the potential to act as a vector for the transmission of prion diseases. This study was undertaken to define the problem of protein contamination and to investigate three alternative cleaning methods. Forty-eight LMAs were allocated to one of four groups, stained with erythrosin and given a total stain score and a grid stain score in order to determine the degree of protein contamination. Eighteen randomly selected LMAs that had been routinely cleaned and sterilised (group 1) were compared with 12 LMAs that had been washed and scrubbed with the benefit of prior staining (group 2), 13 that had been washed and scrubbed without any visual guide (group 3) and 13 that had been cleaned using a Biosonic ultrasonic cleaning system (group 4). The results show that none of the cleaning methods achieved optimal results, as all methods left proteinaceous material on some masks. The study showed that: (i) staining as a guide to cleaning does not lead to more effective removal of proteinaceous material; (ii) systematic cleaning and scrubbing does lead to more effective removal of proteinaceous material from surfaces other than the grid area; and (iii) ultrasonic cleaning was more effective than other methods of cleaning for the removal of proteinaceous material from those areas of the mask most inaccessible, such as the grid.

Cross Infection↗
PubMed2000

The ProSeal laryngeal mask airway: A randomized, crossover study with the standard laryngeal mask airway in paralyzed, anesthetized patients.

BACKGROUND: The ProSeal laryngeal mask airway (PLMA) is a new laryngeal mask device with a modified cuff to improve seal and a drainage tube to provide a channel for regurgitated fluid and gastric tube placement. In the present randomized, crossover study, the authors tested the hypothesis that ease of insertion, airway sealing pressure, and fiberoptic position differ between the PLMA and the standard laryngeal mask airway (LMA). For the PLMA, we also assess ease of gastric tube placement and the efficacy of an introducer tool. METHODS: Sixty paralyzed, anesthetized adult patients were studied. Both devices (only size 4) were inserted into each patient in random order. Airway sealing pressure and fiberoptic position were determined during cuff inflation from 0 to 40 ml in 10-ml increments. Gastric tube insertion was attempted with the PLMA if there was no gas leak from the drainage tube. In 60 additional patients, ease of insertion for the PLMA was compared with and without an introducer. RESULTS: First-time success rates were higher (60 of 60 vs. 52 of 60; P = 0.003) and the effective airway time shorter (9 +/- 3 s vs20 +/- 18 s; P < 0.0001) for the LMA. There were no failed uses of either device within three attempts. Airway sealing pressure was 8-11 cm H2O higher for the PLMA at all cuff volumes (P < 0.00001) and was higher in females for both devices. Fiberoptic position was better with the LMA at all cuff volumes (P < 0.00001), but vocal cord visibility was similar (LMA, 59 of 60; PLMA, 56 of 60). For the PLMA, gastric tube placement was successful in 58 of 58 patients and took 9 +/- 5 s. First-time success rates were higher (59 of 60 vs53/60; P = 0.03) and the effective airway time shorter (15 +/- 13 s vs 23 +/- 18 s; P = 0.008) with the introducer. CONCLUSION: The PLMA is capable of achieving a more effective seal than the LMA and facilitates gastric tube placement, but it is more difficult to insert unless an introducer tool is used. When correctly positioned, the PLMA isolates the glottis from the upper esophagus with possible implications for airway protection.

Adult↗
PubMed1984

Broadened forward-masked tuning curves from intense masking tones: delay-time and probe-level manipulations.

Forward-masked psychophysical tuning curves were obtained from normal-hearing listeners under two conditions: lengthened delay time between masker and probe, and increased probe level. Both conditions required higher-level masking tones and both conditions resulted in broader tuning curves. Comparisons were made of tuning curves obtained with different probe-level and delay-time combinations that were chosen to require equivalent masker levels at the probe frequency. Nearly identical tuning-curve shapes were obtained when masker level at the probe frequency was the same. The results are predicted by a two-process model, consisting of a nonlinear filter followed by an exponential decay. Tuning-curve shapes in forward masking appear to be largely dependent upon the masker level (filter output level) at which one attempts to measure them.

Auditory Perception↗
PubMed1987

Comodulation masking release in a forward-masking paradigm.

Waveforms that yield comodulation masking release (CMR) when they are presented simultaneously with a signal were used in a standard forward-masking procedure. The signal was a 25-ms sample of a 2500-Hz tone. The masker was a band of noise centered at 2500 Hz, 100 Hz in width, and 200 ms in duration. Presented with the masker were two or four cue bands, each 100 Hz wide and centered at various distances from the masker band. These cue bands either all had the same temporal envelope as the masker band (correlated condition) or their common envelope was different from that of the masker band (uncorrelated condition). In the initial experiments, (1) detectability of the tonal signal was 7-18 dB better when the masker band was accompanied by cue bands than when it was not--an effect that would be expected from past research on lateral suppression--but further, (2) the signal was about 3 dB more detectable in the correlated conditions than in the uncorrelated conditions. In follow-up experiments, these CMR-like differences between the correlated and uncorrelated conditions were substantially reduced (although not eliminated) by presenting a contralateral, wideband noise that was gated synchronously with the masker and/or cue bands. The implications are that the initial results were attributable in part to the "confusion effects" known to exist in certain temporal-masking situations, and that listeners are able to obtain greater information about the temporal extent of a masker band from correlated cue bands than from uncorrelated bands.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1990

Across-channel masking and comodulation masking release.

These experiments on across-channel masking (ACM) and comodulation masking release (CMR) were designed to extend the work of Grose and Hall [J. Acoust. Soc. Am. 85, 1276-1284 (1989)] on CMR. They investigated the effect of the temporal position of a brief 700-Hz signal relative to the modulation cycle of a 700-Hz masker 100% sinusoidally amplitude modulated (SAM) at a 10-Hz rate, which was either presented alone (reference masker) or formed part of a masker consisting of the 3rd to 11th harmonics of a 100-Hz fundamental. In the harmonic maskers, each harmonic was either SAM with the same 10-Hz modulator phase (comodulated masker) or with a shift in modulator phase of 90 degrees for each successive harmonic (phase-incoherent masker). When the signal was presented at the dips of the envelope of the 700-Hz component, the comodulated masker gave lower thresholds than the reference masker, while the phase-incoherent masker gave higher thresholds, i.e., a CMR was observed. No CMR was found when the signal was presented at the peaks of the envelope. In experiment 1, we replicated the experiment of Grose and Hall, but with an additional condition in which the 600- and 800-Hz components were removed from the masker, in order to investigate the role of within-channel masking effects. The results were similar to those of Grose and Hall. In experiment 2, the signal was added at the peaks of the envelope of the 700-Hz component, but in antiphase to the carrier of that component and at a level chosen to transform the peaks into dips. No CMR was found. Rather, performance was worse for both the comodulated and phase-incoherent maskers than for the reference masker. This was true even when the flanking components in the maskers were all remote in frequency from 700 Hz. In experiment 3, the masker components were all 50% SAM and the signal was added in antiphase at a dip of the envelope of the 700-Hz component, thus making the dip deeper. Performance was worse for the phase-incoherent than for the reference masker and was worse still for the comodulated masker. The results of all three experiments indicate strong ACM effects. CMR was found only when the signal was placed in the dips of the masker envelope and when it produced an increase in level relative to that in adjacent bands.

Adult↗
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↗
PubMed2001

Laryngeal mask vs intubating laryngeal mask: insertion and ventilation by inexperienced resuscitators.

The laryngeal mask airway (LMA) has been shown to be useful in airway maintenance during resuscitation. The intubating laryngeal mask (ILM) is a modified LMA permitting both ventilation and rapid endotracheal intubation. We aimed to compare the LMA and the ILM with regard to ease of insertion and successful ventilation by inexperienced personnel. We have used anaesthetized, apnoeic, non-paralysed patients as a model to simulate resuscitation. Following standardized training, non-anaesthetic medical staff with no previous experience in laryngeal mask airway insertion (novices) inserted either the LMA or ILM in 55 patients following induction of anaesthesia. There were no differences between the two patient groups included in our study with regard to mean age and body mass index (BMI). The success rate for inserting the airway device and achieving a significant end-tidal CO2 recording within two minutes was 23/28 for the LMA (82.1%) and 22/27 for the ILM (81.5%). Reasons for failure included inability to insert the ILM past the teeth and insertion of the LMA upside down. There were no clinically relevant differences in the mean time to airway insertion and successful ventilation (62.6 vs 62 seconds) or expired tidal volume (781 vs 767 ml) for the LMA and ILM respectively. We conclude that the ILM is as easily inserted and effectively used as an LMA by novices and, because it allows the option offacilitating endotracheal intubation, may be the preferred device for maintaining an airway during resuscitation.

Adult↗
PubMed2006

A comparison of the oropharyngeal leak pressure between the reusable Classic laryngeal mask airway and the single-use Soft Seal laryngeal mask airway.

We tested the oropharyngeal leak pressure with the reusable laryngeal mask airway and the single-use Soft Seal laryngeal mask airway. These two types of laryngeal mask airway (LMA) have a similar design but the reusable LMA cuff is made from silicone whereas the Soft Seal LMA cuff is polyvinylchloride. Thirty-five healthy subjects were anaesthetized and paralyzed and the two types of Soft Seal LMA were compared in a blinded randomized cross-over trial. The oropharyngeal leak pressure was significantly higher with the Soft Seal than the reuable (21 +/- 7.6 and 16 +/- 6.7 cm H2O respectively, P = 0.002). However, in four subjects the oropharyngeal leak pressure was higher with the reusable by > 4 cm H2O. We concluded that the reusable LMA may provide a better seal in some individuals but that, on average, the Soft Seal provides a higher oropharyngeal leak pressure than the reusable LMA.

Adult↗
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↗
PubMed1980

[Frequency characteristics of the masking effect: relationship between the characteristic variation factor and the frequency of the tone being masked].

The irregularity coefficient of the frequency characteristics of masking effect is a function of the frequency of masking tone with constant intensity (10 dB SL). The coefficient is growing by 9--12 dB per octave of the masking tone reaching 60 dB at the frequency 10 kHz. Similar dependence was found by measuring the frequency threshold curves of the cochlear nerve fibers. These values of the coefficient could not be obtained with the aid of classical model of the cochlea.

Auditory Perception↗
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↗
PubMed1993

A comparison of the visual field restrictions with the M17 series protective mask and the MCU-2/P chemical-biological mask.

The U.S. Air Force and U.S. Navy recently adopted the MCU-2/P Chemical-Biological Mask to replace the M17 series of protective masks. Visual field plots were generated on a patient wearing each of these respirators. Although both resulted in a decrease of the visual fields, the magnitude of restrictions was far less with the MCU-2/P Chemical-Biological Mask.

Equipment Design↗
PubMed1994

Laryngeal mask airway vs face mask and Guedel airway during pediatric myringotomy.

OBJECTIVE: To compare perioperative conditions when a face mask and Guedel oral airway (FM-OA) or a laryngeal mask airway (LMA) are used to maintain airway patency during bilateral myringotomy with insertion of tympanostomy tubes (BMT). DESIGN: Randomized controlled trial in children's hospital tertiary-care operating rooms. PARTICIPANTS: Fifty healthy children undergoing BMT procedures during halothane--nitrous oxide (N2O) anesthesia. INTERVENTIONS: During BMT we managed the airway by inserting a Guedel oral airway or an LMA. MAIN OUTCOME MEASURES: We recorded the time taken to insert the airway device along with oxygen saturation during the operation and time from the end of surgery to eye opening, response to commands, and home readiness. In addition the surgeon assessed perioperative conditions on a 10-point scale (1, poor, through 10, excellent). RESULTS: Although insertion of the LMA took longer than the Guedel oral airway (mean +/- SD, 9 +/- 2 seconds vs 6 +/- 2 seconds; P < .05), no differences were noted in the actual operating, anesthesia, or recovery times. However, the frequency of hypoxemic episodes was decreased (8% vs 36%, P < .05) and the lowest recorded oxygen saturations were higher (mean +/- SD, 95% +/- 7% vs 88% +/- 12%; P < .05) in the LMA group than in the FM-OA group. Surgeons rated perioperative conditions better when the LMA was used (median score, 9 vs 8; P < .05). CONCLUSION: The LMA is an excellent alternative to the FM-OA technique for airway maintenance in children undergoing BMT procedures during halothane--N2O anesthesia.

Anesthesia Recovery Period↗
PubMed1998

The incidence of regurgitation during cardiopulmonary resuscitation: a comparison between the bag valve mask and laryngeal mask airway.

The risk of gastric regurgitation and subsequent pulmonary aspiration is a recognised complication of cardiac arrest--a risk which may be further increased by the resuscitative procedure itself. The purpose of this study was to compare the incidence of gastric regurgitation between the bag valve mask (BVM) and laryngeal mask airway (LMA). The resuscitation data collection forms of 996 patients who underwent in-hospital cardiopulmonary resuscitation over a 3.5 year period were reviewed. Of these, 199 patients were excluded from the study because there was no airway management involving a BVM or LMA. The incidence and timing of regurgitation was studied in the remaining 797 patients. Regurgitation was recorded to have occurred at some stage in 180 of these patients (22.6%). However, 84 regurgitated prior to CPR (46.7% of those patients who regurgitated). These patients were excluded from further analysis as regurgitation could not have been affected by any form of ventilation. Of the remaining 713 patients, BVM ventilation was used in 636 cases. In 170 of these the LMA was also used following the BVM. Where the patient was ventilated with the BVM alone or BVM followed by ETT the incidence of regurgitation during CPR was 12.4%. The LMA was used during resuscitation in 256 cases of which 170 had BVM ventilation prior to the LMA. Where the patient was ventilated with the LMA alone or LMA followed by ETT the incidence of regurgitation during CPR was 3.5%. The study confirms experience reported in earlier studies that when an LMA is used as a first line airway device, regurgitation is relatively uncommon.

Cardiopulmonary Resuscitation↗
PubMed2001

Distal oesophageal pH measurement in children during general anaesthesia using the laryngeal mask airway, tracheal tube and face mask.

BACKGROUND: Distal oesophageal pH was measured during controlled ventilation in children with the laryngeal mask airway (LMATM), tracheal tube (TT) and face mask (FM). METHODS: Fifty-six children scheduled for inguinal surgery with a standardized general anaesthetic technique were randomly allocated to receive LMA (n=21), TT (n=18) or FM (n=19). A 14 Fr pH probe was placed into the distal oesophagus and pH values were measured over 1 min at 2-min intervals during the first 20 min of anaesthesia. RESULTS: The median values of pH were 4.4 (3.5-5.5), 4.2 (3.3-4.9), 4.1 (3.2-5.1), 4.1 (3.3-5.0), 4.0 (3.3-4.9), 4.0 (3.4-5.1); 4.2 (3.3-5.1), 4.2 (3.6-5.0), 4.2 (3.5-5.0), 4.2 (3.5-5.2), 4.2 (3.5-5.0), 4.1 (3.5-5.0) and 4.2 (3.6-5.0), 4.2 (3.8-5.8), 4.1 (2.8-5.2), 4.2 (3.3-5.1), 4.2 (3.4-5.1), 4.3 (3.4-5.1) for LMA, TT and FM groups, respectively. CONCLUSION: There was no difference in the median pH values, within and between the groups (P > 0.05). We conclude that there is no difference in gastro-oesophageal reflux, when using a LMA, TT or FM during controlled ventilation in anaesthetized children.

Anesthesia, General↗
PubMed1995

The incidence of gastroesophageal reflux with the laryngeal mask: a comparison with the face mask using esophageal lumen pH electrodes.

To test the hypothesis that the laryngeal mask airway (LMA) predisposes patients to gastroesophageal reflux, we randomly assigned 55 patients having elective surgery to receive standardized anesthesia with the LMA or with conventional face mask (FM) plus airway. A pH-sensitive probe with two electrodes, 10 cm apart, was passed nasally into the esophagus 1 h before induction of anesthesia, and recordings were made continuously until 30 min after surgery. At the distal electrode, 30 cm from the anterior nares, there was a significant difference in the incidence of reflux: 53.6% with the LMA versus 22.2% with the FM (P < 0.05). At the level of the proximal electrode, 20 cm from the anterior nares, there was no difference between groups. Multiple reflux events, defined as two or more reflux events before, during, or after anesthesia, were significantly more frequent in the LMA group (P < 0.05). Reflux events continued in the postanesthesia care unit (PACU) in both groups with no significant difference between groups. There was no clinical evidence of aspiration of gastric contents in either group. Use of the LMA appears to result in increased reflux to the level of the mid to upper esophagus, and is associated with a more frequent incidence of multiple reflux events than use of the FM.

Adult↗
PubMed2000

Pharyngolaryngeal, neck, and jaw discomfort after anesthesia with the face mask and laryngeal mask airway at high and low cuff volumes in males and females.

BACKGROUND: There is controversy over (1) the relative incidence of sore throat between the face mask (FM) and laryngeal mask airway (LMA), (2) the efficacy of LMA intracuff pressure reduction as a mechanism for minimizing sore throat, and (3) the relative incidence of sore throat with the LMA between males and females. In a randomized double-blind study, the authors compared laryngopharyngeal, neck, and jaw discomfort with the FM and LMA at high and low cuff volumes in males and females. METHODS: Three hundred adult patients were randomly assigned to three equal-sized groups for airway management: (1) the FM, (2) the LMA with a fully inflated cuff (LMA-High), or (3) the LMA with a semi-inflated cuff (LMA-Low). Anesthesia was administered with propofol, nitrous oxide, oxygen, and isoflurane. In the FM group, a Guedel-type oropharyngeal airway and jaw thrust were used only if necessary. In the LMA groups, cuff inflation was achieved with either 15 or 30 ml for the size 4 (females) and 20 or 40 ml for the size 5 (males). The LMA was removed when the patient was awake. Patients were questioned 18-24 h postoperatively about surgical pain, sore throat, sore neck, sore jaw, dysphonia, and dysphagia, and about whether they were satisfied with their anesthetic. RESULTS: The incidence of sore throat was lower in the FM (8%) than the LMA-High (42%) and LMA-Low (20%) groups (both: P < or = 0.02). The incidence of sore neck was higher for the FM (14%) than the LMA-High group (6%; P = 0.05) but similar to the LMA-Low group (8%). The incidence of sore jaw was higher in the FM (11%) than the LMA-High (3%) and LMA-Low (3%) groups (both: P = 0. 02). There were no differences among groups for surgical pain or dysphonia. The incidence of dysphagia was lower in the FM (1%) than the LMA-High group (11%; P = 0.003), but similar to the LMA-Low group (1%). The incidence of sore throat and dysphagia was lower in the LMA-Low group than the LMA-High group for both males and females (all: P < or = 0.04). There were no differences in discomfort levels between males and females in any group. Two patients from the FM group and one from the LMA-High group were not satisfied with their anesthetic. These complaints were unrelated to postoperative morbidity. CONCLUSION: The LMA causes more sore throat and dysphagia but less jaw pain than the FM. Sore throat and dysphagia are more common with the LMA if the initial cuff volume is high. There are no differences in discomfort levels between males and females. However, these discomforts do not influence patient satisfaction after LMA or FM anesthesia.

Adult↗
PubMed2002

Complete separation of the tube from the mask during removal of a disposable laryngeal mask airway.

PURPOSE: To describe a complication of the disposable laryngeal mask airway (LMA). CLINICAL FEATURES: A 23-yr-old woman underwent a wide local excision of a chest wall melanoma and sentinel node biopsy under general anesthesia. During use of a single-use LMA-Unique(TM), the airway tube became completely separated from the distal mask (backplate). No sequelae resulted from failure of the airway apparatus. The LMA was examined by LMA North America, and the company stated "no definitive explanation can be made to explain the cause for separation of the airway from the backplate." CONCLUSION: Although the use of the LMA is associated with rare and minimal complications, each airway should be carefully inspected before its use for loss of integrity resulting from sterilization or for defects in manufacturing.

Adult↗