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At least 91 records · Page 5Linked to original sources
PubMed1998

Gas leak and gastric insufflation during controlled ventilation: face mask versus laryngeal mask airway.

PURPOSE: To compare two airway management techniques, face mask (FM) with oropharyngeal airway and laryngeal mask airway (LMA), with respect to the effectiveness of positive pressure ventilation and airway maintenance. METHODS: After induction of anaesthesia, two airway management techniques (FM or LMA) and three peak pressures (20, 25 and 30 cm H2O) were randomly applied during controlled ventilation in 60 patients. Data collected included inspiratory and expiratory volumes and presence of gastro-oesophageal insufflation. Leak was calculated by subtracting the expiratory from the inspiratory volume, expressed as a fraction of the inspiratory volume. RESULTS: Expiratory volumes (mean +/- SD) at 20, 25 and 30 cm H2O for LMA ventilation were 893 +/- 260, 986 +/- 276 and 1006 +/- 262 respectively, and for FM ventilation 964 +/- 264, 1100 +/- 268 and 1116 +/- 261. Leak fractions at 20, 25 and 30 cm H2O for LMA ventilation were 0.21 +/- 0.15, 0.24 +/- 0.18 and 0.26 +/- 0.18 respectively, and for FM ventilation 0.14 +/- 0.09, 0.14 +/- 0.09 and 0.12 +/- 0.08. The frequency of gastro-oesophageal insufflation was 1.6%, 5% and 5% for the LMA and 5%, 15% and 26.6% for the FM for ventilation pressures of 20, 25 and 30 cm H2O respectively which was greater with LMA use. CONCLUSION: Ventilation was adequate in all patients using both techniques. Leak was pressure dependent and greater with LMA use. Most of the leak was vented to the atmosphere via the pharynx. Gastro-oesophageal insufflation was more frequent with ventilation using the face mask. LMA use with positive pressure ventilation would appear to be a better airway management method than the face mask.

Adult↗
PubMed2001

Removal of the connector on the laryngeal mask airway provides a useful alternative to the intubating laryngeal mask.

PURPOSE: We describe two cases in which fiberoptic intubation through the standard laryngeal mask airway (LMA) was successful with large-bore tracheal tubes (TTs) when an intubating LMA (ILMA) could not be used. CLINICAL FEATURES: Patient # 1, with obstructive sleep apnea, underwent elective surgical repair. His mouth opening was just under 25 mm, but difficult intubation was not anticipated. We induced general anesthesia, easily ventilated the patient by mask, and established neuromuscular blockade. Direct laryngoscopy and attempts to insert either a #5 or a #4 ILMA into the mouth failed. A standard #4 LMA, with the connector removed, was inserted, through which a 7.0 mm nasal RAE TT, fiberoptically guided, passed into the trachea at the first attempt. Patient #2, with a loosened implant after left hip arthroplasty, underwent revision prosthesis. Her neck movement was limited. We thus planned awake securing of the airway, but the patient refused. We induced anesthesia and established bag-mask-valve ventilation. The limited neck movement prevented direct laryngoscopy. Visualizing the laryngeal inlet with the fiberoptic bronchoscope (FOB) proved impossible as bloody secretions obscured the FOB's tip. Ventilation by mask was easy. As an ILMA was not available, we removed a #5 LMAs connector and passed an 8.0 mm nasal RAE TT through the LMA. Fiberoptic-guided intubation was easy. In both cases, the remainder of the intraoperative course was uneventful. CONCLUSION: A standard LMA whose connector has been removed to allow passage of TTs of >6.0 mm internal diameter may be substituted for the ILMA when necessary.

Apnea↗
PubMed1994

Masking foods for food challenge: practical aspects of masking foods for a double-blind, placebo-controlled food challenge.

In diagnosing a food allergy or food intolerance, a double-blind, placebo-controlled food challenge (DBPCFC) with the suspected food or food substance is the only method available for objective confirmation of an assumed relationship between a suspected agent and a complaint. When the use of capsules as a vehicle for DBPCFC with the suspected agent is not feasible, recipes have to be developed for masking the suspected food with another food. We describe demands and other aspects of the development of recipes for DBPCFC purposes. The taste, smell, color, and texture of the suspected agent have to be hidden in such a way that the patient cannot tell which of the two foods (the active food or the placebo food) contains the suspected agent. Once developed, the recipes have to be judged carefully to ensure that the foods do not contain ingredients other than the suspected agent that can possibly provoke complaints in the patient. Besides ordinary equipment such as cutlery, glasses, and dishes, the minimal equipment needed for preparing the recipes is an accurate balance. The more laborious a recipe is to make, the more equipment is needed. The development of recipes and the preparation of masked foods are time-consuming, which makes DBPCFC with masked foods difficult to perform in daily clinical practice. Performing a DBPCFC with masked foods in daily clinical practice can be a great challenge to the imagination and creativity of a dietitian.

Capsules↗
PubMed2005

Auditory attentional blink: masking the second target is necessary, delayed masking is sufficient.

When two target items (T1 and T2) are presented in rapid succession among fillers, processing T2 is often impaired. This phenomenon is known as the attentional blink (AB). Within the visual modality, this second-target deficit generally occurs only if T2 is masked by a trailing item. The current study was designed to examine whether masking of T2 also plays a critical role in the auditory AB. Results showed a reliable AB effect even when the item following T2 was replaced by silence. However, the AB deficit was abolished when T2 was the last presented stimulus. Our results suggest that, as in vision, T2 masking is necessary for the AB to take place in audition, but that masking is effective even when delayed, providing evidence that the phenomenon shares some functional mechanisms across sensory modalities.

Adult↗
PubMed2000

A fibreoptic scoring system to assess the position of laryngeal mask airway devices. Interobserver variability and a comparison between the standard, flexible and intubating laryngeal mask airways.

We determined the interobserver reliability of a fibreoptic scoring system for assessing the position of the laryngeal mask airway (LMA), the flexible laryngeal mask airway (FLMA) and the intubating laryngeal mask airway (ILM). We also compare fibreoptic position between the devices. Thirty anaesthetised adult patients were studied in random order in a triple crossover manner. Two observers blinded to each others findings scored the fibreoptic position as follows: 4, only vocal cords visible; 3, vocal cords plus posterior epiglottis visible; 2, vocal cords plus anterior epiglottis visible; 1, vocal cords not seen. Interobserver reliability was examined using intraclass correlation coefficient (ICC). Interobserver reliability was graded as excellent for the LMA (ICC = 0.89), FLMA (ICC = 0.87) and ILM (ICC = 0.79). Fibreoptic scores were higher for the LMA and FLMA compared with the ILM (both p < 0.001). We conclude that interobserver reliability for the fibreoptic scoring system is excellent for the LMA, FLMA and ILM. Fibreoptic position is better for the LMA and FLMA compared with the ILM. Fibreoptic scoring has potential utility for research and clinical practice with laryngeal mask devices.

Adult↗
PubMed1991

The Brain laryngeal mask. A comparative study with the nasal mask in paediatric dental outpatient anaesthesia.

Fifty ASA grade 1 children, who presented for dental outpatient extraction were studied. They were randomly allocated to two groups after induction: group 1 had conventional nasal mask anaesthesia and group 2 anaesthesia with a laryngeal mask. Group 2 had fewer hypoxic episodes and significantly better arterial oxygen saturations (p less than 0.01). There was no difference between the groups as regards surgical access, difficulty of extraction or bleeding. The laryngeal mask appears to provide an alternative to conventional nasal mask anaesthesia, with better overall oxygenation and would seem particularly suitable for prolonged or difficult extractions.

Airway Obstruction↗
PubMed1993

The distance between the grille of the laryngeal mask airway and the vocal cords. Is conventional intubation through the laryngeal mask safe?

The distance between the grille of the laryngeal mask airway and the vocal cords was measured with a fibreoptic bronchoscope in 30 male and 30 female patients. The mean distance was 3.6 cm (SD 0.5 cm; range 2.5-4.7 cm) in males and 3.1 cm (SD 0.5 cm; range 2.0-4.2 cm) in females. These results suggest that the cuff of an uncut 6.0 mm tracheal tube would often lie between the vocal cords when the tube is fully inserted through a laryngeal mask airway. To avoid this complication, the tracheal tube must protrude more than 9.5 cm beyond the grille of the laryngeal mask airway. When either neck extension or flexion is required, the laryngeal mask airway should be removed as the margin of safety is small.

Adult↗
PubMed1978

Simultaneous pure-tone masking: the dependence of masking asymmetries on intensity.

Phase locking between probe and masker was used in a series of pure-tone masking experiments. The masker was a stationary sine wave of variable frequency; the probe a fixed-frequency tone burst. We have observed that for small frequency separation the masking behaves asymmetrically around the probe frequency. This asymmetry depends on intensity. For a 1-kHz probe at low stimulus levels there is a maximum masking effect at about 60 Hz above the probe frequency, whereas at high levels maximum masking is produced at a frequency definitely below the probe frequency. These results are discussed in relation to current neurophysiological and psychophysical data. For the high-level assymetry possible interpretations are suggested in terms of two changes in the excitation pattern of the basilar membrane, (a) a shift of the top and/or (b) a slope asymmetry, both increasing with level. The low-level asymmetry will be treated in a second paper [Vogten, J. Acoust. Soc. Am. 63, 1521-1528 (1978)].

Auditory Perception↗
PubMed2001

The clinical evaluation of the Respi-check mask: a new oxygen mask incorporating a breathing indicator.

UNLABELLED: Study objective-To investigate the correlation between the Respi-check sensor and simultaneous chest auscultation in determining the respiratory rates in adults. METHODS: Random visits to a local accident and emergency (A&E) department were made and all patients wearing oxygen masks were recruited into the study. The new sensor was attached to the outside of the mask. One researcher auscultated the chest to count breaths, the other counted the sensor activity. Each was blinded to the activities of the other. Breaths were counted by each researcher simultaneously and independently over one minute. A total of 40 patients were recruited into the study. A difference of more than two breaths/min compared with chest auscultation was deemed as a sensor failure. RESULTS: The respiratory rates of 40 patients were measured. There were 28 men, 12 women. Twenty six patients were wearing an Intersurgical high concentration (flow 12l/min) mask, 14 were wearing an aerosol mask with variable venturi (flow 3-12l/min) by Medicaid. Over one minute rates determined by the two methods were the same in 28 cases (70%). It was accurate to within one breath in 37 cases (93%) and to within two breaths in 39 (98%) cases and in one case (2.5%) the sensor failed. The mean difference (mean of the differences between rates obtained from auscultation and the new sensor) was -0.1282 breaths/min, with limits of agreement (d (2SD) between -1.414 to 1.157 breaths/min. CONCLUSION: The Respi-check sensor provides an accurate method of estimating the respiratory rate in adult patients attending the A&E department.

Adolescent↗
PubMed1987

Can tinnitus be masked by band erased filtered masker? Masking tinnitus with sounds not covering the tinnitus frequency.

In this study, the effectiveness of masking sound not covering the tinnitus frequency was tested against that of conventional masking sound in 117 subjects. Successful masking was observed in 72% of the former and 70% of the latter. There was no remarkable difference between the two maskers regarding the acceptability and intensity. The duration of residual inhibition, however, was smaller in the masker not covering the tinnitus frequency. The masking sound tested could be useful as an alternative when the conventional one is not accepted.

Adolescent↗
PubMedDate not supplied

[Comparison of masked and endogenous depression using psychometric scales, endocrinological markers and pharmacological responses. Masked depression versus endogenous depression].

Masked depression refers to a concept of a phenomenological state, either endogenous or psychogenic where somatic symptoms replace sadness: Thirty patients were evaluated by RDC (22 endogenous and 8 masked depressions) wherein in the latter dysphoria was replaced by a nonreactive persistent somatic complaint. They were rated on Beck and Hamilton Depression Scales, on Hamilton and Trait-State Anxiety Scales and the NOSIE. All patients presented with insomnia, anorexia, loss of weight, diminished libido and anhedonia. Initial ratings were similar for both diagnostic groups except for a significantly higher agitation factor and lower retardation in masked depression. Although 59.9 percent of the subjects are positive on the dexamethasone test, only 1 masked depression did not suppress secretion of cortisol. After a randomized 30-day drug trial where patients were assigned to Clomipramine or Desipramine, patients in both groups show significant improvement on rating scales but diagnostic group drug treatment interaction exists on anxiety and agitation criteria.

Adult↗
PubMed1999

Comparison of endtidal CO2 and arterial blood gas analysis in paediatric patients undergoing controlled ventilation with a laryngeal mask or a face mask.

Endtidal CO2 (PECO2) and arterial blood gas tensions were compared between laryngeal mask (LMA) and face mask (FM) ventilation in paediatric outpatients. Following premedication with midazolam, anaesthesia was induced with either thiopentone or isoflurane and atracurium. Anaesthesia was maintained with N2O, O2 and isoflurane. Manually controlled ventilation was applied with a nonrebreathing system. Both PECO2 and arterial blood gas tensions were measured at 5 and 15 min after skin incision. The mean PaCO2 values in the LMA group were 36.6+/-7.4 and 37.5+/-6.4 mmHg and PaCO2 -PECO2 were 1. 8+/-2.4 and 2.5+/-3.3 mmHg, respectively. The mean PaCO2 values in the FM group were 41.3+/-8.1 and 43.4+/-8.9 mmHg; and PaCO2 -PECO2 were 5.3+/-3.6 and 8.8+/-7.0 mmHg, respectively. These values were lower in the LMA group (P< 0.05). We have concluded that monitoring of PECO2 is more reliable for estimating blood gas values during controlled ventilation with a LMA than a face mask.

Blood Gas Analysis↗
PubMed2005

Laryngeal mask airway versus bag-mask ventilation or endotracheal intubation for neonatal resuscitation.

BACKGROUND: Providing effective positive pressure ventilation is the single most important component of successful neonatal resuscitation. Ventilation is frequently initiated with a manual resuscitation bag and face-mask (BMV) followed by endotracheal intubation (ETT) if depression continues. These techniques may be difficult to perform successfully resulting in prolonged resuscitation or severe neonatal depression. The laryngeal mask airway (LMA) may achieve initial ventilation and successful resuscitation faster than a bag-mask device or endotracheal intubation. OBJECTIVES: Among newborns requiring positive pressure ventilation for resuscitation, is effective ventilation and successful resuscitation achieved faster with the LMA compared with either BMV or ETT? SEARCH STRATEGY: The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2004), MEDLINE (1966-November 2004), Pre-MEDLINE (November 15, 2004), CINAHL 1982-November 2004), reference lists of published trials, and Society for Pediatric Research abstracts were searched. Experts were contacted for additional references. SELECTION CRITERIA: Randomised and quasi-randomised trials DATA COLLECTION AND ANALYSIS: Two reviewers independently evaluated studies, assessed methodologic quality, and extracted data using the Cochrane Neonatal Review Group criteria. Categorical treatment effects were described as relative risks and risk differences and continuous treatment effects were described as the mean difference. There were insufficient data to perform pooled analyses. MAIN RESULTS: No eligible studies compared the LMA with BMV. One small randomised controlled trial comparing the LMA with ETT when BMV had been unsuccessful was included. There was no statistically significant difference between the LMA and ETT with the exception of a clinically insignificant difference in time to complete insertion of the device favouring the ETT. AUTHORS' CONCLUSIONS: The LMA can achieve effective ventilation during neonatal resuscitation in a time-frame consistent with current guidelines. There is no evidence to evaluate the relative efficacy and safety of the LMA compared with BMV as the primary airway device. A single, small randomised controlled trial found no clinically significant difference between the LMA and ETT when BMV was unsuccessful. Case series and case reports suggest that the LMA can provide an effective rescue airway during resuscitation if both BMV and ETT have been unsuccessful. A well-designed randomised controlled trial comparing the LMA with BMV during neonatal resuscitation is warranted.

Humans↗
PubMed1987

Is pattern masking predicted by the cross-correlation between signal and mask?

We sought to determine whether the cross-correlation between signals and masks consisting of Gaussian modulated grating patterns is consistent with observed psychophysical masking effects. Our experimental results support this relationship, and suggest further specifications for the determinants of pattern masking effects.

Form Perception↗
PubMed1984

Binaural masking-level differences with tones masked by noises of various bandwidths and levels.

Binaural masking-level differences (BMLDs) were measured for tones at frequencies below and above masking noises centred on 250 Hz, having 10, 31.6 or 100 Hz bandwidths and either 40 or 60 dB spectral density levels. The BMLD drops rapidly when masker and signal have no frequency components in common. The magnitude of the decrease in the BMLD is not merely a result of the reduced masking effect and is not to be predicted by the models of Durlach [2] or Schenkel [12].

Auditory Threshold↗
PubMed2006

What is being masked in object substitution masking?

Object substitution masking (OSM) is said to occur when a perceptual object is hypothesized that is mismatched by subsequent sensory evidence, leading to a new hypothesized object being substituted for the first. For example, when a brief target is accompanied by a longer lasting display of nonoverlapping mask elements, reporting of target features may be impaired. J. T. Enns and V. Di Lollo (2000) considered it an outstanding question whether OSM masks some or all aspects of a target. The authors report three experiments demonstrating that OSM can selectively affect target features. Participants may be able to detect a target while being unable to report other aspects of it or to report the color but not the orientation of a target (or vice versa). We discuss these findings in relation to two other visual phenomena.

Analysis of Variance↗
PubMed1999

Laryngeal mask airway intracuff pressure estimation by digital palpation of the pilot balloon: a comparison of reusable and disposable masks.

Digital palpation of the pilot balloon provides information about the intracuff pressure of the laryngeal mask airway. The purpose of this in vitro study was to evaluate this technique for the reusable and disposable laryngeal mask airway. Ten anaesthetists and 10 recovery-unit nurses estimated intracuff pressures from low/high initial pressures before/after training. In the pretraining phase, the mean (95% CI) pressure was 99 (94-105) cmH2O, but this was significantly lower for the reusable laryngeal mask airway (91 vs. 103 cmH2O) and if the initial pressure was low (81 vs. 112 cmH2O). In the post-training phase, there was a significant overall improvement to 75 (66-85) cmH2O, but target pressures remained more accurate if the initial pressure was low. Subjects in the training group could estimate 95% of pressures for both devices to within +/-10 cmH2O of the target if the initial pressure was low. We conclude that anaesthetists and recovery-unit nurses are capable of accurate estimation of intracuff pressures using the digital palpation technique following a brief period of training.

Air Pressure↗