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PubMed1998

Chronic conductive hearing loss in adults: effects on the auditory brainstem response and masking-level difference.

OBJECTIVE: To determine whether chronic conductive hearing loss in adults results in changes in the auditory brainstem response (ABR) similar to those observed in children with histories of otitis media with effusion. DESIGN: Test of effect of unilateral conductive hearing loss on adult ABR using age-matched control group and subjects as their own controls. SUBJECTS: Twelve adults with a history of unilateral conductive ear disease. An age-matched control group of 21 adults was also tested. METHODS: The ABR, an electrophysiologic test of auditory brainstem functioning, was used to evaluate possible brainstem abnormalities in the impaired listeners. In addition, the masking-level difference, a behavioral test of binaural auditory processing in the brainstem, was used. RESULTS: When comparing the patients' diseased ears with their healthy ears, significant delays were seen for wave V as well as for the I-V and III-V interwave intervals. For comparison with the control population, significant prolongations were again seen for wave V and for the III-V interwave intervals. In addition, reduced masking-level differences and significant correlations between the masking-level differences and the ABRs, independent of hearing threshold, were noted. CONCLUSIONS: The results suggest that chronic conductive impairment in adults leads to changes in the ABR similar to those observed in children with histories of otitis media with effusion. As such, these changes do not appear to be related to a critical period of development.

Adult↗
PubMed1998

The effect of otitis media with effusion on complex masking tasks in children.

OBJECTIVE: To determine whether there is a relationship between the presumed complexity of auditory processing and the time course of recovery of auditory function in children with a history of otitis media with effusion (OME). DESIGN: Longitudinal testing over a 1-year period following insertion of tympanostomy tubes in clinical and control groups. SUBJECTS: A total of 34 children with a history of OME were tested. Twenty-five were tested both just before the placement of tympanostomy tubes and on up to 3 separate occasions (1 month, 6 months, and 1 year) after the placement of the tubes. With subject attrition, there were 27, 16, and 10 listeners at the 1-month, 6-month, and 1-year tests, respectively. An age-matched control group of 29 children was tested. METHODS: The comodulation masking release (CMR) paradigm was used to measure the ability of the listener to detect a signal in a noise background composed of a simple (1 amplitude modulation pattern) or more complex (2 amplitude modulation patterns) masking background. RESULTS: Children with a history of OME had reduced masking release before and 1 month after insertion of tympanostomy tubes for both the simple and complex CMR tasks. After surgery, the CMR results for simple task was not significantly different from that in controls by 6 months, but CMR for the complex task remained significantly reduced even 1 year after surgery. CONCLUSION: Our results suggest a slower recovery of auditory function for more complex auditory tasks in children with a history of OME.

Auditory Perception↗
PubMed1977

Masking level differences in central nervous system diseases.

The relationship between the tonal masking level difference performance and the behavior of the "sensitized speech tests" according to Bocca and Calearo, were studied in subjects with normal hearing who were suffering from CNS diseases. The results have shown that pathological masking level difference values are present in all cases with pathological sensitized speech tests, and are related principally to the following two conditions: (1) the bulbo-pontine lesions and (2) the central hearing functional asymmetry. In subjects with normal hearing who have CNS diseases, pathological tonal masking level differences indicate the existence of central hearing pathways lesions.

Adolescent↗
PubMed1996

Pediatric flexible fiberoptic bronchoscopy through the laryngeal mask airway.

OBJECTIVE: To determine the usefulness and safety of the laryngeal mask airway (LMA) as an adjunct to pediatric flexible fiberoptic bronchoscopy (FOB). DESIGN: A case-series retrospective study. SETTING: Pediatric otolaryngology tertiary referral center, outpatient and inpatient operating suites. PATIENTS: Retrospective review of charts of children who had FOB performed with the use of LMA by the pediatric otolaryngology service. The patients were ages 3 months to 18 years with respiratory symptoms requiring FOB for diagnosis. INTERVENTIONS: Use of LMA to support airway during FOB with spontaneous ventilation with the patients under general anesthesia. MAIN OUTCOME MEASURES: Ability to perform airway evaluation with FOB and LMA; number and type of complications. RESULTS: Seventeen patients, ages 3 months to 18 years (median age, 39 months) underwent FOB with use of LMA. In 2 patients use of LMA failed-1 from airway obstruction with LMA in place, which required intubation, and another who could not have LMA appropriately placed. Fifteen patients underwent uncomplicated FOB through the LMA. None of these 15 patients required unplanned endotracheal intubation. Two patients with mandibular hypoplasia required LMA use for airway evaluation when the glottis could not be visualized at direct laryngoscopy. CONCLUSIONS: The LMA is a safe and effective adjunct to pediatric FOB. Laryngeal mask airway use for FOB allows evaluation of the airway during spontaneous ventilation without an endotracheal tube or a face mask. Larger fiberoptic scopes can be used through the LMA compared with pediatric FOB performed through the nose or through an endotracheal tube.

Adolescent↗
PubMed1981

Nosocomial respiratory syncytial viral infections. Should gowns and masks be used?

The efficacy of infection control procedures utilizing gowns and masks in the control of nosocomial respiratory syncytial virus (RSV) infections was evaluated by comparing the rate of nosocomial RSV infections in infants and ward personnel during two sequential periods when gowns and masks were used (period 1) and not used (period 2). All patients (162) and staff (36) on our infants' ward were examined for signs of respiratory infection and had nasal washes obtained for viral isolation every two to four days for two months. Nosocomial RSV infection was identified in a total of 19 infants. Eight of these occurred in period 1 for a nosocomial infection rate of 32% of contact infants who were hospitalized for seven or more days. In comparison, 11 (41%) of the contact infants hospitalized for seven or more days in period 2 became infected. These findings suggest that the additional routine use of masks and gowns does not result in measurable benefit in controlling the nosocomial spread of RSV infection to infants or to ward personnel.

Child, Preschool↗
PubMed1996

Bronchoscopic airway evaluation facilitated by the laryngeal mask airway in pediatric patients.

The laryngeal mask airway (LMA) was introduced for clinical use in 1988. It represents a new concept in airway management. Its role has been described as filling the gap between tracheal intubation and the anesthesia face mask. It is inserted without direct visualization into the hypopharynx and when properly positioned forms a low pressure seal around the laryngeal inlet, allowing spontaneous as well as gentle positive pressure ventilation. Since its introduction, its indications and applications in anesthesia practice have increased. Although initially used as a means of delivering anesthesia and obviating the need for holding a mask on the patient, its position directly over the laryngeal inlet makes it a useful guide during flexible bronchoscopy. We report our experience in six pediatric patients and describe an anesthetic technique for bronchoscopy using the LMA for general anesthesia with spontaneous ventilation.

Anesthesia, General↗
PubMed1984

The schizophrenia spectrum: a study of the relationship among the Rorschach, MMPI, and visual backward masking.

Compared 20 Ss within the schizophrenia spectrum and 20 non-schizophrenia spectrum controls in terms of their MMPI and Rorschach performance. Ss also were studied in terms of their ability to identify a briefly exposed visual stimulus when it was followed by a noninformational mask stimulus and when it was not. Ss did not differ on the MMPI or on their ability to identify an unmasked target stimulus. They differed significantly in the number of deviant verbalizations, a special scoring category of the Rorschach. Ss also differed in their ability to identify the briefly exposed stimulus when it was followed by the noninformational mask. Results indicated a relationship among the deviant verbalization, the masking procedure, and the schizophrenia spectrum.

Adult↗
PubMed1986

Masking and the perception of stop consonants: psychoacoustical and electrophysiological experiments.

Naturally spoken German words Stahl [Sta:1] and Spott [Spot] were prepared with gaps (silent intervals) of different lengths between the fricative (S) and the corresponding stop consonant [t] or [p], and with various fricative sound pressure levels. Reduction of the normally occurring pause between the fricative and the stop consonant [t] or [p] to less than 10 ms or 20 ms, respectively, leads to "suppression" of the acoustically present stop, e.g. Spott [Spot] is heard as Schott [Sot]. We compare the results of single neuron recordings from animals to results from psychophysical tests on humans, since animal experiments exclude the effects of possible speech-specific perceptual processes. The animal experiments were done on anesthetized cats, from which we recorded single unit activity in the medial geniculate body (MGB). For neurons which represented the stop consonant by a discharge increase, we varied the gap between the fricative and its following stop from 0 up to 120 ms. For all neurons the responses to the stop consonant were positively correlated with gap length and always showed a minimum for gaps of 30 ms or less. This critical interval for minimum responses matches that found in the human psychophysical measurements of stop consonant "suppression". The time course of the interval dependence of neural responses follows the pattern of the psychoacoustical measurements in humans. Suppression of neural responses to the stop did not depend on whether the neuron responded to either the preceding fricative or the following vowel. Neural (animal experiment) and perceptual (human experiment) responses to the stop consonant show the same dependence on the fricative sound pressure level. The results are interpreted as forward masking. The neurophysiological data correspond well to experiments in which discharge reduction is elicited with simple signals ("forward masking"). Our experiments are evidence that auditory masking plays a role in the suppression of stop consonants and that this phenomenon can be explained without assuming phonetic processes in speech perception at a higher level or specific for humans.

Animals↗
PubMed1988

Modification of neuromagnetic responses of the human auditory cortex by masking sounds.

We have studied the effects of masking sounds on auditory evoked magnetic fields (AEFs) of healthy humans. The AEFs were elicited by 25-ms tones presented randomly to the left or to the right ear, and the responses were recorded over the right auditory cortex. Without masking, the 100-ms deflection (N100m) was of somewhat higher amplitude and of shorter latency for contra- than ipsilateral stimuli. Continuous speech, music, or intermittent noise, delivered to the left ear, dampened N100m to stimulation of both ears without correlated changes in sensation. Intermittent noise had a weaker effect on N100m than speech or music. Continuous noise fed to the left ear dampened both the sensation of and the responses to the left-ear stimuli, with no significant effect on the responses to the right-ear stimuli. The results suggest that the masking effects of continuous noise, seen at the auditory cortex, derive mainly from the periphery whereas the effects of sounds with intensity and frequency modulations take place at more central auditory pathways.

Acoustic Stimulation↗
PubMed1979

Local cochlear masking by frequency-modulated tone bursts.

Masking experiments are demonstrated for electrical frequency-modulated tone bursts from 1,000 to 10,000 cps and from 10,000 to 1,000 cps with superimposed clicks. The maximum of the masking was found at 3,700 cps ("narrow-band masking").

Acoustic Stimulation↗
PubMed1985

The influence of masking on the ipsi- and contralateral brainstem evoked potential.

We have examined clinically and experimentally the masking effects of white noise in registering brainstem evoked potentials and determining the Jewett-wave V. We studied input-output functions as well as latency periods of evoked potentials with masking of non-stimulated contralateral ears in 18 children aged 5-14 years. When differences of 50 dB or more were found between stimulation and masking, the Jewett-wave V could be partially suppressed. Other changes observed included alterations in potential and phase, as well as shifts in the latency period of the potentials. The clinical importance of the measurements determined indicates that findings may be used in examining patients with unilateral sensory hearing impairments to formulate possible differential diagnoses.

Adolescent↗
PubMed1995

Mask physiotherapy in patients after heart surgery: a controlled study.

OBJECTIVE: Investigate the effects of mask physiotherapy on post-operative complications after thoracic surgery. DESIGN: A prospective, consecutive, randomized, controlled study. SETTING: Department of Thoracic and Heart Surgery at a University Hospital. The treatments were performed by experienced and specially trained physiotherapists. PATIENTS: 97 low-risk male patients undergoing coronary artery by-pass graft surgery were evaluated. 66 patients completed the study. INTERVENTIONS: The patients were treated with routine chest physiotherapy alone or supplied with either positive expiratory pressure (PEP), or inspiratory resistance-positive expiratory pressure (IR-PEP). MEASUREMENTS AND RESULTS: Post-operative pulmonary complications were assessed by forced vital capacity (FVC), arterial oxygen tension (PaO2), and chest X-ray examination, all measured pre-operatively and on the third and sixth post-operative day. There was an almost equal decrease and subsequent rise in spirometric and blood gas values, but patients treated with the PEP mask had a borderly significantly higher increase in PaO2 from day 3 to day 6 compared with patients treated with no mask. There was an almost equal frequency of atelectasis in the 3 treatments. The patients filled in a questionaire expressing their opinion about their treatment. Most patients liked their treatment and found it helpful but a little less so in the IR-PEP group. CONCLUSION: We did not find any significant difference between the three groups; however, a tendency to decreased risk of having post-operative complications was observed in the groups having positive expiratory pressure (PEP) and inspiratory resistance-positive expiratory pressure (IR-PEP).

Aged↗
PubMed1993

Pressure support ventilation via face mask in acute respiratory failure in hypercapnic COPD patients.

OBJECTIVE: To test whether non-invasive ventilation via facial mask could reduce the need for tracheal intubation when mechanical ventilation must be initiated in COPD patients. DESIGN: Open prospective interventional study. SETTING: General Intensive Care Service of a County Hospital. PATIENTS: We have studied 12 COPD patients during 14 episodes of acute exacerbation of chronic respiratory failure who failed to improve with intensive medical therapy and showed impairments in severe respiratory acidosis and/or hypercapnic encephalopathy leading their attending physicians to order mechanical ventilation. INTERVENTIONS: In these circumstances, a trial of pressure-support (PS) ventilation (Servo Ventilator 900C) via facial mask Vital Signs Inc.) was performed. The level of pressure support was adjusted to obtain a tidal volume > 400 ml. If the patient deteriorated, tracheal intubation and standard mechanical ventilation were performed. MEASUREMENTS AND RESULTS: Measurements are presented as means +/- SEM. A pressure-support level of 14 +/- 3 cmH2O was used during a period of 8 +/- 4 h. Low levels of external PEEP were used in 4 patients, while it generated excessive leaks in the others. Significant differences (p < 0.05 ANOVA for repeated measures) in data obtained on admission, when patients deteriorated and after pressure support was administered were only observed in PaCO2 (68 +/- 3 versus 92 +/- 3 versus 67 +/- 3 mmHg), arterial pH (7.27 +/- 0.03 versus 7.19 +/- 0.02 versus 7.31 +/- 0.01). SaO2 (60 +/- 4 versus 86 +/- 3 versus 92 +/- 1%) and respiratory rate (35 +/- 2 versus 32 +/- 2 versus 23 +/- 1 breaths.min-1). Three patients needed intubation and one of them died in the ICU. CONCLUSION: Non-invasive ventilation (pressure-support) via face mask may reduce the need for tracheal intubation in the severe hypercapnic failure of COPD patients.

Acute Disease↗
PubMed1984

[Evaluation of the degree of protection provided by a cartridge-mask system during working with asbestos].

During removal of sprayed-on asbestos coating workers are exposed to high airborne fiber concentrations. The true protection of negative pressure respirators under working conditions was evaluated during an asbestos abatement project. A modification allowing air sampling inside the mask is described. The values for samples collected inside a full-face mask ranged between 0.4 and 5% of the concentrations measured outside. These values were considerably lower than those found inside a half-mask.

Asbestos↗
PubMed1989

Recovery room oxygenation: a comparison of nasal catheters and 40 per cent oxygen masks.

One hundred and sixty-one ASA physical status I-III patients undergoing elective surgery were evaluated using nasal catheters versus 40 per cent O2 venturi masks. Twenty-one per cent of the patients arrived in the recovery room with hypoxia as measured with a pulse oximeter (SaO2 less than 90 per cent). Fifteen minutes later all patients who arrived hypoxic were well oxygenated on their chosen oxygen therapy. Only one patient that arrived normoxic became hypoxic using a nasal catheter 15 minutes later. There was no statistical difference between patients given 40 per cent O2 by mask versus patients given oxygen by nasal catheter. The mean SaO2 for the group given 40 per cent O2 at 15 minutes was 96.7 +/- 2.15 per cent versus 96.6 +/- 2.48 per cent for nasal catheters. Nasal catheters are as effective as 40 per cent O2 masks for treating hypoxia in the recovery room. Obesity and age were statistically significant risk factors in the patients that arrived hypoxic. Patients were 47.4 +/- 15.6 years in the hypoxic group versus 38.3 +/- 15.6 years in the non-hypoxic group (p less than 0.001). Patients having an endotracheal tube with intermittent positive pressure ventilation or having a premedication were more apt to be hypoxic on arrival. These last two factors were closely associated and may reflect bias. The patient's gender, history of smoking, presence of obstructive lung disease, not including asthma, location of incision, or type of anaesthetic were not statistically significant risk factors.

Adolescent↗
PubMed1999

Propofol or sevoflurane for laryngeal mask airway insertion.

PURPOSE: Sevoflurane is a volatile anesthetic agent, which combines rapid, smooth inhalational induction of anesthesia with rapid recovery, making it particularly suitable for day case anesthesia. The laryngeal mask airway is often also used in ambulatory anesthesia, with intravenous propofol being the agent of choice for its insertion. Our objective was to compare the conditions for laryngeal mask airway (LMA) insertion obtained by modified vital capacity breath sevoflurane inhalational induction of anesthesia with propofol intravenous induction. METHODS: Eighty-eight patients, aged 18-65 yr, ASA I-II, undergoing general anesthesia for elective surgery were randomized into two groups in a prospective, single-blind study. Patients in Group P (n=44) received 2.5 mg x kg(-1) propofol i.v. and in Group S (n=44) received sevoflurane 8% in nitrous oxide 50% and oxygen. Ventilation was not assisted. Laryngeal mask airway insertion was attempted at one minute intervals from loss of both verbal response and eyelash reflex, by an anesthesiologist unaware of the induction technique. Complications, such as coughing and head movement, were also noted at each attempt. RESULTS: Mean time to successful LMA insertion was 1.3 (1-3) min in P and 2.2 (1-3) min in S, P < 0.05. Eleven patients in Group P, (25%) required additional propofol compared with four (9%) in S, P < 0.05. Incidence of complications was similar in both groups and by 3 min, LMA was successfully inserted in all patients. CONCLUSION: Modified vital capacity breath inhalational induction with sevoflurane 8% is efficient for LMA insertion in most cases, but takes slightly longer than propofol.

Adolescent↗
PubMed1999

Anesthesia for Freeman-Sheldon syndrome using a laryngeal mask airway.

PURPOSE: To present a case of Freeman-Sheldon syndrome (FSS) with a previously unreported technique of anesthetic management, consisting of a malignant hyperthermia free anesthetic and laryngeal mask airway. CLINICAL FEATURES: Freeman-Sheldon syndrome (also known as whistling face syndrome, Windmill-Vane-Hand syndrome, cranio-carpo-tarsal dysplasia and distal arthrogryposis type 2) is a rare congenital disorder defined by facial and skeletal abnormalities. The three basic abnormalities are microstomia with pouting lips, camptodactyly with ulnar deviation of the fingers and talipes equinovarus. Patients with FSS frequently present for surgical correction of musculoskeletal or facial abnormalities. There are several anesthetic challenges including difficult airway, intravenous cannulation and regional technique. They may be at increased risk for malignant hyperthermia and postoperative pulmonary complications. We present a case of a two-year-old child with FSS undergoing elective unilateral inguinal hernia repair. A non-triggering anesthetic technique was used, consisting of 2 mg x kg(-1) propofol followed by a continuous infusion, nitrous oxide 50%/oxygen, and 3 microg x kg(-1) fentanyl. Intraoperative and postoperative analgesia was provided by an ilioinguinal nerve block with 10 ml bupivacaine 0.25% with epinephrine 1:200,000. The airway was maintained with a #2 laryngeal mask airway. The anesthetic was uneventful and there were no signs or symptoms of malignant hyperthermia. The patient was discharged home later the same day in good health. CONCLUSION: The use of a laryngeal mask airway and non-triggering anesthetic technique should be considered as options for anesthetic management in patients with FSS for short procedures that do not require neuromuscular blockade.

Anesthesia, Inhalation↗
PubMed2000

Intubating laryngeal mask for fibreoptic intubation--particularly useful during neck stabilization.

PURPOSE: To assess the ease of fibrescope-assisted tracheal intubation while the patient's head and neck were placed in the neutral or the manual in-line position, and to determine if the intubating laryngeal mask facilitated fibreoptic intubation in these positions. METHODS: In 84 patients, the patient's head and neck were placed in the neutral position (pillow placed under occiput), and in another 40 patients the head and neck were stabilized by the manual in-line method (no pillows under occiput). In both groups, after induction of anesthesia with 2.0-2.5 mgxkg(-1) propofol, 50-100 microg fentanyl and 1.0 mgxkg(-1) vecuronium, patients were allocated randomly into two groups: in Group C tracheal intubation was attempted using only a fibrescope, whereas in Group L fibreoptic intubation through the intubating laryngeal mask was attempted. RESULTS: In group C the success rate of fibreoptic tracheal intubation within two minutes was higher in the neutral position (31 of 42 patients (73%)) than in the manual in-line position (8 of 20 patients (40%)). In contrast, in group L the success rate was similar between the two positions. Tracheal intubation was easier in group L than in group C (P < 0.01 or 0.001) and the time for intubation was shorter in group L than in group C in both head and neck positions. CONCLUSIONS: Fibreoptic tracheal intubation was more difficult in the manual in-line position than in the neutral position. The intubating laryngeal mask facilitated fibreoptic intubation in both positions.

Anesthesia, Inhalation↗