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PubMed1985

Custom-fabricated masks for aeromechanical measures.

A technique is described for the construction of custom fabricated face masks designed for use in aeromechanical studies of individuals with speech disorders, such as those associated with craniofacial defects. The wax-elimination method of mask fabrication described herein is similar to routine dental laboratory procedures. Materials employed are heat-cured acrylic resin for the body of the mask and heat-cured resilient liner for the tissue contacting surface of the mask.

Acrylic Resins↗

PubMed1985

Nonsimultaneous auditory masking in the budgerigar (Melopsittacus undulatus).

The frequency resolving power of budgerigars and that of humans were compared on several nonsimultaneous masking procedures in which one pure tone is used to mask another. Similar patterns of frequency selectivity were found for all three masking procedures (forward, backward, and combined forward-backward) for both species. Budgerigars showed considerably greater frequency resolving power on all three procedures than humans. Budgerigars also showed differences in frequency resolving power across masking conditions, but human listeners did not. These results indicate that the budgerigar auditory system may be even more highly tuned than was previously thought and suggest fundamental differences between the mechanisms of frequency selectivity of bird and those of humans.

Animals↗

PubMed1985

[Experience in the use of face masks for radiotherapy of head and neck tumors].

By means of positioning and fixation aids, the precision and reproducibility of irradiation fields in radiotherapy of malignant tumors of the head and neck can be considerably improved. Face masks made of different synthetic materials have proved to be a practicable solution of this problem. In our hospital we have developed and tested a simple and not expensive possibility of manufacturing the masks with "Baycast" (producer: Bayer AG Leverkusen). The material is generally well tolerated by the patients, and the head is sufficiently fixed. An increased incidence of radiogenic dermatitides is caused by the overlapping of the depth dose of the Co-60 gamma radiation due to additional secondary electrons emanating from the mask material. This effect can be partly prevented by cutting out the irradiation fields in the masks.

Cobalt Radioisotopes↗

PubMed1978

Investigation of arterial bloodgases at altitude using constant-flow oxygen masks.

Arterial blood oxygen tensions up to 6700 m altitude (FL220) were measured polarographically while subjects breathed from various masks with constant-flow oxygen. The Sierra and Aro masks used for emergency decompression descent in commercial passenger aircraft, gave mean PaO2's of 130 +/- 7.6 and 130 +/- 12.1 torr at 6700 m (FL220) and 90 +/- 3.8 and 77 +/- 3.35 torr at 4260 m (FL140), respectively, when supplied with oxygen flows corresponding to those available in the Boeing 747. These oxygen tensions during descent are acceptable for normal physiological function in a heterogeneous population of air travellers whereas breathing ambient air during return to base at 4260 m (FL 140) (PaO2 of 48 or less) is not acceptable. The valveless Hudson 1007 and Puritan 114011 masks, used for air ambulance service, gave mean PaO2's of 110 +/- 2.7 and 98 +/- 4.5 torr at 6700 m and 80 +/- 3.0 and 77 +/- 2.5 torr at 4260 m under the same condition--significantly less than the Sierra mask.

Adult↗

PubMedDate not supplied

Masking of spondees by interrupted noise in hearing-impaired listeners.

The effects of changing the duty cycle of an interrupted-broad band masker on the spondee thresholds of hearing-impaired subjects were explored. Two diagnostic groups of sensorineural hearing loss, presbycusics and cochlear otosclerotics, were investigated. The interruption rate of the masker was 10/sec, and its duty cycle was varied at 25% intervals. Thresholds also were obtained in continuous noise and in quiet. Results when compared with earlier data from normal listeners revealed that subjects with sensorineural impairment exhibited poorer performance in all instances, including the continuous noise condition, when mean masker levels were adjusted to comparable sound pressure levels. The overall pattern of masking was more similar for the normal and hearing-impaired groups when performance was equated in terms of the mean threshold shift each group experienced in continuous noise. Even under these circumstances, however, hearing-impaired subjects demostrated notably greater residual masking under the 25 and 50% noise-on conditions. A major determinant of speech reception in fluctuating noise backgrounds is the dependence of the pattern of masking upon the difference between an individual's masked threshold in continuous noise and his threshold in quiet, rather than upon the sound pressure level of the masker.

Acoustic Stimulation↗

PubMed1978

[Retention of radioactive aerosols (products of radon-222 decay) by various types of anti-dust masks].

The paper presents results of measurements of the efficiency of retention of radon decay products, occurring as radioactive aerosols, by anti-dust masks. The efficiency of three types of masks: PM-1, PM-3, PP-2 "Delta" was studied under various conditions of equilibrium between radon and products of its decay in the air. It was concluded that the efficiency of retention of radon decay products, occurring as radioactive aerosols, by the mentioned types of masks, comes to 75--87%. Anti-dust PM-1 (F-14 filter) and PM-3 (F-13 filter) masks are recommended as most efficient.

Aerosols↗

PubMed1983

The masking dilemma and its solution. Fusion at the inferred threshold (FIT) and sensorineural acuity level (SAL) tests.

It is difficult or impossible to obtain air or bone conduction threshold levels in some cases of moderately severe conductive involvement because it may be impossible to mask the nontest ear without also masking the test ear. This has been termed the "masking dilemma." In most of these "masking dilemma" cases the fusion at the inferred threshold (FIT) test can determine the air conduction hearing levels, and in some cases the sensorineural acuity level (SAL) test can help determine the sensorineural function.

Adolescent↗

PubMed1981

On the relationship of stapedial contraction to central masking.

The auditory masked threshold of a 1-kc/s pure tone was determined in quiet and with levels of white noise at 50-80 db SL in the non-test ear. Two groups of normal-hearing adults were tested, one (N:14, mn age = 27.4 yrs) with no history of middle-ear pathology, and another (N:12, mn age = 44.7 yrs) with the stapedial tendon severed. Significant differences in the amount of masked-threshold shift were observed, greater shifts being seen for the normal Ss, additional shifts ranging from 0.8-4.3 db as masking increased from 50-80 db SL. These differences were judged to be at least partly the result of stapedial contraction rather than having their origin entirely in central masking as often assumed.

Adolescent↗

PubMed1980

Effectiveness of a portable face mask in attenuating exercise-induced asthma.

Recent investigations have demonstrated that exercise-induced asthma (EIA) can be prevented by inspiration of warm, fully humidified air during exercise. We evaluated the success of a surgical face mask, used to retain warm, humidified, expired air, in preventing EIA in ten asthmatic children. subjects underwent six minutes of exercise on a treadmill during two sessions, in one session breathing room air and in another wearing a mask covering the nose and mouth. On the control day, average group forced expiratory volume in 1 s (FEV1) and maximal midexpiratory flow rate (MMEF) decreased from the preexercise baseline value to 66% and 47% of baseline, respectively, at six minutes; on the mask day, FEV1 and MMEF were 91% and 82% of the baseline values (increased in all subjects). A simple face mask may be an inexpensive, nonpharmacologic alternative for alleviation of EIA.

Adolescent↗

PubMed1978

Self-masking effects from live and recorded vowels.

As a means of determining the masking characteristics of spoken (live) vowels, as compared to recorded vowels, 16 normal Ss were trained to track pure-tone swept-frequency thresholds in the presence of vowels used as masking noise. While tracking thresholds, Ss either phonated the vowels /a/, /i/, or /u/ continuously or listened to a taped playback of their own voices. The resulting continuous-frequency audiograms generally resembles the configurations of the vowel spectra. Overall masking effect was significantly greater for the recorded vowels (air-conducted feedback only) than for the live vowels (both air- and bone-conducted feedback) at equal loudness. Recorded vowels tended to have greater masking effect in the higher frequencies, while live vowels tended to have greater effect in the lower frequencies.

Adult↗

PubMed1995

Airway protection by the laryngeal mask airway in children.

The pediatric laryngeal mask airway (LMA) is a scale-down version of the adult form, and no direct postmortem specimen work has been performed so far. There are several anatomical differences between pediatric and adult airways, and hence, the scale-down version of the adult LMA is not necessarily water-tight in pediatric patients. We performed a prospective study to assess airway protection by the LMA in pediatric patients, using methylence blue (injected in the pharynx outside the LMA) and the fibreoptic bronchoscope to view the inside of the mask, to detect any leakage of the dye. Fifty Patients (40 boys and 10 girls) aged 1-10 years (mean 4.5 yr) were studied. All patients underwent surgery below the level of the umbilicus, under light general anesthesia combined with caudal epidural block. All patients were allowed to breath spontaneously over an Ayre's T-piece. Dye staining of the inside of the mask was detected in 5 patients (10%). The esophageal opening was visualized within the mask in 3 patients (6%). No serious complications occurred in any of our patients.

Anesthesia↗

PubMed1995

The mask: style and volume do not influence rhinomanometry.

We have tested the influence of face-mask style and volume on rhinomanometric measurements. Using an artificial head-and-piston pump to standardize the test conditions, four types of face masks (volumes varying from 120 to 200 ml) have been tested in a series of 20 measurements per mask. No statistical difference could be found between the series using a Chi-square test. We conclude that there is no influence of form and volume of the face mask on the accuracy of the rhinomanometric measurement.

Airway Resistance↗

PubMed1995

[Use of the laryngeal mask in pediatric surgery].

The laryngeal mask is a new method in the control of the airway. In this study we assess the haemodynamic response during the insertion of the laryngeal mask, incidence of complications and recovery from anaesthesia after its use. We also check if the laryngeal mask is easy to place into the patient airway and its versatility in pediatric patients. We have obtain that the use of the laryngeal mask airway is a safe technique, with few complications, easy to learn and with a short recovery time.

Adolescent↗

PubMed1995

[Clinical experience of laryngeal mask airway in lateral position during anesthesia].

BACKGROUND: The laryngeal mask airway (LMA), inserted blindly into hypopharynx in patients in supine position, has been reported to be successful in the management of the airway and can provide adequate ventilation during anesthesia. In our study, we used LMA to maintain airway during anesthesia in patients in lateral position. METHODS: Eighty surgical patients, ASA class I-II, undergoing hemorrhoidectomy, were placed in lateral surgical position before induction. The induction agents were propofol (2 mg/kg), fentanyl (2 micrograms/kg) and atracurium (0.5 mg/kg, i.v.). When mouth opening can be done passively, a LMA was inserted into the mouth and advanced blindly over the tongue into the pharynx until resistance was felt. The rim was immediately inflated with air and several manual positive pressure ventilatory breaths were given to the patient to check for leaks in the LMA system. Chest movement was observed and bilateral lung ausculation was performed to confirm the adequacy of ventilation. Once the LMA was in place, enflurane with oxygen was administered until operation was completed. During the anesthetic course, EKG, blood pressure, pulse oximeter, end-tidal CO2 and inspiratory pressure were monitored. RESULTS: Blind insertion of LMA in lateral position was successful in the first attempt in 70% (56/80) of patients. Twenty (18/80) patients required a second or third trial making the total successful rate of LMA insertion as high as 90% (74/80). In four patients, airway control through LMA was unsatisfactory due to large air leakage during manual ventilation. In two patients the LMA could not be inserted in proper position for maintaining airway. In six cases, the LMA was immediately removed and was substituted by face-mask for anesthesia. Two patients complained of postoperative sore throat. No other specific complications such as cough, laryngospasm and aspiration was noted. CONCLUSION: We demonstrated that LMA can be easily inserted and can provide effective patency of airway during anesthesia even in lateral position. It can be used as a substitute for face-mask in anesthesia in this position to prevent complications such as pressure injury that a face-mask may cause.

Adult↗

PubMedDate not supplied

[Laryngeal mask: a new concept in maintenance of patency of the respiratory tract].

A laryngeal mask is, no doubt, a useful and indispensible device for the majority of adults and children subjected to surgery. Its application is simple and atraumatic, involving the minimal hemodynamic and somatic reactions. A laryngeal mask is a good alternative to facial mask and endotracheal intubation in a great number of clinical situations. Moreover, it provides blind and fibreoptic technique of intubation, though its role in emergency situations is still to be found out. Despite the evident necessity of further investigation, laryngeal masks can be safely used in clinical practice now.

Adult↗

PubMed1993

A new method of maintaining airway during nasotracheal intubation--the hand mask technique.

The efficacy of a new method (The hand mask technique) for airway maintenance during nasotracheal intubation was evaluated in our randomized crossover study. Sixty, age less than 50, ASA physical status class I-II patients undergoing surgery for the extremities with informed consent were randomly chosen for the study. Pulse oximeter, capnometer, EKG, blood pressure monitor and a peripheral nerve stimulator were attached to the patients before induction for continuous monitoring. An arterial cannula was inserted for intermittent blood gas sampling. After baseline room air blood gas data had been obtained from the spontaneously breathing patients, a flow rate of 6L/min pure oxygen was applied through a loosely fitted face mask and a semi-closed anesthesia breathing circuit for a period of 5 minutes. An arterial blood sample was drawn and the patients were put under general anesthesia with full muscle relaxation thereafter. Patients were then randomly assigned into two groups according to the ventilation technique used. Group A patients (n = 30) were manually ventilated first through a face mask for ten minutes and then the hand mask technique for another ten minutes. Blood gas data was sampled and heart rate, blood pressure, peak inspiratory airway pressure and end tidal CO2 were recorded immediately after each ventilation technique. For patients in Group B (n = 30), the sequence of the two ventilation technique were reversed. The results showed significant increases in PaO2 after artificial ventilation in both groups (No significant difference in results between the two groups) and less incidence of nasal bleeding in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

[Prevention of postoperative pulmonary complications after heart-lung surgery. Comparison of 3 different mask physiotherapy regimens].

The object of the investigation was to compare the effect of three different physiotherapy masks on the incidence of postoperative complications after thoracic surgery. It was carried out as a prospective, consecutive, randomized comparison at a Department of Thoracic and Heart Surgery at a University Hospital. The therapy was performed by experienced and specially trained physiotherapists. One hundred and sixty patients were evaluated; 60 patients undergoing heart surgery, 59 patients having pulmonary resection, and 41 patients with exploratory thoracotomy. In each operative category the patients were treated with one of three face mask systems used in addition to routine chest physiotherapy. These were either continuous positive airway pressure (CPAP), positive expiratory pressure (PEP), or inspiratory resistance--positive expiratory pressure (IR-PEP). Postoperative pulmonary complications were assessed by forced vital capacity (FVC), arterial oxygen tension (PaO2), and chest X-ray examination, all parameters were measured preoperatively and on the fourth and ninth postoperative day. The patients filled in a questionnaire concerning their opinions about their mask treatment. IR-PEP showed a lesser decrease in PaO2 on day nine. Otherwise there was an equal decrease in FVC and PaO2, and equal frequency of atelectasis in the three mask treatments. It is therefore concluded that any of the three therapies: continuous positive airway pressure (CPAP), positive expiratory pressure (PEP), and inspiratory resistance--positive expiratory pressure (IR-PEP) may be used as supplement to standard chest physiotherapy.

Cardiac Surgical Procedures↗

PubMed1993

A study of laryngeal mask inflation. Pressures exerted on the pharynx.

Laryngeal mask airway cuff inflation pressures were measured when inflated with the same volume of gas firstly in free space and then in position in the pharynx. A large difference in these pressures was observed and this was related to pharyngeal mucosal perfusion pressure. This study shows that it may be easy to produce pressures on the pharyngeal mucosa in excess of the critical perfusion pressure and thus potentiate mucosal trauma. Furthermore, laryngeal mask cuff pressures were measured at intervals during anaesthesia and were found to rise by a significant amount if room air was used as the cuff inflating gas. This effect could, however, be reversed if inspired gas was used to inflate the mask cuff. We conclude that care must be taken when inflating the laryngeal mask cuff if postoperative morbidity is to be avoided and also that it may not be necessary to use as high a volume of inflating gas as has been recommended during spontaneous respiration.

Adult↗