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PubMed1976

Binaural masking effects in bone-conducted noise.

When pure tones are masked by bone-conducted noise presented at the midline of the forehead, it is possible that binaural unmasking may occur due to the interaural phase relations of the noise. To study this possibility, the amount of masking produced in bone-conducted noise, in correlated air-conducted noise, and in monaural noise was determined using narrow bands of noise centered at 240, 500, 910, and 1900 Hz as markers and a block up-down two-interval forced choice procedure. The subjects were four women under 30 years of age with 10 dB HTL or better (ANSI, 1969) for the frequencies tested. The amount of unmasking (the masking-level difference) was determined by subtracting the masking levels obtained under each noise condition at each frequency from those obtained in the comparable monaural noise-monaural signal condition. Levels of binaural unmasking obtained in correlated air-conducted noise agreed with those in previously reported experiments. Comparable binaural unmasking effects were demonstrated for midline presentation of bone-conducted noise. Some clinical implications of the findings are discussed.

Acoustic Stimulation↗
PubMed2003

A comparison of the effectiveness of pre-hospital bag-valve-mask ventilation performed by Irish emergency medical technicians and anaesthetists working in a tertiary referral teaching hospital.

The objective of this study was to assess the effectiveness of bag-valve-mask ventilation performed by emergency medical technicians with prehospital clinical responsibilities and to compare this with anaesthetists working clinically in tertiary referral teaching hospitals. Participants were asked to perform bag-valve-mask ventilation for three minutes on a Resusi Anne manniquin using a facemask and a two litre self inflating bag. The tidal volumes generated were quantified using a Laerdal skillmeter computer as grades 0-5 corresponding to 0, 335, 434, 561, 673 and > 800 mls. The effectiveness of bag-valve-mask (i.e. the proportion of ventilation attempts which achieved a tidal volume of > 434 mls) was greater for emergency medical technicians [88.2 (17.1)%] than for anaesthetists [40.4 (36.5)%] (P<0.001). Six of the 27 anaesthetists, but none of the 29 emergency medical technicians, were unable to produce even one effective tidal volume i.e. > 434 mls. It is likely that emergency medical technicians are able to perform adequate bag-valve-mask ventilation.

Anesthesiology↗
PubMed2003

Masking effect of music upon oral information processing.

The masking effect of three types of music and white masking noise upon special audiometric tests was determined in laboratory c. The stimulus-noise (S/N) ratio was found to be the most considerable factor influencing oral information processing in spite of the type of music or noise used as a masking agent. All types of music (modern, classic or modern music records in backwards order) showed no significant differences in masking being in the same way stronger maskers as white noise. Some conclusions are made concerning hygienic and ergonomic aspects of the problem.

Audiometry, Speech↗
PubMedDate not supplied

[Experience with 100 anesthetized patients ventilated with laryngeal mask].

We studied 100 adult patients who were anesthetized for different surgical procedures and were ventilated with laryngeal mask either with spontaneous or controlled ventilation. Despite of the inexperience we achieved an appropriate placement of the mask in 99% of cases; 74% at the first attempt, 22% at the second, and 4% at the third. In 87.8% of patients we had an adequate control of the air way. In 12.2% of cases there were problems in relation to the controlled ventilation. In one patient we were unable to correctly place the mask and another anesthetic technique had to be performed. Laryngeal mask is useful in the control of the air way in anesthetized patients with spontaneous ventilation. Some inconvenience may arise when controlled ventilation is used.

Adolescent↗
PubMed2003

Use of a laryngeal mask during medialization laryngoplasty.

OBJECTIVES: In certain instances medialization thyroplasty under local anesthesia is awkward for the patient and complicates surgery. Moreover, for certain operations such as for sulcus vergeture or presbyphonia, subjective auditory appreciation of vocal improvement under operating room conditions is not efficient. In those various instances, we therefore perform thyroplasty under general anaesthesia using a laryngeal mask, and under fibrerscopic control. MATERIAL AND METHOD: A joint connecting the laryngeal mask to the ventilation tube is angled and comprises a small valve through which a fiberscope is slipped. We have used this method since April 99 for 11 surgery procedures. RESULTS AND CONCLUSION: To date, we have not encountered intraoperative complications that have required intubating the patient in order to continue surgery. It can, however, occur that a change in head posture during surgery displaces the mask. In that event, surgery must be momentarily interrupted in order to re-position the mask. The vocal results met expectations.

Adolescent↗
PubMedDate not supplied

Wearing masks in a pediatric hospital: developing practical guidelines.

During the outbreak of Severe Acute Respiratory Syndrome (SARS) in the spring of 2003, strict infection control measures were implemented in Toronto and surrounding hospitals. These measures included extreme restrictions on those who would normally accompany patients to the hospital, screening for SARS, and protective attire for hospital staff, including masks, face shields, goggles, gloves and gowns. At Toronto's Hospital for Sick Children (HSC), patients could only be accompanied or visited by one person, often only in patients' rooms. For the first four weeks, patients and their designated parent had to wear masks in almost all areas of the hospital. Staff wore masks (and other appropriate protective clothing) whenever in contact with patients and in many patient care areas. Although these barriers were an important part of containing SARS, their use created significant challenges for patients and staff. This article focusses on the use of infection control masks in routine pediatric healthcare and the tools developed by HSC staff to reduce the negative psychosocial impact on children and families.

Canada↗
PubMedDate not supplied

[Using non-invasive mask lung ventilation in cardiosurgical patients with acute respiratory distress syndrome].

Twenty patients aged 33 to 71 (54 +/- 6) years (male - 13, female - 7) operated on the heart and main vessels were included in the case study. I.e. those patient were investigated, whose immediate postoperative results were complicated by the syndrome of multiple organ failure (SMOF) that developed due to different-etiology shock, huge blood loss and hemotransfusion or to the syndrome of acute postperfusion lung damage. NIMLV was made at the resolution stage of SMOF and ARDS after artificial pulmonary ventilation (APL) for as long as 5-7 days. The indications for extubation of patients were as follows: PaO2/FiO2 of 200 and more mm Hg, respiratory rate (RR) of less than 30 per min, respiratory volume of more than 6 ml/kg with pressure support at inspiration of less than 5 cm H2O and with the total pressure at the exhalation end of no more than 3 cm H2O. Mask ventilation sessions were started in a growing dyspnea of more than 26 per min, a decreased content of oxyhemoglobin in arterial blood (below 95% at oxygen inhalation of 10-15 l/min), involvement of auxiliary muscles in breathing and at subjective complaints of patients related with complicated breathing and with being short of air. The mask SIMV ventilation with a preset apparatus-aided rate of inhales of 2-6/min, with Bi-PAP and PSV inhale pressure of 15 cm/ H2O and with PEEP of 3-5 cm/ H2O was made by 40-120 min sessions; the number of IFMLV sessions ranged from 6 to 22/patient, mean - 11 +/- 1.1 h. The total IFMLV duration was 10.7 +/- 1.1 h. The need for respiratory support persisted for 4-6 days after extubation. In 18 (90%) of 20 patients, the mask pulmonary ventilation resolved the respiratory insufficiency. Two (10%) patients were reintubated because of progressing multiorgan failure and because of obturation of the left main bronchus. A questioning of patients on the comfort degree of mask ventilation denoted the Flow-by triggering to be by far better tolerated by patients versus the pressure triggering.

Adult↗
PubMed2004

[End-tidal sevoflurane concentrations for laryngeal mask airway insertion and tracheal intubation in children].

BACKGROUND: Sevoflurane, a new inhalation anesthetic agent characterized by a low blood-gas partition coefficient and nonpungent odor, appears suitable as an induction agent for children. This study was conducted to determine the sevoflurane concentration required for tracheal intubation and insertion laryngeal mask in children. METHODS: Thirty patients, aged 3-7 years, scheduled for surgery during general anesthesia were randomly assigned into two groups: Group I (n=15)--tracheal intubation (IT), Group II (n=15)--laryngeal mask insertion (LMI). After the predetermined end-tidal concentration of the sevoflurane, tracheal intubation or laryngeal mask insertion was attempted without neuromuscular relaxants. RESULTS: Sevoflurane MAC-LMI was 1.53 +/- 0.23%, sevoflurane MAC-TI was 2.35 +/- 0.31%, significantly greater than MAC-LMI. CONCLUSIONS: Laryngeal mask insertion can be performed at a lesser sevoflurane concentration than that required for tracheal intubation.

Anesthesia, Inhalation↗
PubMed2005

The mask detection technology for occluded face analysis in the surveillance system.

The surveillance systems have been widely used in automatic teller machines (ATMs), banks, convenient stores, etc. For example, when a customer uses the ATM, the surveillance systems will record his/her face information. The information will help us understand and trace who withdrew money. However, when criminals use the ATM to withdraw illegal money, they usually block their faces with something (in Taiwan, criminals usually use safety helmets or masks to block their faces). That will degrade the purpose of the surveillance system. In previous work, we already proposed a technology for safety helmet detection. In this paper, we propose a mask detection technology based upon automatic face recognition methods. We use the Gabor filters to generate facial features and utilize geometric analysis algorithms for mask detection. The technology can give an early warning to save-guards when any "customer" or "intruder" blocks his/her face information with a mask. Besides, the technology can assist face detection in the automatic face recognition system. Experimental results show the performance and reliability of the proposed technology.

Crime↗
PubMed2005

[Laryngeal mask during emergence from anesthesia in intubated patients with asthmatic attack or ischemic heart disease].

We report two patients in whom the presence of a tracheal tube induced asthmatic attack or hemodynamic instability and the laryngeal mask was useful during emergence from anesthesia. Case 1:A 24-year-old man with asthma was scheduled for reconstruction of an amputated finger. After induction of anesthesia and neuromuscular blockade, the trachea was intubated without complications. At the end of 9.5-h uneventful operation under anesthesia with sevoflurane, nitrous oxide and oxygen, inhalational anesthetics were turned off. During emergence from anesthesia, bucking with asthmatic attack occurred. Sevoflurane and theophilline resolved the attack, which recurred after termination of sevoflurane. Under deep anesthesia with sevoflurane, the laryngeal mask was placed, and then the tracheal tube removed without complications. The laryngeal mask was removed when the patient awoke uneventfully. Case 2: A 69-year-old man with a recent history of myocardial infarction was scheduled for skin grafting. After uneventful operation, sevoflurane and nitrous oxide were turned off. Multiple premature ventricular contractions (PVCs) with hypertension and tachycardia occurred, and necessitated the restart of sevoflurane. Under deep anesthesia, the laryngeal mask was inserted and the trachea extubated, and the patient regained consciousness without complications.

Adult↗
PubMed2006

[Mask anesthesia for cerebral angiography in childhood moyamoya disease].

Cerebral angiography is performed for diagnosis and management of moyamoya disease and in childhood moyamoya disease is usually carried out under general anesthesia after tracheal intubation. Mechanical irritation to trachea resulting in pain,cough,and increase in secretion after termination of the general anesthesia sometimes occurs and it sometimes causes hyperventilation resulting in hypocapnea. Continuous hypocapnea sometimes causes appearance of ischemic attacks in moyamoya disease. In the present study, we examine cerebral angiography conducted under general anesthesia using face mask ventilation in fourteen children with moyamoya disease. Sevoflurane was used as inhalation anesthetics. Face mask anesthesia was sixteen times in total in the 14 patients. Cerebral angiography terminated uneventfully in these patients except one patient who showed bronchospasm after induction of anesthesia and required tracheal intubation. However, the patient showed uneventful course after termination of the angiography. Tracheal irritation did not appear and all the patients were asleep just after termination of face mask anesthesia except for the patient who required tracheal intubation. In the latter case, the patient frequently coughed out phlegm after general anesthesia with tracheal intubation. In conclusion, general anesthesia with face mask ventilation was thought to be one of the suitable anesthetic methods introduced for cerebral angiography in childhood moyamoya disease.

Anesthesia, Inhalation↗
PubMed2006

Masks for influenza patients: measurement of airflow from the mouth.

In case of a new influenza pandemic, provision of masks to coughing patients could be used to slow expansion of the epidemic. To quantitatively assess the efficacy of different masks, we used an ultrasonic anemometer to measure the velocity of airflow from the mouth in coughing. We found that even the cheapest paper masks reduced the air speed to less than 1/10, implicating their effectiveness in decreasing viral spread. We therefore propose that governments provide free masks to coughing patients in the general population upon the emergence of a new human influenza virus.

Cough↗
PubMed1991

Masked high-frequency bone-conduction audiometry: test reliability.

The present study examines the reliability of masked high-frequency bone-conduction threshold measurements in 95 normal-hearing subjects. High-frequency pure-tone air-and bone-conduction thresholds were measured with a dedicated laboratory high-frequency auditory evaluation system using matched, modified Koss Pro/4X Plus earphones, and the Pracitronic KH 70/5 bone vibrator. A 400-Hz wide band masking noise centered at the frequency of the test tone was used to mask the nontest ear. Monaural masked bone-conduction threshold measurements were obtained at the ipsilateral mastoid of the ear with better high-frequency hearing. Two measurements were performed in each session, and each subject participated in two sessions. In several comparisons for test-retest consistency, high-frequency bone-conduction threshold measurements were as repeatable as air-conduction thresholds of identical frequency, or bone-conduction thresholds for frequencies of 4 kHz and less. High-frequency bone-conduction threshold measurement appears to be a sufficiently reliable tool for diagnosis of auditory disorders.

Adolescent↗
PubMed1991

High-level psychophysical tuning curves: forward masking in normal-hearing and hearing-impaired listeners.

Forward-masked psychophysical tuning curves (PTCs) were obtained for 1000-Hz probe tones at multiple probe levels from one ear of 26 normal-hearing listeners and from 24 ears of 21 hearing-impaired listeners with cochlear hearing loss. Comparisons between normal-hearing and hearing-impaired PTCs were made at equivalent masker levels near the tips of PTCs. Comparisons were also made of PTC characteristics obtained by fitting each PTC with three straight-line segments using least-squares fitting procedures. Abnormal frequency resolution was revealed only as abnormal downward spread of masking. The low-frequency slopes of PTCs from hearing-impaired listeners were not different from those of normal-hearing listeners. That is, hearing-impaired listeners did not demonstrate abnormal upward spread of masking when equivalent masker levels were compared. Ten hearing-impaired ears demonstrated abnormally broad PTCs, due exclusively to reduced high-frequency slopes in their PTCs. This abnormal downward spread of masking was observed only in listeners with hearing losses greater than 40 dB HL. From these results, it would appear that some, but not all, cochlear hearing losses greater than 40 dB HL influence the sharp tuning capabilities usually associated with outer hair cell function.

Acoustics↗
PubMed1991

[Changes in arterial pressure and heart rate during laryngeal mask insertion in hypertensive patients: comparison with endotracheal intubation].

The pressor response associated with laryngoscopy and endotracheal intubation may be harmful to patients with ischemic heart disease, hypertension or cerebrovascular disease. The Brain laryngeal mask airway can be inserted blindly and avoid the need for laryngoscopy. Our preliminary study compared the pressor response of tracheal intubation (T group) with that of laryngeal mask insertion (L group) in 19 and 33 hypertensive patients respectively. We also divided the patients of L group into sub-groups I (n = 16) and II (n = 17). All patients in T group and sub-group I were induced with fentanyl, thiopentone and succinylcholine while in subgroup II patients were induced with the same dosage of thiopentone and succinylcholine without fentanyl. The changes of blood pressure and heart rate exhibited a similar but attenuated pattern of response with laryngeal mask insertion in comparison with tracheal intubation. We also found no significant difference in pressor response between sub-group I and sub-group II in L group. In sum, laryngeal mask insertion may therefore offer some advantages over tracheal intubation in the anesthetic management of hypertensive patients in whom less pressor response is of particular concern.

Adult↗
PubMed1991

A latex mask for collection of expired gases from goats.

A latex respiratory mask was developed to collect expired gas from goats in studies of ventilatory adaptation to high altitude. The snouts of 15 animals were dimensioned by taking girth measurements. The procedure requires a rough positive mold of wood which is repeatedly submerged into latex, then slowly rotated upon removal until skim-like layers form a mask. A supporting harness is attached to the mask by use of three flat straps connected by Dot fasteners. A period of several hours per day for up to 2 weeks may be necessary to allow the animal to become accustomed to wearing the mask.

Adaptation, Physiological↗
PubMed1991

High-level psychophysical tuning curves: simultaneous masking by pure tones and 100-Hz-wide noise bands.

Simultaneous-masked psychophysical tuning curves were obtained from normal-hearing listeners using low-level (20-25 dB SPL) probe tones in quiet and high-level (60 dB SPL) probe tones, both in quiet and in the presence of a broad-band background noise. The background noise was introduced to eliminate combination tones or combination bands and other off-frequency listening cues that exist at high levels. Tuning curves were obtained using pure-tone maskers and 100-Hz-wide narrow-band noise maskers for probe tones at 1000 and 4000 Hz. High-level tuning curves for pure-tone maskers demonstrated large discontinuities or "notches" on the low-frequency sides of the tuning curves. Broad-band background noise eliminated those notches, indicating that the notches were due to the detection of off-frequency listening cues at combination-tone frequencies. High-level tuning curves for 100-Hz-wide narrow-band maskers also demonstrated notches on the low-frequency sides. Those notches were eliminated with broad-band background noise, which indicates that combination bands strongly influenced the shapes of high-level tuning curves obtained with narrow-band maskers. The influence of combination bands was dependent upon test frequency. At 1000 Hz, combination bands had very little influence on the shapes of high-level tuning curves. At 4000 Hz, where the masker bandwidth was substantially less than the critical bandwidth, combination bands strongly affected the low-frequency sides of the tuning curves. In 2 subjects tested at a probe frequency of 2000 Hz with 100-Hz-wide masking bands, combination bands also influenced the low-frequency sides of high-level tuning curves. The presence of combination-tone or combination-band cues essentially steepened the low-frequency slopes of tuning curves, resulting in sharper estimates of tuning. Comparisons of tuning curves obtained with pure-tone maskers and narrow-band maskers, in the same listeners, revealed that pure-tone maskers were more effective than narrow-band maskers when the masker frequencies were in the tail region of the tuning curve. The results of these experiments support the notion that tuning in the normal auditory system broadens notably with stimulus level, once off-frequency listening cues such as combination tones or combination bands are eliminated. The low-level simultaneously masked tuning curve demonstrates a sharp bandpass tuning characteristic, whereas the high-level simultaneously masked tuning curve in background noise demonstrates a broad low-pass tuning characteristic.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustics↗
PubMed1986

Effects of small and large face masks and translaryngeal and tracheostomy intubation on ventilation, upper-airway dead space, and arterial blood gases.

Pulmonary function was examined in pentobarbital-anesthetized dogs that were spontaneously breathing through a large poorly fitted face mask, a small snug-fitted face mask, an endotracheal tube, and a tracheostomy tube. Increasing upper-airway dead space volumes were associated with higher minute ventilation and faster breathing rates. Minute and tidal alveolar ventilation, calculated ideal alveolar oxygen, alveolar-arterial oxygen gradient, venous admixture, arterial pH and blood gases, cardiac output, and systemic and pulmonary arterial blood pressure were not changed. The functional dead space of each mask was considerably less than that measured by water displacement. The small mask only slightly increased, and the endotracheal tube slightly decreased, the dead space estimated for a nasally breathing healthy dog.

Anesthesia, General↗