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PubMed1994

Effect of masking on circadian adjustment and interindividual differences on a rapidly rotating shift schedule.

OBJECTIVES: The aim of the present study was to define the effect of masking on the estimation of circadian adjustment of and interindividual differences between nurses on a rapidly rotating shift schedule. METHODS: The phase shift of the circadian rhythm of rectal temperature was studied in 17 subjects. The following three different methods for estimating the circadian phase shift were compared: (i) cosinor analysis, (ii) a method using normative endogenous data in which the masking effects are removed ("purification"), and (iii) a method using normative endogenous data in which the masking effects are not removed. RESULTS: The mean phase delay during the second night shift (compared with the morning shift) was 6.3 h according to the cosinor analyses of the raw data and 6.2 h according to the cross-correlation method of the raw data. When the masking effects were removed ("purification"), the phase shift was only 1.7 h. Diurnal type did not significantly explain the differences between individuals in the amount of phase shift of the raw data but was the only significant factor, explaining 32% of the variation between individuals in the phase shift of the purified data. CONCLUSIONS: Masking effects on body temperature should be taken into account before any definite conclusions can be drawn about the relation between individual factors and the adjustment of the circadian rhythm of body temperature.

Adaptation, Psychological↗
PubMed1991

Comparison of tidal volumes, minute ventilation, and respiratory frequencies delivered by paramedic and respiratory care students with pocket mask versus demand valve.

BACKGROUND: The importance of establishing the airway and providing ventilation during resuscitation is well recognized; however, the effectiveness of demand-valve ventilation has not been fully addressed. METHODS & MATERIALS: We examined the differences in respiratory frequency (f), tidal volume (VT), and minute ventilation (VE) achieved by 15 emergency medical technicians (EMT) in a paramedic training course (EMT-4) and 16 second-year respiratory care students (RC) when ventilating a mannequin by three different methods: Laerdal pocket mask, a mask designed for mouth-to-mask ventilation (Method I), demand valve with one hand (Method II), and demand valve with two hands (Method III). RESULTS: The RC f was much higher for all three methods compared to the EMT-4. The EMT-4 demonstrated larger VT for each method compared to the RC. The RC only achieved acceptable VT with Method III. The EMT-4 and RC demonstrated statistically significant differences in VE between each method. However, the clinical importance of these differences for EMT-4 is negligible. Although the mean values indicated achievement of minimum VTS by the EMT-4 with the pocket mask, 40% were unable to do so at 1 minute and 60% at 5 minutes. A great difference was seen in VE produced by RC with Method I at both 1 and 5 minutes vs Methods II and III. CONCLUSIONS: EMT-4 appear to have superior ventilation skills compared to RC. Superior performance skills may be related to (1) different instructional methodologies, (2) effects of various amounts of experience in ventilating actual victims, and (3) greater familiarity of EMTs with the demand valve. As a consequence of this study, we are re-evaluating the instructional methodology used in our programs; we encourage other programs to do the same. We recommend that EMS providers and hospitals consider changing to an acceptable alternate mask in light of these and previous data.

Competency-Based Education↗
PubMed1985

Arterial oxygen values achieved by COPD patients breathing oxygen alternately via nasal mask and nasal cannula.

Ten patients with known but clinically stable chronic obstructive pulmonary disease (COPD) were studied while breathing low-flow (1-2 L/min) supplemental oxygen by nasal cannula and by biflow nasal mask. Although the increase in inspired oxygen when breathing with the cannula has been documented, the nasal mask has not been tested by measurement of PaO2 change. The mean age of the group was 64.6 years, and their mean PaO2 was 54 +/- 10.5 torr while they were at rest and breathing room air. Patients were each given oxygen alternately with the mask and cannula, with no change in flowrate; time was allowed between the two for equilibration and return to baseline values. PaO2 values were compared by t test for nonindependent samples, which provided a t value of 1.893, with P = 0.09. Differences in measured arterial saturation (SaO2) and PaCO2 also proved to be insignificant when patients breathed via the two devices. The conclude that the nasal cannula and the biflow nasal mask produce comparable PaO2 in patients who may need low-flow supplemental oxygen at rest. The mask can be considered an alternative oxygen appliance if preferred by patients because of comfort.

Masks↗
PubMed1999

Pressures exerted against the cervical vertebrae by the standard and intubating laryngeal mask airways: a randomized, controlled, cross-over study in fresh cadavers.

UNLABELLED: In this randomized, controlled, cross-over study, we measured the pressures exerted by the standard laryngeal mask airway (LMA) and the intubating laryngeal mask airway (ILM) against the cervical vertebrae during insertion, intubation, and maneuvers commonly used to facilitate intubation. We also assessed the effect of these pressures on cervical spine (C-spine) movement. Twenty cadavers (6-24 h postmortem) without cervical abnormality were initially studied. Three microchip pressure sensors were implanted into the pharyngeal surface of C2-3. The size 5 ILM and LMA were inserted in random order into each cadaver with the head-neck in the neutral position. Maximal cervical pressures (CPmax) were recorded for both devices during cuff inflation from 0-40 mL and with the intracuff pressure (ICP) at 60 cm H2O, insertion, fiberscope-guided intubation, partial withdrawal/reinsertion (ILM only), elevation/depression of the handle with 20 N of force applied (ILM only). In five additional matched cadavers, the effect of pressure on posterior displacement of C3 was assessed, and CPmax was measured during laryngoscope- and fiberscope-guided oro/nasotracheal intubation (controls). CPmax was higher for the ILM than the LMA over the inflation range (96 vs 15 cm H2O; P < 0.0001) and with the ICP at 60 cm H2O (95 vs 10 cm H2O; P < 0.0001). During cuff inflation, CPmax was generally unchanged for the ILM but was always increased for the LMA. CPmax for the LMA and ILM was similar during insertion (224 vs 273 cm H2O) but higher for the ILM during fiberscope-guided intubation (96 vs 43 cm H2O; P < 0.0001). At 60 cm H2O ICP, CPmax increased during LMA (224 cm H2O; P < 0.0001) and ILM insertion (273 cm H2O; P < 0.0001) and increased for the LMA (43 cm H2O; P < 0.0001) but was unchanged for the ILM (96 cm H2O) during fiberscope-guided intubation. For the ILM, CP-max increased during handle depression (394 cm H2O; P < 0.0001) and partial withdrawal/reinsertion (265 cm H2O; P < 0.0001) but decreased during handle elevation (6 cm H2O; P < 0.00001). CPmax for the controls was usually zero and was always less than the LMA/ ILM (P < 0.0001). The mean (range) for posterior displacement of C3 was 0.8 (0-2) mm at 100 cm H2O and 2.8 (1-5) mm at 400 cm H2O. Laryngeal mask devices exert greater pressures against the cervical vertebrae than established intubation techniques and can produce posterior displacement of the C-spine. IMPLICATIONS: Laryngeal mask devices exert greater pressures against the cervical vertebrae than established intubation techniques and can produce posterior displacement of the cervical spine. We recommend that laryngeal mask devices only be used in the unstable cervical spine if difficulties are anticipated or encountered with established techniques, pending the results of studies demonstrating its relative safety.

Aged↗
PubMedDate not supplied

Malleable registration mask: application of a novel registration method in image guided sinus surgery.

Image-guided systems are becoming more widely used in endoscopic sinus and skull base surgery. All systems require initial registration to correlate the CT scan images to the patient's anatomy. Multiple registration techniques can be used. The ideal technique is one that is easy, reproducible, and provides the most accurate registration in the least amount of time. This study used an optical-based image-guided system (LandmarX) to test a unique mask registration technique and (compared it to a previously used anatomic registration technique. Twenty-one patients were scanned with the mask and underwent surgery. Registration was performed using both the registration mask and the anatomic landmarks. Mean registration error and time were recorded. Results are reported for 20 patients. Mean registration error for the mask technique was 0.96 mm and took a mean of 41 seconds. Anatomic registration error using five or six points resulted in a mean initial error of 2.08 mm and took 31.2 seconds. Mean final anatomic registration error was 1.53 mm, requiring reregistration of a mean of 4.6 points, and took 106 seconds. Statistically significant differences were obtained between the two techniques with regard to registration error and time to final registration. We found that the registration mask technique is a more reliable technique in ease, accuracy, and time of registration. This technique should be especially beneficial to the less experienced image-guided surgeon.

Female↗
PubMedDate not supplied

Comparative evaluation of intraocular pressure changes subsequent to insertion of laryngeal mask airway and endotracheal tube.

AIMS: To evaluate the intraocular pressure and haemodynamic changes subsequent to insertion of laryngeal mask airway and endotracheal tube. SUBJECTS AND METHODS: The study was conducted in 50 adult patients. A standard general anaesthesia was administered to all the patients. After 3 minutes of induction of anaesthesia baseline measurements of heart rate, non-invasive blood pressure and intraocular pressure were taken following which patients were divided into two groups: laryngeal mask airway was inserted in group 1 and tracheal tube in group 2. These measurements were repeated at 15-30 second, every minute thereafter up to 5 minutes after airway instrumentation. RESULTS: A statistically significant rise in heart rate, systolic blood pressure, diastolic blood pressure and intraocular pressure was seen in both the groups subsequent to insertion of laryngeal mask airway or endotracheal tube. Mean maximum increase was statistically more after endotracheal intubation than after laryngeal mask airway insertion. The duration of statistically significant pressure responses was also longer after endotracheal intubation. CONCLUSION: Laryngeal mask airway is an acceptable alternative technique for ocular surgeries, offering advantages in terms of intraocular pressure and cardiovascular stability compared to tracheal intubation.

Adult↗
PubMed2002

[Bronchoscopic treatment for upper tracheal lesions with a laryngeal mask].

A laryngeal mask provides maintaining airway with a larger inner diameter of the tube. A little information is available about bronchoscopic treatment for upper tracheal lesions. Three patients undergoing bronchoscopic treatment for upper tracheal lesions with a laryngeal mask were reviewed. The patients include 3 women, having 2 thyroid cancers and 1 thyroid goiter. The aims of the procedure were hemostasis and reduction of the tumor with subsequent endotracheal stenting in 2 patients, and endotracheal stenting in one patient. The treatment was performed under general anesthesia using a laryngeal mask. All cases were successfully treated without operative and postoperative complications related to the use of the laryngeal mask placement. Use of a laryngeal mask may facilitate insertion and retrieval of a flexible bronchoscope and instruments with an excellent manipulation in therapeutic bronchoscopy for subglottic and upper tracheal lesions.

Aged↗
PubMed2002

[Is use of surgical caps and masks obsolete during percutaneous heart catheterization?].

INTRODUCTION: Despite the lack of scientific evidence, surgical caps and masks are worn routinely by many physicians and nurses in the catheterisation laboratories to avoid local and generalised infections. When we changed our practice, we performed a randomised study to assure the quality of our routine. MATERIAL AND METHODS: All patients undergoing left- or right-sided cardiac catheterisation were randomly allocated to our five laboratories. About two months after the procedure, the patients were sent a questionnaire concerning signs and symptoms of possible inflammation or infection after the procedure. RESULTS: Of 1,034 patients, 855 (82.7%) responded to the questionnaire. Although 25 patients in the caps and mask group vs 19 patients in the other group (6.1% vs 4.3%, ns) had complaints from the procedural access site in the groin, none of these could be ascribed to definite infection. DISCUSSION: The use of caps and masks during percutaneous cardiac catheterisation procedures is based on the concept that the infection rate of patients is reduced. The size of the catheter used, procedure time, and the use of caps and masks by both the surgeon and the assisting staff are discussed. CONCLUSION: The routine use of caps and masks does not seem to have that much beneficial impact on the occurrence of procedure-related inflammations or infections in the cardiac catheterisation laboratory.

Angioplasty, Balloon, Coronary↗
PubMed2002

Noise frame duration, masking potency and whiteness of temporal noise.

PURPOSE: Because of the limited contrast range, increasing the duration of the noise frame is often the only option for increasing the masking potency of external, white temporal noise. This, however, reduces the high-frequency cutoff beyond which noise is no longer white. This study was conducted to determine the longest noise frame duration that produces the strongest masking effect and still mimics white noise on the detection of sinusoidal flicker. METHODS: Contrast energy thresholds (E(th)) were measured for flicker at 1.25 to 20 Hz in strong, purely temporal (spatially uniform), additive, external noise. The masking power of white external noise, characterized by its spectral density at zero frequency N0, increases with the duration of the noise frame. RESULTS: For short noise frame durations, E(th) increased in direct proportion to N0, keeping the nominal signal-to-noise ratio [SNR = (E(th)/N0)(0.5)] constant at threshold. The masking effect thus increased with the duration of the noise frame and the noise mimicked white noise. When noise frame duration and N0 increased further, the nominal SNR at threshold started to decrease, indicating that noise no longer mimicked white noise. The minimum number of noise frames per flicker cycle needed to mimic white noise decreased with increasing flicker frequency from 8.3 at 1.25 Hz to 1.6 at 20 Hz. CONCLUSIONS: The critical high-frequency cutoff of detection-limiting temporal noise in terms of noise frames per signal cycle depends on the temporal frequency of the signal. This is opposite to the situation in the spatial domain and must be taken into consideration when temporal signals are masked with temporal noise.

Adult↗
PubMed1992

[Facial or nasal mask pressure support ventilation in managing acute exacerbation of chronic respiratory failure in chronic obstructive pulmonary diseases].

11 COPD patients (age: 65 +/- 9 Yrs) with acute exacerbation of chronic respiratory failure (PaCO2 11.3 +/- 1.1kPa) were treated with mask pressure support ventilation, another 10 similar patients (age: 68 +/- 12 Yrs) served as control. BiPAP ventilator was used with the following modifications: (1) Non-rebreathing valve set-in proximal to mask; (2) 5 LPM oxygen flow delivered into mask to reduce the dead space effect. Mask ventilation was given 2-3 hours every time and 1-2 time daily for 7 days. Synchrony and airway patency were specially monitored. The results suggested that mask ventilation could reduce PaCO2, improve PaO2, relieve dyspnea and decrease the possibility of intubation.

Aged↗
PubMed2003

[Differential lung ventilation by use of a combination of a laryngeal mask airway and an endotracheal tube in a pediatric patient with atelectasis of the right lung].

A 5-month-old boy was diagnosed as having complete atelectasis of the right lung due to RS virus infection at the age of 1 month. Conventional respiratory physical therapy, inhalation therapy and mechanical ventilation through an endotracheal tube failed to re-expand the right lung, while the left lung gradually became overinflated. We therefore tried differential lung ventilation by using a combination of a laryngeal mask airway and an extra long endotracheal tube (ID, 3.5 mm; length, 280 mm; Portex Pediatric Tracheal Tube, Extra length; SIMS Portex Co., Ltd. UK). Following induction of anesthesia, a laryngeal mask airway #2 was inserted. Then, an extra long endotracheal tube was inserted through the laryngeal mask airway and was guided to the right main bronchus with the aid of a fiberscope. The right lung was selectively lavaged and inflated with high pressure while ventilation was maintained through the laryngeal mask airway. The SpO2 value was maintained at more than 95% throughout the procedure despite some leakage from the ventilation system. The case demonstrates that differential lung ventilation by use of a combination of a laryngeal mask airway and extra long endotracheal tube is useful for the treatment of a pediatric patient with severe atelectasis.

Humans↗
PubMed1992

Effects of cochlear impairment and equivalent-threshold masking on psychoacoustic tuning curves.

Psychoacoustic tuning curves in simultaneous masking were measured in three groups: listeners with hearing impairment of primarily cochlear origin, normal listeners with equivalent-threshold masking (ETM) and normal listeners tested in the quiet. ETM was produced by presenting a continuous back-ground noise that was spectrally shaped to yield masked thresholds within 3 dB of each impaired listener's quiet thresholds. For the tuning curves, the level of a 50-Hz-wide noise band necessary to mask a 10-dB SL tone was measured for six masker frequencies. Results under ETM indicate that the shape of the tuning curve depends not only on masked threshold at the probe frequency but also on the spectral shape of the masker. Tuning curves are abnormally broad in some impaired listeners even when the effects of their elevated thresholds, audiometric configuration and altered intensity perception are taken into account by comparisons with normal listeners with ETM.

Acoustic Stimulation↗
PubMedDate not supplied

The effectiveness of surgical face masks: what the literature shows.

The use and withdrawal of surgical face masks in recent years has occurred in an ad hoc manner that is incompatible with evidence-based practice. Much of the literature on masks consists of anecdotal evidence or summaries of previous studies. The rationale for wearing masks has shifted from protection of the patient to protection of the health care professional wearing the mask. Currently there is little evidence that wearing a surgical mask provides sufficient protection from all the hazards likely to be encountered in an acute health care setting: the use of a respirator and face shield should be considered depending on the circumstances.

Cost-Benefit Analysis↗
PubMed2003

Intubating laryngeal mask airway versus laryngoscopy and endotracheal intubation in the nuclear, biological, and chemical environment.

OBJECTIVE: Intubation is a difficult skill under normal circumstances and more so with a limited visual field such as wearing a protective mask in a chemical or biological incident. This study sought to determine whether successful intubation using the intubating laryngeal mask airway (ILMA) under protective mask conditions was equivalent to standard endotracheal intubation. METHODS: A pilot study was conducted using emergency medicine personnel. Participant's attempted intubation of a manikin while wearing a standard U.S. Army M-40 protective mask. Two attempts were performed with each method. RESULTS: One hundred percent of the ILMA placements were successful with only 78% success with endotracheal intubation (p = 0.1). Time to successful intubation and ventilation was significantly less for the ILMA versus endotracheal intubation (p = 0.005). CONCLUSION: This study suggests that under simulated chemical and biological conditions using an M-40 protective mask, intubation is accomplished faster and with more success with the ILMA.

Biological Warfare↗
PubMed2003

[Laryngeal mask].

A laryngeal mask is a very useful instrument to use both in easy as well as difficult handling situations related to the air tract. This mask is placed in the pharynx and it permits a patient to breathe in different modes, either spontaneously or mechanically. Different models are available; some even facilitate the tracheal intubation through the mask. The authors highlight that this type of mask does not protect nor isolate the air tract. As advantages, the authors point out its easy installation; thus, it is an alternative when an air tract presents difficulties; therefore, it is necessary that all personnel who have to deal with the air tract be aware of this mask and know how to handle it.

Equipment Design↗
PubMedDate not supplied

Individualized nasal mask fabrication for positive pressure ventilation using dental methods.

PURPOSE: The aim of this study was to develop a simple technique to manufacture individualized ventilatory nasal masks for pediatric patients using materials and procedures commonly applied in dentistry. MATERIALS AND METHODS: Three cases of pediatric patients who met with severe difficulties in their adaptation to commercially available nasal masks are described: one premature infant, one child diagnosed with achondroplasia, and one child with congenital central hypoventilation syndrome. RESULTS: In each case, a light nasal mask was designed with two independent parts that become perfectly adapted to the patient's nose: one soft for the skin contact, and another rigid for dimensional stability. In all patients, adequate levels of ventilation were reached. CONCLUSION: This easy, inexpensive nasal mask fabrication technique can be used in a great number of patients, increasing the efficacy of individualized masks.

Achondroplasia↗
PubMedDate not supplied

Survey of the effectiveness of masking noises during dental treatment--a pilot study.

OBJECTIVE: The aim of this study was to test the effectiveness of a newly developed system, using masking noises with specific frequencies and amplitudes, adjusted to typical noises experienced during dental treatment such as the high-speed hand-held drill. METHOD AND MATERIALS: In accordance with an analysis of typical noises experienced during dental treatment, masking noises with specific frequencies (frequency range 0.02 to 20 kHz) and amplitudes were created, with the aim of reducing the patients' awareness of typical treatment noises by overlaying frequencies. Two hundred fifty-four outpatients (113 males, 141 females) with a mean age of 32 years (+/- 10.5 years) were enrolled in this study. Patients were treated 15 minutes with and 15 minutes without the masking noise. Patients and practitioners filled out questionnaires aimed to evaluate the effectiveness of the system, sensitivity to noise (scale 0 to 10; 0 = effective, 10 = noneffective), psychologic aspects, and statements of fear. RESULTS: There was a significant reduction in patients' awareness of noise using this system during dental treatment. Most of the patients regarded the masking noise as a pleasureable supplementation to common treatment and would select this manner of dental treatment employing the device again (81.5%); 48.2% said they were more relaxed. The system does not, in principle, interfere with dental treatment, and in most instances, the device does not impede the communication between practitioners and patients. CONCLUSION: The present study demonstrates that using masking noises during dental treatment reduces the sensitivity to drill noise, reduces fear and stress, and may be useful in dental practice as an adjunct to common dental treatment.

Adult↗
PubMed1992

[The usefulness of the laryngeal mask in ambulatory anesthesia. An evaluation of 200 cases of ambulatory anesthesia].

We studied the value of Brain's laryngeal mask on 200 patients undergoing ambulatory operations under general anaesthesia using propofol and alfentanil. Continuous registration of maximal airway pressure and pulse oximetry were carried out. The operations were performed mainly in the following four specialities: urology, general surgery, gynaecology, and ophthalmology. The mean operation time was 39 min (6-82 min). All patients belonged to ASA groups I-III. No patient was premedicated. We encountered no difficulties in introducing the mask using the technique described by Brain except in one 6-year-old boy with hypertrophic tonsils in whom it was impossible. Insufficient sealing of the trachea occurred in a 29-year-old woman with thyroid hypertrophy. In most patients (70%) the oxygen saturation (spO2) could be maintained above 95%; only 6 (2%) showed an spO2 value of less than 90%. Peak inspiratory pressures--a measure of tight fitting of the mask--are shown in Table 2. Laryngospasm occurred in 2 children who had inhalation inductions with halothane. This complication was never seen after induction with propofol. The most important positive finding was that relaxant drugs became largely unnecessary after we started working with the mask, which reduced postoperative recovery time as well as costs. CONCLUSION. We consider the laryngeal mask to be not only an important new technique, but in combination with propofol and alfentanil the method of choice for ambulatory anaesthesia in day-case surgery.

Adolescent↗