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PubMed1999

[From tracheostomy to non-invasive mask ventilation: a study in children with congenital central hypoventilation syndrome].

BACKGROUND: Children with congenital central hypoventilation syndrome (CCHS) have to be ventilated during sleep due to respiratory insensitivity to CO2. This long-term mechanical ventilation sometimes requires a tracheostomy during infancy, leading to increased risk of infections and of tracheal problems, and later on to stigmatization and restrictions in social life. PATIENTS AND METHOD: We therefore evaluated non-invasive mask ventilation in 4 children between 6 and 15 years of age, who had been ventilated via tracheal canula since early infancy under polysomnographic control. RESULTS: Best results were obtained with standard face masks in connection with pressure controlled timed ventilation. In 1 child we used a volume-controlled ventilator. The lack of dyspnea in these patients can worsen the acceptance of a face mask, which is more uncomfortable than a tracheal cannula. In 2 children we waited with the definite closure of the tracheostomy due to pavor-like symptoms and laryngeal closure during sleep and problems in acceptance of the mask, respectively. In the other 2 children we could demonstrate effective non-invasive mask ventilation during temporary tracheal closure for several nights. Therefore the tracheostomy was definitely closed. Long-term follow-up with home monitoring showed effectiveness of non-invasive ventilation in these cases.

Adolescent↗

PubMed2000

[Density-mask spiral computed tomography in patients who are candidates for a lung-volume-reduction intervention: a preliminary study].

PURPOSE: To investigate the usefulness of helical CT with multiplanar reconstructions and density mask in emphysematous patients candidate for lung volume reduction surgery (LVRS), in order to assess the feasibility of surgery and for surgical planning. MATERIAL AND METHODS: Twenty emphysematous patients (5 women and 15 men; age range: 55-67 years, mean: 61) candidate for LVRS were submitted to isotope perfusion scanning, chest radiography during maximal inspiration and expiration and Helical CT with the low volume contrast technique, multiplanar reconstructions and density mask. RESULTS: Only 8 of the 20 patients examined were submitted to LVRS. They had irregular distribution of emphysema at isotope perfusion scanning and density mask CT. Surgery consisted in an atypical resection of the upper lobe portions which appeared most damage with both techniques. Six of the remaining 12 nonsurgical patients were excluded because of homogeneous distribution of emphysema at both CT and perfusion scanning, which was incompatible with surgery. Lung transplant was considered for 4 of these patients, but only 2 of them actually received it. Three patients were excluded from LVRS because of excessive diaphragm excursion during expiration at chest radiography and of multiple confluent areas of emphysema in both lung at CT and perfusion scanning. One patient with a large area of emphysema in the right upper lobe at CT and perfusion scanning was excluded due to associated severe interstitial disease. Another patient with emphysema mainly involving the lower lobes, as clearly depicted with both techniques, was excluded because the emphysema was secondary to alpha 1-antitrypsin deficiency, a condition known to have a less favorable surgical outcome. Finally, one patient was excluded due to a previous upper transverse laryngectomy, although CT and perfusion scanning patterns were compatible with surgery. CONCLUSIONS: In our opinion, density mask helical CT yields more accurate and clearer images than perfusion scanning, and allows the patients candidate for surgery to undergo a single examination to evaluate the extent and distribution of emphysema and to detect other possible pathological conditions. Though ours was a small series, the results suggest that perfusion scanning be integrated with density mask helical CT, the latter a very important technique for surgical planning.

Aged↗

PubMedDate not supplied

Effectiveness of mask ventilation performed by hospital doctors in an Irish tertiary referral teaching hospital.

The objective of this study was to assess the effectiveness of mask ventilation performed by 112 doctors with clinical responsibilities at a tertiary referral teaching hospital. Participant doctors were asked to perform mask ventilation for three minutes on a Resusci Anne mannequin 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, 334, 434, 561, 673 and > 800 ml respectively. The effectiveness of mask ventilation (i.e. the proportion of ventilation attempts which achieved a volume delivery of > 434 mls) was greater for anaesthetists [78.0 (29.5)%] than for non anaesthetists [54.6 (40.0)%] (P = 0.012). Doctors who had attended one or more resuscitation courses where no more effective at mask ventilation than their colleagues who had not undertaken such courses. It is likely that first responders to in-hospital cardiac arrests are commonly unable to perform adequate mask ventilation.

Clinical Competence↗

PubMedDate not supplied

Threshold contrast ratio and masking ability of porcelain veneers with high-density alumina cores.

PURPOSE: The purposes of this study were to: (1) investigate the correlation between the color difference of bilayer porcelain veneers over white and black backgrounds (deltaE1) and their opacity (contrast ratios); (2) determine whether there is a recommendable threshold contrast ratio above which the color difference is clinically acceptable (when deltaE < or = 5); and (3) compare the ability of porcelain veneers to mask a color change from white to black backgrounds (deltaE1) and their ability to mask a color change from white to clinically discolored teeth (deltaE2). MATERIALS AND METHODS: Forty-four maxillary anterior teeth of eight patients with severe tetracycline discoloration were prepared for bilayer porcelain veneers in shade A2 porcelain. The cores were 0.25 mm thick. The color (CIE L*a*b*) and reflectance (Y) of the midbuccal region of each veneer were measured over white and black backgrounds using a colorimeter under artificial daylight. The veneers were bonded to discolored teeth, and their color was measured after 1 week. RESULTS: The mean color difference deltaE1 was 10.6 (SD 2.6). The mean contrast ratio was 0.75 (SD 0.1). There was a close and statistically significant correlation between deltaE1 and contrast ratio. The determined threshold contrast ratio was 0.91. The mean color difference deltaE2 was 11.6 (SD 5.5). A paired t test showed no difference between deltaE1 and deltaE2. CONCLUSION: There was a significant correlation between the masking ability of veneers (deltaE1) and their opacity (contrast ratio). There was no significant difference in the ability of the porcelain veneers in masking a color change from white to black backgrounds compared to their ability to mask the color change from white to the discolored teeth.

Aluminum Oxide↗

PubMed1997

The efficiency of tools used to retract a football helmet face mask.

OBJECTIVE: The purpose of this study was to evaluate time, head movement, and ratings of satisfaction with several popular tools used for retracting a football helmet face mask. DESIGN AND SETTING: Subjects retracted the face mask using a Phillips screwdriver, a Trainer's Angel, and an anvil pruner. A utility knife had to be eliminated from the study after the first two subjects were injured. SUBJECTS: Five certified athletic trainers, five emergency medical technicians, and five student athletic trainers retracted a face mask with each tool. MEASUREMENTS: Time was measured by stopwatch and movement by a force platform. Efficiency was calculated from total time and radial area. Ratings of satisfaction were reported by the subjects. RESULTS: There was no difference in the total time to retract the face mask using the three tools. Movement was significantly (p < .05) greater with the Trainer's Angel than with the anvil pruner or screwdriver. Subjects were more satisfied with the anvil pruner than the Trainer's Angel or screwdriver. When grouped by the subjects' credentials, there were no differences in time or rating of satisfaction among the certified athletic trainers, emergency medical technicians, or student athletic trainers, but there was a difference for movement. The student athletic trainers produced the least movement and the certified athletic trainers produced the most. CONCLUSIONS: It is suggested that the skill of face mask retraction be learned and practiced.

Journal Article↗

PubMed2006

Oxygen delivery comparison of two constant-flow masks during flight to 6863 m.

OBJECTIVE: Differences in mask design may alter the oxygen flow required to gain similar oxygenation at a particular altitude. The selection of the most efficient mask would be advantageous for general aviation and other applications where oxygen supply is limited. METHODS: We compared a basic mask (BAS) without valves or oxygen reservoir bag to a test mask (TST) with three valves and a reservoir designed to deliver up to 80% oxygen for critically ill patients. Randomly assigned parachutists (n = 31) used the masks during a flight with a gradual climb to 6863 m (22,500 ft). The oxygen flow was individually controlled to produce oxygen saturation (SpO2) of 95-97% as determined by pulse oximetry. Oxygen flow and SpO2 were obtained every 305 m (1000 ft). RESULTS: Baseline age, lung function indices, and SpO2 were comparable for the two groups. Mean in-flight Spo2 values were 95.3 +/- 0.5% for the BAS and 96.2 +/- 1.1 % for the TST, respectively. Above 3965 m (13,000 ft) the TST required significantly less oxygen flow than the BAS to maintain the target SpO2. At 6863 m (22,500 ft), mean oxygen flow was 5.5 +/- 3.5 L x min(-1) for the BAS vs. 3.4 +/- 2.3 L x min(-1) for the TST (p = 0.029). No adverse reactions were reported from either group. CONCLUSION: The TST required significantly less oxygen flow compared with the BAS at high altitudes and may, therefore, reduce total oxygen use, resulting in reduced costs and longer oxygen availability during a flight.

Adult↗

PubMed2006

Masking interference and the evolution of the acoustic communication system in the Amazonian dendrobatid frog Allobates femoralis.

The efficacy of communication relies on detection of species-specific signals against the background noise. Features affecting signal detection are thus expected to evolve under selective pressures represented by masking noise. Spectral partitioning between the auditory signals of co-occurring species has been interpreted as the outcome of the selective effects of masking interference. However, masking interference depends not only on signal's frequency but on receiver's range of frequency sensitivity; moreover, selection on signal frequency can be confounded by selection on body size, because these traits are often correlated. To know whether geographic variation in communication traits agrees with predictions about masking interference effects, we tested the hypothesis that variation in the male-male communication system of the Amazonian frog, Allobates femoralis, is correlated with the occurrence of a single species calling within an overlapping frequency range, Epipedobates trivittatus. We studied frogs at eight sites, four where both species co-occur and four where A. femoralis occurs but E. trivittatus does not. To study the sender component of the communication system of A. femoralis and to describe the use of the spectral range, we analyzed the signal's spectral features of all coactive species at each site. To study the receiver component, we derived frequency-response curves from playback experiments conducted on territorial males of A. femoralis under natural conditions. Most geographic variation in studied traits was correlated with either call frequency or with response frequency range. The occurrence of E. trivittatus significantly predicted narrower and asymmetric frequency-response curves in A. femoralis, without concomitant differences in the call or in body size. The number of acoustically coactive species did not significantly predict variation in any of the studied traits. Our results strongly support that the receiver but not the sender component of the communication system changed due to masking interference by a single species.

Animals↗

PubMed1984

Middle-component AERs during backward masking.

This study examined the middle-component averaged electroencephalic response (AER) to tonal stimuli presented in a backward-masking paradigm. Ss were 4 normal-hearing young adults. Tone-Only (TO), Masker-Only (MO), and Tone-Masker (TM) responses were collected. The visual impression was that the TO response was not significantly different from the extracted response to the tone (T) from the TM response. This result obtained when the tone in the TM condition was presented either slightly above (+5 db) or slightly below (-5 db) perceptual threshold. Backward masking was discussed in terms of two contrasting views of the auditory system: the classical auditory nervous system alone and a parallel system combining the classical auditory and the reticular sensory systems. Speculations were made for each system regarding the type of AER expected for a stimulus submerged in backward masking. The mechanism responsible for backward masking was seen as a preperceptual device that allows discrete samples of the auditory environment to be processed. This mechanism was discussed in terms of its possible relation to forward masking and to loudness enhancement.

Acoustic Stimulation↗

PubMed1994

Change-to-Open-Label Design. Proposal and discussion of a new design for clinical parallel-group double-masked trials.

The "Change-to-Open-Label Design" (COLA-design) is proposed to overcome some of the ethical and organizational problems of the usual double-masked design in certain situations while preserving its scientific rigor. Patients are randomized on a doubled-masked basis into treatment groups. During the trial the patient or the treating physician may ask for a change from the masked treatment to any open-label treatment of their choice (experimental or not), if the masked treatment is thought to be unsatisfactory. It seems to be easier to obtain a patient's informed consent to participate in placebo controlled double-masked trials especially for long term studies. The main outcome variable in COLA-design is the time until a patient demands for such a change. "Survival analysis" is a powerful statistical method to evaluate this outcome variable. Even patients lost from observation can be included in the evaluation: they still deliver censored outcome values. Evidently, in trials with a COLA-design the patient's personal impression of the therapy is the most important factor in its assessment. Therapeutical success is mingled with undesirable effects into the outcome measure; therefore this design is especially applicable to investigate treatments supposed to increase quality of life.

Double-Blind Method↗

PubMedDate not supplied

The erodible mask in photorefractive keratectomy for myopia and astigmatism.

This paper reports a new approach for performing photorefractive keratectomy (PRK) that uses an erodible mask to control shape transfer processes. The advantages of this technique, when compared to conventional PRK performed with mechanical diaphragm, are 1) the possibility of transferring almost any shape onto corneal surface; 2) a smoother corneal surface following photoablation; 3) easier eye fixation; and 4) a controlled humidified environment over ablation zone. We report our experimental study on scanning electron microscopy of polymethylmethacrylate (PMMA) plates ablated using conventional technique versus erodible mask technique; the results showed a smoother surface in the PMMA plate ablated using the erodible mask. We also report our preliminary clinical results of four eyes treated for the correction of myopia combined with astigmatism. Myopia ranged from -2.00 to -10.00 D, and astigmatism ranged from -1.50 to -2.50 D. Three months after surgery, all four eyes were within +/- 1.00 D of myopic attempted correction, but astigmatism was completely corrected only in one eye. No complications or scarring have been reported. We believe the erodible mask could be effective in the correction of myopia and myopic astigmatism, but further improvements are necessary to allow easier alignment of the mask over the eye. All commonly available excimer laser devices produce photorefractive keratectomy as a concentric ablation of the corneal stroma, deeper in the center than in the peripheral part; this is produced by means of an iris or diaphragm which, depending on the type of laser, progressively opens or closes, allowing a greater laser beam delivery in the center.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

[Masked depression].

Masked depression is a condition in which the classic affective and cognitive symptoms of depression are hidden behind a variety of somatic complaints or behavioural problems. Patients suffering from masked depression are usually incorrectly diagnosed and treated symptomatically with little success. The condition is often encountered in the medical literature from the late 1960s to the early 1980s, but little has been published about it in recent years. This review discusses the changing ideas and approach with regard to masked depression and examines whether they are still relevant today. The literature published in each of the previous decades is studied and specific attention is given to cultural differences in a South African context. Although little has been published on masked depression in the past few years, somatic complaints in depression are still regularly examined in the literature. A significant number of patients with depression are still not correctly diagnosed and masked depression therefore remains relevant. Doctors should be aware of the presenting complaints in these patients and should understand the reasons for somatisation.

Depressive Disorder↗

PubMed1996

Effect of a mask and pneumotachograph on tracheal and nasopharyngeal pressures, respiratory frequency, and ventilation in horses.

OBJECTIVE: To investigate the effect of a mask and pneumotachograph on ventilation, respiratory frequency, and tracheal and nasopharyngeal pressures in horses running on a treadmill. DESIGN: Six horses ran at 50, 75, and 100% of the speed that resulted in maximum oxygen consumption, with and without a mask and pneumotachograph. Tracheal and pharyngeal inspiratory and expiratory pressures, respiratory frequency, and arterial blood gases were measured. ANIMALS: Six Standardbred horses. PROCEDURE: Oxygen consumption was measured during an incremental exercise test to determine the speed that resulted in maximal oxygen consumption for each horse. Tracheal and pharyngeal pressures were measured, using transnasal tracheal and pharyngeal side-hole catheters connected to differential pressure transducers. Carotid arterial blood samples were collected and PAO2, PaCO2, and pH were measured with a blood gas analyzer. RESULTS: Peak tracheal and pharyngeal inspiratory pressures were significantly more negative, peak tracheal and pharyngeal expiratory pressures were significantly more positive, and respiratory frequency was significantly lower (all P < 0.05) at all speeds when horses wore a mask. The PaCO2 was higher and arterial pH and PaO2 were lower (P < 0.05) when horses wore a mask. CONCLUSIONS: The mask and pneumotachograph altered upper airway pressures, respiratory frequency, and ventilation in horses running on a treadmill.

Animals↗

PubMed1997

Photorefractive keratectomy for the treatment of compound myopic astigmatism using the ablatable mask.

Eight eyes of 8 patients with compound myopic astigmatism were treated with excimer laser photorefractive keratectomy (PRK) using a hand-held ablatable mask in conjunction with the Summit excimer laser. The attempted correction ranged from -1.25 to -400 dioptres (D) of astigmatism and 0 to -8.00 D of myopia. All eyes had attained at least 6 months of postoperative follow-up. Five of the 8 eyes achieved an unaided visual acuity of 6/12 or better. Postoperative refractions ranged from -0.50 to -3.50 D of refractive cylinder and from +0.50 to -3.75 D of spherical error. Decentration of the ablation zone was encountered in 3 eyes due to shifts in patients' fixation. Technical difficulty with the use of the hand-held ablatable mask limited the widespread application of this procedure and it has now been superseded by newer excimer laser systems which can correct astigmatism without having to employ a mask. Despite this, because of the theoretical ability of the mask to correct any form of refractive error, the concept of the mask shape transfer process will remain as a potential alternative in refractive surgery, especially for correction of hyperopia and hyperopic astigmatism.

Adult↗

PubMed1995

The laryngeal mask airway in obstetrical anaesthesia.

The laryngeal mask airway (LMA) has been used extensively to provide a safe airway in spontaneously breathing patients who are not at risk from aspiration of gastric contents. The role of the LMA in the event of a failed intubation in an obstetrical patient, and its place in a failed intubation drill remains unclear. Two hundred and fifty consultant obstetric anaesthetists in the United Kingdom were asked to complete an anonymous questionnaire regarding their views about using the laryngeal mask airway (LMA) in obstetrical anaesthesia. The LMA was available in 91.4% of obstetric units. Seventy-two per cent of anaesthetists were in favour of using the LMA to maintain oxygenation when tracheal intubation had failed and ventilation using a face mask was inadequate. Twenty-four respondents had had personal experience with the LMA in obstetrical anaesthesia, eight of whom stated that the LMA had proved to be a lifesaver. We believe that the LMA has a role in obstetrical anaesthesia when tracheal intubation has failed and ventilation using a face mask proves to be impossible, and it should be inserted before attempting cricothyroidectomy.

Anesthesia, Obstetrical↗

PubMed2004

Laryngeal mask airway: is the management of neonates requiring positive pressure ventilation at birth changing?

OBJECTIVE: To evaluate the impact of the laryngeal mask airway (LMA) on neonatal resuscitation policy. DESIGN: We analyzed retrospectively the records of neonates requiring positive pressure ventilation (PPV) at birth before (1996) and after (2000) the introduction of the LMA into our delivery suites. In addition, the outcome of neonates treated with the LMA was compared with that of neonates matched for gestational age and mode of delivery who were resuscitated using a face mask. RESULTS: During the year 2000, 95 out of 380 (25%) resuscitated neonates were treated with the LMA. The LMA was effective in 94 out of 95 (99%) of these infants. Over the same period, the percentage of neonates receiving tracheal intubation (TI) at birth (34%) was significantly reduced compared with the figure for 1996 (67%). There were no reported complications associated with the use of the LMA. Seventy-four out of the 95 neonates treated with the LMA were considered suitable for matching for gestational age and mode of delivery with 74 neonates treated with a face mask. No differences were found between the two groups for birth weight, Apgar scores, need for tracheal intubation, need for admission to the Neonatal Intensive Care Unit (NICU), primary diagnosis at discharge and primary outcomes. The LMA provided effective ventilation in four neonates in whom the face mask failed. CONCLUSIONS: The LMA is changing neonatal resuscitation practice in our Institution. Our data suggest that it is a safe and useful alternative method for respiratory support in neonates requiring PPV at birth, which merits further study.

Birth Weight↗

PubMed1992

Effect of the laryngeal mask airway on lower oesophageal sphincter pressure in patients during general anaesthesia.

We have studied the tone of the lower oesophageal sphincter (LOS) in 40 adults undergoing routine body surface surgery and allocated randomly to receive anaesthesia either by face mask and Guedel airway or by laryngeal mask airway. In the laryngeal mask group there was a mean (SEM) decrease in barrier pressure (LOS minus gastric pressure) of 3.6 (1.4) cm H2O, compared with a mean increase of 2.2 (1.2) cm H2O in the face mask group (P < 0.005).

Adult↗

PubMed1999

Effect of the laryngeal mask airway on oesophageal pH: influence of the volume and pressure inside the cuff.

We studied gastro-oesophageal reflux (GOR) with a face mask and laryngeal mask airway (LMA), and the effects of inflation pressure and volume of the LMA cuff on oesophageal pH, in 60 patients. Patients were managed with either a face mask (group I) or LMA inflated to obtain a seal in the anaesthesia circuit at 7 cm H2O (group II) or 15 cm H2O (group III). A pH-sensitive probe with two electrodes, 10 cm apart, was placed in the oesophagus during anaesthesia and recordings were made continuously until patients awakened. There was a significant difference in the incidence of GOR between the face mask (group I) and the LMA (groups II-III) (P < 0.05) in the lower oesophagus but there was no difference in the mid-oesophagus. No correlation was found between pressure and volume inside the cuff and variations in oesophageal pH. We conclude that LMA use was associated with increased reflux in the low oesophagus but oesophageal pH was not influenced by variations in pressure or volume inside the LMA cuff.

Adult↗

PubMed2026

Association between orthostatic blood pressure change and masked and white coat hypertension: the Nagahama study.

BACKGROUND: Exaggerated blood pressure (BP) response to orthostatic stimuli is indicative of cardiovascular frailty and may be associated with masked and white coat hypertension, which are BP abnormalities associated with cardiovascular outcomes. We aimed to clarify this possible association in a cross-sectional analysis of a large general population. METHODS: We enrolled 7618 community residents (mean age: 57.7 years). Orthostatic BP change was calculated as the difference between systolic BP measured in a seated position and at 3 min after standing. Orthostatic hypertension and hypotension were defined as >20 mmHg increase or decrease in systolic BP, respectively. Masked and white coat hypertension were defined based on office and home morning BP measurements. RESULTS: The frequency of orthostatic hypotension and hypertension was 1.8% and 1.6%, respectively. A significant association was observed between orthostatic BP change and office-to-home BP differences, that is, the greater the increase in orthostatic BP, the higher the home BP than the office BP. The association between orthostatic hypertension and masked hypertension (crude odds ratio: 3.15; P  < 0.001) remained significant even after adjusting for potential covariates, including office seated BP. In addition, orthostatic hypotension was independently associated with white coat hypertension (crude odds ratio: 2.14; P  = 0.002). Orthostatic BP change measured at 3 min showed a clearer association with masked and white coat hypertension than that measured at 1 min. CONCLUSION: We identified a physiological association between exaggerated postural BP variability and office-to-home BP differences, which were previously considered unrelated.

Humans↗