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At least 523 records · Page 29Linked to original sources
PubMed1995

[Laryngeal masks in emergency medicine].

Airway control and maintenance of effective assisted ventilation are an absolute priority in emergency medicine. Developed by Brain in 1988, the laryngeal mask offers a new means of ventilation management and is a reliable compromise between the face mask and endotracheal tubing. The laryngeal mask ensures no protection against gastric contents inhalation and its use is limited in patients with decreased thoracopulmonary compliance. However, compared to the face mask, the laryngeal mask offers several benefits in the management of cardiorespiratory arrests by paramedical staff and rescue teams: the procedure is easy to learn, the device improves airway patency, leaves the operator's hands free, allows endotracheal aspiration to be performed and reduces the risk of hyperinsufflation. These advantages make the use of the laryngeal mask a technique which should be taught to any staff liable to face and manage cases of cardiorespiratory arrest. The laryngeal mask cannot and does not replace endotracheal tubing which remains the only technique that guarantees upper airway patency and protection as well as efficient ventilation control. However, in some situations tubing may prove difficult and even, at times, impossible to perform. This is when the laryngeal mask will come in handy, either as a temporary solution or as an alternative to difficult or impossible tubing techniques.

Cardiopulmonary Resuscitation↗
PubMed1977

Efficient oxygen mask for patients undergoing hyperbaric oxygen therapy.

Hyperbaric oxygen (HBO) is established therapy for various disorders, but its effectiveness depends on the efficiency of the oxygen delivery system. A mask oxygen delivery system, consisting of the standard USAF aviator's A-14 regulator and the MBU-5/P oxygen mask, is installed in all USAF hyperbaric chambers. The efficiency of the mask oxygen delivery system at the USAF Hyperbaric Center, Brooks AFB, Tx, was evaluated breath-by-breath at sea level and 2.4 ATA via two different measuring techniques. Three groups of subjects were evaluated. Four subjects in Group I and seven subjects in Group II were randomly selected to use a single instrumented mask which was improperly fitted. The result was variable inspired oxygen levels from 64% to 100%. Six subjects in Group III wore properly fitted masks and achieved end-inspired oxygen levels ranging from 96% to 99%, for a mean of 97.8 +/- 0.5 (S.E.)%. A mean end-inspired oxygen level of 88,5 +/- 3,5 (S.E.)% was achieved within 5 min of mask donning. Inspiratory gas analyses indicate that the USAF aviator MBU-5/P mask and the A-14 regulator as used at the USAF Hyperbaric Center constitute a highly efficient oxygen delivery system for HBO therapy. This view has been refleced in arterial blood gas measurements and in preliminary data from tissue oxygen measurements in a gas gangrene patient. Future improvements in patient therapy masks are recommended.

Air↗
PubMed1996

[Mouth mask method for fiberoptic tracheal intubation in difficult intubations].

We tried 72 fiberoptic tracheal intubations (FTI) using a mouth mask in difficult intubation cases. In this method, ventilation is performed via only the mouth using a mask applied over the mouth (mouth mask) and FTI can be done via a nostril with no hindrance from the mask in anesthetized patients. We have been using an infant or child type Seal Mask (Gibeck Respiration) for the mouth mask or a specially made mouth mask. An oral airway is usually inserted and the nostril of one side is plugged with cotton. FTI is performed by another anesthesiologist. An endotracheal (ET) tube capped with a rubber diaphragm is passed through another nostril, and a fiberscope is inserted through the ET tube. The subsequent technique is the same as that of the usual FTI for awake patients. Intubations were successful in all cases except 2; in one, ventilation was impaired even with oral airway in place, and in the other, bleeding in upper airway due to jaw injury from traffic accident hindered the sight of the scope. Mouth mask method for FTI is safe, useful and practical in difficult intubations with little discomfort to the patient.

Adolescent↗
PubMed1998

[Use of laryngeal mask in bronchoscopy or bronchoscopic treatment].

Laryngeal mask which is widely used in clinical anesthesiology permits establishment of airway without tracheal intubation. Flexible bronchoscopy or bronchoscopic treatment using the laryngeal mask was evaluated to determine its safety, less invasiveness, and usefulness. Fifty-two patients underwent flexible bronchoscopy or bronchoscopic treatment using laryngeal mask 54 times. Bronchoscopy was performed under either local or general anesthesia. The laryngeal mask was positioned in the larynx, as a rule without a laryngoscope. A flexible bronchoscope was introduced into the airway, passed through the rubber slit at the tip of the laryngeal mask tube, and the examination was performed. Complications observed during the course of the examinations consisted of only two cases of poorly fitting laryngeal mask and one case of catching of a part of the epiglottis in the rubber slit at the tip of the laryngeal mask tube. Both cases were not particularly problematic. There were three patients with sore throat and one with an unpleasant feeling in the pharynx following the examination, however, all of these complaints resolved within three days after the examination. Laryngeal masks are less invasive and have very little effect on either the respiratory system or the circulatory system. They may be used safely even in aged patients and appears to be highly effective for diagnostic and therapeutic bronchoscopy.

Adolescent↗
PubMed2004

Masked hypertension in children and young adults.

Masked hypertension, a high ambulatory blood pressure (ABP) in the presence of normal office blood pressure (BP), is recognized as a risk factor for cardiovascular complications in the adult population. We evaluated the prevalence of masked hypertension in pediatric patients. We studied 136 patients (59 boys and 77 girls, aged 6-25 years, mean 13.1+/-4.7 years). In all patients, office BP measurements with auscultatory technique were less than the 95th percentile for sex and age or <140/90 mmHg for those over 18 years. Masked hypertension was diagnosed when either systolic or diastolic daytime ABP values were equal to or greater than the 95th percentile for sex and height of reference values or > or =135 mmHg systolic or 85 mmHg diastolic BP for those over 15 years. Among 136 patients, 15 (11%) had masked hypertension. The prevalence of masked hypertension was higher in boys (19%) than in girls (5%), but not different between younger (< or =15 years) and older (>15 years) patients (11% vs. 12%). The diagnoses in the group with masked hypertension included 3 patients with diabetic nephropathy, 2 with obesity, and 2 with orthostatic dysregulation. In conclusion, masked hypertension is present in pediatric patients, and is more common in boys. Further study is needed to identify patients who may benefit from recognition of masked hypertension.

Adolescent↗
PubMed1987

Forward masking and unmasking of the offset cochlear compound action potential of the gerbil: comparison with suppression areas of the onset cochlear compound action potential.

Simultaneous and forward maskers were used to generate 'onset' and 'offset' compound action potential tuning curves (TCs) in the gerbil. The simultaneously masked offset TC, generated in response to a 16 kHz, 65 dB SPL probe stimulus, is W-shaped, with a low frequency tip at 11 kHz, a high frequency tip at 20 kHz, and a peak which occurs at 16 kHz. The 16 kHz forward masked onset TC has a single tip which occurs at 11 kHz. Although it lacks the finely tuned peak and high frequency tip of the stimultaneously masked offset TC, its single tip is more finely tuned than the low frequency tip of the simultaneously masked offset TC. Normalizing these two TCs [(1977) J. Acoust. Soc. Am. 62, 1048-1051] produces a figure which resembles 11 kHz onset TCs with their nonoverlapping regions which are analogs of two-tone suppression (2TS). A similar pattern occurs when probe stimuli at frequencies from 13 to 24 kHz are used to generate offset TCs; i.e., the forward masked offset TC resembles an onset TC and normalizing it to a simultaneously masked offset TC produces areas which resemble analogs of 2TS. Unmasking of the forward masked onset TCs [(1979) Hear, Res. 1, 133-154] produces regions of 2TS which are very similar to those produced by unmasking the forward masked offset TC which is generated by a higher frequency tone. These regions of 2TS for the Offset TC, as determined by unmasking, are very similar to the analogs of 2TS described above.

Acoustic Stimulation↗
PubMed2005

Masked hypertension assessed by ambulatory blood pressure versus home blood pressure monitoring: is it the same phenomenon?

BACKGROUND: Masked hypertension is defined as normal clinic blood pressure (CBP) and elevated out-of-clinic blood pressure assessed using either self-monitoring of blood pressure (BP) by the patients at home (HBP) or ambulatory BP (ABP) monitoring. This study investigated the level of agreement between ABP and HBP in the diagnosis of masked hypertension. METHODS: Participants referred to an outpatient hypertension clinic had measurements of CBP (two visits), HBP (4 days), and ABP (24 h). The diagnosis of masked hypertension based on HBP (CBP <140/90 mm Hg and HBP > or =135/85) versus ABP (CBP <140/90 and awake ABP > or =135/85) was compared. RESULTS: A total of 438 subjects were included (mean age +/- SD, 51.5 +/- 11.6 years; 59% men and 41% women, 34% treated and 66% untreated). Similar proportions of subjects with masked hypertension were diagnosed by ABP (14.2%) and HBP (11.9%). In both treated and untreated subjects, the masked hypertension phenomenon was as common as the white coat phenomenon. Among 132 subjects with normal CBP, there was disagreement in the diagnosis of masked hypertension between the HBP and the ABP method in 23% of subjects for systolic and 30% for diastolic BP (kappa 0.56). When a 5-mm Hg gray zone for uncertain diagnosis was applied to the diagnostic threshold, the disagreement was reduced to 9% and 6% respectively. CONCLUSIONS: Similar proportions of subjects with masked hypertension are detected by ABP and HBP monitoring. Although disagreement in the diagnosis between the two methods is not uncommon, in the majority of these cases the deviation of the diagnostic BP above the threshold in not clinically important. Both ABP and HBP monitoring appear to be appropriate methods for the detection of masked hypertension.

Blood Pressure↗
PubMed2006

Reproducibility of white-coat and masked hypertension in ambulatory BP monitoring.

BACKGROUND: White-coat hypertension and masked hypertension have clinical and prognostic consequences. However, reproducibility of these phenomena is unknown. We examined the reproducibility of the white-coat and masking effects with real-life ambulatory blood pressure monitoring (ABPM). METHODS: In a retrospective analysis of a prospectively assembled ABPM database there were 196 subjects (age 58+/-16 years, 59% female, 73% treated for hypertension) who underwent repeat ABPM for standard clinical indications. White-coat hypertension (or isolated manual uncontrolled hypertension) was defined as normal (<135/85 mmHg) awake blood pressure (BP) and abnormal (>or=140/90 mmHg) manual BP. Masked hypertension (or isolated ambulatory uncontrolled hypertension) was defined as abnormal awake BP with normal manual BP. RESULTS: Treated and untreated subjects had similar distribution among hypertension subgroups; 16% white-coat hypertension (in treated subjects, isolated manual uncontrolled hypertension), 13% masked hypertension (in treated subjects, isolated ambulatory uncontrolled hypertension), 59% uncontrolled hypertension, 12% normal blood pressure (or controlled hypertension). In the second session the prevalence of white-coat and masked hypertension increased. Of 31 subjects with white-coat hypertension in the first session 19 (61%) remained ambulatory normotensive in the second session, while 18 of 25 (72%) masked hypertensive subjects remained ambulatory hypertensive. The reproducibility of the systolic manual-awake blood pressure difference was not inferior to that of other ambulatory variables. In untreated subjects the reproducibility of white-coat hypertension, masked hypertension and the white-coat effect was even better. CONCLUSION: In a real-life ABPM database, we found white-coat hypertension and the masking phenomenon to be reasonably reproducible, as compared to other BP variables.

Blood Pressure Determination↗
PubMed2005

Neural mechanisms of visual backward masking revealed by high temporal resolution imaging of human brain.

Backward masking is one of the potent ways to reveal the neural mechanism of visual awareness in humans. Although previous neuroimaging studies have reported that the visual masking involves the attenuation of hemodynamic signals to the masked stimulus in visual ventral regions such as the fusiform and inferior temporal gyrus, the temporal profiles of this attenuation as a whole neural population is mostly unclear. Here we used magnetoencephalography and investigated the neural response changes in higher visual region induced by backward masking. The combination of our previous random dot blinking method with the sensor-based analysis isolated the neural responses in the higher visual cortex relating to shape perception. The results revealed that, as the visibility of the target stimulus was reduced by the mask following it, the neural response to the target in the ventral regions showed gradual decreases both in its peak amplitude and peak latency. Furthermore, this decrease in the peak amplitudes was significantly correlated with the behavioral accuracy of the target identification, while the peak latency was not. These results indicate that backward masking simultaneously produces two types of neural changes in higher visual regions: attenuation of the populational neural activity itself and temporal interruption of this activity by the subsequent mask response. Especially, our data suggest that the response attenuation in higher visual response is a main cause of the perceptual impairment observed in the backward masking paradigm.

Brain↗
PubMed1986

Partial purification and characterization of masking protein for beta-type transforming growth factor from rat platelets.

beta-Transforming growth factor (TGF-beta) is stored in platelets and secreted as a high molecular weight latent form associated with a carrier protein of about 440 KD. This carrier protein could be separated from TGF-beta in 1 N acetic acid and could again mask the activity of TGF-beta under neutral conditions. Therefore, it was named the masking protein of TGF-beta. The masking protein was separated from TGF-beta by gel filtration on a Sephacryl S-300 column or by anion-exchanger FPLC on a Mono Q column in the presence of 6 M urea. Partially purified masking protein from rat platelets neutralized the activity of TGF-beta dose-dependently and was effective at 0.3 microgram/ml. This masking protein could also mask the activity of human TGF-beta, suggesting that it was not species specific. The masking protein was a heat- and acid-stable protein, but was inactivated by treatment with dithiothreitol. The Physiological role of the masking protein in the mechanisms of wound healing and liver regeneration is discussed.

Animals↗
PubMed1998

Effect of contralateral masking on the latency of otoacoustic emissions elicited by acoustic distortion products.

Otoacoustic emissions (OAE) are sound products generated by the outer hair cells (OHC) in the inner ear. The OHC are capable of moving spontaneously or in response to acoustic stimuli (spontaneous otoacoustic emissions and evoked otoacoustic emissions), these movements are known as electromotility. Electromotility is affected when contralateral acoustic stimulation is introduced to the ear. Different types of stimuli may produce this response. Clicks, pure tones, and white masking noise have been used as contralateral stimulation. This effect appears to be mediated by the medial efferent olivocochlear bundle. Contralateral masking produces suppression of OAE, especially on the amplitude. However, the effect of contralateral masking on the latency of distortion product otoacoustic emissions (DPOAE) has not been studied. The purpose of this paper is to investigate whether contralateral masking, with wide band masking noise, may produce a significant change on the latency of the DPOAE. Three different latency measurements of DPOAE measurements were made on low, middle and high frequencies of fl including 574 Hz, 2454 Hz and 4919 Hz. Each one of these frequencies was measured with and without contralateral masking. Twenty-eight ears of 15 subjects were studied. Non-significant differences (P > 0.05) between masked and unmasked conditions were found in all cases. It is concluded that contralateral masking does not appear to affect latency of DPOAE.

Audiometry↗
PubMed2000

Suppression on neuronal responses by a metacontrast masking stimulus in monkey V4.

We studied the temporal characteristics of suppression in area V4 of the monkey using a visual stimulus for metacontrast masking. Visual responses of V4 neurons to a brief test stimulus presented within the receptive field were recorded, and the effect of a mask stimulus that did not spatially overlap the test stimulus was examined. Responses to the test stimulus were suppressed by the mask stimulus, which either preceded or followed the test stimulus. To study the temporal characteristics of suppression, the interval between the onset of the test stimulus and that of the mask stimulus (stimulus onset asynchrony, SOA) was varied. Maximum suppression occurred with a simultaneous presentation of the two stimuli, and the suppression gradually weakened as the SOA increased. The suppressive effect of the mask stimulus lasted on average about 77 ms in the negative SOA (forward masking) and 65 ms in the positive SOA (backward masking). These results indicate that surround suppression in V4 neurons has considerable temporal width, which is longer than that previously reported in areas V1 and V2. There were marked differences between the time course of suppression in V4 neurons in the present study and those reported in human metacontrast masking.

Animals↗
PubMed2000

What's new in visual masking?

A brief display that is clearly visible when shown alone can be rendered invisible by the subsequent presentation of a second visual stimulus. Several recently described backward masking effects are not predicted by current theories of visual masking, including masking by four small dots that surround (but do not touch) a target object and masking by a surrounding object that remains on display after the target object has been turned off. A crucial factor in both of these effects is attention: almost no masking occurs if attention can be rapidly focused on the target, whereas powerful masking ensues if attention directed at the target is delayed. A new theory of visual masking, inspired by developments in neuroscience, can account for these effects, as well as more traditional masking effects. In addition, the new theory sheds light on related research, such as the attentional blink, inattentional blindness and change blindness.

Journal Article↗
PubMed2006

Increased airway hyperreactivity with the M40 protective mask in exercise-induced bronchospasm.

OBJECTIVE: Exercise-induced bronchospasm (EIB) has a prevalence of 6% to 7% in United States Army personnel and 3% to 13% in professional athletes. There are reported concerns that military personnel with EIB will have increased airway hyperreactivity or significant dyspnea while wearing the standard military M40 protective mask. The objective of this study is to determine whether the M40 protective gas mask increases airway hyperreactivity in military personnel with exertional dyspnea and the diagnosis of EIB. METHODS: Ten active duty military with EIB (defined as history of exertional dyspnea, normal spirometry, and reactive methacholine challenge test) and 10 normal control subjects were evaluated. Both the participants and control subjects underwent baseline exercise challenge testing (ECT) with and without the M40 protective mask. Forced expiratory volume in one second (FEV1) (percent predicted) post ECT was compared to baseline FEV1 within and between groups along with exercise time. RESULTS: There was no statistical difference in between individuals and between groups wearing the M40 mask. None of the study group had a positive ECT exercising without the M40 mask while 20% of the study group with EIB had a positive ECT wearing the M40 mask. CONCLUSION: Military personnel with EIB who exercised with the M40 protective mask did not overall have significantly increased airway hyperreactivity compared to control subjects. Screening ECT may be beneficial in identifying those susceptible persons who report symptoms while wearing the M40 protective mask.

Adult↗
PubMed1995

Respirator mask effects on exercise metabolic measures.

To test effects of respirator masks on maximum oxygen uptake, ventilation threshold, and lactate threshold, 14 subjects underwent incremental bicycle exercise with and without masks. There was a statistically significant difference in final oxygen consumption between the two conditions, but other results suggest that the physiological measure of maximum oxygen uptake was not reached at termination for the full-mask condition. Lactate and ventilation thresholds were not affected by mask condition. Hypoventilation while wearing masks caused higher amounts of blood lactate accumulation. The resulting higher mask CO2 levels and lower O2 levels, normally attributed to mask dead volume, may instead be due to mask resistance.

Adult↗
PubMed2002

Intensity-modulated radiation therapy using only jaws and a mask.

Intensity-modulated radiation therapy (IMRT) generally requires complex equipment for delivery. Just one study has investigated the use of 'jaws-only' IMRT with not discouraging conclusions. However, the monitor-unit efficiency is still considered to be too low compared with the use of a multileaf collimator (MLC). In this paper a new IMRT delivery technique is proposed which does not require the MLC and is only moderately more complex than the use of jaws alone. In this method a secondary collimator (mask) is employed together with the jaws. This mask may translate parallel to the jaw axes. Two types of mask have been investigated. One is a regular binary-attenuation pattern and the other is a random binary-attenuation pattern. Studies show that the monitor-unit efficiency of this 'jaws-plus-mask' technique, with a random binary mask, is more than double that of the jaws-only technique for typical two-dimensional intensity-modulated beams of size 10 x 10 bixels2 and with a peak value of 10 MU (or quantized into 10 fluence increments). For two-dimensional intensity-modulated beams of size 15 x 15 bixels2 with a peak value of 10 MU (or quantized into 10 fluence increments), the monitor-unit efficiency of the 'jaws-plus-mask' technique with a random binary mask is almost triple that of the jaws-only technique. Some further extensions to this concept are presented showing that some more practical mask arrangements are possible but with somewhat compromised monitor-unit efficiency. Some comments are provided on practicalities and on delivery times.

Algorithms↗
PubMed2006

A fast and symmetric DUST implementation to mask low-complexity DNA sequences.

The DUST module has been used within BLAST for many years to mask low-complexity sequences. In this paper, we present a new implementation of the DUST module that uses the same function to assign a complexity score to a sequence, but uses a different rule by which high-scoring sequences are masked. The new rule masks every nucleotide masked by the old rule and occasionally masks more. The new masking rule corrects two related deficiencies with the old rule. First, the new rule is symmetric with respect to reversing the sequence. Second, the new rule is not context sensitive; the decision to mask a subsequence does not depend on what sequences flank it. The new implementation is at least four times faster than the old on the human genome. We show that both the percentage of additional bases masked and the effect on MegaBLAST outputs are very small.

Genome, Human↗
PubMed2001

Clinical bitterness masking test for phantogeusia.

It is difficult to determine the reason why a patient complains of a bitter taste when their mouth is empty. We examined a new diagnostic test using a bitterness masking substance. The bitterness masking substance, 'Benecoat BMI-60' (hereafter BMI-60), is a masking substance specific to the taste cells' bitterness receptors. After patients gargled with BMI-60 solutions, the phantom sensation of bitterness was masked in some patients, but was not masked in others. Bitter substances in saliva seemed to be masked by BMI-60, but bitterness did not seem to be masked when the locus of the phantom sensation was within the peripheral nerve and/or the brain. The bitterness masking test is useful for diagnosis of the phantom sensation of bitter taste.

Aged↗