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At least 19 recordsLinked to original sources

Retention of pediatric bag-mask ventilation efficacy skill by inexperienced medical student resuscitators using standard bag-mask ventilation masks, pocket masks, and blob masks.

OBJECTIVE: To measure the ventilation efficacy with three single-sized mask types on infant and child manikin models. METHODS: Medical students were recruited as study subjects inasmuch as they are inexperienced resuscitators. They were taught proper bag-mask ventilation (BMV) according to the American Heart Association guidelines on an infant and a child manikin. Subjects completed a BMV attempt successfully using the adult standard mask (to simulate the uncertainty of mask selection), pocket mask, and blob mask. Each attempt consisted of 5 ventilations assessed by chest rise of the manikin. Study subjects were asked which mask was easiest to use. Four to six weeks later, subjects repeated the procedure with no instructions (to simulate an emergency BMV encounter without immediate pre-encounter teaching). RESULTS: Forty-six volunteer subjects were studied. During the first attempt, subjects preferred the standard and blob masks over the pocket mask. For the second attempt, the blob mask was preferred over the standard mask, and few liked the pocket mask. Using the standard, blob, and pocket masks on the child manikin, 39, 42, and 20 subjects, respectively, were able to achieve adequate ventilation. Using the standard, blob, and pocket masks on the infant manikin, 45, 45, and 11 subjects, respectively, were able to achieve adequate ventilation. CONCLUSIONS: Both the standard and blob masks are more effective than the pocket mask at achieving adequate ventilation on infant and child manikins in this group of inexperienced medical student resuscitators, who most often preferred the blob mask.

Adult↗

Variations in backward masking with different masking stimuli: II. The effects of spatially quantised masks in the light of local contour interaction, interchannel inhibition, perceptual retouch, and substitution theories.

In part I we showed that with spatially non-overlapping targets and masks both local metacontrast-like interactions and attentional processes are involved in backward masking. In this second part we extend the strategy of varying the contents of masks to pattern masking where targets and masks overlap in space, in order to compare different masking theories. Images of human faces were backward-masked by three types of spatially quantised masks (the same faces as targets, faces different from targets, and Gaussian noise with power spectra typical for faces). Configural characteristics, rather than the spectral content of the mask, predicted the extent of masking at relatively long stimulus onset asynchronies (SOAs). This poses difficulties for the theory of transient-on-sustained inhibition as the principal mechanism of masking and also for local contour interaction being a decisive factor in pattern masking. The scale of quantisation had no effect on the masking capacity of noise masks and a strong effect on the capacity of different-face masks. Also, the decrease of configural masking with an increase in the coarseness of the quantisation of the mask highlights ambiguities inherent in the re-entrance-based substitution theory of masking. Different masking theories cannot solve the problems of masking separately. They should be combined in order to create a complex, yet comprehensible mode of interaction for the different mechanisms involved in visual backward masking.

Attention↗

Positive pressure ventilation during fibreoptic intubation: comparison of the laryngeal mask airway, intubating laryngeal mask and endoscopy mask techniques.

BACKGROUND: The efficacy of delivery of mechanical ventilation through different airway devices during fibreoptic intubation is not known. METHODS: We compared the laryngeal mask airway (LMA), intubating laryngeal mask (ILM) and endoscopy mask for positive pressure ventilation (PPV) during fibreoptic intubation. In 80 adult paralysed patients, fibreoptic intubation was performed during PPV using a combination of a size 3 or 4 LMA with a 6.0 mm nasal RAE tracheal tube (LMA3/4 group; n=22), a size 5 LMA with a 7.0 mm nasal RAE tube (LMA5 group; n=18), an ILM with an 8.0 mm special reinforced tracheal tube (ILM group; n=20) or an endoscopy mask (Patil mask) with a 7.5 mm standard tracheal tube (Patil group; n=20). The inspiratory and expiratory tidal volumes (VI and VE) with a ventilation pressure of 20 cm H2O were measured using a pneumotachograph. RESULTS: Mean VE values during fibreoptic intubation in the LMA5 [5.3 (SD 1.5) ml kg(-1)] and ILM [7.1 (2.3) ml kg(-1)] groups were greater than in the LMA3/4 group [2.6 (1.0) ml kg(-1), P<0.0001]. The mean VE was greater in the Patil group [20.6 (4.9) ml kg(-1)] than in the other three groups (P<0.0001). Gastric insufflation during intubation was more frequent in the Patil group (30%) than in the other three groups (4.5-5.6%) (P<0.05). CONCLUSION: PPV is possible with the LMA, ILM or endoscopy mask during fibreoptic intubation. With an airway pressure of 20 cm H2O, ventilation during intubation using a size 3 or 4 LMA was almost insufficient, while ventilation using a size 5 LMA or an ILM was almost acceptable. Ventilation during intubation with the endoscopy mask was greater than that with the LMA or ILM, but gastric insufflation was more frequent.

Adult↗

The effects of two kinds of mask (with or without exhaust valve) on clothing microclimates inside the mask in participants wearing protective clothing for spraying pesticides.

AIM: The study aimed at discovering the effects of wearing two types of protective mask on the clothing microclimate (temperature, humidity) inside the mask, physiological parameters and subjective sensations. METHOD: Five healthy female students performed intermittent step exercise while wearing the protective clothing in a climate chamber at 28 degrees C and 60% relative humidity (RH). One mask was made of non-woven fabric and had no exhaust valve (mask A), and the other had an exhaust valve (mask B). RESULTS: (1) Clothing microclimate temperature inside the mask was significantly lower in mask B than in mask A. The final values were 35.5 +/- 0.3 degrees C in mask A and 34.6 +/- 0.8 degrees C in mask B. (2) Clothing microclimate humidity inside the mask was significantly lower in mask B than in mask A. The final values were 37.9 +/- 0.9 g/m3 in mask A and 35.7 +/- 2.0 g/m3 in mask B. (3) Cheek skin temperature inside the mask was kept significantly lower in mask B than in mask A. (4) Clothing microclimate humidity at trunk level increased more slowly with mask B than with mask A for four participants. (5) Rectal temperature increased more slowly with mask B than with mask A for three participants. (6) Tympanic temperature increased more slowly with mask B than with mask A for two out of four participants. DISCUSSION: We discussed these findings from the viewpoint that the dry and wet heat loss was accelerated through the nose under the influence of a reduced level of clothing microclimate inside mask B, having probably helped selective brain cooling by cooling more effectively the vein circulating blood through the nose.

Agricultural Workers' Diseases↗

[Evaluation of quantitative fit-testing of N95 filtering facepiece respirators using Mask-Fitting Tester and improvement of mask fitting by instruction].

OBJECTIVE: To evaluate quantitative fitness of N95 filtering facepiece respirators (N95 Mask) using Mask Fitting Tester and improvement of fitness by instruction. MATERIALS AND METHODS: One hundred and thirty-three health care workers working at our hospital were tested as to quantitative fitness of N95 Mask using Mask Fitting Tester Model MT-02, Roken type that counts particles more than 0.7 microm in diameter. Based on counting the number of particles more than 0.7 microm in diameter of the air inside and outside the mask, leakage rate is calculated. Permissible range of leakage rate is 10% or below. In case of leakage rate more than 10%, we instructed way of wearing N95 Mask or change a type of N95 Mask. We usually provide three types of N95 Mask. RESULTS: Eighty-seven (65.4%) out of 133 health care workers achieved leakage rate 10% or below at the first test. Forty-six (34.6%) who did not achieve leakage rate 10% or below at the first test received instruction or changed a mask type. Twenty-one (15.8%) achieved desired value by instruction and 19 (14.3%) by changing a mask type. But 6 (4.5 %) could not achieve desired value in spite of instruction or changing to another type of masks available to us. Leakage rate changed from 20.5 +/- 10.9% (10.1-58.6) to 6.3 +/- 4.9% (0-29.5) by instruction or changing a type of mask (p < 0.001). At the first test, mask fitness is better in male than female, and worse in workers who always use N95 Mask at isolation ward or laboratory room than workers who usually do not use N95 Mask. Main problems were choice of mask, fitness to nose, incorrect use of headband. CONCLUSION: It is useful to evaluate N95 Mask quantitative fitness using Mask Fitting Tester Model MT-02, Roken type. At the first test, 34.6% of health care workers have large amount of leakage more than 10%, and by instruction or changing a mask type, most of them could achieve 10% or below. But 4.5% could not achieve desired value. On Infection control, it is important to test quantitative fitness of N95 Mask and to provide more than three types of N95 Mask.

Equipment Design↗

[The clinical use of an individually fitted nasal mask ("Freiburg Respiratory Mask") within the scope of a case report of controlled BiPAP ventilation].

PURPOSE: Noninvasive mechanical ventilation with nasal or face mask using either BiPAP or IPPV (intermittent positive pressure ventilation) modes is meanwhile the standard type of mechanical ventilation instead of endotracheal intubation or tracheostomy in many patients with chronic and acute respiratory failure. However, problems occur very often in noninvasive mechanical ventilation due to mask problems with leakage of air out of the mask or erasions and necrosis of the skin by constant pressure through the mask frame. Hence, some clinical work groups developed customized molded masks mostly in cooperation with dentistry labs. These masks, however, are often very expensive and take several weeks to be manufactured. Our aim was to develop an inexpensive (less than 600 USS) and easy-(in one day)-to-produce customized nasal mask, the so-called "Freiburg nasal mask". We wish to show by a case report the clinical efficacy of this customized mask in severe respiratory failure. CASE AND METHOD: A 52 y old women (BMI 19, nonsmoker) suffering from a severe hypercapnic respiratory failure (PCO2 over 100 mmHg) due to a severe kyphoscoliosis as result of a postpoliosyndrome and already on controlled nasal BiPAP with a standard respironics nasal mask, was referred to our clinic as an emergency case. After not succeeding to normalise blood gases and clinical status of the patient in mechanical ventilation on BiPAP mode and additional 2 lit/min of oxygen insufflation via the mask (patient was refusing invasive ventilation) for 12 days due to mask leakage and mask discomfort we made a mould of the patients face. Using this mould in a vacuum process the two EVA polymers Erkoflex and Erkodent were combined to build up the customized mask over the mould on the same day. In the first three days using the customized mask in the patient PCO2 decreased below 70 mmHg, on the 8th day after starting with the customized mask, blood gases almost normalised. Patient compliance in using the BiPAP device increased from 8 h a day to 16 h a day. CONCLUSION: This case shows that sometimes due to leakage of air in standard nasal masks noninvasive mechanical ventilation may fail in patients with severe respiratory failure. Therefore, in these patients customized moulded nasal or face masks should be used instead of standard masks. We think that the Freiburg nasal mask is an example of an easy to produce and nonexpensive customized mask and may be used in such patients, as this case report shows.

Equipment Design↗

Masking author identity in peer review: what factors influence masking success? PEER Investigators.

CONTEXT: In a previous study, we found that masking success was higher at a journal that masked reviewers to author identity. We hypothesized that masking policy or other factors could be associated with masking success. OBJECTIVES: To evaluate differences in success of masking reviewers to author identity at 7 biomedical journals and to identify factors associated with these differences. DESIGN: Written questionnaire. PARTICIPANTS: Reviewers at 3 journals with a long-standing policy of masking author identity (Annals of Emergency Medicine, Epidemiology, and Journal of the American Geriatrics Society) and 4 journals without a policy of masking author identity (Annals of Internal Medicine, JAMA, Obstetrics & Gynecology, and Ophthalmology). MAIN OUTCOME MEASURES: Masking success (percentage of reviewers successfully masked) and reviewer characteristics associated with masking. RESULTS: There was no significant difference in masking success between journals with a policy of masking (60%) and those without (58%) (P= .92). We found no association between masking success and a policy of masking when adjusted for the reviewer characteristics of age, sex, years of reviewing experience, number of articles published, number of articles reviewed, percentage of time spent in research, editorial experience, or academic rank (odds ratio [OR], 1.3; 95% confidence interval [CI], 0.64-2.8; P=.43). In multivariable analysis of reviewer characteristics, reviewers spending a greater percentage of time in research, the only significant predictor of masking success, were less likely to be successfully masked (OR, 1.01; 95% CI, 1.00-1.02) (P=.04). CONCLUSIONS: Masking success appears unrelated to a journal policy of masking, but is associated with reviewers' research experience and could be affected by other characteristics. Using reviewers with less research and reviewing experience might increase masking success, but the effect on review quality is unknown.

Authorship↗

Thermal load of laser aperture masks in nonmechanical trephination for penetrating keratoplasty with the Er:YAG laser: comparison between stainless steel and ceramic masks.

PURPOSE: Thermal effects on the laser aperture mask may play a major role in the thermal loading of the cornea during nonmechanical trephination in penetrating keratoplasty. The purpose of this study was to assess the temperature increase on the laser mask using the 2.94-microm Er:YAG laser in order to find suitable parameters for avoidance of thermal damage to the cornea. METHODS: Thermal load measurements were performed on donor (7.5 mm trephination diameter, 0.7 mm thickness, central hole 3.0 mm) and recipient (7.5 mm trephination diameter, 0.7 mm thickness, outer diameter 13.0 mm) aperture masks. The masks were either mounted on a thermal isolator or fixed directly on porcine corneal samples. Temperature increase was measured either under static conditions in the ablation area (setup 1) and at the opposite side of the mask (setup 2) or in the ablation area under dynamic conditions, rotating the whole globe to simulate a constant trephination speed with the mask positioned directly on a porcine cornea (setup 3). We used the NWL Er:YAG solid-state laser in a 1.3-mm free-running spot mode focused on the trephination margin (half of the beam on the mask and half of it on the cornea) with a pulse energy of 200 or 400 mJ and 18CrNi10 stainless steel versus three different types of ceramic masks (silicium carbide, silicium nitrite, aluminum oxide). Temperature was assessed using an infrared pyrometer with automatic data acquisition software for a personal computer. RESULTS: Overall, the temperature rise ranged between 43.6 K (metal donor mask at the trephination area with 400 mJ pulse energy) and 3.3 K (silicium carbide recipient mask at the opposite side of the mask with 200 mJ pulse energy). With all setups and both energy levels, the heating of the metal mask was significantly higher (P<0.02) than the heating of the three types of ceramic masks. The silicium carbide masks revealed the lowest temperature rise. Comparing the three setups, the temperature rise was maximal under static conditions in the ablation area and minimal at the opposite side, with the dynamic setup ranging in between. Temperature rise was significantly greater (P<0.04) in donor masks than in recipient masks for each mask material and both energy levels. CONCLUSION: The physical characteristics of silicium carbide masks seem superior to those of metal masks with regard to minimizing the thermal load of the epithelium or superficial stroma during Er:YAG laser trephination of the cornea for penetrating keratoplasty.

Animals↗

A comparison of local and remote masking on tactile pulse detection using different masking patterns.

Forward and backward masking functions were obtained for the detection of a 2-msec. tactile "test" pulse using two different masking patterns (5- or 10-pulse sequences) under conditions of both local and remote masking. Twelve ISIs (interval between "test" pulse and onset of the masking sequence) ranging from 10 to 76 msec. were used. A two-interval forced-choice (2-IFC) procedure was used in which observers were presented with two successive trains of tactile pulses, one having the "test" pulse at varying intervals prior (backward masking) to or after (forward masking) the masking sequence and one train having only a masking sequence. Observers were asked to report in which train of pulses they detected the "test" pulse. With local masking, i.e., when "test" pulse and masking sequence were presented to the same locus, there was substantially more forward than backward masking, and the 10-pulse sequence resulted in consistently greater amounts of masking than the 5-pulse mask. When the "test" pulse and masking sequence were delivered to different loci, i.e., the remote masking, the results were much less systematic. The data suggest that both peripheral and central factors contribute to the obtained masking functions and that both integration and interruption are producing the masking interference.

Discrimination Learning↗

Influence of mask design on bag-mask ventilation.

Adequate positive pressure ventilation in the field or emergency department continues to represent a major challenge. A new face mask design that recently has been introduced consists of a low-pressure "balloon" through which a Guedel airway is attached and extended proximally through the mask to allow the attachment of a ventilation bag. The mask is designed to seal the nares and mouth when pressed against the face. Ventilation is achieved through the airway which extends through the mask to just above the epiglottis. We designed a study to evaluate ventilating volumes and mask leak with this mask design, and to compare these parameters with those achieved with standard masks. Thirty volunteers with varied experience in bag-mask ventilation were chosen to ventilate a specially adapted ventilation manikin connected to a test lung that was capable of simulating varied compliances. Spirometers measured volumes delivered to the ventilating bag and lung, and mask leak could be calculated from these readings. A constant rate of 12 ventilations per minute was maintained by each volunteer for two minutes. Volunteers ventilated the test lung using three masks in random sequence: the SealEasy mask (Respironics Inc, Monroeville, PA), a Laerdal mask (old type), and a transparent Robertshaw mask with inflatable black rim. The average tidal volume delivered by the SealEasy mask was consistently higher than either of the other two. Significantly (P less than .05) higher volumes were delivered with the SealEasy mask when compared to the Laerdal, and significantly lower mask leaks were seen when the SealEasy was compared to both.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗

Airway management during cardiopulmonary resuscitation--a comparative study of bag-valve-mask, laryngeal mask airway and combitube in a bench model.

Gastric inflation and subsequent regurgitation are a potential risk of ventilation during cardiopulmonary resuscitation (CPR). In respect of recent investigations, principal respiratory components such as respiratory system compliance, resistance and lower esophageal sphincter pressure were adapted according to CPR situations. The purpose of our study was to assess lung ventilation and gastric inflation when performing ventilation with bag-valve-mask, laryngeal mask airway, and combitube in a bench model simulating an unintubated cardiac arrest patient. Twenty-one student nurses, without any experience in basic life support measures, ventilated the bench model with all three devices. Mean ( +/- S.D.) gastric inflation with the laryngeal mask airway (seven cases) was significantly lower than with the bag-valve-mask (0.6 +/- 0.8 vs 3.0 +/- 2.11 min(-1), P < 0.01). There was no gastric inflation when ventilation was performed with the combitube. Only seven of 21 volunteers exceeded 1-min lung volumes of > 5 1 when using the bag-valve-mask, whereas mean (+/-S.D.) 1-min lung volumes with both laryngeal mask airway and combitube were significantly higher (laryngeal mask airway 15.0+/-6.61, combitube 16.6 +/- 6.81 vs bag-valve-mask 4.8 +/- 2.71, P < 0.01). The time for insertion was significantly faster with both bag-valve-mask and laryngeal mask airway compared with the combitube (median: bag valve mask 22 s, laryngeal mask airway 37 s vs combitube 70 s, P < 0.01). This may tip the scales towards using the laryngeal mask airway during basic life support airway management. In conclusion, our data suggests that both laryngeal mask airway and combitube may be appropriate alternatives for airway management in the first few minutes of CPR.

Adult↗

Forward masking of faces by spatially quantized random and structured masks: on the roles of wholistic configuration, local features, and spatial-frequency spectra in perceptual identification.

The forward masking of faces by spatially quantized masking images was studied. Masks were used in order to exert different types of degrading effects on the early representations in facial information processing. Three types of source images for masks were used: Same-face images (with regard to targets), different-face images, and random Gaussian noise that was spectrally similar to facial images. They were all spatially quantized over the same range of quantization values. Same-face masks had virtually no masking effect at any of the quantization values. Different-face masks had strong masking effects only with fine-scale quantization, but led to the same efficiency of recognition as in the same-face mask condition with the coarsest quantization. Moreover, compared with the noise-mask condition, coarsely quantized different-face masks led to a relatively facilitated level of recognition efficiency. The masking effect of the noise mask did not vary significantly with the coarseness of quantization. The results supported neither a local feature processing account, nor a generalized spatial-frequency processing account, but were consistent with the microgenetic configuration-processing theory of face recognition. Also, the suitability of a spatial quantization technique for image configuration processing research has been demonstrated.

Adult↗

Variations in backward masking with different masking stimuli: I. Local interaction versus attentional switch.

The types of stimuli used as targets and masks considerably change the masking functions in a way that requires us to abandon any single mechanism of masking as the sole explanation of backward masking. In the first of two reports in which the problem of the mask-dependence of masking is addressed, we explore the role of the relative spatial positioning of targets and masks in order to differentiate between local interaction and attentional models. If single letters were masked by double-letter masks then the relative spatial arrangement of the letters, which was changed in order to vary the involvement of metacontrast-like processes, had an effect at shorter SOAs, but not at longer SOAs where strong masking still persisted. This poses difficulties for proposing local contour interaction as the main mechanism of masking. Similarly, crowding effects alone cannot explain the results. Backward masking also involves attention being directed to working-memory processing of the succeeding object while abandoning the preceding object.

Attention↗

Reading with central field loss: number of letters masked is more important than the size of the mask in degrees.

When the center of a readers, visual field is blocked from view, reading rates decline and eye movement patterns change. This is true whether the central visual field is blocked artificially (i.e. a mask) or through disease (e.g. a retinal scotoma due to macular degeneration). In past studies, when mask size was defined in terms of the number of letters masked from view, reading rates declined sharply as number of letters masked increased. Patients with larger central scotomas (in degrees of visual angle) also read slower. We sought to determine whether number of letters masked or size of the mask in degrees is the predominant factor affecting reading rates and eye movement behavior. By matching number of letters masked across several mask sizes (and compensating for reduced acuity in the periphery), we found that number of letters masked is the more important factor until mask size is quite large (> or = -7.5 degrees) and number of letters masked from view is more than seven.

Adult↗

Comparison of face masks in the bag-mask ventilation of a manikin.

BACKGROUND AND OBJECTIVE: We conducted a study investigating the effectiveness of four face mask designs in the bag-mask ventilation of a special manikin adapted to simulate a difficult airway. METHODS: Forty-eight anaesthetists volunteered to bag-mask ventilate the manikin for 3 min with four different face masks. The primary outcome of the study was to calculate mean percentage leak from the face masks over 3 min. Anaesthetists were also asked to rate the face masks using a visual analogue score. RESULTS: The single-use scented intersurgical face mask had the lowest mean leak (20%). This was significantly lower than the mean leak from the single-use, cushioned 7,000 series Air Safety Ltd. face mask (24%) and the reusable silicone Laerdal face mask (27%) but not significantly lower than the mean leak from the reusable anatomical intersurgical face mask (23%). CONCLUSIONS: There was a large variation in both performance and satisfaction between anaesthetists with each design. This highlights the importance of having a variety of face masks available for emergency use.

Anesthesia↗

Masking and partial masking in listeners with a high-frequency hearing loss.

3 listeners with sensorineural hearing loss ranging from moderate to moderate-severe starting at frequencies higher than 1 kHz participated in two masking experiments and a partial masking experiment. In the first masking experiment, fM = 1 KHz and LM = 50 dB SPL, higher than normal masked thresholds were obtained for listeners whose hearing was impaired in the frequency region of clear hearing loss as well as in the region of near-normal absolute thresholds. The second masking experiment showed that for hearing-impaired listeners the elevation of the masked thresholds, in decibels, in this frequency region of "near-normal' absolute thresholds was equal to the elevation of the absolute thresholds, in decibels. The third experiment, a partial masking experiment with fM = 975-1025 Hz and LM = 75 dB SPL, showed similar partial-masking functions for hearing-impaired and normal listeners, but the functions for the hearing-impaired listeners were at much higher levels of the partially masked probe tone. Thus the higher masked thresholds of the hearing-impaired can result in a dramatic reduction of the dynamic range of hearing under masking in the frequency region of the hearing loss and also in the region with only a small hearing loss (less than 30 dB). It is suggested that this may explain the speech perception difficulties which these listeners experience, especially in the presence of ambient noise.

Adult↗

Fibreoptic views through the laryngeal mask and the intubating laryngeal mask.

BACKGROUND AND OBJECTIVE: The intubating laryngeal mask (intubating laryngeal mask airway) was designed to facilitate blind intubation. Its value as an adjunct to fibreoptic laryngoscopy has not been evaluated. This study compares the intubating laryngeal mask airway with the standard laryngeal mask airway as conduits for fibreoptic laryngoscopy. METHODS: The fibreoptic view of the laryngeal inlet was graded via both devices in 60 anaesthetized patients. The fibreoptic view through the intubating laryngeal mask airway was assessed after the central epiglottic elevator bar had been lifted out of the field of vision by an 8-mm Euromedical tracheal tube, which was inserted to a depth of 18 cm. The fibreoptic view from the aperture bars of the laryngeal mask was recorded. RESULTS: The vocal cords were viewed less frequently through the intubating laryngeal mask airway (52%) than through the laryngeal mask airway (92%) [difference = 40% (95% CI = 26% to 54%), P < 0.0001]. CONCLUSION: The view of the laryngeal inlet is better through the laryngeal mask airway than through a tracheal tube inserted to 18 cm in the intubating laryngeal mask.

Adolescent↗

Efficiency of constant-flow oxygen masks for general aviation: a new method of mask evaluation.

Three commercially popular oxygen masks for general aviation were tested by measuring arterial blood gases at altitude and alveolar gases at ground level with a respiratory mass spectrometer. At 4,575 m (15,000 ft) and 3.65 1/min oxygen flow, calculated fractional inspired oxygen (F102) averaged 38.1% for the Hudson-type mask; 49.6% for the Scott Sky Mask; and 52.4% for the Scott Duo Seal Mask. At ground level, 1280 m (4,200 ft) 2.6 1/min oxygen flow, F102 calculated from alveolar gases averaged 41.5% plus or minus S.D. 5.3 for the Hudson Mask; 48.0% plus or minus 5.2 for the Scott Sky Mask; and 54.9% plus or minus S.D. 6.2 for the Scott Duo Seal Mask. The asymptomatic hyperventilation observed in all subjects at altitude degraded the performance of all three masks to a sufficient degree to offset the benefits of increased oxygen flow achieved through the regulator at higher altitudes. The respiratory mass spectrometer provides a new technique for analyzing efficiency of oxygen masks and the effect of changes in mask design.

Aerospace Medicine↗