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A history of latex allergy.

Archaeologists have found that latex items were used as early as 1600 BC, but it took until approximately 1900 AD before surgical gloves were commonly used. Descriptions of apparent allergic reactions to natural rubber appeared in the medical literature in 1927, and irritant and delayed-contact reactions were reported in 1933. Although irritant and delayed-contact reactions to rubber products were increasingly recognized, immediate-type allergic reactions were not reported again until 1979. However, after 1980, increasing numbers of contact urticarial reactions to latex were reported, and investigations suggested that many of these reactions were IgE-mediated. In 1984, the first anaphylactic reactions caused by latex surgical gloves were reported, followed in 1991 by the first report of a fatal anaphylactic reaction to latex. Increasing recognition of latex allergy led to divergent paths of investigation. Critical early questions were whether the observed reactions were truly IgE-mediated, and if they were IgE-mediated, what was the source of the allergen? If the allergen was present in latex products, where did it come from? Was it present in raw latex or was it added during processing? As knowledge about the allergens improved, efforts were made to develop and test materials for skin testing and for allergen-specific IgE assays. Now more than 10 unique proteins are recognized as major latex allergens. Although much has been learned about latex allergy, important unanswered questions remain, including the sources of latex exposure that led to sensitization, why latex allergy increased dramatically during the 1980s, and the prevalence of latex allergy in diverse populations. This review concentrates on the history of latex use in medicine and the dramatic emergence of immediate-type latex allergy.

Gloves, Protective↗

Critical review of international standards for respiratory protective equipment - II. Gas and vapor removal efficiency and fit testing.

The purpose of a Respiratory Protective Equipment (R.P.E.) standard is to assure that a minimum level of performance is reached by the respirator. Standards from a number of countries and standards organizations require that certain specifications are met in construction and that respirators be evaluated by specific performance tests. This is the second of three critical review papers related to respirator standards. We here summarize in tabular form, compare and critically review how the different countries or standards organizations test respirators designed for protection against gases and vapors for leakage due to improper fitting of the respirator facepiece and gas and vapor removal efficiency of the cartridge/canister. Two general aspects as they relate to removal capacity testing are discussed. The first issue deals with the selection of test gases and vapors that best represent the sorptive behavior of a class or group of compounds. The second issue deals with the extrapolation of laboratory testing under rigidly specified conditions to conditions of actual use. Fit testing varies from country to country. The fit testing conditions specified in the various standards are summarized along with a discussion of test material selection, the test panel selection, and the range of controlled test activities.

Air Pollutants, Occupational↗

A laboratory and clinical study of pneumatic 'grip strength' devices.

The use of inflated bags or cuffs to measure grip strength is now a well established technique. The method does have a number of problems. Bags of different diameter and volume were seen to give statistically significantly different pressure readings when squeezed by the same subjects. Different initial pressures (from 20 mmHg to 60 mmHg) also gave significantly different results both in laboratory tests on a materials testing machine and when patients with rheumatoid arthritis squeezed the bag. The technique of squeezing also affected the results. Despite the intrinsic drawbacks of the system, it is likely to remain in general use because of familiarity and convenience. We recommend the minimum details required when pneumodynamometer-derived data are published.

Adult↗

Biomechanical analysis of location of lag screw of a dynamic hip screw in treatment of unstable intertrochanteric fracture.

OBJECTIVE: The aim of this study was to assess the most adequate location of a lag screw of a dynamic hip screw in the treatment of an unstable intertrochanteric fracture. METHODS: Six pairs of proximal femora obtained from fresh adult cadavers were inflicted with iatrogenic unstable intertrochanteric fractures. Fractures of both sides were stabilized with two different favored locations of a lag screw and tested by a Material Testing System machine with increased loads to evaluate the relative migration of the femoral head. RESULTS: There was significant difference (p < 0.05) with less migration of the femoral head by inferior insertion of a lag screw in the frontal plane and central insertion in the coronal plane. CONCLUSIONS: Based on theoretical and experimental considerations, the most adequate location of a lag screw of a dynamic hip screw should be inferior in the frontal plane and central in the coronal plane.

Adult↗

Biomechanical comparison for different configurations of tension band wiring techniques in treating an olecranon fracture.

BACKGROUND: The aim of this study was to compare the superiority between the newly designed modified AO tension band wiring technique and the traditional modified AO tension band wiring technique in treating an olecranon fracture. METHODS: Eight pairs of fresh cadaveric ulnae were tested biomechanically. After transverse osteotomy of the olecranon, all left ulnae were fixed by the traditional modified AO technique with two Kirschner wires inserted through the anterior ulnar cortex and all right ulnae by the new technique with two Kirschner wires inserted into the marrow cavity from the olecranon to the ulnar styloid process. All specimens were tested by the Material Testing System machine to evaluate fragment displacement and the maximal failure load. A dual linear variable displacement transducer was used to measure relative minimal displacement. RESULTS: There was no significant difference between the techniques. The maximal failure load by either technique was more than 80 kg. Even at testing failure, no Kirschner wires migrated proximally. CONCLUSION: The new technique may be applied widely to treat all olecranon fractures, because it is a technically easier and safer technique. Less than 5.5-kg loads could be permitted in daily activity postoperatively. A single tolerable loading weight should not exceed 8 kg. Kirschner wires will not migrate proximally, despite increased joint loading. Clinically, this study may confirm indirectly the hypothesis that proximal migration of Kirschner wires was mainly due to triceps traction.

Adolescent↗

Laboratory studies of visible-light cured fissure sealants: setting times and depth of polymerization.

Measurements were made, using an acoustic transmission method, of the setting times of three visible-light curing sealants (two filled, one unfilled). Five commercially available visible-light polymerizing sources were tested with each material. Only three of the light sources gave setting times not significantly different from the manufacturers' recommended times for all three materials tested. The variation in microhardness with depth of sealant was measured to study the depth of polymerization of the sealants, all of which were adequate. The filled sealants had microhardness values greater than the unfilled sealant, at all depths studied.

Chemical Phenomena↗

A review of modern impression materials.

A number of new elastic impression materials have been developed over the past few years. The working time, setting time, elasticity at set, permanent deformation, dimensional change on setting and long-term stability were determined for several of these impression materials. The new addition type silicone impression materials proved superior to the other materials tested, but all materials were capable of giving good clinical results.

Dental Impression Materials↗

Coccidioidin and merthiolate in previously sensitized animals.

The effect of merthiolate, which is used as a preservative in skin test materials, on skin test reactions was determined in guinea pigs. In four groups of animals, merthiolate in basal medium produced skin tests at 24 and 48 h characterized by erythema and/or induration in an intermediate region, i.e., 5 plus or minus 2.2 mm. One of the four groups of animals was a nonsensitized control group. The other three groups were subcutaneously sensitized with (i) merthiolate and saline, (ii) killed Coccidioides immitis arthrospores, and (iii) merthiolate with killed C. immitis arthrospores. Coccidioidin only and merthiolate in coccidioidin produced positive delayed results in groups 3 and 4, which were sensitized with arthrospores. A synergistic effect of merthiolate and coccidioidin was observed in animals of group 4 sensitized by merthiolate with killed C. immitis arthrospores. This effect was observed at 24 h when positive reactions of coccidioidin with merthiolate were significantly greater than skin tests with plain coccidioidin.

Animals↗

Biomechanical evaluation of immediate stability with rectangular versus cylindrical interbody cages in stabilization of the lumbar spine.

BACKGROUND: Recent cadaver studies show stability against axial rotation with a cylindrical cage is marginally superior to a rectangular cage. The purpose of this biomechanical study in cadaver spine was to evaluate the stability of a new rectangular titanium cage design, which has teeth similar to the threads of cylindrical cages to engage the endplates. METHODS: Ten motion segments (five L2-3, five L4-5) were tested. From each cadaver spine, one motion segment was fixed with a pair of cylindrical cages (BAK, Sulzer Medica) and the other with paired rectangular cages (Rotafix, Corin Spinal). Each specimen was tested in an unconstrained state, after cage introduction and after additional posterior translaminar screw fixation. The range of motion (ROM) in flexion-extension, lateral bending, and rotation was tested in a materials testing machine, with +/- 5 Nm cyclical load over 10 sec per cycle; data from the third cycle was captured for analysis. RESULTS: ROM in all directions was significantly reduced (p < 0.05) with both types of cages. There was no significant difference in reduction of ROM in flexion-extension (p = 0.6) and rotation (p = 0.92) between the two cage groups, but stability in lateral bending was marginally superior with the rectangular cages (p = 0.11). Additional posterior fixation further reduced the ROM significantly (p < 0.05) in most directions in both cage groups, but did not show any difference between the cage groups. CONCLUSIONS: There was no significant difference in immediate stability in any direction between the threaded cylindrical cage and the new design of the rectangular cage with endplate teeth.

Journal Article↗

The link between the peel force of adhesive dressings and subjective discomfort in volunteer subjects.

OBJECTIVE: The study compared the level of discomfort experienced by healthy volunteers on the removal of a range of adhesive wounds. METHOD: This was an open, within subject comparative study of six adhesive dressings in 24 volunteers. The test site was the lower back. Allocation of test materials to the test sites was randomised. The peel force of removal was recorded after 24 hours of application using a device that removed the dressing at a constant speed and angle to the skin surface. The discomfort experienced at each removal was assessed by the subjects themselves using an electronic visual analogue scale. RESULTS: Overall, Mepilex Border was given a significantly lower discomfort score (p < or = 0.01) by the subjects than the other dressings. There were no clear differences between the five other products tested. Tielle and Allevyn Adhesive had significantly higher (p < or = 0.05) peel force than the other products. Mepilex Border caused less discomfort on removal than Duoderm Extra Thin, Biatain and Versiva, even though the peel force was similar. Tielle and Allevyn had higher peel force, but the levels of discomfort were not significantly higher for these products. CONCLUSION: It may be that the level of discomfort experienced by subjects on removal of an adhesive dressing is not entirely dependent on the peel force and that other aspects of the interaction of the skin surface and adhesive play a role.

Adhesives↗

A screening test of auditory comprehension for individuals with severe physical disability (PACST).

Tests of auditory comprehension are frequently unsuitable for patients with physically disabling conditions as they require abilities such as good vision or physical manipulation of test materials. A suitable test is required to assess patients who can only indicate 'yes' or 'no'. This has implications for enabling patients to make decisions about their care. A test consisting of 60 Yes-No questions was developed from a larger set tested on normals. A clinical trial was completed and the test found to be a useful tool. It allocates patients to three groups: normal, impaired and chance performance.

Adolescent↗

The influence of a local injection of cortisol on the mechanical properties of tendons and ligaments and the indirect effect on skin.

The effects of local cortisol treatment on the mechanical properties of muscle tendon and ligament in rats were studied. In addition to the local effects, possible systemic effects as reflected in the properties of the skin, remote from the site of the injection, were investigated. Two groups of rats were given cortisol injections, 20 mg/kg, every third day for 24 days. In one of the groups the injections were given bilaterally around the peroneal tendons and in the other they were given into both knee joint cavities. Specimens from the peroneal tendons, the posterior cruciate ligament with bone attachments, and strips of skin from the dorsum, were tested in a materials testing machine. The local treatment resulted in increased "tensile strength" of the peroneus brevis tendon and increased maximum load and stiffness of the peroneus longus tendon with no change in the collagen content in any of the samples. The posterior cruciate ligament always broke at one of the two sites of attachment to the bone and the maximum load value at these points was decreased after local cortisol treatment. The systemic effects of this local cortisol treatment on the skin were decreased thickness and fat content, increased collagen concentration and higher "tensile strength" and failure energy. From this study it is concluded that local cortisol injections for 24 days increase the strength and stiffness of muscle tendons, but decrease the strength of the bone attachments of ligaments. This treatment also results in a systemic effect which shows itself as increased strength of the skin remote from the site of the injections.

Animals↗

The biochemical properties of tendon and skin as influenced by long term glucocorticoid treatment and food restriction.

The influence of long term systemic glucocorticoid treatment and food restriction on the mechanical properties of muscle tendons and skin was investigated. A group of male, albino rabbits received prednisolone intramuscularly for 63 days. Another group was food restricted to achieve the same weight loss as the prednisolone treated group. The untreated control group had free access to food and water. Peroneus tertius and longus tendons and strip specimens of lumbal skin were tested in a materials testing machine. Long term prednisolone treatment reduced the dry weights of the muscle tendons, with no change in collagen content and "stress"-strain parameters. The elastic stiffness measured after exhaustion of the viscosity in the tendons was found to be increased. The collagen content of skin was reduced, which resulted in a weakening of the skin as such. However, the extensibility of the skin strips was reduced and the maximum "stress" value, i.e. load value normalized to collagen content, was increased. The food restriction did not change the mechanical properties of muscle tendons. For skin the collagen content was reduced and so were the maximum load and "stress" values after food restriction. It is concluded that both long term glucocorticoid treatment and food restriction reduce the amount of collagen and strength of skin, consistent with clinical experiences. However, in long term glucocorticoid treatment the remaining collagen has increased stability, probably caused by a changed cross-linking pattern, in contrast to a reduced stability of skin collagen in food restriction. Skin is thus influenced more easily than muscle tendon.

Animals↗

A developmental approach to preschool vision screening.

A developmental approach to preschool vision screening is described. The choice of acuity testing material in this test is determined by the child's capabilities, assessed prior to acuity testing. When compared with the Society for Prevention of Blindness test, this approach yields approximately half the number of untestables. Further, the acuity data from the two screening tests are quite similar, and both agree well with data from an additional screening by a pediatric ophthalmologist. Screening of preschool children usually requires a number of compromises in methods felt to be ideal for adults. Sacrifices in cost (i.e., additional personnel to assist the tester), additional effort (i.e., prior training of the children), or precision of acuity measures (i.e., cruder picture type targets for all children and use of isolated targets) are typically made to assure testability. These problems have been minimized by the Experimental method. Because of its low untestability rate and its apparently valid acuity data, this developmental vision screening test can be recommended as a cost effective approach to preschool vision screening. Previous research has shown that ratings of a child's behavior during this developmentally oriented vision screening test predict results of diagnostic cognitive tests as accurately as extensive tests designed exclusively for developmental screening. This test is then extremely cost effective when used for comprehensive preschool screening.

Child, Preschool↗

Attempts at analysis of toxicity of pertussis vaccine. III. Effects of endotoxin on leukocytosis in mice due to lymphocytosis-promoting factor and reference preparations for determination of lymphocytosis-promoting factor.

The effect of bacterial endotoxin on the change in peripheral leukocyte population in mice due to the lymphocytosis-promoting factor (LPF) was investigated. Endotoxin affected not only the total leukocyte count but also the leukocyte proportions at any observation time. Both the coefficient and the intercept of regression of the leukocytic response on dose of LPF were modified by endotoxin. Therefore, in a valid biological assay for LPF using the peripheral leukocyte count as a response, a common reference preparation available for any test materials, irrespective of presence or absence of endotoxin, will be impracticable. Two reference preparations were tentatively established, one being a vaccine and the other an LPF preparation containing little endotoxin. A unitage of LP activity was assigned to each reference preparation. The results also showed that an LPF material to be tested for its possible effects on the lymphatic tissues or the reticuloendothelial system should be free from endotoxin.

Animals↗

Validation of a finite element model of the Kirschner-Ehmer external skeletal fixation system.

OBJECTIVE: To determine the validity of finite element analysis (FEA) as a means of examining biomechanical properties of the Kirschner-Ehmer external skeletal fixation system. SAMPLE POPULATION: 10 paired tibiae harvested from skeletally mature dogs weighing between 30 and 38 kg immediately following euthanasia for reasons unrelated to musculoskeletal disease. PROCEDURE: A gap fracture was created in each bone; fragments were stabilized with 3 frame configurations (type I, type II, and type III), using enhanced-profile threaded pins. Each bone-frame construct was tested, using a materials testing machine in 3 modes of testing: axial compression (AC), mediolateral (ML) bending, and craniocaudal (CC) bending, for a total of 9 tests/bone. The elastic limit of the constructs was not exceeded during testing. Mean stiffness values were determined from load-displacement curves. A finite element model of each construct was created, using three-dimensional elastic beam elements, and stiffness values were calculated, using FEA. Correlations between experimental and FEA data then were determined. RESULTS: Significant differences in stiffness were seen among all 3 constructs in CC bending and AC, with stiffness increasing with construct complexity. No significant difference in ML bending stiffness was seen between type-II and type-III constructs; however, both were significantly stiffer than the type-I constructs. The experimental and FEA stiffness data were strongly correlated (AC, r = 0.994; ML bending, r = 0.998; CC bending, r = 0.985). CONCLUSIONS AND CLINICAL RELEVANCE: Strong correlations among experimental and FEA data indicate that FEA is a valid method of comparing stiffness of Kirschner-Ehmer external skeletal fixation constructs.

Animals↗

Prediction and statistical evaluation of speech recognition test scores.

A speech test evaluation and presentation system is described. The test presentation subsystem has the flexibility and speed of live-voice testing while using recorded test materials. The speech test evaluation subsystem compares an individual subject's test performance on a monosyllabic word test with that of an average person with the same hearing loss. The elements needed to make such evaluations are discussed. Also, a trial of the procedure is described. The primary purpose of the trial was to obtain data that would provide a basis for statistical probability statements about individual monosyllabic word test results obtained in clinical settings. Data were collected from three audiology clinics in three different types of settings. Except for a few cases with highly asymmetric speech scores, all nonconductive hearing losses were included. Subject ages ranged from 8 to 92 years. Importance-weighted average pure-tone hearing losses ranged from 0.4 to 97.6 dB HL. Fifty-word recognition scores and audiograms for 2609 ears were included in the main analysis. Twenty-five-word recognition scores and audiograms for another 932 ears from one clinic were used in a subsidiary analysis. Results indicated that distributions of absolute speech recognition scores in hearing-impaired samples are highly skewed. However, after transformation of the scores into rationalized arcsine units (rau), the differences between individual subject scores and scores predicted from the audiogram were reasonably well described by the normal distribution. The standard deviation of this distribution of differences, for the data combined across the three audiology clinics, was approximately 13 rau.

Adolescent↗