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The intensity and quality of scattered radiations incident on the eye during mantle-field therapy were measured for 4-MV x rays. Beam-shaping appliances were found to introduce considerable soft scatter. Eye shields reduce radiation exposure from the anterior field approximately threefold.
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To the authors' knowledge there have been no previous reports on the protection afforded by powered filtering respirators in farmers with occupational asthma attributed to the inhalation of organic dust. In order to investigate this question, 26 farmers with occupational asthma were challenged with an exposure to work-related dusts for up to 60 min. This resulted in highly significant increases in airway resistance (Raw), thoracic gas volume (TGV) and specific airway resistance (sRaw) compared to baseline values. After a mean period of 21 weeks the farmers were subjected to a second challenge, this time wearing a protective respiratory device (RD) with a P2 filter. Significant increases in Raw, TGV and sRaw were again observed, but on average these were 50-80% smaller than the increases seen when RDs were not worn. These differences were found to be statistically significant. This shows that the use of a respiratory device in farmers suffering from occupational asthma reduces the development of bronchial obstruction but does not prevent it. The use of this kind of respiratory device cannot substitute for the proper management of asthma since the devices do not offer complete protection.
Phosphorylcholine (PC)-surfaced alloplastic materials improve the biocompatibility of medical devices in contact with blood or tears. Recent experimental studies support the contention that PC surfaces also retard bacterial and crystal adhesion in urine.
The authors worked out and applied a new device of positive pressure valve encased in the rebreathing circuit and one-way Ruben's valve, as well as a modification of Rees's system making it possible to conduct excess gases containing anaesthetics outside the operating theatre. These devices and modifications are completely reliable owing to their simplicity and their construction is cheap. They effectively reduce the degree of atmospheric pollution in the operating theatre with anaesthetics used in inhalation anaesthesia. They may be applied to every type of apparatus used for general anaesthesia.
This article is the first of two parts of a comprehensive survey of the biomechanics of head injury since its inception in 1939 in the United States, the separation being made for temporal and spatial reasons. The second portion of this material will be published at a later time in this journal. The discussion will be almost exclusively limited to nonpenetrating events. The topics presented in the following sections include an introduction that discusses the magnitude of the problem, the basic tools of biomechanics, and significant major reference sources covering this subject. This is succeeded by a brief description of the components of the head, classification of head injuries, early experimental investigations and human tolerance considerations, measurement techniques of kinetic parameters, and head motion and head injury investigations prior to 1966. A Head Injury Conference sponsored by the National Institutes of Neurological Diseases and Stroke in 1966 changed the landscape of investigations in this area. While informal collaboration between neurosurgeons and engineers had existed prior to this time, the conference established a permanent mechanism of synergism between these disciplines, produced the first zero-order realistic model of biomechanical head injury investigation, and established a 4-year program of federally funded research into the mechanical properties of the tissues of the cranium. While a recession precluded a continuation of the national sponsorship of such work, this 4-year period of intensive research resulted in a nationwide individual effort to develop further knowledge in this area. The current presentation, then, covers the mechanical and structural properties of solid and fluid tissues of the head, emphasizing progress during the past 3 decades; fetal cranial properties; analytical and numerical head injury models; experimental cranial loads applied to human volunteers and cadaver heads, dynamic loading of surrogate heads; and, finally, head injury mechanisms. The future publication will encompass experimental, analytical, and some numerical and regulatory information and that will be divided into the following sections: 1. head injury experimentation involving translatory and rotational motion: equipment, subjects and mechanical and physiological consequences 2. diffuse axonal injury: production and traumatic effects; mechanical properties at the axonal and neuronal level 3. vehicular crash investigation and simulation: reconstruction methodologies, staging, surrogate validation, and occupant protection, including vehicular design 4. injury thresholds and tolerances, including skull and vessel failure and brain and brainstem damage, including consideration of loading directions 5. criteria for head injury: governmental and industry regulations, including effects of combined motion- and tissue-level loading 6. further discussions of cranial component properties and injury mechanisms 7. sports head injury considerations: boxing, baseball, softball, football, ice hockey, and skiing activities; protective head devices for these activities 8. vehicular protective devices: design, efficacy, standards, and limitations; models for helmets and experimental validation. This presentation is based on my nearly 4 decades of head injury research, continuous collaboration and discussions with prominent members of the neurosurgical and orthopedic community, and an exhaustive, 2-year search of the literature. While every effort has been made to include all relevant information, it is inevitable that some important research has not come to my attention, and I apologize for any such omissions. It is hoped that this survey will serve as a resource for researchers and practitioners in the area of traumatic head injury and provide a roadmap for further investigations that are urgently needed. For example, this could include a determination of the rate of absorption of blood emitted from broken vessels, and, hopefully, some correlation between mechanical failure and physiological dysfunction of the various relevant tissues of the head. Although a good beginning has been initiated, additional information at the neuronal and axonal level concerning the effect of loading on function as well as age-related changes in geometry and tissue properties is also needed.
Sports-related eye injuries pose a substantial and preventable problem. Ophthalmologists, by educating their patients regarding the risks of eye injuries in various sports and the benefits availability of protective equipment, have the potential to prevent injury to well over 100,000 eyes each year. General guidelines and recommended levels of eye protection for various sports are given. The appendix lists suppliers of protective equipment.
The visual consideration in the selection of respiratory protective masks and the visual correction required by the wearer are discussed. Included is a list of manufacturers and suppliers of protective masks that have been designed for the mounting of corrective lenses inside the mask.
An eye shield was developed for use in neurological examinations in projections in which it does not interfere with the information sought. Use of this shield in A.P., oblique, 30 deg Towne's and 12 deg carotid Towne's projections reduced the corneal dose to approximately 5% of the unshielded value. For lateral projections, doses were reduced to approximately 5-15%. Use of the shield resulted in corneal doses of the order of 0.5 mrad/mAs and 1.0 mrad/mAs for standard and magnified projections respectively, with the exception of the lateral projections for which the corresponding values were approximately 0.3 mrad/mAs and 0.7 mrad/mAs. Corneal dose for a typical carotid angiogram was estimated to be reduced from 6.2 rad to 0.33 rad by the use of the shield.
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The helmet used in forestry work is the same as that in industrial use. The eye protector, which is usually a face shield made from wire mesh, is fastened to the helmet. The aim of the present study was the clarification of the frequency of use of, the protection afforded by, and the need for improvement in the helmet and eye protector. A questionnaire, an interview, observations, accident and near-accident reports, and user and laboratory tests were used for this purpose. Eighty-eight percent of loggers always use a helmet, and 32% an eye protector. According to official statistics and the questionnaire, in 1980, 8 to 15 of every 100 accidents in logging injured the head or eyes. Loggers reported that the helmet was too hot in summer and too cold in winter. The low utilization rate for eye protectors is partly explained by design defects. The protectors become frosted in the winter; there is poor visibility through the protectors when it rains or is dark; the protectors cause glare in sunshine. Product development seems to be necessary so that the helmet and eye protector can better fulfill the special requirements of forestry work.
PURPOSE: Protected carotid artery stent placement is currently under clinical evaluation as a potential alternative to carotid endarterectomy. The current study was undertaken to determine the incidence of new ischemic lesions found on diffusion-weighted MR imaging (DWI) in nonselected patients after protected carotid artery stent placement using a filter device and to determine the potential relationship between these new ischemic lesions and the presence or absence of a clear amount of debris captured by the neuroprotection filter device. MATERIALS AND METHODS: A nonrandomized cohort of 52 patients (40 men, 12 women) presenting with carotid occlusive disease underwent protected carotid artery stent placement using a filter device. DWI obtained 1 day before stent placement was compared with that obtained 1 day after stent placement. In addition, the macroscopic and microscopic analysis of debris captured by the filter device during the carotid stent placement procedure was assessed. RESULTS: Neuroprotected carotid stent placement was technically successful in all 53 procedures but was complicated by a transient ischemic attack in 3 patients (5.6%). In 22 patients (41.5%), new ischemic lesions were found on DWI, and in 21 filter devices (39.6%), a substantial amount of atheromatous plaque and/or fibrin was found. No clear relationship between the presence of debris captured by the filter device and new lesions detected by DWI was found (P = .087; odds ratio 3.067). CONCLUSION: Neuroprotected carotid artery stent placement will not avoid silent cerebral ischemia. Systematic microscopic analysis of debris captured by the filter device has no predictive value for potential cerebral ischemia after carotid artery stent placement.
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The purpose of this study was to determine the potential effects on progressive aerobic work while breathing through a new military type chemical and biological (CB) respirator loaded with three different types of purifying canisters. Twelve healthy well-motivated male subjects (mean age 23 +/- 3 years) participated in the study. Results indicated that mean maximal oxygen uptake (VO2max), time to exhaustion, respiratory exchange ratio, rate of perceived exertion, respiratory rate and tidal volume at exhaustion, maximal lactate and the 2-min post-exercise lactate were not significantly influenced when breathing with the respirator and the canisters in comparison to a laboratory valve. Mean pulmonary ventilation, however, was reduced by 21% while oxygen and carbon dioxide ventilatory equivalents were significantly lower by 9% and 8% respectively. Review of the stage-by-stage responses to the treadmill test between the laboratory valve and respirator/canister conditions indicated no significant differences (NS) in oxygen uptake but slightly lower heart rates (NS). Ventilation was not influenced by the canisters until 80% of VO2max at which time the mean oxygen ventilatory equivalent became significantly lower. Blood lactate was significantly depressed between 60% and 90% VO2max under the respirator/canister conditions. It was concluded that, although physiological adaptation occurred, breathing with the new CB respirator and each of the three purifying canisters had no detrimental effect on progressive aerobic work to exhaustion. However, prolonged work at intensities greater than 80-85% of VO2max would in all probability be impaired when breathing with the CB mask and the canisters.
During removal of sprayed-on asbestos coating workers are exposed to high airborne fiber concentrations. The true protection of negative pressure respirators under working conditions was evaluated during an asbestos abatement project. A modification allowing air sampling inside the mask is described. The values for samples collected inside a full-face mask ranged between 0.4 and 5% of the concentrations measured outside. These values were considerably lower than those found inside a half-mask.
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