Dehydration in Extreme Temperatures While Conducting Stability and Support Operations in a Combat Zone
This analysis reports the effects of extreme temperatures (temperatures exceeding 100°F) on the hydration of infantrymen conducting stability and support operations during phase IV Operation Iraqi Freedom in the months of June and July 2003 in An Nasiriyah, Iraq. Fifty-three infantrymen were evaluated for signs of dehydration after completing questionnaires regarding their activities during the previous 24 hours. We conducted an analysis comparing these activities and their state of hydration. The most significant factors contributing to dehydration in extreme environments proved to be the individual’s level of exertion and exposure to the sun while levels of water and caffeine consumed showed no correlation to one’s level of hydration. We conclude that integrating a proactive, field-expedient means to monitor a unit’s level of hydration can increase the combat effectiveness of units in training and combat alike.
An infantry company consisting of 158 Marines and Saflors in southern Iraq was conducting stabUity and support operations (SASO) during the summer months of 2003. Southern Iraq is a region exposed to extremely high daUy temperatures during the spring and summer months. During the months of June and July, the average temperatures in An Nasiriyah, Iraq, range from lows in the 90s to highs exceeding 1 1O°F as shown in Figure 1 . Temperatures during June and July of 2003 in An Nasiriyah were reported to exceed 12O°F and showed sirmlar averages from 90 to 110°F in June and 95 to 1 14°F in July.1
Dehydration can result in physical fatigue as well as cause significant decreases in performance of physical and mental skills.2-4 Dehydration of individual Sailors and Marines has a direct effect on the performance and military readiness of their unit in a combat environment. Extreme environments make hydration a critical factor in military planning and combat command. The basic guidance from our medical personnel directed Marines and Sailors to prevent dehydration by drinking as much water as possible and avoiding caffeine, summarized in Figure 2.
Extreme conditions push the body to its physiological Umlts.5 Combat operations in such environments further compound the difficulties of staying hydrated. To determine proper prophylactic measures to guard against dehydration in extreme temperatures, it is necessary to understand which mUitary tasks are most likely to result in the dehydration of infantrymen and how to mitigate their effects. Monitoring individual hydration can minimize dehydration,6 and monitoring hydration levels throughout a unit would improve its combat effectiveness.
Co. F 2/25 occupied three positions within the heart of An Nasiriyah, Iraq, among the local populace. The situation Umited the comfort living features, such as electricity and air conditioning, afforded to the company’s Marines and Sailors. Furthermore, SASO required 24-hour operations throughout our area of operation. At least one patrol through every portion of our area of operation was conducted each 8 hours, totaling -600 patrols over 85 days.
Our company’s presence in An Nasiriyah provided a unique opportunity to evaluate the effects of combat operations and SASO on dehydration of infantrymen as weU as the guidance we received regarding hydration. As far as we are aware, the majority of references on this topic detail studies on units in training scenarios or are case studies of combat experiences in hot environments; whereas, this is an analysis of data coUected on dehydration in a theater of continuing combat. We beUeve this makes our analysis new and useful to current and future units deploying to the Iraqi theater or other environments exposed to extreme temperatures. We conducted this analysis during the opportunities our mission requirements aUowed and beUeve that our findings are appUcable to combat arms and combat support units alike.
Methods
Co. F 2/25 simultaneously occupied three positions within An Nasiriyah during this period. One hundred of the 158 Marines and Sailors of the company were in the company headquarter position where the authors were. The other two company positions, each consisting of a platoon, were occupied by the other 58 Marines and Sailors. The data collected were solely from the company headquarter position, consisting of a rifle platoon, weapons platoon, and company headquarters personnel. Measurements from additional positions exceeded mission constraints.
Members of the company were exposed to the local climate for 3 months before the time measurements were taken in June and July 2003; therefore, we assumed all members of the company were accUmated to the extreme temperatures. The company position was a multistoried, war-torn, government buüding. Sleeping, eating, and working areas within the position were exposed to the ambient atmosphere. The single air conditioner used within the position was used to cool water and food, for which ice had previously been used. None of the vehicles used by the company were air-conditioned.
The command originally used routine measuring of vital signs as a means of monitoring hydration before any collection of ‘data. Upon realizing the surprising number of “walking dehydration” cases, the authors proposed that further information be gathered from members of the company headquarters position to determine causative factors of dehydration. Realizing that information was to be gathered, analyzed, and potentially reported, data were recorded only from those that provided informed consent after being briefed on the goals, benefits, and risks of such an analysis.
Soluble film holds problem’s solution: packaging unit doses of water-treatment chemicals in water-soluble film ensures safety and accuracy
The powerful chemicals used to treat industrial water can be a little hard to handle.
But by using a special film, Buckman Laboratories and its contract packager made their problems dissolve.
Buckman Laboratories, a manufacturer of specialty chemical compounds, is using water-soluble film from MonoSol LLC for pre-measured unit doses of its water treatment chemicals. These chemicals inhibit the growth of microorganisms that could cause fouling problems in industrial heating and cooling systems. MonoSol’s M9500 film addresses the dual challenges of environmental safety and container management. Packaging these chemicals in water-soluble pouches minimizes risks for product handlers, reduces pollution and eliminates product spillage, while assuring mixing accuracy.
“In solid form, the water treatment chemicals can be easily mixed and packaged in a much safer-to-handle package,” says Rick Clark, technology director for water treatment at Buckman Laboratories. “The total concept–formulation and packaging–is to limit human contact with the chemical and also to eliminate the need to dispose of waste packaging.”
Buckman uses contract packer Bartlo Packaging Services (BPS) to package the water-treatment chemical. “We’ve been using water-soluble film in our New Jersey facility since there was water-soluble film,” says BPS President Al Bartlo. “Packaging in unit doses is where the agrochemical and cleaning-products industries are headed.”
Material is shipped in drums or bulk delivery systems for BPS to repackage into unit doses for industrial and commercial use. BPS handles liquid, powdered and gel chemicals on its 13 packaging lines, packaging a variety of chemicals from active detergents to toxic insecticides.
Films for BPS customers are specified by MonoSol’s state-of-the-art testing laboratory in Portage, Ind. Laboratory technicians perform tests to determine the long-term chemical and physical compatibility of a water-soluble film.
MonoSol’s M9500 water-soluble film was selected for Buckman’s water treatment chemicals. The M9500 produces mechanically tough packages with excellent heat-sealing characteristics, better seal area integrity and faster solubility at the point of use. Other improvements designed into the M9500 film are improved resistance to embrittlement and excellent cold storage capabilities.
The M9500 film offers a range of packaging possibilities, increasing the number of products that can be packaged in PVA water-soluble films. With enhanced machinability, the M9500 widens the scope of packaging equipment choices to include all types of vertical-form-fill-seal machinery. Appropriate for packaging neutral, mildly alkaline and acidic formulations, the M9500 is suitable for many powder, gel and liquid forms of chemicals and detergents as well as other products.
Ecotoxicological Effects of Combined UVB and Organic Contaminants in Coastal Waters
Organisms living in coastal waters are exposed to anthropogenic contaminants from terrestrial drainage, ice melting and maritime traffic and to enhanced UVB radiation UVBR; 280-320 nm) caused by decreased concentrations of ozone in the stratosphere. This article reviews available information about the combined effects of UVBR and selected hydrosoluble contaminants potentially present in surface waters on marine species and especially on plankton community structure in high-latitude coastal zones. Effects of UVBR on three selected pesticides (Atrazine, carbaryl and Acifluorfen) and possible induction of phototoxicity are reviewed. Most toxicological studies have been conducted under laboratory conditions with questionable relevance for coastal marine ecosystems. Similarly, photoactivation of polycyclic aromatic hydrocarbons (PAHs) has been closely examined and reported effects on aquatic species summarized. Experiments with field-sampled communities demonstrated the complexity and the difficulty in determining the impact of multiple stressors on an aquatic ecosystem, even for ecosystems simplified by eliminating large grazers and fish. Nutrient status, specific composition and light history have influenced the different responses of planktonic assemblages exposed to enhanced UVBR and water-soluble fraction (WSF) from crude oil or to tributyltin. Plankton assemblages subjected to changes in the ozone hole were physiologically stressed and more susceptible to WSK toxicity than communities from less enhanced UVBR-impacted sites. A close relationship between phytoplankton assemblages and bacteria was observed in all experiments in mesocosms. A contaminant-induced phytoplankton crash after a bloom event may release important carbon and nutrient sources for bacteria. The magnitude of phytoplanktonic mortality induced by a contaminant probably influenced how rapidly bacteria grew over time. The transition from a herbivorous food web to a microbial food web has significant ecological implications for carbon cycling and energy flow in pelagic systems. A high phytoplankton mortality implies a situation in which the potential for downward carbon export from surface waters is high. In contrast, high bacterial enrichment implies that the phytoplankton carbon is largely recycled in surface waters through a microbial loop and does not contribute significantly to sinking particle flux. The most ecologically relevant results were obtained with mesocosm studies using field-collected communities. The enhancement of hydrocarbon toxicity in the presence of a high level of UVBR cannot be described as being a synergistic or an additive effect, because the WSF alone is not toxic and may even be beneficial by increasing bacterial activity. This is a case in which one stressor has the ability to modify another stressor to cause it to be toxic to target organisms. These abiotically induced interactions may be important for biological communities exposed to extreme conditions when physical, chemical or photochemical reactions modify the nature of environmental stressors before they interact with biological functions. The need for models on the impacts of multiple stressors on biodiversity and ecosystem functioning is emphasized.
Estimating the extent of the health hazard posed by high-production volume chemicals
We used structure–activity relationship modeling to estimate the number of toxic chemicals among the high-production volume (HPV) group. We selected 200 chemicals from among the HPV chemical list and predicted the potential of each for its ability to induce a variety of adverse effects including genotoxicity, carcinogenicity, developmental, and systemic toxicity. We found a significantly less than expected proportion of toxic chemicals among the HPV sample when compared to a reference set of 10,000 chemicals representative of the universe of chemicals. Key words: high-production volume (HPV) chemicals, prevalence, structure-activity relationships, toxicity. Environ Health.
The TestSmart program is a collaborative project between the Johns Hopkins Center for Alternatives to Animal Testing, the Environmental Defense Fund, Carnegie-Mellon University, and the University of Pittsburgh(1). The TestSmart program was conceived in response to the U.S. Environmental Protection Agency’s (U.S. EPA’s) Chemical Right-to-Know Initiative High Production Volume (HPV) Chemical Challenge Program with the goal of providing a humane, economical, and efficient method of collecting basic toxicologic data for HPV chemicals (2-4). For this purpose, HPV chemicals are defined as those produced or imported into the United States in quantities greater than 1 million pounds per year. The program asks chemical producers and importers to voluntarily provide basic toxicologic data on HPV chemicals (5). These chemicals were identified under the Toxic Substance Control Act 1990 Inventory Update Rule (6). Overall, the HPV Chemical Challenge Program list contains 2,800 chemicals (7). The Screening Information Data Set (SIDS) of the Organization for Economic Cooperation and Development was selected as the toxicologic criteria needed to meet the goals of the HPV Chemical Challenge Program (8). SIDS includes tests for genotoxicity, acute and chronic toxicity, reproductive toxicity, ecotoxicity, and environmental fate.
One of the challenges, as part of the TestSmart Program, was to assess the overall magnitude of the health hazards posed by HPV chemicals based on structure–activity relationship (SAR) modeling. The U.S. EPA will consider test result submission for the HPV Program based on SAR models that are scientifically justifiable (9). As part of this program we undertook an analysis of a random set of 200 HPV chemicals and predicted the probability of each to induce a variety of toxic effects including genotoxicity, carcinogenicity, developmental toxicity, and systemic toxicity. The majority of these chemicals are not part of the learning sets used to derive the SAR models, thereby eliminating the possibility of tautological artifacts. Although SAR projections may not have perfect predictivity, the current study seeks to assess the prevalence of toxicants among HPV chemicals. Such estimates based on SAR techniques can be derived for populations of molecules provided the SAR model has been validated and its predictivity is known.
HPV chemical selection. A sample of 200 chemicals was selected from among the HPV chemicals (7). The chemicals chosen were randomly selected and a) were pure and unique substances; b) were organic; c) were nonpolymeric; and d) did not contain metals.
Reference chemicals. A reference set of 10,000 chemicals representing the universe of chemicals was used as a control set. The composition of this set is consistent with estimates produced by the National Academy of Science (13). This set was derived through sampling chemical structure libraries and the National Institutes of Health Developmental Therapeutics Program. This reference set was used to assess whether the HPV chemicals represent a greater or lesser toxicologic risk than other chemicals. For this evaluation we compared the percentage of chemicals predicted to be toxic in the HPV sample to the percentage of chemicals predicted to be toxic in the reference chemical set.
The CASE modeling process begins with the compilation of a set of chemical structures and an experimentally derived biological activity value. These data are placed into a learning set for the program. Each chemical in the learning set is broken down, in silico, to all possible fragments from 2 to 10 heavy (i.e., nonhydrogen) atoms. Each fragment is labeled with the name and activity of its parent chemical. Upon completion of this process, the program organizes the list of fragments and tabulates the number of chemicals containing each of them. The program then identifies those fragments that were identified predominantly in active chemicals and refers to these fragments as biophores. The selection of biophores is based on the binary experimental results of each chemical. For example, biophores for a cancer causation model are identified that are predominantly found in chemicals that tested positive for carcinogenicity compared to those that were noncarcinogenic. The particular potency value associated with each biophore is then determined from the experimental potencies for the chemicals making up the biophore. The total list of biophores is then used to derive a global quantitative SAR (QSAR) equation. These biophores serve as the basis for both predictive and mechanistic analysis of toxicity.
The HPV chemicals can be considered to present an elevated toxicologic risk to humans and to the environment based solely on their large production volume and the consequent potential for exposure (55). However, it would be of interest to know whether the HPV chemicals, as a group, are more or less toxic than “average” chemicals. To assess this, we compared the proportion of chemicals in the HPV sample predicted to be toxic to the proportion of chemicals predicted to be toxic in the reference set representing the universe of chemicals. These comparisons were done one toxic end point at a time. Unexpectedly, for all toxic effects assessed except one (the in vitro induction of SCEs), the proportion of chemicals predicted to be toxic among the HPV sample was significantly less than the proportion of chemicals predicted to be toxic in the reference set. The question obviously arises as to the reason for this decrease in the number of potentially toxic HPV chemicals when compared to what would be expected from a random sample of chemicals. This is particularly relevant given that the underlying reason for the HPV Challenge program is that little is known about the toxicities of the HPV chemicals (55). From this reasoning, it can be assumed that hazardous chemicals were not excluded from production based on the results of toxicologic prescreens.
The Salmonella mutagenicity assay is usually the first screen used, but the results are frequently confirmed by an in vivo test for genotoxicity. The assay frequently used to confirm that in vitro assay is the mouse micronucleus assay (58). The proportion of chemicals predicted as in vivo micronucleus inducers among the HPV sample is also significantly less than that for the reference set. The same is true for the other in vivo assay, the induction of SCEs in mice. It should be noted that although the micronucleus assay is confirmatory when the Salmonella assay indicates the potential for mutagenicity, the micronucleus assay response can also be elicited by nongenotoxicants such as inhibitors of tubulin polymerization and of microtubular integrity, as well as by aneugens. This may explain the greater projected proportion of micronuclei inducers when compared to Salmonella mutagens.
Based on predicted positive responses in both the Salmonella mutagenicity and the micronucleus assays, which define in vivo genotoxicants, we estimate that 8% of the chemicals in the HPV sample possess that potential, in contrast to 23% of chemicals in the reference set, thus further suggesting that the HPV chemicals, as a group, represent less of a genotoxic risk than chemicals at large.
In this study we predicted the occurrence of chemicals capable of inducing 10 separate toxicologic end points in a sample of HPV chemicals and compared these values to those from a reference set of 10,000 chemicals. Regardless of the nature of the toxicologic phenomenon, the subset of HPV chemicals was estimated to contain a significantly lower proportion of toxicants than the reference set.
Transfer machining with a twist
Multiaxis turret modules are an emerging machining technology that offers system builders and users an alternative to conventional single-spindle modules. Compared to a single spindle, the turret head brings advances in speed, accuracy, and power, and when mated to the three-axis module, a degree of flexibility. Together, the benefits of the two machine tool systems offer a new dimension of performance for flexible or dedicated machining systems.
The modern turret head has its origins in high-volume machining applications in the automotive industry. Transfer line manufacturers often include large turret heads in their systems, usually for the purpose of using multispindle heads. A typical application is making multiple holes in automatic transmission housings. A turret with multihead spindles allows completion of drilling, reaming, and tapping operations with accuracy and speed. These large turret heads can be in excess of 31.5″ (800 mm) across the turret, and are normally mated to a single-axis slide unit.
Modern multiaxis modules grew in part out of the requirement to add a measure of flexibility to dedicated machining systems. Instead of relying on sinde-axis slide units and fixed machine configurations, machining system manufacturers could purchase multiaxis “building blocks” for each station. These multiaxis modules offer the ability to be reprogrammed for new parts, without making major modifications to the basic machine structure. They also allow programming functions such as circular and helical interpolation to be used, minimizing the need for dedicated tooling.
Multi turret modules at their most basic have at least three linear axes. Although large turret heads have been utilized in the past, these were typically on a single, horizontal axis. The addition of two more linear axes separates the modern design from its predecessor.
The essence of what makes the module unique, the turret head contains from two to eight spindles in a radial or semi-radial arrangement. Indexing the turret to the next spindle changes the tool, replacing the function of a normal toolchanger. The size of a turret head is typically determined by the transmittable horsepower, and the dimension across the turret from one spindle mounting surface to the one directly opposite it. Spindles are typically of either a cartridge or multispindle design, with different taper sizes and internal constructions possible to match application requirements.
Optional rotary axes add the ability to access more than one side of the workpiece, and allow machining of complex forms. A fourth axis is becoming a standard, while the fifth axis is typically called for in aerospace applications and for complex automotive parts.
The concept of a multiaxis turret module can also be used as the basis for a highly productive turret machining center. Such machines can be designed with multiple turrets that approach the workpiece simultaneously to complete multiple features in a fraction of the time it would take a conventional, single-spindle machining center. Multiple turrets can also machine the same set of features on multiple workpieces for increased throughput.
Unique machine configurations not possible with cartridge spindles and toolchangers are straightforward with a turret machining center. Because the tool-change operation does not require accessing a tool magazine and changing arm, the cutting axis of the turret head can be positioned in any orientation. This can be of particular benefit for workpieces with features on four or five sides, eliminating the expense and complexity of additional rotary axes.
Current turret technology offers users two to eight spindle stations in the turret. Odd numbers of turret stations are possible, but most turret heads feature an even number of stations, which can be configured to mount an odd number of spindles. Balance of the spindles and tooling around the turret head is important. The mass of the spindles should be as evenly distributed around the turret head as possible for the fastest index times and minimal controller tuning. In some cases, dummy spindles or counterweights of solid steel can provide the necessary balance.
Indexing is accomplished using a sliding pinion shaft that alternately engages the working spindle, or by a ring gear or jackshaft in the turret. This feature allows a single spindle motor to power the cutting spindle and index the turret. Standard AC servomotors with encoders can be used. Similarly, indexing requires no special control features; typically, the control’s spindle-orient function can handle the job. Bidirectional indexing capability can bring the next required spindle into position as quickly as possible.
Modern turrets no longer require a “lift to index” function as part of the tool-change sequence. The turret and its spindles stay in the same plane during indexing, reducing indexing time and eliminating the possibility of introducing contaminants into the turret.
Multi turret modules at their most basic have at least three linear axes. Although large turret heads have been utilized in the past, these were typically on a single, horizontal axis. The addition of two more linear axes separates the modern design from its predecessor.
The essence of what makes the module unique, the turret head contains from two to eight spindles in a radial or semi-radial arrangement. Indexing the turret to the next spindle changes the tool, replacing the function of a normal toolchanger. The size of a turret head is typically determined by the transmittable horsepower, and the dimension across the turret from one spindle mounting surface to the one directly opposite it. Spindles are typically of either a cartridge or multispindle design, with different taper sizes and internal constructions possible to match application requirements.
Optional rotary axes add the ability to access more than one side of the workpiece, and allow machining of complex forms. A fourth axis is becoming a standard, while the fifth axis is typically called for in aerospace applications and for complex automotive parts.
The concept of a multiaxis turret module can also be used as the basis for a highly productive turret machining center. Such machines can be designed with multiple turrets that approach the workpiece simultaneously to complete multiple features in a fraction of the time it would take a conventional, single-spindle machining center. Multiple turrets can also machine the same set of features on multiple workpieces for increased throughput.
Unique machine configurations not possible with cartridge spindles and toolchangers are straightforward with a turret machining center. Because the tool-change operation does not require accessing a tool magazine and changing arm, the cutting axis of the turret head can be positioned in any orientation. This can be of particular benefit for workpieces with features on four or five sides, eliminating the expense and complexity of additional rotary axes.
Current turret technology offers users two to eight spindle stations in the turret. Odd numbers of turret stations are possible, but most turret heads feature an even number of stations, which can be configured to mount an odd number of spindles. Balance of the spindles and tooling around the turret head is important. The mass of the spindles should be as evenly distributed around the turret head as possible for the fastest index times and minimal controller tuning. In some cases, dummy spindles or counterweights of solid steel can provide the necessary balance.
Indexing is accomplished using a sliding pinion shaft that alternately engages the working spindle, or by a ring gear or jackshaft in the turret. This feature allows a single spindle motor to power the cutting spindle and index the turret. Standard AC servomotors with encoders can be used. Similarly, indexing requires no special control features; typically, the control’s spindle-orient function can handle the job. Bidirectional indexing capability can bring the next required spindle into position as quickly as possible.
Modern turrets no longer require a “lift to index” function as part of the tool-change sequence. The turret and its spindles stay in the same plane during indexing, reducing indexing time and eliminating the possibility of introducing contaminants into the turret.
The turret head must be locked securely into position during cutting to maintain accuracy and to transmit cutting vibrations to the machine’s mass center. This is accomplished using either tapered shot pins or face tooth couplings.
Unlike standard cylindrical shot pins, which require clearance between the pin and bore, tapered shot pins lock up with no leftover clearance. As a result, accuracy improves substantially. Tapered shot pins are typically used for turrets under 15.75″ (400 mm) and in applications involving moderate cutting forces.
Originally designed as an efficient method of dynamic torque transmission, the face tooth or Hirth-gear coupling has proved an extremely stable platform for the transmission of cutting forces in the static condition. Applications such as dial index tables and the turret head benefit from the six– dimensional accuracy and high rigidity of the Hirth gear. Clamping and unclamping of the coupling is usually hydraulic, with a backup spring set that locks the gear together as a default. This prevents any undesired rotation in case of a power failure.
The Hirth gear system can be used for any size turret. It is especially suited for turrets 15.75″ and larger, for applications involving heavy cutting forces, and when extreme precision is required.
Some turret designs employ simultaneous spindle rotation. Modern turret head designs use isolated spindle rotation-only the working spindle used for cutting rotates-resulting in more power available for the working spindle and elimination of vibration from other rotating spindles.
The included angle of the turret head refers to the angle between the axes of the spindles. Turret heads are generally configured at 90 deg or 180 deg; the 90 deg configuration is more compact, while 180 deg or flat arrangements offer more radial space for large-diameter tools.
Spindle size and internal construction can be tailored to match application requirements. Users can specify the types and quantities of bearings, sealing methods, speed, and precision of the spindle.
Multispindle heads give turret heads capabilities beyond the conventional single-spindle module with tool changer. Multispindle heads that offer dual feature patterns allow the same turret station to machine two unique sets of features. While small multispindle heads are available for single-spindle modules, their size and complexity is limited by the capacity of the toolchanger. Depending on turret size, the turret head can accommodate multispindle heads up to 18″ (457 mm) or larger.
Regardless of taper, all spindles must have locking methods that are accessible from the front of the spindle. Examples are HSK version C, ABS, ER collets, and DIN 55058. Spindle taper sizes can range from HSK50C to HSK125C-equivalent to CAT30V to CAT60V in capability.
Spindle reaches can be specified to minimize tool gage lengths, and allow full utilization of the tools’ capabilities. Right-angle heads, double-ended spindles, and adjustable-angle spindle heads can complement the capabilities of standard in-line spindles.
Turret spindle designs are modular, facilitating change-out for repair, change to a different spindle design entirely, or modification of the order of a given set of spindles in the turret head. This flexibility allows easy future reconfiguration.
Other features of modern multiaxis turret modules include coolant-through or flood-coolant capability and contamination protection via air purge, which maintains a low internal pressure within the turret and spindles to exclude contaminants.
Construction of three-axis modules uses either box ways or linear bearings. Box way slides offer high rigidity, excellent damping, and superior transmission of cutting vibrations. They’re also less sensitive to crashes and contamination.
Linear bearing construction features much lower friction forces, allowing use of smaller axis servomotors and drives as well as higher linear-speed capability. Box ways are used for applications involving high cutting forces and those in which durability, not speed, is the primary objective. Linear bearing construction is used in applications requiring higher feed rates.
Advocacy update: the new Congress: how the recent elections will affect initiatives in 2007
The 2006 midterm elections caused a seismic shift in the U.S. Congress that could have far-reaching effects for parks and recreation for at least the next two years. Early predictions by election experts that the Democrats would gain control of both Houses of Congress proved to be true, albeit by only a razor-thin margin in the Senate.
But what will the results mean for parks and recreation?
Committee and Subcommittee Chairmanships
First and foremost, the most significant impact of the Democratic takeover of Congress is the resulting change in leadership of both the House and the Senate. Every Senate and House committee and subcommittee chairmanship will transfer from Republican control to Democratic control before the start of the 110th Congress. All legislation must pass through the committees, and the influence and control of the chairs and the subcommittee chairs is manifold.
The Democrats are in the process of naming new chairmen now. The Democratic leadership has named most of the major committee chairmen as of this writing, although subcommittee chairs have yet to be chosen. As the Republicans cede control of Congress to the Democrats, their role changes to minority status and their highest status on committees and subcommittees is ranking member.
The 109th Congress was continually challenged by adopting a comprehensive budget for each fiscal year. This past year, the committees made excellent progression preparing appropriations bills for the 2007 fiscal year. However, only two of the 12 appropriations bills were passed before Congress got caught up in election year politics.
When the results of the 2006 elections became clear, the Republican leadership made little attempt to pass the remaining appropriations bills. For many reasons the Republican leadership preferred to punt the thorny budget deliberations to the 110th Congress, and chose to fund the federal government with a series of Continuing Resolutions. The last CR funding federal government operations was expected to expire in mid-February.
The budgets of the Bush years have not been kind in providing adequate funding for federal technical assistance and grant programs to local, regional and state park and recreation agencies. Valuable programs, such as the Rivers, Trails, and Conservation Assistance Program of the National Park Service, which provides planning services and technical assistance to local and state governments on greenway projects, trails and conservation projects, has been proposed for cuts in the past two years, just as many other assistance programs have been cut.
While prospects for the new Congress would seem to be much better for NRPA’s policy and legislative agenda with regard to re-building these diminished federal programs, it should be noted that there is no quick fix on the horizon. Funding will be tight for a number of years to come, and our gains can at best be incremental. However, on the bright side, this should be a Congress that is more willing to agree with our agenda and more receptive to our point of view on these appropriations and assistance programs.
One of the most anticipated and expected changes from the new Congress will be new direction in environmental policy and conservation initiatives. Sustainable energy resources, climate change, public lands use policies, endangered species protection, clean water, air pollution and a host of other environmental and conservation issues will be high on the priority list.
A Mathematical Model for Interplanetary Logistics
This article demonstrates a methodology for designing and evaluating the operational planning for interplanetary exploration missions. A primary question for space exploration mission design is how to best design the logistics required to sustain the exploration initiative. Using terrestrial logistics modeling tools that have been extended to encompass the dynamics and requirements of space transportation, an architectural decision method has been created. The model presented in this article is capable of analyzing a variety of mission scenarios over an extended period of time with the goal of defining interesting mission architectures that enable space logistics. This model can be utilized to evaluate different logistics trades, such as a possible establishment of a push-pull boundary, which can aid in commodity pre-positioning. The model is demonstrated on an Apollo-style mission to both provide an example and validate the methodology.
The development of an interplanetary supply chain requires the unification of two traditionally separate communities: aerospace engineering and operations research. In order to create an effective means of communication between both communities, a distinct terminology has been developed and is detailed extensively in Section I. Specifically, the definition of the commodities or supplies, and the elements or physical containment and propulsion units used to transport the commodities are detailed. Furthermore, the network definition is presented as well as the definition and description of the time expanded network, which is the terrestrial modeling technique employed for the space logistics model. Section II describes the components of the interplanetary logistics problems. Section III presents the problem formulation and constraints. In Section IV a description of the optimization methodology developed to solve this problem is discussed. In Section V the problem formulation and solution methodology is applied for the example of an Apollo-style mission to both explain the implementation and validate the methodology presented. Section VI reviews the contributions of this article and describes continuing work in this area.
The goal of the interplanetary logistics problem is to determine feasible mission architectures to satisfy the demand generated by the needs of exploration. The key concept of the interplanetary logistics problem is that the demand of crew, consumables, equipment and other exploration requirements at in-space locations drives the mission requirements. Therefore, the first required input for the interplanetary logistics problem is the definition of these supplies. For example, if the exploration mission is a sortie style mission to investigate a particular location, the demand might consist of a few crew members at a specific location and the supplies necessary to both support the crew and enable the exploration activities.
Given the demand of the mission, it is necessary to determine how and when the supplies on Earth will be transported to the in-space locations. As missions become more complex and evolve over a period of time, a solution may become less obvious. Since the goal is to minimize the cost of any mission, it is desirable to optimize the timing and method of transport of the supplies to in-space locations. Therefore, it is necessary to define all pathways and structures used for transport, and allow the optimizer to analyze the different architectures to select the best one.
Given this information, the interplanetary logistics problem can determine low cost mission architectures that satisfy the exploration demand. The solution generated will detail the scheduling and assignment of supplies to vehicles for in-space transport and launch scheduling requirements. More importantly, however, the output of this problem can be used to determine a push-pull boundary for the supplies, the potential of a specific location, either on a surface or in-space for storing supplies, benefits of in-situ resource utilization over multiple missions, or even the sensitivity of mission architectures to changes in vehicle parameters.
The first step in developing a model for interplanetary logistics is defining a concrete nomenclature that describes the components of the problem. The problem fundamentally consists of three components: the commodities or supplies that must be shipped to satisfy a mission demand, the elements or physical structures used to both hold and move the commodities, and the network or pathways the elements and commodities travel on. The following sub-sections define the parameters that describe each of these components.
The goal of the space logistics project is to determine how to meet the demand for the exploration missions. As such, we are investigating how to optimally ship multiple types of commodities. For the purpose of the logistics problem, a commodity will be defined as a high-level aggregate of a type of supply, such as crew provisions. Thus, we will define a set of k = 1,…, K commodities, each with the following parameters:
* Denote the demand of each commodity as d^sup k^.
* Denote the origin of each commodity as so^sup k^.
* Define the destination of each commodity as sd^sup k^.
* Define the availability interval of each commodity as to^sup k^ = [sto^sup k^, eto^sup k^], where sto^sup k^ is the starting time of the interval and eto^sup k^ is the ending time of the interval.
* Define the delivery interval of each commodity as td^sup k^ = [std^sup k^, etd^sup k^], where std^sup k^ is the starting time of the interval and etd^sup k^ is the ending time of the interval.
* Define the unit mass of each commodity as m^sup k^ when it arrives at the destination.
* Define the unit volume of each commodity as v^sup k^ when it arrives at the destination.
* Define the number of specified waiting sequences as nw^sup k^.
By defining a waiting sequence as part of the commodity input, a number of wait arcs along the path can be specified, which allows onroute destinations to be designated. For each waiting arc sequence I where 0
* Define the static node of the wait sequence as sw^sub l^^sup k^.
* Define the required waiting time period as pw^sub l^^sup k^.
* Define the wait interval for each wait sequence as = [tw^sub l^^sup k^, etw^sub l^^sup k^], where stw^sub l^^sup k^ is the starting time of wait interval l of commodity k, etw^sub l^^sup k^ is the ending time of wait interval l of commodity k, and etw^sub l^^sup k^ - stw^sub l^^sup k^ ? pw^sup l^^sup k^.
It is important to note that in this model a crew member is treated as a commodity. In practice crewed missions are treated differently during mission planning: however, for the purposes of the architectural design tool created by this model, crew can be considered a commodity with highly restrictive parameter values. By narrowing the availability and delivery windows for a crew commodity, the feasible shipment pathways are limited and reasonable architectures for crewed flights can be obtained.
Elements
In order to ship the commodities from the origin to the destination locations, we require ‘containers’ to both hold the commodities and provide propulsion to move the mass through space. These components can be abstracted to a single definition of an element. Elements are physical, indivisible functional units that transport the commodities from origin to destination. An element is classified by the amount of commodity capacity and propulsive capability it possesses. Elements can be divided into two classes: non-propulsive elements M^sub N^ and propulsive elements Mp. The element parameters are (Figure 1) as follows:
* The maximum fuel mass of a propulsive element m, m euro M^sub p^ is denoted by mf^sup m^.
* The specific impulse of the fuel in element m is denoted by I^sub sp^^sup m^.
* The structural mass of element m is denoted by ms^sup m^.
* The mass capacity of element m is denoted by CM^sup m^.
* The volume capacity of element m is denoted by CV^sup m^.
* The cost of element m is denoted by Cost^sup m^.
Networks
In order to transfer the commodities and elements from the origin node to the destination node, the trajectories must be defined. The purpose of the interplanetary logistics model developed in this article is to analyze the multiple choices available for routing all of the commodities and elements to determine the best logistics architecture. To model the different available trajectories, a network model of space is created to represent the possibilities available for transferring commodities to their respective destination. The following sections detail the development of the space network utilized to form the model presented in this article.
The physical network, or static network, represents the set of physical locations, or nodes, and the connections, or arcs, between them. The physical nodes, or static nodes, represent the different physical destinations in space, including the origin and destination of all the commodities, as well as the possible locations for transshipment. Three types of nodes have been identified: Body nodes, Orbit nodes and Lagrange point nodes. These classifications distinguish the type of information required to define a node of each type. The physical arcs, or static arcs, represent the physical connections between two nodes, that is, an element can physically traverse between these two nodes. We define an arc (si, sj) to be a static arc that represents a feasible transfer from static node si to static node sj.
The mathematical description of the static network is given below:
* Define the static network as a graph GS, where GS = (NS, AS).
* Define the set of nodes, NS = {s1,…, sn}, in the static network.
* Define the set of arcs, AS ? NS × NS in the static network.
An example of an Earth-Moon static network is provided in Figure 2. In this picture we can see the connection of the Earth surface nodes to the Earth orbit node, representing launches and returns. Similarly, the lunar surface nodes are connected to the lunar orbit node, representing descent and ascent trajectories. In addition, the orbit nodes, as well as the first Earth-Moon Lagrangian point, are connected by in-space trajectories.
In order to analyze sequences of missions that evolve over an extended period of time, and to account for the time-varying properties that can arise in certain astrodynamic relationships, we have chosen to introduce time expanded networks as a modeling tool. In the time expanded network the absolute time interval under consideration is discretized into T time periods of length ?t. A copy of each static node is made for each of the time points and the nodes are connected by arcs according to the following rules:
* The arc must exist in the static network.
* The arc must create a connection that moves forward in time.
* The arc must represent a feasible transfer, with respect to the orbital dynamics.
The mathematical description of the time expanded network is given below:
* Define the time expanded network as a graph G, where G = (N, A).
* Define the set of nodes in the time expanded network as N = {i = (si, t) si euro NS, t = 1,…,T}. To simplify the notation, for a given node i euro N, let s(i) and t(i) denote the physical node and the time period corresponding to node i, i.e., if i = (si, t) then s(i)= si and t(i)= t.
* Define node s as the general source that generates the supply of elements. This node is connected to every node in the network where an element can originate.
* Define the set of arcs in the time expanded network as A ? N x N. An arc a = (i, j) = ((si, t), (sj, t + T^sup t^^sub si,sj^)) exists if and only if there exists an arc (si, sj) in the static network, and the transit time from static node si to static node sj starting at time t is T^sup t^^sub si,sj^. Note that if si = sj, then T^sup t^^sub si,sj^ =1 for all t.
* Define path p as a sequence of nodes. In particular, let f(p) and l(p) denote the first node and the last node of path p. If path p originates at node s, f(p) = s for all such p.
Using the static network depicted in Figure 2, we can create the time expanded network in Figure 3. Here, the time expanded network is notional as not all arcs are represented, but how the trajectories evolve in time can be readily seen.
To account for the fact that on certain transfer arcs two burns occur, we slightly modify the time expanded network. We first introduce a new fictitious static node labeled fie. Note that this node is not related to the static network. On every transfer arc (i, j), s(i) ? s(j) requiring two burns we add a new auxiliary node k = (fic, t) with two arcs; one connects i to k and the other one k to j. The value of t is irrelevant. In this new network, each arc (i, j) with s(i) ? s(j) corresponds to a single burn. All such arcs are called burn arcs and we denote the set of all burn arcs as AB.
The fuel mass fraction, which represents the ratio of the fuel mass to the initial mass, for element m to execute the burn corresponding to arc a C A^sub 8^ is defined as:
The execution of a space mission requires logistical decisions at every step. Logistics are required to accumulate all of the required commodities for space missions, as well as procure and assemble all elements at the launch site. However, since at the time of launch all of the items required to perform a space mission are co-located at the launch pad, the terrestrial logistics can be decoupled from the interplanetary logistics model. Therefore, the interplanetary logistics model encompasses all of the logistical decisions required between the launch pad and the locations in-space.
There are numerous decisions made during space missions that can be modeled and optimized to create a better mission description. Although, from a system perspective, it would be desirable to make all of these decisions concurrently, due to computational limitations this is not a reasonable approach. Instead, the interplanetary logistics model is decomposed into three fundamental components: launch packing and scheduling, element packing and in-space network optimization.
Launch is a highly constrained transportation activity, where although traditional allocation and packing decisions are required, many additional constraints are necessary to model a feasible launch. For this reason the launch problem is decoupled at Low Earth Orbit (LEO), creating a boundary between the launch allocation and the in-space network optimization. This assumption is assumed to be only slightly restrictive, since for many mission architectures there exists a delay at LEO before proceeding to in-space destinations. Launching focuses on selecting the appropriate elements to perform the launch, satisfying the payload requirements for launch, and scheduling requirements for launch vehicles and launch sites.
threads that link the Falklands to Iraq
Twenty-five years ago this weekend British territory was invaded by a foreign power. The Argentine invasion of the Falkland Islands followed six months in which the British government, for extraneous reasons, claimed that no such threat existed, corrupting the conduit of intelligence to that end. It blinded itself to the possibility of conflict. In the subsequent war, 255 British troops died and £3 billion was spent recapturing the islands. An inquiry, under Lord Franks, was staged to exonerate ministers of guilt.
Four years ago a British government was in an eerily inverse predicament. It spent six months claiming, again for an extraneous reason, that a foreign power posed an imminent threat to Britain, corrupting the conduit of intelligence to that end. It blinded itself to the possibility of no conflict. In the subsequent war 134 British troops, so far, have died and well over £3 billion has been spent. Two inquiries, under Lord Hutton and Lord Butler, have been staged to exonerate ministers of guilt.
After the Falklands war, stern efforts were made to ‘learn the lessons’ of what appeared to be a failure of intelligence and deterrence. Yet a dense fog still surrounds the run-up to that war. There are few accounts of the war seen from the Argentine side, as defeat is always an orphan. Last year’s official British history by Sir Lawrence Freedman broadly accepted the Franks thesis that the invasion came as a bolt from the blue. It was a spur-of-the-moment response by the Argentine junta to a threatened general strike, capitalising on a visit to South Georgia by some scrap-metal merchants in March 1982. Such an invasion, said Franks in 1982, ‘could not have been foreseen’ and therefore, ‘We would not be justified in attaching any criticism or blame to the present government.’ The truth is that the Argentine invasion was a complex operation that had been long in the preparation. Although plans for an invasion were standard exercises in Argentine navy circles, 1981 was different.
The British government was clearly signalling that it had lost interest in its South Atlantic possessions. At the United Nations in New York the Foreign Office had been negotiating to transfer sovereignty over the islands to Argentina and then ‘lease them back’ to enable the islanders to continue as self-governing. These negotiations deteriorated abruptly when Margaret Thatcher indicated to Foreign Office ministers that she was unwilling to pressure the islanders to agree terms. To the intelligence community the result was clear. It meant a seriously increased risk of Argentina staging an occupation, against which the islands had to be better defended, the so-called ‘fortress Falklands’ option.
Thatcher’s desire to appease islander opinion was equalled only by her desire to cut defence spending, best illustrated by the navy review boldly engineered by her defence secretary, John Nott. This embraced the end of ‘out of area’ seaborne operations, the withdrawal of HMS Endurance from its patrol duties in the South Atlantic and even an offer to sell the carrier, HMS Invincible, to Buenos Aires. To Argentina’s naval attaché in London, Gualtar Allara, Britain was pulling in its colonial horns. The Falklanders were not being offered full British citizenship, Rhodesia had gone and Hong Kong was going. The Diego Garcians had been sold down the river.
Earlier Argentine plans for seizing the Falklands had been codenamed Plan Goa, after the similar seizure by India of the Portuguese colony in 1961, a seizure that had been accepted by the United Nations (and by Britain). In December 1981, the navy commander, Admiral Jorge Anaya did exactly what a Joint Intelligence Committee assessment the previous July had warned.
That same December Anaya’s close associate, Leopoldo Galtieri, seized power in a coup. He was a bombastic soldier much favoured by the Reagan team in Washington. Anaya agreed to support him on condition that the navy were allowed not just to occupy South Georgia but to realise its fondest dream — a full invasion to ‘recover’ the Falklands before the 150th anniversary of their occupation by the British in 1833. Galtieri agreed and the invasion plan was authorised by the new junta on 15 December.
This was a wholly different scale of operation from that on South Georgia. Since glory was to be shared, it required a full tri-service planning team under Lombardo, with associated legal, diplomatic and public relations support. The invasion would take place in the depths of the southern winter, between 15 May and Argentine independence day on 9 July, when any British response would be near impossible. This was approved by the junta on 12 January. It was to be a bloodless exercise in ‘coercive diplomacy’ as a preliminary to resumed UN negotiations.
Demographics, Stone Characteristic, and Treatment of Urinary Calculi at the 47th Combat Support Hospital during the First 6 Months of Operation Iraqi Freedom
There are few publications describing urolithiasis in deployed military personnel. Renal colic was the most common urologic indication for air evacuation from the 47th Combat Support Hospital during the first 6 months of Operation Iraqi Freedom and we describe our observations and experience herein. Institutional review board approval was obtained to create a database of patients presenting to the 47th Combat Support Hospital with urolithiasis. Patient demographics, stone characteristic, imaging modality, urinalysis results, treatment course, and outcomes were evaluated for 182 patients. Sixty percent of patients qualified for conservative treatment and spontaneous stone passage was documented in 28%. We conclude that conservative therapy is safe and appropriate initial treatment for the majority of deployed personnel with urinary calculi, however, many patients were lost to follow-up. No patient treated conservatively required admission for sepsis, azotemia, or other serious stone-related complication.
Although the impact of urinary calculi on the military mission is difficult to quantify, renal colic was a frequent reason for referral to the 47th Combat Support Hospital (CSH), Camp Wolf, Kuwait, and the most common urologie indication for air evacuation out of theater. Yet, despite the apparent prevalence of stone disease in military personnel deployed to desert environments, there are few publications addressing basic information such as patient demographics, stone characteristics, necessity for air evacuation, and the success of treatment in the field.
The influx of military and civilian Department of Defense personnel into southwestern Asia in support of Operation Enduring Freedom and Operation Iraqi Freedom (OIF) provided a unique opportunity to observe stone disease in the deployed population. Southwestern Asia is a high risk area for urolithiasis with a reported incidence of urinary calculi up to five times higher than other regions of the world.1-4 During the 6-month period of this study, the 47th CSH was the largest tertiary referral hospital for the military theater and was the main evacuation route for southwestern Asia. As a result, the majority of renal colic requiring definitive diagnosis, subspecialty care, hospitalization, or evacuation was cared for at the 47th CSH. The objectives of this study were to evaluate patient and stone demographics, determine the time interval until formation of a symptomatic stone, and evaluate treatment outcomes and indications for air evacuation at a single, level III military treatment facility (MTF) deployed in support of OIF. Herein, we summarize our experience diagnosing and treating urolithiasis in the combat and early posthostilities operations during the first 6 months of 0IF. Our goals are to provide information to aid in the diagnosis and treatment of renal colic in the deployed environment, improve the planning of medical support operations, and provide insight into the timing of stone formation.
Methods
Database Construction and Demographics
Institutional review board approval was obtained to construct a database of all patients who presented to the 47th CSH from March through July 2003 for the diagnosis, treatment, or further air evacuation of symptomatic urinary calculi. The database included the patient demographics, stone characteristics, imaging modality, date of arrival into theater, date of the onset of renal colic, urinalysis results, treatment outcomes, and indication for air evacuation.
Imaging Modality, Stone Characteristics, Time Interval
All patients included in the database were evaluated by a urologist at the 47th CSH and had urinary calculi or evidence of a recently passed calculi documented by standard radiographie criteria. Imaging studies were not repeated if the patient arrived with images adequate to confirm the diagnosis or if the patient was referred from an outlying facility by a urologist who included in the medical summary a description of the radiographie findings adequate to confirm the diagnosis and characterize the stone. If more than one modality was performed, only the diagnostic imaging modality was recorded in the database.
Patient demographics and stone characteristics were entered into the database at the time of the evaluation. The patients were asked the date of the onset of renal colic and medical records, when available, were used for confirmation. The date of arrival into theater was supplied by the patient and was cross-referenced with the Joint Theater Personnel Roster. The stone location, laterally, number, and size and other pertinent radiographic findings were documented. A history of stone disease was not exclusionary, but patients who had undergone treatment for stone disease in the 30 days immediately before deployment, and patients presenting with a second or subsequent episode of stone disease since arriving in Southwestern Asia, were excluded from the analysis of the time interval.
Chemstrip (”dipstick”) urinalysis was performed when clinically indicated and results were recorded in the database. Urinalysis was not repeated if the results from a referring facility were adequately documented. The study patients were compared to 292 controls comprised of outpatients who underwent urinalysis at the 47th CSH during the study period for a diagnosis other than urinary tract infection or urolithiasis.
Treatment Outcomes
The treatment course and initiation of air evacuation was determined by the treating urologist and dictated by the clinical scenario. For the purposes of this analysis, patients were divided into two initial groups. The first group consisted of patients manifested for evacuation during their first evaluation at the 47th CSH. The indications for air evacuation included failure of inpatient management and/or stone characteristics, radiographie findings, or concomitant medical conditions not conducive to conservative therapy. Inpatient management consisted of intravenous and/or oral hydration, pain control, and treatment for constipation, admission did not equate to treatment failure. Patients were considered to have failed inpatient management if they had pain and/or nausea/emesis that required intravenous therapy for longer than 48 hours. Patients who failed inpatient management were not candidates for conservative management.
The second group consisted of patients given a trial of conservative outpatient management and returned to duty. Conservative therapy was initiated for patients with stones 4 mm or less in size, who could hydrate well, and whose pain was controlled with oral medications. The size criterion was selected based on published rates of spontaneous stone passage.5″7 Conservative therapy consisted of 2 to 3 weeks of duty restrictions, oral narcotic pain management, and hydration. All patients were instructed to return for repeat evaluation by a urologist at the 47th CSH even if their symptoms resolved, and they were issued appropriate documentation for their chain of command. Patients who received an initial trial of conservative management were further divided into patients with radiographie evidence of spontaneous stone passage, patients who failed to pass their stones, and patients who were lost to follow-up. Successful conservative management was defined as documentation of stone passage on follow-up radiography.
The U.S. Transportation Command Regulating and Command and Control Evacuation System fTRAC2ES) was searched by name and social security number for records that matched patients in the study database and the matching records were reviewed. TRAC2ES records for medical condition other than urinary calculi and TRAC2ES records documenting transfer for the purposes of demobilization were eliminated from analysis.
Statistical Methods
The arithmetic mean and range were calculated for the age. Stone size and number were compared using an unpaired Student’s t test with a two-tailed distribution. The locations of the stones were compared using a ?^sup 2^ test of distribution. The time interval until the development of symptomatic urinary calculi was calculated for each patient by subtracting the date of entry into Southwestern Asia from the date of onset of symptoms. Histograms were constructed for the time interval and the date of the onset of symptoms. SD, mean, median, skew, SE of skew, kurtosis, and SE of kurtosis were calculated for the time interval. The distribution of the time interval was evaluated with the Kolomogrorov-Smimov test, which compares the data set to a normal distribution. An insignificant p value from the Kolomogrorov-Smirnov test signifies the data set is not statistically different from the normal distribution. SPSS software was used to compute the results.
Comparison of Three Strategies for Preventing Hypothermia in Critically Injured Casualties during Aeromedical Evacuation
Critically injured patients are at risk for hypothermia. This study determined the efficacy of three hypothermia prevention strategies: the ChillBuster warming blanket, ChillBuster with a reflective blanket, and two wool blankets. A quasi-experimental design was used to compare changes in core temperature. Following resuscitation from hypovolemic shock, 20 swine were assigned to one of the three interventions, placed in an environmental chamber set to reproduce in-flight conditions onboard a military cargo aircraft (50°F/airspeed 0.2 m/s), and monitored for 6 hours. A repeated measures analysis of variance and least-squared difference post hoc were performed. The ChillBuster/reflective blanket group was significantly warmer than the ChillBuster only group and the wool blanket group.
Under operational conditions, military medical personnel provide patient care In a variety of austere settings including deployable field hospitals, nonmedical buildings, and during aeromedical evacuation (AE) in military cargo aircraft. Since the beginning of Operation Enduring Freedom/Iraqi Freedom, the Air Force AE System and Critical Care Air Transport Teams have transported more than 1,000 critically ill/injured patients. AE may involve patient transport from the combat zone to definitive medical care in Europe and the United States. During these medical flights, which may last from 1 to 14 hours, casualties are exposed to nine stresses of flight.1 These nine stresses include decreased barometric pressure, hypoxia, noise, vibration, gravitational forces, dehydration, third spacing, fatigue, and thermal stress. Thermal stress is the particular focus of this article. Onboard the military cargo aircraft, the temperature decreases dramatically during the first 60 to 90 minutes of flight, reaching an average temperature of 59°F (15°C),2 which may place the casualty at risk for developing hypothermia. Exposure to a cold environment can also occur in a variety of combat environments and hypothermia is a common medical condition encountered in recent combat operations.
In addition to the risk of primary hypothermia due to exposure to a cold environment, trauma victims are at further risk for secondary hypothermia due to an inability to produce body heat because of impaired oxygen consumption.5-7 Body heat production is necessary to maintain normothermia if the ambient temperature is less than 28°C.8 Trauma victims are at further risk for hypothermia because resuscitative measures such as mechanical ventilation and the administration of large volumes of room temperature intravenous (FV) fluids independently cause hypothermia.9 In addition, medications used during patient transport such as sedatives, narcotics, and neuromuscular blockade prevent the warming effect of shivering thermogenesls.
To prevent hypothermia in the AE environment or on a cold battlefield, metabolic heat production and conservation must equal heat loss to the environment. Under conditions where the casualty has impaired thermoregulation and the environmental conditions further exacerbate heat loss, interventions to minimize heat loss and to transfer heat to the body are necessary. The austere environment of care associated with AE operations limits the availability and feasibility of resources to keep patients warm. Interventions typically used in a stateside hospital will not work or are not appropriate for this unique care environment due to Issues such as safety, electrical power requirements, and weight. In addition, field expedient methods such as warming FV fluids with the flameless element on the Meals Ready to Eat has limited utility during long distance transport.19 Based on the risk of hypothermia in combat casualties and the limited utility of many standard wanning devices, there was a need to evaluate alternative methods for preventing hypothermia during the initial field and evacuation phases of care for combat causalities.
The purpose of this study was to determine the efficacy of three hypothermia prevention strategies that are suitable for the operational AE environment. Specifically, this study compared the ChillBuster, the ChillBuster plus a reflective blanket, and two standard military wool blankets. Core body temperature was the measure of the efficacy of each strategy in preventing a decrease in body temperature.