Monitoring Metabolic Status Predicting Decrements in Physiological and Cognitive Performance (2004) / Chapter Skim
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Executive Summary
Executive Summary
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Metabolic monitoring techniques would also be valuable in the practice of telemedicine and would enable healthcare workers to predict when an individual might need special attention or transport to a medical facility. CHARGE TO COMMITTEE This report examines appropriate biological markers, monitoring technologies currently available and in need of development, and appropriate algorithms to interpret the data obtained in order to provide information for command decisions relative to the physiological and psychological "readiness" of each combat service member.
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Biomarkers of Overall Physical Status The overall physical status of service members in the field can be evaluated by analyzing either objective physiological measurements (e.g., energy expenditure, vital signs) or subjective measurements of self-assessments (or assessments by peers)
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Biomarkers of Physiological Status The specific metabolic systems of particular concern to the military are: bone and muscle metabolism, kidney function and hydration, and stress and immune function. Maintaining a healthy bone is essential to minimize the incidence of fracture, which is predicted by measuring bone mineral density.
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The efficiency of combatants in sustained operations can be significantly compromised by inadequate sleep, which can cause increased reaction time, mood declines, perceptual disturbances, motivational decrements, impaired attention, short-term memory loss, carelessness, reduced physical endurance, degraded verbal communication skills, and impaired judgment. In all probability most technologies in development will be useful only in laboratory environments or in fixed-based operational facilities (such as posts in which radar and sonar equipment are monitored or stations from which remotecontrolled vehicles are piloted)
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Irrespective of the biological or cognitive markers selected, there is a need for baseline measurements of individual combat service members so that it can be determined, on an individual basis, if a marker is significantly altered under stress. Biomarkers for Bone and Muscle Metabolism Bone Bone remodeling is a relatively slow biological process and thus not amenable to monitoring in field situations.
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The assessment of weight loss or loss of body mass, plasma sodium or plasma osmolality, urinary specific gravity, fluid balance, and the recovery of weight 24 hours after dehydration can be used for the identification of extent and type of dehydration. In the military setting, weight changes over a short period of time reflect fluid changes, and loss of body water coupled with measures of serum sodium or serum osmolality can define the degree of concomitant salt loss.
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The military should consider providing and training personnel in the use of simple urine dipstick-type test strips that would provide information on levels of urine protein (a marker for potential kidney damage) , ketones and glucose (potential markers for energy metabolism)
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Renal Function and Hydration Simple methods that measure renal function and hydration already exist. As mentioned previously, the military should train personnel in the field use of simple urine dipstick-type test strips that would provide information on levels of urine protein, ketones and glucose, and leukocyte esterase and nitrates as indica
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In addition, single-axis accelerometers or pedometers and most multidimensional accelerometers are not useful in detecting the increased energy costs of high-intensity exercise, upper-body exercise, carrying a load, or changes in surface or terrain. The combination of doubly labeled water as a measure of total energy expenditure and hand-held indirect calorimetry to measure resting energy expenditure could be used to monitor metabolic status and assess energy metabolism over periods of up to 2 weeks.
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What additional measurements would improve specif city of the predictions? Models, such as the Acute Physiologic and Chronic Health Evaluation Scores and Simplified Applied Physiological Score, that use physiological variables to predict health outcomes have worked quite well in the intensive care unit setting where pathological changes in physiological parameters are the rule, but there is little evidence that similar algorithms would be equally effective in the military setting where such parameters vary over a narrower range.
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In addition to performing more research on the utility of traditional approaches using self-reported data, a significant focus should be placed on further developing and implementing new psychophysiological methods for monitoring brain activity, heart-rate variability, eye movements, and metabolites and validating these techniques as predictors of cognitive responses to stress and fatigue. New performance assessment methodologies may soon be available for computerized tasks in which cognitive probes can be unobtrusively introduced during the completion of primary operational demands.
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Predictive medical algorithms can be utilized to generate specific recommendations and interventions from complex biological information gathered by metabolic monitoring systems. Further research is needed to develop and validate these models, with a particular emphasis on identifying prognostic factors in asymptomatic subjects.
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These should include studies of markers of bone loss, especially related to fracture risk and the prevention of lost duty time during initial entry training, advanced training, and combat operations. · To continue to study cortisol levels during training and operations to ensure that its elevation is not a contributor to bone loss.
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From page 14... ...
· To continue research on the use of NIRS to monitor muscle function and skin hydration status concurrently. This particular technology also has the potential for detecting the occurrence of inflammation.
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