Using Digital Methods to Reconstruct Original Topography and Landscape Wetness in the Judicial Ditch 66 Watershed, Polk County, Minnesota

The excavation of Judicial Ditch #66 has altered the topography of its hydrologic basin in Polk County, Minnesota. Records of how the pre-ditch landscape appeared do not exist. The original aim of this study was to develop and evaluate a method of manual data manipulation and combination to digitally restore the topography of a human-altered landscape. Trial and error with the combination of spatial data from separate sources provided inadequate results. The study was subsequently divided into four parts. First, drainage area and its potential wetness were estimated using the 10 meter U.S. Geological Survey Digital Elevation Model (DEM). The ln(a/tan β) potential wetness index is used, which is directly related to drainage area. Second, points representing ditches and berms were eliminated from National Resources Conservation Service (NRCS) spatial survey data. Third, we compared wetness indices of the restored and original landscapes. Finally, the wetness index for the restored landscape was compared to a soil map of the study area to determine if the areas of wetness correspond with hydric soils. GIS software provides helpful tools, which can produce models that can simultaneously show multiple layers of information for an area. By estimating areas of wetness, this method allows the effects of restoration to be determined prior to any physical alteration of the landscape. The display of data and models on GIS maps will play a large part in helping to solve other restoration issues in the future

A study to derive a clinical decision rule for triage of emergency department patients with chest pain: design and methodology

<p>Abstract</p> <p>Background</p> <p>Chest pain is the second most common chief complaint in North American emergency departments. Data from the U.S. suggest that 2.1% of patients with acute myocardial infarction and 2.3% of patients with unstable angina are misdiagnosed, with slightly higher rates reported in a recent Canadian study (4.6% and 6.4%, respectively). Information obtained from the history, 12-lead ECG, and a single set of cardiac enzymes is unable to identify patients who are safe for early discharge with sufficient sensitivity. The 2007 ACC/AHA guidelines for UA/NSTEMI do not identify patients at low risk for adverse cardiac events who can be safely discharged without provocative testing. As a result large numbers of low risk patients are triaged to chest pain observation units and undergo provocative testing, at significant cost to the healthcare system. Clinical decision rules use clinical findings (history, physical exam, test results) to suggest a diagnostic or therapeutic course of action. Currently no methodologically robust clinical decision rule identifies patients safe for early discharge.</p> <p>Methods/design</p> <p>The goal of this study is to derive a clinical decision rule which will allow emergency physicians to accurately identify patients with chest pain who are safe for early discharge. The study will utilize a prospective cohort design. Standardized clinical variables will be collected on all patients at least 25 years of age complaining of chest pain prior to provocative testing. Variables strongly associated with the composite outcome acute myocardial infarction, revascularization, or death will be further analyzed with multivariable analysis to derive the clinical rule. Specific aims are to: i) apply standardized clinical assessments to patients with chest pain, incorporating results of early cardiac testing; ii) determine the inter-observer reliability of the clinical information; iii) determine the statistical association between the clinical findings and the composite outcome; and iv) use multivariable analysis to derive a highly sensitive clinical decision rule to guide triage decisions.</p> <p>Discussion</p> <p>The study will derive a highly sensitive clinical decision rule to identify low risk patients safe for early discharge. This will improve patient care, lower healthcare costs, and enhance flow in our busy and overcrowded emergency departments.</p