Cost minimization using an artificial neural network sleep apnea prediction tool for sleep studies.

RATIONALE: More than a million polysomnograms (PSGs) are performed annually in the United States to diagnose obstructive sleep apnea (OSA). Third-party payers now advocate a home sleep test (HST), rather than an in-laboratory PSG, as the diagnostic study for OSA regardless of clinical probability, but the economic benefit of this approach is not known. OBJECTIVES: We determined the diagnostic performance of OSA prediction tools including the newly developed OSUNet, based on an artificial neural network, and performed a cost-minimization analysis when the prediction tools are used to identify patients who should undergo HST. METHODS: The OSUNet was trained to predict the presence of OSA in a derivation group of patients who underwent an in-laboratory PSG (n = 383). Validation group 1 consisted of in-laboratory PSG patients (n = 149). The network was trained further in 33 patients who underwent HST and then was validated in a separate group of 100 HST patients (validation group 2). Likelihood ratios (LRs) were compared with two previously published prediction tools. The total costs from the use of the three prediction tools and the third-party approach within a clinical algorithm were compared. MEASUREMENTS AND MAIN RESULTS: The OSUNet had a higher +LR in all groups compared with the STOP-BANG and the modified neck circumference (MNC) prediction tools. The +LRs for STOP-BANG, MNC, and OSUNet in validation group 1 were 1.1 (1.0-1.2), 1.3 (1.1-1.5), and 2.1 (1.4-3.1); and in validation group 2 they were 1.4 (1.1-1.7), 1.7 (1.3-2.2), and 3.4 (1.8-6.1), respectively. With an OSA prevalence less than 52%, the use of all three clinical prediction tools resulted in cost savings compared with the third-party approach. CONCLUSIONS: The routine requirement of an HST to diagnose OSA regardless of clinical probability is more costly compared with the use of OSA clinical prediction tools that identify patients who should undergo this procedure when OSA is expected to be present in less than half of the population. With OSA prevalence less than 40%, the OSUNet offers the greatest savings, which are substantial when the number of sleep studies done annually is considered.

Watershed and discharge influences on the phase distribution and tributary loading of total mercury and methylmercury into Lake Superior.

Knowledge of the partitioning and sources of mercury are important to understanding the human impact on mercury levels in Lake Superior wildlife. Fluvial fluxes of total mercury (Hg(T)) and methylmercury (MeHg) were compared to discharge and partitioning trends in 20 sub-basins having contrasting land uses and geological substrates. The annual tributary yield was correlated with watershed characteristics and scaled up to estimate the basin-wide loading. Tributaries with clay sediments and agricultural land use had the largest daily yields with maxima observed near the peak in water discharge. Roughly 42% of Hg(T) and 57% of MeHg was delivered in the colloidal phase. Tributary inputs, which are confined to near-shore zones of the lake, may be more important to the food-web than atmospheric sources. The annual basin-wide loading from tributaries was estimated to be 277 kg yr(-1) Hg(T) and 3.4 kg yr(-1) MeHg (5.5 and 0.07 mg km(-2) d(-1), respectively).

Continuity of care in intensive care units: a cluster-randomized trial of intensivist staffing.

RATIONALE: Little is known about the consequences of intensivists' work schedules, or intensivist continuity of care. OBJECTIVES: To assess the impact of weekend respite for intensivists, with consequent reduction in continuity of care, on them and their patients. METHODS: In five medical intensive care units (ICUs) in four academic hospitals we performed a prospective, cluster-randomized, alternating trial of two intensivist staffing schedules. Daily coverage by a single intensivist in half-month rotations (continuous schedule) was compared with weekday coverage by a single intensivist, with weekend cross-coverage by colleagues (interrupted schedule). We studied consecutive patients admitted to study units, and the intensivists working in four of the participating units. MEASUREMENTS AND MAIN RESULTS: The primary patient outcome was ICU length of stay (LOS);we also assessed hospital LOS and mortality rates. The primary intensivist outcome was physician burnout. Analysis was by multivariable regression. A total of 45 intensivists and 1,900 patients participated in the study. Continuity of care differed between schedules (patients with multiple intensivists = 28% under continuous schedule vs. 62% under interrupted scheduling; P < 0.0001). LOS and mortality were nonsignificantly higher under continuous scheduling (ΔICU LOS 0.36 d, P = 0.20; Δhospital LOS 0.34 d, P = 0.71; ICU mortality, odds ratio = 1.43, P = 0.12; hospital mortality, odds ratio = 1.17,P = 0.41). Intensivists experienced significantly higher burnout, work­home life imbalance, and job distress working under the continuous schedule. CONCLUSIONS: Work schedules where intensivists received weekend breaks were better for the physicians and, despite lower continuity of intensivist care, did not worsen outcomes for medical ICU patients.

Acquired weakness, handgrip strength, and mortality in critically ill patients.

RATIONALE: ICU-acquired paresis (ICUAP) is common in survivors of critical illness. There is significant associated morbidity, including prolonged time on the ventilator and longer hospital stay. However, it is unclear whether ICUAP is independently associated with mortality, as sicker patients are more prone and existing studies have not adjusted for this. OBJECTIVES: To test the hypothesis that ICUAP is independently associated with increased mortality. Secondarily, to determine if handgrip dynamometry is a concise measure of global strength and is independently associated with mortality. METHODS: A prospective multicenter cohort study was conducted in intensive care units (ICU) of five academic medical centers. Adults requiring at least 5 days of mechanical ventilation without evidence of preexisting neuromuscular disease were followed until awakening and were then examined for strength. MEASUREMENTS AND MAIN RESULTS: We measured global strength and handgrip dynamometry. The primary outcome was in-hospital mortality and secondary outcomes were hospital and ICU-free days, ICU readmission, and recurrent respiratory failure. Subjects with ICUAP (average MRC score of < 4) had longer hospital stays and required mechanical ventilation longer. Handgrip strength was lower in subjects with ICUAP and had good test performance for diagnosing ICUAP. After adjustment for severity of illness, ICUAP was independently associated with hospital mortality (odds ratio [OR], 7.8; 95% confidence interval [CI], 2.4-25.3; P = 0.001). Separately, handgrip strength was independently associated with hospital mortality (OR, 4.5; 95% CI, 1.5-13.6; P = 0.007). CONCLUSIONS: ICUAP is independently associated with increased hospital mortality. Handgrip strength is also independently associated with poor hospital outcome and may serve as a simple test to identify ICUAP. Clinical trial registered with www.clinicaltrials.gov (NCT00106665).

Strong colloidal and dissolved organic ligands binding copper and zinc in rivers.

The speciation or physicochemical form of copper and zinc in freshwater plays an important role in reactivity, bioavailability, and toxicity. Strong metal-binding ligands, which determine speciation, were detected by voltammetric methods, both anodic stripping voltammetry (ASV) and competitive ligand equilibration adsorptive stripping voltammetry (CLE-AdSV); the latter technique can detect nanomolar levels of extremely strong (log K' > 13) ligands. Through careful field site selection and the investigation of ultrafiltration permeate samples, natural organic ligands were measured with limited interferences of colloidal inorganic iron- and aluminum-based trace metal-binding phases. Furthermore, ultrafiltration allowed measurement of colloidal and dissolved ligands independently, and differences of ligand abundance and strength in different size classes are reported. For copper, ultrafilterable (<3 kDa) organic ligand site concentrations (expressed normalized to dissolved organic carbon) were on average 33% of the colloidal level, but ultrafilterable ligand log K' values were 0.5 log units stronger than those of the 0.4 microm filterable concentration. The ultrafilterable copper-binding ligand concentration showed a smaller variation across the rivers (25% rsd) than zinc-binding ligands (90% rsd). For all field sites and size fractions, strong ligand sites greatly exceeded metal concentrations; subsequently, equilibrium speciation modeling predict picomolar levels of free metal. Modeling also indicated that the very strong ligands (detected by CLE-AdSV) predominate, so modeling based solely on ASV data in freshwater may be inadequate. Competition experiments indicated that the very strong ligand sites are metal specific for copper and zinc.

Specificity of computerized physician order entry has a significant effect on the efficiency of workflow for critically ill patients.

BACKGROUND: Critically ill patients require rapid care, yet they are also at risk for morbidity from the potential complications of that care. Computerized physician order entry (CPOE) is advocated as a tool to reduce medical errors, improve the efficiency of healthcare delivery, and improve outcomes. Little is known regarding the essential attributes of CPOE in the intensive care unit (ICU). OBJECTIVE: To assess the effect of CPOE on ICU patient care. DESIGN: Retrospective before and after cohort study. SETTING: An academic ICU. PATIENTS: Patients admitted to the ICU during use of the initial CPOE application and those admitted after its modification. INTERVENTIONS: Comprehensive order interface redesign improving clarity, specificity, and efficiency. MEASUREMENTS: Orders for complex ICU care were compared between the two groups. In addition, the use of higher-efficiency CPOE order paths was tracked. RESULTS: Patients treated with both the initial and modified CPOE system were similar for all measured characteristics. With the modified CPOE system, there were significant reductions in orders for vasoactive infusions, sedative infusions, and ventilator management. There was also a significant increase in orders executed through ICU-specific order sets after system modifications. LIMITATIONS: This retrospective study cannot assess issues related to learner expertise and is meant to only suggest the importance of developing CPOE systems that are appropriate for specialty care environments. CONCLUSION: Appropriate CPOE applications can improve the efficiency of care for critically ill patients. The workflow requirements of individual units must be analyzed before technologies like CPOE can be properly developed and implemented.

Physical and kinetic speciation of copper and zinc in three geochemically contrasting marine estuaries.

The physical and kinetic speciation of Cu and Zn in three impacted marine estuaries was examined. Contrasts in sources of metal-binding ligands, solution chemistry, and hydrologic forcing between and withinthethree study systems (Cape Fear River Estuary, North Carolina; Norfolk-Hampton Roads-Elizabeth River, Virginia; San Diego Bay, California) were exploited to enhance our understanding of Cu and Zn speciation. Trace metal-optimized tangential-flow ultrafiltration at 1 kDa nominal molecular weight limit (NMWL) was used to fractionate <0.4 microm species into colloidal and "dissolved" pools. Colloidal species of dissolved organic matter (DOM) and copper were significant and often the dominant pools in each of the three study systems. Characteristic colloidal fractions of both DOM and Cu ranged from near 70% of <0.4 microm concentrations in Cape Fear to 50% in San Diego Bay. Colloidal Cu and DOM were strongly coupled, and variability in observed <0.4 microm Cu concentrations was closely related to the concentrations of colloidal-associated metal. Colloidal fractions were much smaller for Zn than that of Cu; ranging from 10-30% in Cape Fear to less than 5% in San Diego Bay, and no relationship to DOM was observed. Kinetic separations on Chelex resin revealed the presence of large nonlabile pools of Cu in each of the study systems, with the highest fractions (70-100%) in Cape Fear and Norfolk and lowest (30-50%) in San Diego Bay. A close relationship was observed between colloidal and nonlabile Cu species, implying slow reactivity of colloidal-bound Cu. The fraction of filterable Zn labile to Chelex averaged 97%, 85%, and 60% in San Diego, Norfolk, and Cape Fear, respectively. Anthropogenic Zn appeared almost exclusively in the <1 kDa fraction, while anthropogenic Cu was distributed between dissolved and colloidal pools. Copper particle-partition coefficients (Kd) followed the trend: San Diego >> Norfolk > Cape Fear and were inversely correlated with DOC concentrations. Colloid-based partition coefficients were significantly greater, in many cases an order of magnitude greater, than particle-based partition coefficients. The partitioning data suggest the presence of metal-enriched bacterial-derived exudates and/or discrete metal phases in colloidal-sized particles in impacted regions of these estuaries. The strong relationships observed between Cu and DOC indicate that Cu partitioning behavior over a range of estuarine environments may be modeled effectively with a limited set of coefficients. Our measurements of metal lability and size distribution imply that the fraction of <0.4 microm Zn that is likely to be bioavailable is greater than that for Cu, especially in impacted regions of the study systems.

Cost-effectiveness of Advair: fluticasone propionate and salmeterol combination.

The National Heart, Lung and Blood Institute guidelines for the treatment of asthma suggest that inhaled corticosteroids, with the addition of a long-acting bronchodilator, may be the most effective long-term control medication for asthma. Five inhaled corticosteroids are approved for use in the USA, including beclomethasone dipropionate, budesonide, flunisolide, triamcinolone acetonide and fluticasone propionate. Fluticasone propionate (Flixotide) and the long-acting beta2 agonist salmeterol (Serevent), are now available in the USA together in an easy to use dry powder inhaler Advair. The cost-effectiveness of this combination in the treatment of persistent asthma is reviewed. This review evaluates all the cost-effectiveness studies comparing fluticasone propionate and salmeterol from two separate inhalers or one single inhaler available in the literature. Cost-effectiveness was compared with inhaled corticosteroids alone, leukotriene receptor antagonists and other combination therapies in patients with persistent asthma.

Update in pulmonary medicine.

Chronic inflammation in many pulmonary diseases, such as sarcoidosis and IPF, lead to end-stage lung disease and fibrosis. In other diseases, such as chronic thromboembolic disease and emphysema, long-term complications can result in pulmonary hypertension and cor pulmonale. Therapeutic options for end-stage lung disease are quite limited. One possible solution is lung transplantation. Although fraught with potential serious complications, including infection, rejection, and death, lung transplantation may offer overall improvement in mortality rates and quality of life.