We constructed and internally validated an artificial neural network (ANN) model for prediction of in-hospital major adverse outcomes (defined as death, cardiac arrest, coma, renal failure, cerebrovascular accident, reinfarction, or prolonged mechanical ventilation) in patients who received “on-pump” coronary artery bypass grafting (CABG) surgery. We retrospectively analyzed a 5-year CABG surgery database with a final study population of 563 patients. Predictive variables were limited to information available before the procedure, and outcome variables were represented only by events that occurred postoperatively. The ANN’s ability to discriminate outcomes was assessed using receiver-operating characteristic (ROC) analysis and the results were compared with a multivariate logistic regression (LR) model and the QMMI risk score (RS) model. A major adverse outcome occurred in 12.3% of all patients and 18 predictive variables were identified by the ANN model. Pairwise comparison showed that the ANN model significantly outperformed the RS model (AUC = 0.886 vs.0.752, p = 0.043). However, the other two pairs, ANN vs. LR models (AUC = 0.886 vs. 0.807, p = 0.076) and LR vs. RS models (AUC = 0.807 vs. 0.752, p = 0.453) performed similarly well. ANNs tend to outperform regression models and might be a useful screening tool to stratify CABG candidates preoperatively into high-risk and low-risk groups.
The number of off-pump coronary artery surgery procedures in high-risk patients such as renal failure, hepatic failure and in anticoagulant drug using patients is increasing. The associated co morbidity and repeated use of electrocautery in postoperative bleeding, caused a susceptibility of patients to pressure or electrocautery ulcers. During a period of three years, 1400 off-pump coronary artery bypass surgery were performed in our center. Of these patients, 20 (A group) suffered from electrocautery sore (ES) and 40 (B group) had pressure sore (PS). These patients were compared with respect to variables such as age, hypertension, hypercholesterolemia, operating time, smoking, opium using, diabetes, weight, sex, respiratory failure, renal failure, and cerebrovascular accident, intra aortic balloon pump using, inotropic drug using by x2 or t test, according to categorical or continuous variables consequently. Electrocautery sore and pressure ulcer as dependence variables and others variables with p value less than 0.1 entered a multivariable logistic regression model and odd ratio of significant variables were obtained. These two groups of patients were different with respect to variables such as age, sex, respiratory failure and cerebrovascular accident and...
An auxiliary service unit is normally idle, or in cold
standby. If a demand for the unit's service occurs, the unit
must be available to satisfy it, or else "catastrophe" occurs.
Policies for periodic inspection and maintenance of such a unit
are derived in this paper that maximize the expected time until a
catastrophe occurs. The policies recognize that inspection,
maintenance, and repair periods are of non-zero duration, during
which the unit is vulnerable. They also account for the possibility of hazardous inspection that may damage the unit, and various forms of imperfect repair.
Important examples occur in the nuclear power industry: a unit may be a pump, or emergency diesel generator, and a demand may be caused by an initiating event such as pipe break or loss of off site power; "catastrophe" equates to loss-of coolant accident or melt down. Other examples occur in the military, and in emergency services to hospitals.; support of the Probability and
Statistics Program of the Office of Naval Research, Arlington, VA; http://archive.org/details/inspectionpolici00thom; N0001484WR24011; NA
O programa computacional P ANTERA-2 (Programa para Análise Termo-hidráulica de Reatores a Água, Versão 2), cujos fundamentos são descritos neste trabalho, efetua a análise por subcanais de feixes de varetas em conjunção com a simulação de múltiplos circuitos. O programa resolve simultaneamente as equações de conservação da massa, dos momentos axial e lateral e da energia para a geometria de subcanais acopladas com as equações de balanço que descrevem o escoamento de um fluido em um número arbitrário de circuitos de remgeração conectados a um vaso de pressão que contém o feixe. Atendo-se à formulação de subcanais, a estratégia computacional básica de P ANTERA-2 provém dos códigos COBRA, mas um método implícito alternativo de solução orientado para o campo de pressões é usado para resolver as aproximações de diferenças finitas das leis de balanço. Os resultados previstos pelo modelo de subcanais compreendem as distribuições de densidades, entalpias, vazões de massa e pressões nos subcanais. O modelo de circuitos prevê as vazões nos circuitos individuais, a vazão total através do vaso de pressão e as velocidades de rotação das bombas em função do tempo subseqüente à falha de qualquer número das bombas de circulação. Os transitórios de vazão nos circuitos podem ser ocasionados pelas perdas de potência elétrica...