60 resultados para Multiple Additive Regression Trees (MART)
Resumo:
Background In Switzerland there are about 150,000 equestrians. Horse related injuries, including head and spinal injuries, are frequently treated at our level I trauma centre. Objectives To analyse injury patterns, protective factors, and risk factors related to horse riding, and to define groups of safer riders and those at greater risk Methods We present a retrospective and a case-control survey at conducted a tertiary trauma centre in Bern, Switzerland. Injured equestrians from July 2000 - June 2006 were retrospectively classified by injury pattern and neurological symptoms. Injured equestrians from July-December 2008 were prospectively collected using a questionnaire with 17 variables. The same questionnaire was applied in non-injured controls. Multiple logistic regression was performed, and combined risk factors were calculated using inference trees. Results Retrospective survey A total of 528 injuries occured in 365 patients. The injury pattern revealed as follows: extremities (32%: upper 17%, lower 15%), head (24%), spine (14%), thorax (9%), face (9%), pelvis (7%) and abdomen (2%). Two injuries were fatal. One case resulted in quadriplegia, one in paraplegia. Case-control survey 61 patients and 102 controls (patients: 72% female, 28% male; controls: 63% female, 37% male) were included. Falls were most frequent (65%), followed by horse kicks (19%) and horse bites (2%). Variables statistically significant for the controls were: Older age (p = 0.015), male gender (p = 0.04) and holding a diploma in horse riding (p = 0.004). Inference trees revealed typical groups less and more likely to suffer injury. Conclusions Experience with riding and having passed a diploma in horse riding seem to be protective factors. Educational levels and injury risk should be graded within an educational level-injury risk index.
Resumo:
We report the identification of quantitative trait loci (QTL) affecting carcass composition, carcass length, fat deposition and lean meat content using a genome scan across 462 animals from a combined intercross and backcross between Hampshire and Landrace pigs. Data were analysed using multiple linear regression fitting additive and dominance effects. This model was compared with a model including a parent-of-origin effect to spot evidence of imprinting. Several precisely defined muscle phenotypes were measured in order to dissect body composition in more detail. Three significant QTL were detected in the study at the 1% genome-wide level, and twelve significant QTL were detected at the 5% genome-wide level. These QTL comprise loci affecting fat deposition and lean meat content on SSC1, 4, 9, 10, 13 and 16, a locus on SSC2 affecting the ratio between weight of meat and bone in back and weight of meat and bone in ham and two loci affecting carcass length on SSC12 and 17. The well-defined phenotypes in this study enabled us to detect QTL for sizes of individual muscles and to obtain information of relevance for the description of the complexity underlying other carcass traits.
Resumo:
OBJECTIVE: To analyse risk factors in alpine skiing. DESIGN: A controlled multicentre survey of injured and non-injured alpine skiers. SETTING: One tertiary and two secondary trauma centres in Bern, Switzerland. PATIENTS AND METHODS: All injured skiers admitted from November 2007 to April 2008 were analysed using a completed questionnaire incorporating 15 parameters. The same questionnaire was distributed to non-injured controls. Multiple logistic regression was performed. Patterns of combined risk factors were calculated by inference trees. A total of 782 patients and 496 controls were interviewed. RESULTS: Parameters that were significant for the patients were: high readiness for risk (p = 0.0365, OR 1.84, 95% CI 1.04 to 3.27); low readiness for speed (p = 0.0008, OR 0.29, 95% CI 0.14 to 0.60); no aggressive behaviour on slopes (p<0.0001, OR 0.19, 95% CI 0.09 to 0.37); new skiing equipment (p = 0.0228, OR 59, 95% CI 0.37 to 0.93); warm-up performed (p = 0.0015, OR 1.79, 95% CI 1.25 to 2.57); old snow compared with fresh snow (p = 0.0155, OR 0.31, 95% CI 0.12 to 0.80); old snow compared with artificial snow (p = 0.0037, OR 0.21, 95% CI 0.07 to 0.60); powder snow compared with slushy snow (p = 0.0035, OR 0.25, 95% CI 0.10 to 0.63); drug consumption (p = 0.0044, OR 5.92, 95% CI 1.74 to 20.11); and alcohol abstinence (p<0.0001, OR 0.14, 95% CI 0.05 to 0.34). Three groups at risk were detected: (1) warm-up 3-12 min, visual analogue scale (VAS)(speed) >4 and bad weather/visibility; (2) VAS(speed) 4-7, icy slopes and not wearing a helmet; (3) warm-up >12 min and new skiing equipment. CONCLUSIONS: Low speed, high readiness for risk, new skiing equipment, old and powder snow, and drug consumption are significant risk factors when skiing. Future work should aim to identify more precisely specific groups at risk and develop recommendations--for example, a snow weather index at valley stations.
Resumo:
Conservation and monitoring of forest biodiversity requires reliable information about forest structure and composition at multiple spatial scales. However, detailed data about forest habitat characteristics across large areas are often incomplete due to difficulties associated with field sampling methods. To overcome this limitation we employed a nationally available light detection and ranging (LiDAR) remote sensing dataset to develop variables describing forest landscape structure across a large environmental gradient in Switzerland. Using a model species indicative of structurally rich mountain forests (hazel grouse Bonasa bonasia), we tested the potential of such variables to predict species occurrence and evaluated the additional benefit of LiDAR data when used in combination with traditional, sample plot-based field variables. We calibrated boosted regression trees (BRT) models for both variable sets separately and in combination, and compared the models’ accuracies. While both field-based and LiDAR models performed well, combining the two data sources improved the accuracy of the species’ habitat model. The variables retained from the two datasets held different types of information: field variables mostly quantified food resources and cover in the field and shrub layer, LiDAR variables characterized heterogeneity of vegetation structure which correlated with field variables describing the understory and ground vegetation. When combined with data on forest vegetation composition from field surveys, LiDAR provides valuable complementary information for encompassing species niches more comprehensively. Thus, LiDAR bridges the gap between precise, locally restricted field-data and coarse digital land cover information by reliably identifying habitat structure and quality across large areas.
Resumo:
OBJECTIVE: The primary aim of the present study was to investigate whether there is a relationship between central hypersensitivity (assessed by pressure pain thresholds of uninjured tissues) and intradiscal pain threshold during discography. The secondary aim was to test the hypothesis that peripheral noxious stimulation dynamically modulates central hypersensitivity. PATIENTS: Twenty-four patients with positive provocation discography were tested for central hypersensitivity by pressure algometry before and after the intervention with assessments of pressure pain detection and tolerance thresholds. Intradiscal pain threshold was assessed by measuring intradiscal pressure at the moment of pain provocation during discography. Correlation analyses between intradiscal pain threshold and pressure algometry were made. For the secondary aim, pressure algometry data before and after discography were compared. RESULTS: Significant correlation with intradiscal pain threshold was found for pressure pain detection threshold at the toe (regression coefficient: 0.03, P = 0.05) and pressure pain tolerance thresholds at the nonpainful point at the back (0.02, P = 0.024). Tolerance threshold at the toe was a significant predictor for intradiscal pain threshold only in multiple linear regression (0.036, P = 0.027). Detection as well as tolerance thresholds significantly decreased after discography at the painful and the nonpainful point at the back, but not at the toe. CONCLUSIONS: Central hypersensitivity may influence intradiscal pain threshold, but with a modest quantitative impact. The diagnostic value of provocation discography is therefore not substantially impaired. Regional, but not generalized central hypersensitivity is dynamically modulated by ongoing peripheral nociceptive input.
Resumo:
Burnout is a pathologic reaction in response to long-term work-related stress. The aim of this study was 2-fold: first, to assess the prevalence and degree of burnout among surgical residents and surgeons in Switzerland and, second, to identify predictors of burnout in the surgical community. Four hundred five of 618 anonymous questionnaires (65.5%) were returned. Among respondents, 3.7% and 35.1% showed high and moderate degrees of burnout, respectively. Respondents with high and moderate degrees of burnout had higher summary scores of perceived stress (P < .001). In multiple logistic regression analysis, the strongest predictors of burnout were poor interaction with nurses, disturbances due to telephone consultations, and high overall workload. To reduce burnout, new work models should be sought, in addition to decreasing work intensity and workload rather than restricting work hours alone.
Resumo:
Excessive consumption of acidic drinks and foods contributes to tooth erosion. The aims of the present in vitro study were twofold: (1) to assess the erosive potential of different dietary substances and medications; (2) to determine the chemical properties with an impact on the erosive potential. We selected sixty agents: soft drinks, an energy drink, sports drinks, alcoholic drinks, juice, fruit, mineral water, yogurt, tea, coffee, salad dressing and medications. The erosive potential of the tested agents was quantified as the changes in surface hardness (ΔSH) of enamel specimens within the first 2 min (ΔSH2-0 = SH2 min - SHbaseline) and the second 2 min exposure (ΔSH4-2 = SH4 min - SH2 min). To characterise these agents, various chemical properties, e.g. pH, concentrations of Ca, Pi and F, titratable acidity to pH 7·0 and buffering capacity at the original pH value (β), as well as degree of saturation (pK - pI) with respect to hydroxyapatite (HAP) and fluorapatite (FAP), were determined. Erosive challenge caused a statistically significant reduction in SH for all agents except for coffee, some medications and alcoholic drinks, and non-flavoured mineral waters, teas and yogurts (P < 0·01). By multiple linear regression analysis, 52 % of the variation in ΔSH after 2 min and 61 % after 4 min immersion were explained by pH, β and concentrations of F and Ca (P < 0·05). pH was the variable with the highest impact in multiple regression and bivariate correlation analyses. Furthermore, a high bivariate correlation was also obtained between (pK - pI)HAP, (pK - pI)FAP and ΔSH.
Resumo:
A growing body of literature addresses possible health effects of mobile phone use in children and adolescents by relying on the study participants' retrospective reconstruction of mobile phone use. In this study, we used data from the international case-control study CEFALO to compare self-reported with objectively operator-recorded mobile phone use. The aim of the study was to assess predictors of level of mobile phone use as well as factors that are associated with overestimating own mobile phone use. For cumulative number and duration of calls as well as for time since first subscription we calculated the ratio of self-reported to operator-recorded mobile phone use. We used multiple linear regression models to assess possible predictors of the average number and duration of calls per day and logistic regression models to assess possible predictors of overestimation. The cumulative number and duration of calls as well as the time since first subscription of mobile phones were overestimated on average by the study participants. Likelihood to overestimate number and duration of calls was not significantly different for controls compared to cases (OR=1.1, 95%-CI: 0.5 to 2.5 and OR=1.9, 95%-CI: 0.85 to 4.3, respectively). However, likelihood to overestimate was associated with other health related factors such as age and sex. As a consequence, such factors act as confounders in studies relying solely on self-reported mobile phone use and have to be considered in the analysis.
Resumo:
Long-term endurance sports are associated with atrial remodeling and an increased risk for atrial fibrillation (AF) and atrial flutter. Pro-atrial natriuretic peptide (pro-ANP) is a marker of atrial wall tension and elevated in patients with AF. The aim of this study was to test the hypothesis that atrial remodeling would be perpetuated by repetitive episodes of atrial stretching during strenuous competitions, reflected by elevated levels of pro-ANP. A cross-sectional study was performed on nonelite runners scheduled to participate in the 2010 Grand Prix of Bern, a 10-mile race. Four hundred ninety-two marathon and nonmarathon runners applied for participation, 70 were randomly selected, and 56 entered the final analysis. Subjects were stratified according to former marathon participations: a control group (nonmarathon runners, n = 22), group 1 (1 to 4 marathons, n = 16), and group 2 (≥5 marathons, n = 18). Results were adjusted for age, training years, and average weekly endurance training hours. The mean age was 42 ± 7 years. Compared to the control group, marathon runners in groups 1 and 2 had larger left atria (25 ± 6 vs 30 ± 6 vs 34 ± 7 ml/m(2), p = 0.002) and larger right atria (27 ± 7 vs 31 ± 8 vs 35 ± 5 ml/m(2), p = 0.024). Pro-ANP levels at baseline were higher in marathon runners (1.04 ± 0.38 vs 1.42 ± 0.74 vs 1.67 ± 0.69 nmol/L, p = 0.006). Pro-ANP increased significantly in all groups after the race. In multiple linear regression analysis, marathon participation was an independent predictor of left atrial (β = 0.427, p <0.001) and right atrial (β = 0.395, p = 0.006) remodeling. In conclusion, marathon running was associated with progressive left and right atrial remodeling, possibly induced by repetitive episodes of atrial stretching. The altered left and right atrial substrate may facilitate atrial arrhythmias.
Resumo:
Abstract Objectives: To assess the reporting quality of Cochrane and non-Cochrane systematic reviews (SR) in orthodontics and to compare the reporting quality (PRISMA score) with methodological quality (AMSTAR criteria). Materials and Methods: Systematic reviews (n = 109) published between January 2000 and July 2011 in five leading orthodontic journals were identified and included. The quality of reporting of the included reviews was assessed by two authors in accordance with the PRISMA guidelines. Each article was assigned a cumulative grade based on fulfillment of the applicable criteria, and an overall percentage score was assigned. Descriptive statistics and simple and multiple linear regression analyses were undertaken. Results: The mean overall PRISMA score was 64.1% (95% confidence interval [CI], 62%-65%). The quality of reporting was considerably better in reviews published in the Cochrane Database of Systematic Reviews (P < .001) than in non-Cochrane reviews. Both multivariable and univariable analysis indicated that journal of publication and number of authors was significantly associated with the PRISMA score. The association between AMSTAR score and modified PRISMA score was also found to be highly statistically significant. Conclusion: Compliance of orthodontic SRs published in orthodontic journals with PRISMA guidelines was deficient in several areas. The quality of reporting assessed using PRISMA guidelines was significantly better in orthodontic SRs published in the Cochrane Database of Systematic Reviews.
Resumo:
INTRODUCTION: Surgical site infections (SSI) are the most common hospital-acquired infections among surgical patients, with significant impact on patient morbidity and health care costs. The Basel SSI Cohort Study was performed to evaluate risk factors and validate current preventive measures for SSI. The objective of the present article was to review the main results of this study and its implications for clinical practice and future research. SUMMARY OF METHODS OF THE BASEL SSI COHORT STUDY: The prospective observational cohort study included 6,283 consecutive general surgery procedures closely monitored for evidence of SSI up to 1 year after surgery. The dataset was analysed for the influence of various potential SSI risk factors, including timing of surgical antimicrobial prophylaxis (SAP), glove perforation, anaemia, transfusion and tutorial assistance, using multiple logistic regression analyses. In addition, post hoc analyses were performed to assess the economic burden of SSI, the efficiency of the clinical SSI surveillance system, and the spectrum of SSI-causing pathogens. REVIEW OF MAIN RESULTS OF THE BASEL SSI COHORT STUDY: The overall SSI rate was 4.7% (293/6,283). While SAP was administered in most patients between 44 and 0 minutes before surgical incision, the lowest risk of SSI was recorded when the antibiotics were administered between 74 and 30 minutes before surgery. Glove perforation in the absence of SAP increased the risk of SSI (OR 2.0; CI 1.4-2.8; p <0.001). No significant association was found for anaemia, transfusion and tutorial assistance with the risk of SSI. The mean additional hospital cost in the event of SSI was CHF 19,638 (95% CI, 8,492-30,784). The surgical staff documented only 49% of in-hospital SSI; the infection control team registered the remaining 51%. Staphylococcus aureus was the most common SSI-causing pathogen (29% of all SSI with documented microbiology). No case of an antimicrobial-resistant pathogen was identified in this series. CONCLUSIONS: The Basel SSI Cohort Study suggested that SAP should be administered between 74 and 30 minutes before surgery. Due to the observational nature of these data, corroboration is planned in a randomized controlled trial, which is supported by the Swiss National Science Foundation. Routine change of gloves or double gloving is recommended in the absence of SAP. Anaemia, transfusion and tutorial assistance do not increase the risk of SSI. The substantial economic burden of in-hospital SSI has been confirmed. SSI surveillance by the surgical staff detected only half of all in-hospital SSI, which prompted the introduction of an electronic SSI surveillance system at the University Hospital of Basel and the Cantonal Hospital of Aarau. Due to the absence of multiresistant SSI-causing pathogens, the continuous use of single-shot single-drug SAP with cefuroxime (plus metronidazole in colorectal surgery) has been validated.
Resumo:
Long-term endurance sports are associated with atrial remodeling and atrial arrhythmias. More importantly, high-level endurance training may promote right ventricular (RV) dysfunction and complex ventricular arrhythmias. We investigated the long-term consequences of marathon running on cardiac remodeling as a potential substrate for arrhythmias with a focus on the right heart. We invited runners of the 2010 Grand Prix of Bern, a 10-mile race. Of 873 marathon and nonmarathon runners who applied, 122 (61 women) entered the final analysis. Subjects were stratified according to former marathon participations: control group (nonmarathon runners, n = 34), group 1 (1 marathon to 5 marathons, mean 2.7, n = 46), and group 2 (≥6 marathons, mean 12.8, n = 42). Mean age was 42 ± 7 years. Results were adjusted for gender, age, and lifetime training hours. Right and left atrial sizes increased with marathon participations. In group 2, right and left atrial enlargements were present in 60% and 74% of athletes, respectively. RV and left ventricular (LV) dimensions showed no differences among groups, and RV or LV dilatation was present in only 2.4% or 4.3% of marathon runners, respectively. In multiple linear regression analysis, marathon participation was an independent predictor of right and left atrial sizes but had no effect on RV and LV dimensions and function. Atrial and ventricular ectopic complexes during 24-hour Holter monitoring were low and equally distributed among groups. In conclusion, in nonelite athletes, marathon running was not associated with RV enlargement, dysfunction, or ventricular ectopy. Marathon running promoted biatrial remodeling.
Resumo:
INTRODUCTION: In recent years, the surgical technique for open radical prostatectomy has evolved and increasing attention is paid to preserving anatomic structures and the impact on outcome and quality of life. METHODS: Technical aspects of nerve-sparing open radical retropubic prostatectomy (RRP) are described. Patient selection criteria and functional results are discussed, focusing on postoperative urinary continence. RESULTS: The video demonstrates the nerve-sparing open RRP and important steps are elucidated with schematic drawings. The value of nerve sparing, not only for preserving erectile function, but also for preserving urinary continence is discussed and results from our institution are presented. In our series, urinary incontinence was present in 1 of 71 patients (1%) with attempted bilateral nerve-sparing, 11 of 322 (3%) with attempted unilateral nerve-sparing, or 19 of 139 (14%) without attempted nerve-sparing surgery. In multiple logistic regression analysis, the only statistically significant factor influencing urinary continence after open RRP was attempted nerve sparing (odds ratio, 4.77; 95% confidence interval, 2.18-10.44; p=0.0001). CONCLUSIONS: Nerve-sparing surgery has a significant impact on erectile function and urinary continence and should be performed in all patients provided radical tumour resection is not compromised. For successful nerve preservation we advocate a lateral approach to the prostate to improve visualisation and simplify separation of the neurovascular bundles from the dorsolateral prostatic capsule. Bunching, ligating, and incising Santorini's plexus over the prostate and not over the sphincter ensures a bloodless surgical field. Mucosa-to-mucosa adaptation of the reconstructed bladder neck and the urethra is another important factor to be observed.
Resumo:
PURPOSE: We prospectively assessed the role of nerve sparing surgery on urinary continence after open radical retropubic prostatectomy. MATERIALS AND METHODS: We evaluated a consecutive series of 536 patients who underwent open radical retropubic prostatectomy with attempted bilateral, unilateral or no nerve sparing, as defined by the surgeon, without prior radiotherapy at a minimum followup of 1 year with documented assessment of urinary continence status. Because outlet obstruction may influence continence rates, its incidence and management was also evaluated. RESULTS: One year after surgery 505 of 536 patients (94.2%) were continent, 27 (5%) had grade I stress incontinence and 4 (0.8%) had grade II stress incontinence. Incontinence was found in 1 of 75 (1.3%), 11 of 322 (3.4%) and 19 of 139 patients (13.7%) with attempted bilateral, attempted unilateral and without attempted nerve sparing, respectively. The proportional differences were highly significant, favoring a nerve sparing technique (p <0.0001). On multiple logistic regression analysis attempted nerve sparing was the only statistically significant factor influencing urinary continence after open radical retropubic prostatectomy (OR 4.77, 95% CI 2.18 to 10.44, p = 0.0001). Outlet obstruction at the anastomotic site in 33 of the 536 men (6.2%) developed at a median of 8 weeks (IQR 4 to 12) and was managed by dilation or an endoscopic procedure. CONCLUSIONS: The incidence of incontinence after open radical retropubic prostatectomy is low and continence is highly associated with a nerve sparing technique. Therefore, nerve sparing should be attempted in all patients if the principles of oncological surgery are not compromised.
Resumo:
Class II cavities were prepared in extracted lower molars filled and cured in three 2-mm increments using a metal matrix. Three composites (Spectrum TPH A4, Ceram X mono M7 and Tetric Ceram A4) were cured with both the SmartLite PS LED LCU and the Spectrum 800 continuous cure halogen LCU using curing cycles of 10, 20 and 40 seconds. Each increment was cured before adding the next. After a seven-day incubation period, the composite specimens were removed from the teeth, embedded in self-curing resin and ground to half the orofacial width. Knoop microhardness was determined 100, 200, 500, 1000, 1500, 2500, 3500, 4500 and 5500 microm from the occlusal surface at a distance of 150 microm and 1000 microm from the metal matrix. The total degree of polymerization of a composite specimen for any given curing time and curing light was determined by calculating the area under the hardness curve. Hardness values 150 microm from the metal matrix never reached maximum values and were generally lower than those 1000 microm from the matrix. The hardest composite was usually encountered between 200 microm and 1000 microm from the occlusal surface. For every composite-curing time combination, there was an increase in microhardness at the top of each increment (measurements at 500, 2500 and 4500 microm) and a decrease towards the bottom of each increment (measurements at 1500, 3500 and 5500 microm). Longer curing times were usually combined with harder composite samples. Spectrum TPH composite was the only composite showing a satisfactory degree of polymerization for all three curing times and both LCUs. Multiple linear regression showed that only the curing time (p < 0.001) and composite material (p < 0.001) had a significant association with the degree of polymerization. The degree of polymerization achieved by the LED LCU was not significantly different from that achieved by the halogen LCU (p = 0.54).