bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crooked‐line 2D seismic reflection imaging in crystalline terrains: Part 2, migration
Authors: Nedimović Mladen R. , West Gordon F. 
Published: March 2003

Seismic reflection surveys are frequently conducted over very complicated geological structure, but surveying often must be confined to existing crooked roads or tracks. Typically, data from such 2D crooked‐line surveys are processed using standard common midpoint (CMP) stacking techniques to obtain a 2D time section which is then 2D migrated. In Part I, we show that a reflector dip component across the processing line can cause serious problems for standard CMP stacking. We also propose a supplementary processing step in which cross‐dip is determined locally and cross‐dip moveout (CDMO) is removed from data to form an optimum cross‐dip stack. However, a crooked‐line survey is really a swath 3D survey, and ideally we would like to obtain a 3D image of reflectivity surrounding the profile. Here we investigate the potential of 3D prestack Kirchhoff migration to directly image all observed reflections; i.e., we attempt to construct a 3D image volume of all reflectors viewed by the survey. Because reflectors that face away from the acquisition line cannot return much wave energy from available sources to available receivers, they cannot be imaged even if they lie directly beneath the survey profile. Tests show that the cross‐profile spread of trace midpoints usually is sufficient to provide a useful degree of cross‐line positioning of reflection points. A very helpful image volume is thus obtained. Kirchhoff 3D prestack migration is computationally laborious. A much quicker but less complete method is to create the 3D migrated image volume from the 2D optimum cross‐dip stack and the associated set of cross‐dips. Robustness of migration methods to time errors in the prestack data traces such as poorly corrected statics is also an issue. Tests show that in difficult cases, particularly where only 2D processing is warranted, migration of trace absolute amplitude rather than standard phase data may lead to a superior result.
Seismic trace interpolation in the Fourier transform domain
Authors: Gülünay Necati 
Published: March 2003

A data adaptive interpolation method is designed and applied in the Fourier transform domain (f‐k or f‐kx‐kyfor spatially aliased data. The method makes use of fast Fourier transforms and their cyclic properties, thereby offering a significant cost advantage over other techniques that interpolate aliased data.The algorithm designs and applies interpolation operators in the f‐k (or f‐kx‐kydomain to fill zero traces inserted in the data in the t‐x (or t‐x‐y) domain at locations where interpolated traces are needed. The interpolation operator is designed by manipulating the lower frequency components of the stretched transforms of the original data. This operator is derived assuming that it is the same operator that fills periodically zeroed traces of the original data but at the lower frequencies, and corresponds to the f‐k (or f‐kx‐kydomain version of the well‐known f‐x (or f‐x‐y) domain trace interpolators.The method is applicable to 2D and 3D data recorded sparsely in a horizontal plane. The most common prestack applications of the algorithm are common‐mid‐point domain shot interpolation, source‐receiver domain shot interpolation, and cable interpolation.
Latest views of the sparse Radon transform
Authors: Trad Daniel , Ulrych Tadeusz , Sacchi Mauricio 
Published: March 2003

The Radon transform (RT) suffers from the typical problems of loss of resolution and aliasing that arise as a consequence of incomplete information, including limited aperture and discretization. Sparseness in the Radon domain is a valid and useful criterion for supplying this missing information, equivalent somehow to assuming smooth amplitude variation in the transition between known and unknown (missing) data. Applying this constraint while honoring the data can become a serious challenge for routine seismic processing because of the very limited processing time available, in general, per common midpoint. To develop methods that are robust, easy to use and flexible to adapt to different problems we have to pay attention to a variety of algorithms, operator design, and estimation of the hyperparameters that are responsible for the regularization of the solution. In this paper, we discuss fast implementations for several varieties of RT in the time and frequency domains. An iterative conjugate gradient algorithm with fast Fourier transform multiplication is used in all cases. To preserve the important property of iterative subspace methods of regularizing the solution by the number of iterations, the model weights are incorporated into the operators. This turns out to be of particular importance, and it can be understood in terms of the singular vectors of the weighted transform. The iterative algorithm is stopped according to a general cross validation criterion for subspaces. We apply this idea to several known implementations and compare results in order to better understand differences between, and merits of, these algorithms.
Amiodarone and Bretylium in the Treatment of Hypothermic Ventricular Fibrillation in a Canine Model
Authors: Stoner Jason , Martin Gerard , O'Mara Kevin , Ehlers Joseph , Tomlanovich Michael 
Published: March 2003

AbstractRefractory ventricular fibrillation (VF) is a complication of severe hypothermia. Despite mixed experimental data, some authors view bretylium as the drug of choice in hypothermic VF. Bretylium was removed from Advanced Cardiac Life Support guidelines, and, to date, efficacy of amiodarone in hypothermia is unknown. Objectives: To compare defibrillation rates from hypothermic VF after drug therapy with amiodarone, bretylium, and placebo. Methods: This was a randomized, blinded, and placebo‐controlled laboratory experiment. Thirty anesthetized dogs were mechanically ventilated and instrumented to monitor coronary perfusion pressure (CPP), rectal core temperature, and electrocardiogram (ECG). Animals were cooled to 22°C or the onset of spontaneous VF. Ventricular fibrillation was induced as needed with a transthoracic AC current. Cardiopulmonary resuscitation (CPR) was initiated and animals were randomized (n= 10 each group) to receive amiodarone 10 mg/kg (A), bretylium 5 mg/kg (B), or placebo (P) intravenously. CPR was continued while monitoring for chemical defibrillation. Rewarming was limited to removal from the cold environment. After 10 minutes, up to three escalating defibrillatory shocks were administered. Hemodynamic monitoring continued after resuscitation. Return of spontaneous circulation (ROSC) was defined as a sustainable ECG rhythm generating a corresponding arterial pressure tracing lasting a minimum of 15 minutes. Sample size permitted 80% power to detect a 60% difference in conversion rate between groups. Results: CPR was adequate based on CPP > 15 mm Hg in all animals. Mean (±SD) CPP was 35.3 ± 18.8 mm Hg with an overall lower trend in the amiodarone group (p = 0.06). Baseline variables were similar between groups. No instance of chemical defibrillation was noted. There was no significant difference in ROSC rates between groups. Resuscitation rates were: amiodarone = 1/10, bretylium = 4/10, and placebo = 3/10 (p = 0.45). Conclusions: In this model of severe hypothermic VF, neither amiodarone nor bretylium was significantly better than placebo in improving the resuscitation rate.
A Randomized Controlled Trial of Intravenous Aminophylline for Atropine‐resistant Out‐of‐hospital Asystolic Cardiac Arrest
Authors: Mader Timothy J. , Smithline Howard A. , Durkin Lou , Scriver Geoffrey 
Published: March 2003

Abstract Objectives: Myocardial ischemia, during cardiopulmonary arrest, can lead to atropine‐resistant bradyasystole from interstitial accumulation of endogenous adenosine. Aminophylline is a nonspecific adenosine receptor antagonist capable of reversing ischemia‐induced bradyasystole in a variety of settings. The hypothesis of this study was that aminophylline improves the rate of return of spontaneous circulation (ROSC) in atropine‐resistant asystolic out‐of‐hospital cardiac arrest when used early in the resuscitation effort. Methods: This was a prospective, randomized, double‐blinded, placebo‐controlled trial set in an urban emergency medical services system serving a population of 250,000. All non‐pregnant, normothermic adults suffering nontraumatic out‐of‐hospital cardiac arrest (February 1999 to August 2000) with asystole were eligible. Patients remaining in asystole after initial doses of epinephrine and atropine received either aminophylline 250 mg or matching placebo as a bolus injection through a peripheral intravenous line. All other aspects of the attempted resuscitation proceeded in accordance with standard Advanced Cardiac Life Support (ACLS) guidelines. A sample size of 102 patients was calculated to yield a power of 80% to show an absolute improvement of 25% in ROSC. The aminophylline and control groups were compared by calculating 95% confidence intervals (95% CIs) and the data were modeled using logistic regression. Results: The investigators enrolled 112 consecutive patients. One subject was dropped prior to analysis because of missing data. Data for 111 patients were analyzed on an intention‐to‐treat basis. Baseline characteristics were similar for the two groups. Comparing the control and aminophylline groups, ROSC was achieved in 15.6% (95% CI = 6% to 29%) and 22.7% (95% CI = 13% to 35%), while reversal of asystole occurred in 26.7% (95% CI = 15% to 42%) and 40.9% (95% CI = 29% to 54%), respectively. Group allocation had an odds ratio of 1.8 (95% CI = 0.6 to 5.3) for ROSC. Witnessed arrest was an independent predictor of outcome with an odds ratio of 3.8 (95% CI = 1.3 to 11.2). Conclusions: Addition of aminophylline appears to be a promising new intervention in the ACLS treatment of atropine‐resistant asystolic out‐of‐hospital cardiac arrest.
Uncovering Heart Failure in Patients with a History of Pulmonary Disease: Rationale for the Early Use of B‐type Natriuretic Peptide in the Emergency Department
Authors: McCullough Peter A. , Hollander Judd E. , Nowak Richard M. , Storrow Alan B. , Duc Philippe , Omland Torbjørn , McCord James , Herrmann Howard C. , Steg Philippe G. , Westheim Arne , Knudsen Cathrine Wold , Abraham William T. , Lamba Sumant , Wu Alan H.B. , Perez Alberto , Clopton Paul , Krishnaswamy Padma , Kazanegra Radmila , Maisel Alan S. 
Published: March 2003

AbstractPlasma B‐type natriuretic peptide (BNP) can reliably identify acute congestive heart failure (CHF) in patients presenting to the emergency department (ED) with acute dyspnea. Heart failure, asthma, and chronic obstructive pulmonary disease (COPD) are syndromes where dyspnea and wheezing are overlapping signs, and hence, these syndromes are often difficult to differentiate. Objective: To determine whether BNP can distinguish new‐onset heart failure in patients with COPD or asthma presenting with dyspnea to the ED. Methods: The BNP Multinational Study was a seven‐center prospective study of 1,586 adult patients presenting to the ED with acute dyspnea who had blinded BNP levels measured on arrival with a rapid, point‐of‐care device. This study evaluated the 417 patients with no previous history of heart failure and a history of asthma or COPD as a subgroup from the 1,586 adult patients in the BNP Multinational Study. The reference standard for CHF was adjudicated by two independent cardiologists, also blinded to BNP results, who reviewed all clinical data and standardized CHF scores. Results: A total of 417 subjects (mean age 62.2 years, 64.4% male) had a history of asthma or COPD without a history of CHF. Of these, 87/417 (20.9%, 95% CI = 17.1% to 25.1%) were found to have CHF as the final adjudicated diagnosis. The emergency physicians identified a minority, 32/87 (36.8%), of these patients with CHF. The mean BNP values (± SD) were 587.0 ± 426.4 and 108.8 ± 221.3 pg/mL for those with and without CHF (p < 0.0001). At a cutpoint of 100 pg/mL, BNP had the following decision statistics: sensitivity 93.1%, specificity 77.3%, positive predictive value 51.9%, negative predictive value 97.7%, accuracy 80.6%, positive likelihood ratio 4.10, and negative likelihood ratio 0.09. If BNP would have been added to clinical judgment (high ≥ 80% probability of CHF), at a cutpoint of 100 pg/mL, 83/87 (95.4%) of the CHF subjects would have been correctly diagnosed. Multivariate analysis found BNP to be the most important predictor of CHF (OR = 12.1, 95% CI = 5.4 to 27.0, p < 0.0001). In the 87 subjects found to have CHF, 39.0%, 22.2%, and 54.8% were taking angiotensin‐converting enzyme inhibitors (ACEIs), beta‐blockers (BBs), and diuretics on a chronic basis, respectively. Conclusions: The yield of adding routine BNP testing in patients with a history of asthma or COPD in picking up newly diagnosed CHF is approximately 20%. This group of patients presents a substantial therapeutic opportunity for the initiation and chronic administration of ACEI and BB therapy, as well as other CHF management strategies.
Can Electrocardiographic Criteria Predict Adverse Cardiac Events and Positive Cardiac Markers?
Authors: Blomkalns Andra L. , Lindsell Christopher J. , Chandra Abhinav , Osterlund Mary E. , Gibler W. Brian , Pollack Charles V. , Tiffany Brian R. , Hollander Judd E. , Hoekstra James W. 
Published: March 2003

Abstract Objectives: To determine electrocardiogram (ECG) predictors of positive cardiac markers and short‐term adverse cardiac events in an undifferentiated chest pain population presenting to emergency departments (EDs). The authors hypothesized that specific ECG findings, other than those previously identified in higher‐risk populations, would be predictive of cardiac outcomes and positive cardiac markers. Methods: This study used data from a prospectively collected, retrospectively analyzed Internet‐based data registry of undifferentiated chest pain patients (i*trACS). Logistic regression modeling was performed to determine the ECG findings that were predictive of 1) positive cardiac markers and 2) short‐term adverse cardiac events. Results: ST‐segment elevation (STE), ST‐segment depression (STD), pathological Q‐waves (PQW), and T‐wave inversion were associated with increased odds of percutaneous coronary intervention or catheterization, myocardial infarction, or coronary artery bypass grafting. The odds of creatine kinase–MB (CK‐MB) measuring positive were increased if STE, STD, or PQW were present [odds ratio (OR) 2.495, 2.582, and 1.295, respectively]. A right bundle branch block tended to decrease the odds of CK‐MB measuring positive (OR 0.658). A similar pattern of results was observed for troponin I (OR 3.608 for STE, 3.72 for STD, 1.538 for PQW). Troponin T showed an increased odds of measuring positive if any of STE, STD, left bundle branch block, or T‐wave inversion were evident (OR 2.313, 2.816, 1.80, and 1.449, respectively). Conclusions: Initial ECG criteria can be used to predict short‐term cardiac outcomes and positive cardiac markers. These findings can be important aids in the risk‐stratification and aggressive treatment regimens of chest pain patients presenting to EDs.
Visual Analog Pain Scores Do Not Define Desire for Analgesia in Patients with Acute Pain
Authors: Blumstein Howard A. , Moore Dave 
Published: March 2003

AbstractIncreased attention to improving the provision of analgesia has led to calls for increased use of pain measurement systems, including visual analog scales, which have not been validated for use in clinical care. Objective: To evaluate the ability of the visual analog scale to differentiate between patients with acute, painful conditions requiring pain medication, and those not requiring analgesia. Methods: This was a prospective, observational study of a convenience sample of patients with acute pain. Subjects were asked about their desire for medication. Visual analog scale pain scores were determined. Results: One hundred four patients participated. Patients requesting pain medication had a mean visual analog scale score of 66. The mean score for those not requesting medication was 45. The difference between the means was 21 [95% confidence interval (95% CI) for difference between the means was 10.7]. The area under the receiver operating characteristic curve for the visual analog scale was 0.72 (95% CI = 0.61 to 0.82). Conclusions: The visual analog scale cannot adequately discriminate between those patients who do and do not desire analgesia.
Nebulized Fentanyl for Relief of Abdominal Pain
Authors: Bartfield Joel M. , Flint Robert D. , McErlean Mara , Broderick John 
Published: March 2003

Abstract Objective: To compare the efficacies of nebulized vs. intravenous fentanyl for the relief of abdominal pain.Methods: This randomized, double‐blind, double‐placebo‐controlled study compared nebulized and intravenous fentanyl (1.5 μg/kg). Group I received intravenous fentanyl and nebulized saline. Group II received nebulized fentanyl and intravenous saline. Pain scores were measured at baseline and at 15 and 30 minutes after the study drug, using a 100‐mm visual analog scale. Thirty minutes after the study drug, the subjects were offered rescue medication. The groups were compared for changes in pain scores at 30 minutes (primary outcome, t‐test), changes in pain scores at 15 minutes (t‐test), and need for rescue medication (Fisher's exact test). Significance was defined as p < 0.05. Results: Fifty subjects (24 group I, 26 group II) were enrolled. The groups were similar with respect to mean baseline pain (72 mm group I, 74 mm group II) and demographics. A statistically significant difference in changes in pain scores at 15 minutes favoring group I (25 mm vs. 10 mm, p = 0.005) was not evident by 30 minutes (25 mm vs. 16 mm, p = 0.24). The groups were not different with respect to need for rescue medication (50% in group I compared with 69% in group II, p = 0.25). Conclusions: Nebulized fentanyl provides comparable analgesia to that of intravenous fentanyl.
Evaluation of Emergency Medicine Resident Death Notification Skills by Direct Observation
Authors: Benenson Ronald S. , Pollack Marc L. 
Published: March 2003

AbstractEmergency physicians commonly perform death notifications. Physician training in death notification has been limited. Resident physicians are rarely evaluated in their performance of death notifications. Objective: To evaluate death notification skills by direct observation of actual notifications performed by trained emergency medicine (EM) residents. Methods: This was a prospective, observational study of EM resident death notification performance. EM residents received training and then were directly observed and evaluated by trained evaluators during actual death notifications in a 64,000‐visit community teaching hospital emergency department. Results: There were 327 evaluations of 70 different EM residents. Overall performance evaluations were 55% excellent, 40% satisfactory, and 5% unsatisfactory. Third‐year EM residents and female EM residents were more likely to be rated excellent. Conclusions: Death notification is a skill that can be evaluated like other EM skills. Trained EM residents performed well in actual death notifications when directly observed and evaluated. Senior residents and female residents were more likely to be rated excellent.
A Brief Risk‐stratification Tool to Predict Repeat Emergency Department Visits and Hospitalizationsin Older Patients Discharged from the Emergency Department
Authors: Meldon Stephen W. , Mion Lorraine C. , Palmer Robert M. , Drew Barbara L. , Connor Jason T. , Lewicki Linda J. , Bass David M. , Emerman Charles L. 
Published: March 2003

Abstract Objectives: To evaluate the predictive ability of a simple six‐item triage risk screening tool (TRST) to identify elder emergency department (ED) patients at risk for ED revisits, hospitalization, or nursing home (NH) placement within 30 and 120 days following ED discharge. Methods: Prospective cohort study of 650 community‐dwelling elders (age 65 years or older) presenting to two urban academic EDs. Subjects were prospectively evaluated with a simple six‐item ED nursing TRST. Participants were interviewed 30 and 120 days post‐ED index visit and the utilization of EDs, hospitals, or NHs was recorded. Main outcome measurement was the ability of the TRST to predict the composite endpoint of subsequent ED use, hospital admission, or NH admission at 30 and 120 days. Individual outcomes of ED use, hospitalization, and NH admissions were also examined. Results: Increasing cumulative TRST scores were associated with significant trends for ED use, hospital admission, and composite outcome at both 30 and 120 days (p < 0.0001 for all, except 30‐day ED use, p = 0.002). A simple, unweighted five‐item TRST (“lives alone” item removed after logistic regression modeling) with a cut‐off score of 2 was the most parsimonious model for predicting composite outcome (AUC = 0.64) and hospitalization at 30 days (AUC = 0.72). Patients defined as high‐risk by the TRST (score ≥ 2) were significantly more likely to require subsequent ED use (RR = 1.7; 95% CI = 1.2 to 2.3), hospital admission (RR = 3.3; 95% CI = 2.2 to 5.1), or the composite outcome (RR = 1.9; 95% CI 1.7 to 2.9) at both 30 days and 120 days than the low‐risk cohort. Conclusions: Older ED patients with two or more risk factors on a simple triage screening tool were found to be at significantly increased risk for subsequent ED use, hospitalization, and nursing home admission.
Rapid Two‐stage Emergency Department Intervention for Seniors: Impact on Continuity of Care
Authors: McCusker Jane , Dendukuri Nandini , Tousignant Pierre , Verdon Josée , Poulin de Courval Louise , Belzile Eric 
Published: March 2003

Abstract Objectives: A two‐stage intervention comprising screening and a brief standardized nursing assessment and referral, for emergency department (ED) patients aged 65 years and over, reduced the rate of functional decline four months after the visit, without increasing societal costs. In this study, the authors investigated the effects of the intervention on the process of care at, and during the month after, the ED visit. Methods: Patients at four Montreal hospital EDs were randomized by day of visit to the intervention or to usual care. Patients admitted to the hospital were excluded. Measures of process of care included: referrals and visits to the primary physician and to the local community health center, for home care or other services, and return ED visits. Data sources included hospital charts, patient questionnaires, and provincial administrative databases. Results: The study sample included 166 intervention and 179 control group patients ready for discharge from the ED. Intervention group patients were more likely to have a chart‐documented referral to their local community health center [adjusted odds ratio (OR) 4.0, 95% confidence interval (95% CI) = 1.7 to 9.5] and their primary physician [adjusted OR 1.9, 95% CI = 1.0 to 3.4], and to have received home care services one month after the ED visit [adjusted OR 2.3, 95% CI = 1.1 to 5.1]. Unexpectedly, they were also more likely to make a return visit to the ED [adjusted OR 1.6, 95% CI = 1.0 to 2.6]. Conclusions: The beneficial outcomes of the intervention appear to result primarily from the early provision of home care rather than early contact with the primary physician.