Group sequential monitoring of years of life saved with paired censored survival data.

This research develops non-parametric methodology for sequential monitoring of paired time-to-event data when comparing years of life saved, or years where any unpleasant outcome is delayed, is of interest. The recommended family of test statistics uses integrated differences in survival estimates that are available during the study period, where adjustments are made for dependence in the survival and censoring outcomes under comparison. In the context of paired censored survival data, the joint asymptotic closed form distribution of these sequentially monitored test statistics is developed and shown to have a dependent increments structure. Simulations verifying nice operating characteristics of the proposed monitoring methods also reveal consequences of ignoring an underlying paired data structure in terms of size and power properties. A motivating example is also presented via the Early Treatment Diabetic Retinopathy Study, which did not have methods available for sequentially monitoring paired censored survival data at the time.     

Repeated apneas do not affect the hypercapnic ventilatory response in the short term

Long-term training of breath-hold diving reduces the hypercapnic ventilatory response (HCVR), an index of the CO₂ sensitivity. The aim of the present study was to elucidate whether also short-term apnea training (repeating apneas with short intervals) reduces the HCVR, thereby being one contributing factor explaining the progressively increasing breath-holding time (BHT) with repetition of apneas. Fourteen healthy volunteers performed a series of five maximal-duration apneas with face immersion and two measurements of the HCVR, using the Read rebreathing method. The BHT increased by 43% during the series of apneas (P < 0.001). However, the slope of the HCVR test was not affected by the series of apneas, being 2.52 (SD 1.27) and 2.24 (SD 1.14) l min⁻¹ mmHg⁻¹ in the control test and in the test performed within 2 min after the last apnea of the series, respectively (NS). Thus, a change in the HCVR cannot explain the observed short-term training effect on BHT.     

Comparison of hypercapnia‐based calibration techniques for measurement of cerebral oxygen metabolism with MRI

MRI may be used to measure fractional changes in cerebral oxygen metabolism via a metabolic model. One step commonly used in this measurement is calibration with image data acquired during hypercapnia, which is a state of increased CO₂ content of the blood. In this study some commonly used hypercapnia‐inducing stimuli were compared to assess their suitability for the calibration step. The following stimuli were investigated: (a) inspiration of a mixture of 4% CO₂, 21% O₂ and balance N₂; (b) 30‐s breath holding; and (c) inspiration of a mixture of 4% CO₂ and 96% O₂ (i.e., carbogen). Measurements of BOLD and cerebral blood flow made on nine subjects during the different hypercapnia‐inducing stimuli showed that each stimulus leads to a different calibration of the model. We argue that of the aforementioned stimuli, inspiration of 4% CO₂, 21% O₂ and balance N₂ should be preferred for the calibration as the other stimuli produce responses that violate assumptions of the metabolic model. Magn Reson Med 61:391–398, 2009. © 2009 Wiley‐Liss, Inc.     

Influence of film and monitor display luminance on observer performance and visual search

RATIONALE AND OBJECTIVES: The purpose of this study was to measure the influence of display luminance on detection performance and visual search behavior. The results of the study should be helpful in establishing minimally acceptable display conditions for viewing radiographs on cathode-ray tube (CRT) monitors. MATERIALS AND METHODS: Two groups of six radiologists each viewed 50 pairs of mammograms. One group viewed film images on a standard mammographic view box; the other viewed images on a high-resolution CRT monitor. Two luminance levels were studied for each display type. Observers reported on the presence or absence of masses or microcalcification clusters and on their confidence in that decision. Confidence data were analyzed by using alternative free-response receiver operating characteristic (AFROC) techniques. Eye position also was recorded as observers viewed the images. RESULTS: For both the film and monitor studies, detection performance (AFROC area under the curve) was not affected significantly by display luminance, but search behavior was. Total viewing and decision dwell times were shorter with the higher-luminance displays, especially for true-negative decisions. Significantly more fixation clusters were generated during the search of lesion-free than of lesion-containing images with the lower-luminance displays. CONCLUSION: Display luminance affects visual search performance with both film and monitor displays without affecting detection performance significantly. Higher-luminance displays yield more efficient search performance. The true-negative dwell times and number of clusters are suggestive that lower-luminance levels prolong the search and recognition of normal, lesion-free areas compared with lesion-containing areas.     

模拟跳伞着陆冲击力与冲击时间的关系

在实验室模拟条件下,研究着陆冲击力与着陆冲击时间的关系。被试者为3名年轻健康的男伞兵。当其负荷26.5k或无负荷,分别从1.0,1.5和2.0m的平台上跳下时,用高速摄影法记录他们身上的标记。计算结果表明:(1)作用在各活动节段上的着陆冲击力,随着陆冲击时间的延长而减少,作用在足部的着陆冲击力峰值与着陆冲击时间亦有相同的关系;(2)着陆冲击时间为0.08～O.26s时,上述诸力与其在0.08s时的值相比,减少40.6～64.1％;(3)作用在足部的着陆冲击力峰值与着陆冲击时间的关系曲线,与其回归方程的曲线相比,非常接近。     

How social media,training, and demographics influence online reviews across three leading review websites for spine surgeons

Background Context

The future of health care is consumer driven with a focus on outcome metrics and patient feedback. Physician review websites have grown in popularity and are guiding patients to certain health-care providers, for better or worse. No prior study has specifically evaluated Internet reviews of spine surgeons, determined if social media (SM) correlates with patient reviews, or evaluated Google as a physician review website.

Point-of-care and standard laboratory coagulation testing during cardiovascular surgery: balancing reliability and timeliness

Objective. The use of point-of-care technology has increased faster than efforts to validate its effectiveness compared to standard laboratory testing modalities. To address this issue with a current point-of-care coagulation system (HEMOCHRON® Jr, International Technidyne Corporation (ITC), Edison, NJ), we designed a study to test the hypothesis that data obtained from point-of-care coagulation equipment correlates with data obtained from standard laboratory coagulation equipment. One of the potential advantages gained using point-of-care testing is the ability to obtain more rapid results. To address this issue, turnaround time, defined as the elapsed time (in minutes) from when the sample was acquired from the patient until the investigators knew the results, was also determined. Methods. Following Human Investigation Committee approval and informed consent, a prospective study was conducted to compare results obtained from point-of-care coagulation equipment with those results obtained from standard laboratory coagulation equipment. The study was performed in three groups of patients undergoing cardiovascular surgery, each requiring different levels of anticoagulation. Results. Of the 83 patients who met the inclusion criteria, the correlation (combining data from groups 1–3) between results obtained from point-of-care and standard laboratory prothrombin time was r = 0.867, p < 0.001. The correlation (group 3) between point-of-care and standard laboratory international normalized ratio was r = 0.943, p < 0.001. The correlation (combining data from groups 1 & 2) between point-of-care and standard laboratory activated partial thromboplastin time was r = 0.825, p < 0.001. Median turnaround time for the standard laboratory was 90 minutes, with a mean turnaround time of 74 to 78 minutes, depending upon the group. In contrast, the median turnaround time for point-of-care testing was two minutes and 14 seconds. Conclusions.The results from this study population reveal that data obtained from point-of-care prothrombin time, international normalized ratio and activated partial thromboplastin time results correlate with results obtained from standard laboratory coagulation testing. The value of obtaining reliable results in a timely fashion offers a potential advantage for point-of-care testing in clinical situations, such as in the operating room, where saving time may translate into financial savings.     

应用脑电生物反馈仪诊断和治疗儿童注意力缺陷和多动症

目的:探讨应用脑电生物反馈仪诊断和治疗儿童注意力缺陷和多动症的效果。方法:以60名6-10岁儿童为研究对象。实验组30名已确诊为注意力缺陷伴多动症,对照组30名为正常儿童,两组儿童应用A620脑电生物反馈ASSESSMENT程序记录脑电图。结果:实验组与对照组儿童θ/β比值差异有显著意义,t=5.525,P<0.01。男女生的θ/β比值无明显差异。据此说明θ/β比值可作为诊断注意力缺陷的一个神经生理指标。10名例接受脑电生物反馈训练,统计表明,10次以上训练例脑功能有明显改善。结论:脑电生物反馈训练对ADHD儿童的效果是显著的,但必须坚持10次以上,才能取得成果。