Dataset Information

Between-centre variability in transfer function analysis, a widely used method for linear quantification of the dynamic pressure-flow relation: the CARNet study.

ABSTRACT: Transfer function analysis (TFA) is a frequently used method to assess dynamic cerebral autoregulation (CA) using spontaneous oscillations in blood pressure (BP) and cerebral blood flow velocity (CBFV). However, controversies and variations exist in how research groups utilise TFA, causing high variability in interpretation. The objective of this study was to evaluate between-centre variability in TFA outcome metrics. 15 centres analysed the same 70 BP and CBFV datasets from healthy subjects (n=50 rest; n=20 during hypercapnia); 10 additional datasets were computer-generated. Each centre used their in-house TFA methods; however, certain parameters were specified to reduce a priori between-centre variability. Hypercapnia was used to assess discriminatory performance and synthetic data to evaluate effects of parameter settings. Results were analysed using the Mann-Whitney test and logistic regression. A large non-homogeneous variation was found in TFA outcome metrics between the centres. Logistic regression demonstrated that 11 centres were able to distinguish between normal and impaired CA with an AUC>0.85. Further analysis identified TFA settings that are associated with large variation in outcome measures. These results indicate the need for standardisation of TFA settings in order to reduce between-centre variability and to allow accurate comparison between studies. Suggestions on optimal signal processing methods are proposed.

SUBMITTER: Meel-van den Abeelen AS

PROVIDER: S-EPMC4155942 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Between-centre variability in transfer function analysis, a widely used method for linear quantification of the dynamic pressure-flow relation: the CARNet study.

Meel-van den Abeelen Aisha S S AS Simpson David M DM Wang Lotte J Y LJ Slump Cornelis H CH Zhang Rong R Tarumi Takashi T Rickards Caroline A CA Payne Stephen S Mitsis Georgios D GD Kostoglou Kyriaki K Marmarelis Vasilis V Shin Dae D Tzeng Yu-Chieh YC Ainslie Philip N PN Gommer Erik E Müller Martin M Dorado Alexander C AC Smielewski Peter P Yelicich Bernardo B Puppo Corina C Liu Xiuyun X Czosnyka Marek M Wang Cheng-Yen CY Novak Vera V Panerai Ronney B RB Claassen Jurgen A H R JA

Medical engineering & physics 20140413 5

Transfer function analysis (TFA) is a frequently used method to assess dynamic cerebral autoregulation (CA) using spontaneous oscillations in blood pressure (BP) and cerebral blood flow velocity (CBFV). However, controversies and variations exist in how research groups utilise TFA, causing high variability in interpretation. The objective of this study was to evaluate between-centre variability in TFA outcome metrics. 15 centres analysed the same 70 BP and CBFV datasets from healthy subjects (n= ...[more]

PMID: 24725709

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Project description:In the search for renewable sources of energy, bioethanol stands out as a benchmark biofuel because its production is based on a proven technological platform. Bioethanol is produced mainly from the fermentation of carbohydrates derived from agricultural feedstocks by the yeast Saccharomyces cerevisiae. One of the most widely adopted strains is PE-2, a heterothallic diploid naturally adapted to the sugar cane fermentation process used in Brazil. Here we report the molecular genetic analysis of a PE-2 derived diploid (JAY270), and the complete genome sequence of a haploid derivative (JAY291). The JAY270 genome is highly heterozygous (~2 SNPs per kilobase), and has several structural polymorphisms between homologous chromosomes. These chromosomal rearrangements are confined to the peripheral regions of the chromosomes, and appear to reflect ectopic homologous recombination between repetitive DNA sequences. Despite the complex karyotype of JAY270, this diploid, when sporulated, had a high frequency of viable spores (~93%). Crosses of haploids derived from JAY270 to a haploid of the unrelated laboratory strain S288c also resulted in diploids that had good spore viability (75-95%). Thus, the rearrangements that exist near the ends of chromosomes do not impair meiosis and spore viability, as they do not span regions that contain essential genes. This observation is consistent with a model in which the peripheral regions of chromosomes represent plastic domains of the genome that are free to recombine ectopically and experiment with alternative structures that may be associated with a fitness benefit. We also explore features of the JAY270 and JAY291 genomes that help explain their high adaptation to industrial environments, exhibiting desirable phenotypes such as high cell mass production and fermentation kinetics, high temperature growth and oxidative stress tolerance. The genomic manipulation of such strains could enable the creation a new generation of industrial organisms, ideally suited for use as delivery vehicles for future bioenergy technologies.

Project description:Background Prior research has shown inconclusive findings regarding the relationship between blood pressure variability (BPV) in acute ischemic stroke (AIS) and functional outcomes. Most research has examined the connection between short-term BPV during the early 24–72 h after the occurrence of ischemic stroke and functional prognosis. We sought to determine the relationship between daily BPV at 7 days of commencement and functional outcomes during the 3 months following AIS. Methods Altogether, 633 patients with AIS admitted within 72 h of commencement were enrolled. AIS was defined as the time from the onset of symptoms to 7 days. Throughout this period, blood pressure (BP) was recorded twice daily (casual BP cuffs). The daily BPV, with standard deviation (SD) and coefficient of variation (CV), was calculated and matched to the functional results. The adverse outcome was characterized as a modified Rankin scale (mRS)≥3, which comprised the recurrence of stroke, clinical intracranial bleeding, and death. Results In total, 633 participants were included, and the incidence of adverse outcomes was 14.06% (89/633). There was a significant positive correlation between daily BPV and adverse outcomes but not between mean BP and risk. Smooth curve fitting revealed a U-shaped connection between the mean BP and adverse clinical outcomes. Multivariable logistic regression analysis showed an independent correlation between daily BPV and an adverse outcome in the top vs. bottom quartile of systolic BPV (odds ratio [OR] = 2.4, 95% confidence interval [CI]: 1.17–4.96, P = 0.018 for SD; OR = 2.4, 95% CI: 1.17–4.93, P = 0.017 for CV) during a 3-month follow-up period. Identical results have been reported for diastolic BPV. Conclusion Irrespective of BP level, elevated daily systolic BPV and diastolic BPV in AIS were associated with an increased risk of adverse outcomes within 3 months. We also discovered a U-shaped association between the mean BP and adverse clinical outcomes. These findings suggested that BPV should be a risk factor for adverse outcomes after ischemic stroke, which provided new insight into BP management strategy.

Dataset Information

Between-centre variability in transfer function analysis, a widely used method for linear quantification of the dynamic pressure-flow relation: the CARNet study.

Publications

Between-centre variability in transfer function analysis, a widely used method for linear quantification of the dynamic pressure-flow relation: the CARNet study.

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