1,722,370 research outputs found
Model-Based Evaluation of Methods for Respiratory Sinus Arrhythmia Estimation
No full textOBJECTIVE: Respiratory sinus arrhythmia (RSA) refers to heart rate oscillations synchronous with respiration, and it is one of the major representations of cardiorespiratory coupling. Its strength has been suggested as a biomarker to monitor different conditions and diseases. Some approaches have been proposed to quantify the RSA, but it is unclear which one performs best in specific scenarios. The main objective of this study is to compare seven state-of-the-art methods for RSA quantification using data generated with a model proposed to simulate and control the RSA. These methods are also compared and evaluated on a real-life application, for their ability to capture changes in cardiorespiratory coupling during sleep. METHODS: A simulation model is used to create a dataset of heart rate variability and respiratory signals with controlled RSA, which is used to compare the RSA estimation approaches. To compare the methods objectively in a real-life application, regression models trained on the simulated data are used to map the estimates to the same measurement scale. RESULTS AND CONCLUSION: RSA estimates based on cross entropy, time-frequency coherence and subspace projections showed the best performance on simulated data. In addition, these estimates captured the expected trends in the changes in cardiorespiratory coupling during sleep similarly. SIGNIFICANCE: An objective comparison of methods for RSA quantification is presented to guide future analyses. Also, the proposed simulation model can be used to compare existing and newly proposed RSA estimates. It is freely accessible online
The walk-bicycle: A new assistive device for Parkinson's patients with freezing of gait?
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154274.pdf (Publisher’s version ) (Open Access)BACKGROUND: Previous studies reported a preserved ability to cycle in freezers, creating opportunities for restoring mobility and independence. However, use of a bicycle is not always feasible. Here, we investigated the effectiveness of a "walk-bicycle" in reducing freezing of gait (FOG). METHODS: Eighteen Parkinson patients with FOG performed the following tasks, each four times, with and without the walk-bicycle: (1) normal walking; (2) walking with small steps, at normal speed; (3) walking with small steps, as rapidly as possible. RESULTS: Seven patients showed FOG during walking without the walk-bicycle. In those patients, the walk-bicycle afforded a 12% reduction of time frozen (p = 0.026). In 11 patients no FOG was observed during walking without the walk-bicycle. Two of them showed FOG when using the walk-bicycle. CONCLUSIONS: The walk-bicycle may help to reduce FOG in some patients, but not in all. Future studies need to evaluate its usefulness in a home environment.01 juli 201
The value of uterine artery Doppler flow velocity in the prediction of uncomplicated pregnancies
No full textA review of the literature was performed in order to investigate whether uterine artery Doppler flow velocity at 22 weeks' pregnancy would be an appropriate test to distinguish low risk from high risk pregnancies. A search of the literature identified 65 studies on uterine artery Doppler flow velocity in relation to pregnancy complications. There remained 14 low risk population studies, involving 31,621 pregnant women. The negative predictive value in the low risk population for pre-eclampsia is 99% and for IUGR 95%. The negative predictive values for early pre-eclampsia and early IUGR with the highest risk of perinatal mortality and severe maternal morbidity are 100%. Sensitivity for severe adverse complications before 32 weeks is 89% and specificity is 90%. Likelihood ratio of a positive test is 8.9% and of a negative test is 0.12. The Dutch obstetric system is based on risk selection. Routine screening by uterine artery Doppler around 22 weeks' pregnancy might be appropriate because of the high negative predictive value for severe pregnancy complications
Assessment of respiratory effort during sleep: Esophageal pressure versus noninvasive monitoring techniques
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151935.pdf (Publisher’s version ) (Closed access)Monitoring of respiratory effort is paramount in the clinical diagnostic recording of sleep. Increased respiratory effort is a sign of obstructive sleep-disordered breathing and is associated with arousals from sleep. Respiration is the result of muscle activity that induces negative intrathoracic pressure and expansion of the thoracic and abdominal cavities. Therefore respiratory effort may be recorded from mechanical, electrical and electromechanical signals. Several techniques are available for the recording of respiratory effort. Monitoring of esophageal pressure is still the method of choice, as the pressure signal directly reflects the respiratory muscle force. However, esophageal pressure monitoring is cumbersome and may be replaced with noninvasive techniques. In order to be reliable, these techniques must be validated against the esophageal pressure standard. The present review presents a concise description of the technical principles and, if available, a comparison with esophageal pressure data, based on a systematic literature search. Most data are available on respiratory inductance plethysmography, and confirm that this technique is suitable for routine diagnostic investigation of respiratory effort during sleep. Pulse transit time, diaphragmatic electromyography, snoring loudness, suprasternal pressure monitoring, midsagittal jaw movement and forehead venous pressure monitoring are promising alternative techniques although only limited validation is available
Intensive care geneeskunde in Nederland, 1997-2001: I. Patiëntenpopulatie en resultaten van behandelingI. Patiëntenpopulatie en resultaten van behandeling
No full textObjective. To describe the patients admitted to intensive care units (ICUs) in the Netherlands between 1997-2001 and the treatment outcome. Design. Descriptive. Method. For the years 1997-2001, prospective admission and discharge data as well as all data necessary for calculating prospective severity of illness scores (e.g. APACHE II and SAPS II) were collected for all patients that were admitted to 18 ICUs participating in the Dutch National Intensive Care Evaluation (NICE). Outcome measures were ICU mortality and hospital mortality, length of hospital and ICU admission, and standardised mortality ratio (SMR). Results. Data from 55,016 admissions were registered. The median APACHE II score was 15 (P25-P75: 10-20) and the median SAPS II score was 29 (19-43). The median ICU length of admission for individual ICUs varied between 0.86 and 2.76 days. The occupied ICU capacity of individual ICUs varied between 220 and 1260 days per 100 patients admitted for non-cardiosurgical patients and between 110 and 330 days per 100 patients admitted for cardiosurgical patients. The ICU mortality and hospital mortality were 9.0% and 12.9% respectively. The mean SMR according to APACHE II was 0.95 (95% CI: 0.93-0.98). The SMR of the individual participating hospitals varied between 0.55 (95% CI: 0.37-0.80) and 1.20 (1.13-1.28). Conclusion. Hospital mortality for ICU-admitted patients in the NICE registration was 12.9%. For patients who could be evaluated with the APACHE II model, actual hospital mortality was lower than predicted by this model. Significant differences in length of admission, hospital mortality and SMR were found between individual hospitals
Pandemic influenza vaccine & narcolepsy: simulations on the potential impact of bias
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168016.pdf (Publisher’s version ) (Open Access)Several studies have identified an association between Pandemrix(TM), an AS03 adjuvanted pandemic influenza A(H1N1) vaccine, and narcolepsy, a rare and under-diagnosed sleep disorder with a median onset-to-diagnosis interval of ten years. This paper reviews potential sources of bias in published studies and aims to provide, through simulation, methodological recommendations for assessment of vaccine safety signals. Our simulation study showed that in the absence of an association between the vaccine and the outcome, presence of detection bias and differential exposure misclassification could account for elevated risk estimates. These may play a major role, particularly in alert situations when observation times are limited and the disease has a long latency period. Estimates from the case-control design were less inflated than those from the cohort design when these biases were present. Overall, these simulations provide useful insights for the design and interpretation of future studies
Response to Letter-to-Editor by M. Tenhunen and S. Himanen: "Assessment of respiratory effort during sleep: Esophageal pressure versus noninvasive monitoring techniques"
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152673.pdf (Publisher’s version ) (Closed access
External cephalic version: a safe procedure?:a systematic review of version-related risks
No full text\u3cp\u3eBackground. The Term Breech Trial has considerably increased the number of cesareans. External cephalic version (ECV) might be an effective method of lowering the rate of cesareans; its efficacy has been well established. However, although in the absence of anesthesia the risks are thought to be low, most studies have used populations too small to allow definite conclusions on version-related risks. Methods. In an attempt to make an inventory of these risks, we have systematically analyzed 44 studies, covering a total of 7377 patients from 1990 to 2002. The studies used were derived from a Medline and Embase search. Results. The most frequently reported complications were transient abnormal cardiotocography (CTG) patterns (5.7%). Persisting pathological CTG readings (0.37%) and vaginal bleeding occur rarely (0.47%). The incidence of placental abruption was even lower, at 0.12%. Fetomaternal transfusion was absent in five out of seven studies, with a mean incidence of 3.7%. Emergency cesareans were performed in 0.43% of all versions. Perinatal mortality was 0.16%. Conclusions. External cephalic version seems to be a safe procedure.\u3c/p\u3
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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