Christian Popow

Effective data validation of high-frequency data: time-point-, time-interval-, and trend-based methods.

Real-time systems for monitoring and therapy planning, which receive their data from on-line monitoring equipment and computer-based patient records, require reliable data. Data validation has to utilize and combine a set of fast methods to detect, eliminate, and repair faulty data, which may lead to life-threatening conclusions. The strength of data validation results from the combination of numerical and knowledge-based methods applied to both continuously-assessed high-frequency data and discontinuously-assessed data. Dealing with high-frequency data, examining single measurements is not sufficient. It is essential to take into account the behavior of parameters over time. We present time-point-, time-interval-, and trend-based methods for validation and repair. These are complemented by time-independent methods for determining an overall reliability of measurements. The data validation benefits from the temporal data-abstraction process, which provides automatically derived qualitative values and patterns. The temporal abstraction is oriented on a context-sensitive and expectation-guided principle. Additional knowledge derived from domain experts forms an essential part for all of these methods. The methods are applied in the field of artificial ventilation of newborn infants. Examples from the real-time monitoring and therapy-planning system VIE-VENT illustrate the usefulness and effectiveness of the methods.

Cognitive functions and glycemic control in children and adolescents with type 1 diabetes.

BACKGROUND The relationship between metabolic control and cognitive function in adolescents with type 1 diabetes (DM type 1) is not clear. We compared the quality of glycemic control (GC) and cognitive measures in adolescents with DM type 1 to find out if the quality of diabetes management is related to cognitive impairment. METHOD We assessed executive functions (EFs) and other neuropsychological and psychosocial variables in 70 adolescent patients with DM type 1 and 20 age-matched controls. Patients were divided into two groups according to their last hemoglobin A1c (HbA1c): acceptable (HbA1c 5.9-8.0%, mean 6.9%, 36 patients, mean age 14 years) and non-optimal (HbA1c 8.2-11.6%, mean 9.3%, 34 patients, mean age 15.6 years). RESULTS We found impaired EFs, mainly problems of concept formation (p=0.038), cognitive flexibility (p=0.011) and anticipation (p=0.000), in the patients with DM type 1. Both groups did not differ in intelligence, most assessed EFs and adjustment to chronic illness (Youth Self-Report; YSR). Younger patients (<15 years) were cognitively less flexible. GC was worse in older patients and in patients with longer duration of the disease. We also found significant differences between patients with diabetes and controls concerning somatic complaints, internalizing problems (Child Behavior Checklist; CBCL) and social activity (CBCL and YSR). CONCLUSIONS DM type 1 is associated with cognitive deficits in adolescents independent of the quality of metabolic control and the duration of the disease. These deficits are probably related to the disease, especially in patients with early-onset diabetes.

Therapy Planning Using Qualtitative Trend Descriptions

This paper addresses a method of therapy planning applicable in the absence of an appropriate curve-fitting model. It incorporates knowledge about data points, data intervals, and expected qualitative trend description to arrive at unified qualitative descriptions of parameters (temporal data abstraction). Our approach benefits from derived qualitative values which can be used for recommending therapeutic actions as well as for assessing the effectiveness of these actions within a certain period. It results in an easily comprehensible and transparent concept of therapy planning. Furthermore, we improved the system model of data interpretation and therapy planning by using importance ranking of variables, priority lists of attainable goals, and pruning of contradictory therapy recommendations.

Development and evaluation of VIE-PNN, a knowledge-based system for calculating the parenteral nutrition of newborn infants

Calculating the daily changing composition of parenteral nutrition for small newborn infants is troublesome and time consuming routine work in neonatal intensive care. The task needs expertise and experience and is prone to inherent calculation errors. We designed VIE-PNN (Vienna Expert System for Parenteral Nutrition of Neonates), a knowledge-based system (KBS) in order to reduce daily routine work and calculation errors. VIE-PNN was redesigned several times because the clinicians accepted the system only when it saved time. The most recent version of VIE-PNN uses an Hypertext Markup Language (HTML)-based client-server architecture and is integrated into the intranet of the local patient data management system. Since more than 3 years all parenteral nutrition plans are calculated using VIE-PNN. Evaluating the systems performance and the users contentedness, we compared 50 nutrition plans calculated in parallel using VIE-PNN or a hand-held calculator, retrospectively analyzed more than 5000 nutrition plans stored in VIE-PNNs database and evaluated a user questionnaire. Nutrition plans were calculated in a mean time of 2.4 versus 7.1min using VIE-PNN or the hand-held calculator. Errors and omissions in the nutrition plans were detected in 22% versus 56% and errors in the VIE-PNNs plans occurring only with interactively changed values. Reviews of stored plans show that a mean of 4 out of 16 parameters were interactively changed. VIE-PNN was well accepted. Most important reasons for the successful operation of VIE-PNN in the daily routine work were time savings and robustness of the system.

Effects of endotracheal suctioning in high-frequency oscillatory and conventionally ventilated low birth weight neonates on cerebral hemodynamics observed by near infrared spectroscopy (NIRS)

Adverse changes in cerebral hemodynamics during endotracheal suctioning have been reported in conventionally ventilated newborns, whereas observations on the effect of endotracheal suctioning during high‐frequency ventilation have not been reported to date. The present study was designed to investigate the effect of endotracheal suctioning on cerebral hemodynamics in high‐frequency and conventionally ventilated infants. Changes in cerebral concentration of oxygenated (cO2Hb) and deoxygenated hemoglobin (cHHb) and oxidized cytochrome aa3 (cCyt.aa3) were measured by noninvasive near‐infrared spectroscopy. In an open prospective study, 26 suctioning periods in 9 high‐frequency and in 6 conventionally ventilated newborn infants were investigated. Heart rate, arterial oxygen saturation (SaO2), mean blood pressure (MABP), and transcutaneous carbon dioxide tension (TcpCO2) were monitored continuously.

Abstracting Steady Qualitative Descriptions over Time from Noisy, High-Frequency Data

On-line monitoring at neonatal intensive care units produces high volumes of data. Numerous devices generate data at high frequency (one data set every second). Both, the high volume and the quite high error-rate of the data make it essential to reach at higher levels of description from such raw data. These abstractions should improve the medical decision making. We will present a time-oriented data-abstraction method to derive steady qualitative descriptions from oscillating high-frequency data. The method contains tunable parameters to guide the sensibility of the abstraction process. The benefits and limitations of the different parameter settings will be discussed.

Using Time-Oriented Data Abstraction Methods to Optimize Oxygen Supply for Neonates

Therapy management needs sophisticated patient monitoring and therapy planning, especially in high-frequency domains, like Neonatal Intensive Care Units (NICUs), where complex data sets are collected every second. An elegant method to tackle this problem is the use of time-oriented, skeletal plans. Asgaard is a framework for the representation, visualization, and execution of such plans. These plans work on qualitative abstracted time-oriented data which closely resemble the concepts used by experienced clinicians.This papers presents the data abstraction unit of the Asgaard system. It provides a range of connectable data abstraction methods bridging the gap between the raw data collected by monitoring devices and the abstract concepts used in therapeutic plans. The usability of this data abstraction unit is demonstrated by the implementation of a controller for the automated optimization of the fraction of inspired oxygen (FiO2). The use of the time-oriented data abstraction methods results in safe and smooth adjustment actions of our controller in a neonatal care setting.

Position dependent changes of cerebral blood flow velocities in premature infants.

Abstract. The supine or prone positioning of infants has been a cause of much controversy. Recently it has been postulated that the position dependent hypoperfusion of the brainstem represents a possible cause of sudden infant death. To demonstrate position dependency and maturational changes of cerebral perfusion in premature newborn infants we investigated cerebral blood flow velocities (CBFV) in the main supratentorial and brainstem cerebral arteries. Measurements of CBFV were done with transfontanellar colour-coded Doppler sonography in the internal carotid artery (ICA), basilar artery (BA), and vertebral artery (VA) in the prone (head centered-baseline) and supine positions (maximal rotation to both sides) in 23 premature infants aged between 3–5 days of life. We performed follow-up measurements in 17 infants 7–10 days later and in 16 infants at the corrected age of 1 month. There was no difference in mean CBFVs between the prone and supine position at the first investigation. At the third investigation, CBFVs were significantly higher in the supine compared to the prone position. The CBFVs of the ICA were higher than in the BA and VA. This difference was not influenced by the body position but increased with post-natal age more in the VA (159%) than in the BA (129%) and ICA (128%). Position dependency was not seen in the ICA perfusion. In the prone position, five infants showed an incomplete steal effect in the contralateral VA. There was no significant side difference in the CBFVs of the ICA and VA, but in the resistance indices in the VA (left >right). Conclusion: in premature newborns, position dependent changes of cerebral blood flow velocity develop with maturation and are most pronounced in the vertebrobasilar system. These changes are possibly due to compression of the vertebral artery by neck movement and suggest an individual risk of brainstem perfusion deficits that may be aggravated with age and head rotation in a prone position.

Evaluating an InfoVis Technique Using Insight Reports

The evaluation of Information Visualization (InfoVis) techniques can help to identify specific strengths and weaknesses of these methods. The following article describes the results of an empirical study assessing the contribution of an interactive InfoVis method based on a spring metaphor (GRAVI), exploratory data analysis (EDA) and machine learning (ML) to ease understanding. The application domain is the psychotherapeutic treatment of anorectic young women. The three methods are supposed to support the therapists in finding the variables which influence success or failure of the therapy. To conduct the evaluation we developed a report system which helped subjects to formulate and document in a self-directed manner the insights they gained when using the three methods. The results indicate that the three methods are complementary and should be used in conjunction.

Time-Oriented Skeletal Plans: Support to Design and Execution

Skeletal plans are a powerful way to reuse existing domain-specific procedural knowledge. In the Asgaard project, a set of tasks that support the design and the execution of skeletal plans by a human executing agent other than the original plan designer are designed. The underlying requirement to develop task-specific problem-solving methods is a modeling language. Therefore, within the Asgaard project, a time-oriented, intention-based language, called Asbru, was developed. During the design phase of plans, Asbru allows to express durative actions and plans caused by durative states of an observed agent. The intentions underlying these plans are represented explicitly as temporal patterns to be maintained, achieved or avoided. We will present the underlying idea of the Asgaard project and explain the time-oriented Asbru language. Finally, we show the benefits and limitations of the time-oriented, skeletal plan representation to be applicable in real-world, high-frequency domains.