Kaj Lindecrantz

Automatic classification of background EEG activity in healthy and sick neonates.

The overall aim of our research is to develop methods for a monitoring system to be used at neonatal intensive care units. When monitoring a baby, a range of different types of background activity needs to be considered. In this work, we have developed a scheme for automatic classification of background EEG activity in newborn babies. EEG from six full-term babies who were displaying a burst suppression pattern while suffering from the after-effects of asphyxia during birth was included along with EEG from 20 full-term healthy newborn babies. The signals from the healthy babies were divided into four behavioural states: active awake, quiet awake, active sleep and quiet sleep. By using a number of features extracted from the EEG together with Fishers linear discriminant classifier we have managed to achieve 100% correct classification when separating burst suppression EEG from all four healthy EEG types and 93% true positive classification when separating quiet sleep from the other types. The other three sleep stages could not be classified. When the pathological burst suppression pattern was detected, the analysis was taken one step further and the signal was segmented into burst and suppression, allowing clinically relevant parameters such as suppression length and burst suppression ratio to be calculated. The segmentation of the burst suppression EEG works well, with a probability of error around 4%.

Current Source for Multifrequency Broadband Electrical Bioimpedance Spectroscopy Systems. A Novel Approach

New research and clinical applications of broadband electrical bioimpedance spectroscopy arise; increasing the upper limit frequency used in the measurement systems. The current source, an essential block of an electrical bioimpedance impedance analyzer, must have a large-enough output impedance at any frequency of operation to keep the output current constant regardless of the value of working load. In this paper a novel approach to increase the output impedance of a common voltage controlled current source is proposed. The circuit is analyzed, implemented and tested. The results, remarking the significant effect of the circuit parasitic capacitances, show a clear increment of the output impedance, but smaller than the originally expected

Spectroscopy study of the dynamics of the transencephalic electrical impedance in the perinatal brain during hypoxia

Hypoxia/ischaemia is the most common cause of brain damage in neonates. Thousands of newborn children suffer from perinatal asphyxia every year. The cells go through a response mechanism during hypoxia/ischaemia, to maintain the cellular viability and, as a response to the hypoxic/ischaemic insult, the composition and the structure of the cellular environment are altered. The alterations in the ionic concentration of the intra- and extracellular and the consequent cytotoxic oedema, cell swelling, modify the electrical properties of the constituted tissue. The changes produced can be easily measured using electrical impedance instrumentation. In this paper, we report the results from an impedance spectroscopy study on the effects of the hypoxia on the perinatal brain. The transencephalic impedance, both resistance and reactance, was measured in newborn piglets using the four-electrode method in the frequency range from 20 kHz to 750 kHz and the experimental results were compared with numerical results from a simulation of a suspension of cells during cell swelling. The experimental results make clear the frequency dependence of the bioelectrical impedance, confirm that the variation of resistance is more sensitive at low than at high frequencies and show that the reactance changes substantially during hypoxia. The resemblance between the experimental and numerical results proves the validity of modelling tissue as a suspension of cells and confirms the importance of the cellular oedema process in the alterations of the electrical properties of biological tissue. The study of the effects of hypoxia/ischaemia in the bioelectrical properties of tissue may lead to the development of useful clinical tools based on the application of bioelectrical impedance technology.

Classification of burst and suppression in the neonatal electroencephalogram

Fishers linear discriminant (FLD), a feed-forward artificial neural network (ANN) and a support vector machine (SVM) were compared with respect to their ability to distinguish bursts from suppressions in electroencephalograms (EEG) displaying a burst-suppression pattern. Five features extracted from the EEG were used as inputs. The study was based on EEG signals from six full-term infants who had suffered from perinatal asphyxia, and the methods have been trained with reference data classified by an experienced electroencephalographer. The results are summarized as the area under the curve (AUC), derived from receiver operating characteristic (ROC) curves for the three methods. Based on this, the SVM performs slightly better than the others. Testing the three methods with combinations of increasing numbers of the five features shows that the SVM handles the increasing amount of information better than the other methods.

Spectral analysis of heart rate variability during desflurane and isoflurane anaesthesia in patients undergoing arthroscopy

Background: We studied the effect of desflurane (DES) and isoflurane (ISO) on heart rate variability (HRV) using power spectral analysis (PSA) of RR‐interval in 30 patients undergoing arthroscopy, prior to induction, during anaesthesia and up to 3 h of recovery. PSA can distinguish low‐frequency (LF) component and respiratory sinus arrhythmia (RSA) that are known to reflect predominantly sympathetic and parasympathetic activity, respectively.

Spectral analysis of burst periods in EEG from healthy and post-asphyctic full-term neonates

OBJECTIVE To investigate whether the periodic EEG patterns seen in healthy and sick full term neonates (trace alternant and burst suppression, respectively) have different frequency characteristics. METHODS Burst episodes were selected from the EEGs of 9 healthy and 9 post-asphyctic full-term neonates and subjected to power spectrum analysis. Powers in two bands were estimated; 0-4 and 4-30 Hz, designated low- and high-frequency activity, respectively (LFA, HFA). The spectral edge frequency (SEF) was also assessed. RESULTS In bursts, the LFA power was lower in periods of burst suppression as compared to those of trace alternant. The parameter that best discriminated between the groups was the relative amount of low- and high-frequency activity. The SEF parameter had a low sensitivity to the group differences. In healthy neonates, the LFA power was higher over the posterior right as compared to the posterior left region. CONCLUSIONS Spectral power of low frequencies differs significantly between the burst episodes of healthy and sick neonates. SIGNIFICANCE These results can be used when monitoring cerebral function in neonates.

A randomized controlled study about the use of eHealth in the home health care of premature infants

BackgroundOne area where the use of information and communication technology (ICT), or eHealth, could be developed is the home health care of premature infants. The aim of this randomized controlled study was to investigate whether the use of video conferencing or a web application improves parents’ satisfaction in taking care of a premature infant at home and decreases the need of home visits. In addition, nurses’ attitudes regarding the use of these tools were examined.MethodThirty-four families were randomized to one of three groups before their premature infant was discharged from the hospital to home health care: a control group receiving standard home health care (13 families); a web group receiving home health care supplemented with the use of a web application (12 families); a video group with home health care supplemented with video conferencing using Skype (9 families). Families and nursing staff answered questionnaires about the usefulness of ICT. In addition, semi-structured interviews were conducted with 16 families.ResultsAll the parents in the web group found the web application easy to use. 83% of the families thought it was good to have access to their child’s data through the application. All the families in the video group found Skype easy to use and were satisfied with the video calls. 88% of the families thought that video calls were better than ordinary phone calls. 33% of the families in the web group and 75% of those in the video group thought the need for home visits was decreased by the web application or Skype. 50% of the families in the web group and 100% of those in the video group thought the web application or the video calls had helped them feel more confident in caring for their child. Most of the nurses were motivated to use ICT but some were reluctant and avoided using the web application and video conferencing.ConclusionThe families were satisfied with both the web application and video conferencing. The families readily embraced the use of ICT, whereas motivating some of the nurses to accept and use ICT was a major challenge.

Attitudes among healthcare professionals towards ICT and home follow-up in chronic heart failure care

BackgroundeHealth applications for out-of-hospital monitoring and treatment follow-up have been advocated for many years as a promising tool to improve treatment compliance, promote individualized care and obtain a person-centred care. Despite these benefits and a large number of promising projects, a major breakthrough in everyday care is generally still lacking. Inappropriate organization for eHealth technology, reluctance from users in the introduction of new working methods, and resistance to information and communication technology (ICT) in general could be reasons for this. Another reason may be attitudes towards the potential in out-of-hospital eHealth applications. It is therefore of interest to study the general opinions among healthcare professionals to ICT in healthcare, as well as the attitudes towards using ICT as a tool for patient monitoring and follow-up at home. One specific area of interest is in-home follow-up of elderly patients with chronic heart failure (CHF). The aim of this paper is to investigate the attitudes towards ICT, as well as distance monitoring and follow-up, among healthcare professionals working with this patient group.MethodThis paper covers an attitude survey study based on responses from 139 healthcare professionals working with CHF care in Swedish hospital departments, i.e. cardiology and medicine departments. Comparisons between physicians and nurses, and in some cases between genders, on attitudes towards ICT tools and follow-up at home were performed.ResultsOut of the 425 forms sent out, 139 were collected, and 17 out of 21 counties and regions were covered in the replies. Among the respondents, 66% were nurses, 30% physicians and 4% others. As for gender, 90% of nurses were female and 60% of physicians were male. Internet was used daily by 67% of the respondents. Attitudes towards healthcare ICT were found positive as 74% were positive concerning healthcare ICT today, 96% were positive regarding the future of healthcare ICT, and 54% had high confidence in healthcare ICT. Possibilities for distance monitoring/follow-up are good according to 63% of the respondents, 78% thought that this leads to increased patient involvement, and 80% thought it would improve possibilities to deliver better care. Finally, 72% of the respondents said CHF patients would benefit from home monitoring/follow-up to some extent, and 19% to a large extent. However, the best method of follow-up was considered to be home visits by nurse, or phone contact.ConclusionThe results indicate that a majority of the healthcare professionals in this study are positive to both current and future use of ICT tools in healthcare and home follow-up. Consequently other factors have to play an important role in the slow penetration of out-of-hospital eHealth applications in daily healthcare practice.

AD5933-based electrical bioimpedance spectrometer. Towards textile-enabled applications

Advances on System-On-Chip and Textile technology allows the development of Textile-enabled measurement instrumentation. Textile Electrodes (Textrodes) have been proven reliable for performing Electrical Bioimpedance Spectroscopy (EBIS) measurements, and the availability of a integrated circuit impedance spectrometer, the AD5933, has allowed the implementation of small size EBIS spectrometers. In this work an AD5933-based spectrometer has been implemented, and its performance on 2R1C circuits and for tetrapolar total right side EBIS measurements has been compared against the commercially available spectrometer SFB7. The study has been focused on the working upper frequency range and the estimation of the Cole parameters required for assessment of body fluid distribution: R0 and R∞. The results indicate that AD5933-based spectrometer implemented in this work can perform accurate impedance measurements well above the upper limits recommended in the datasheet. The AD5933-EBIS presents a good performance compared with the SFB7 on the 2R1C circuit and the total right side measurements, showing a smaller error in the resistance spectrum and small deviation error in the reactance when measuring over 270 kHz. The comparison on the Cole parameters estimation obtained with the SFB7 and the AD5933-based spectrometer exhibit a difference below 1% for the estimation of R0 and R∞. Consequently the overall measurement performance shown by the implemented AD5933-based spectrometer suggests its feasible use for EBIS measurements using dry Textrodes. This is of special relevance for the proliferation of EBI-based personalized health monitoring systems for patients that require to monitor the distribution of body fluids, like in dialysis.

Textile electrodes in electrical bioimpedance measurements – a comparison with conventional Ag/AgCl electrodes

Work has been intensified around the integration of textile and measurement technology for physiological measurements in the last years. As a result nowadays it is possible to find available commercial products for cardiovascular personal healthcare monitoring. Most of the efforts have been focused in the acquisition of EKG for cardiovascular monitoring where textile electrodes have shown satisfactory performance. Electrical Bioimpedance is another type of physiological measurement that can be used for personal healthcare monitoring where the integration and the performance of the textile electrodes has not been investigated that thoroughly. In this work, the influence of the textile electrodes on the measurements and on the estimation of the Cole (R0, R∞, fC and α) and body composition (TBW, ICW, ECW and FFM) parameters has been especially addressed. Complex Spectroscopy 4-electrode wrist-to-ankle electrical bioimpedance measurements taken with conventional Ag/AgCl and textile-electrodes on customized bracelets have been compared and analyzed in the frequency range 3 to 500 kHz. The obtained results suggest that the use of textile electrodes do not influence remarkably on the complex spectral measurements neither in the estimation of Cole nor body composition parameter. In any case any possible effect introduced by the use of textile is smaller than the effect of preparing the skin by the using abrasive conductive paste.