Glycocalyx Sensing with a Mathematical Model of Acoustic Shear Wave Biosensor.

The article deals with an idea of exploiting an acoustic shear wave biosensor for investigating the glycocalyx, a polysaccharide polymer molecule layer on the endothelium of blood vessels that, according to recent studies, plays an important role in protecting against diseases. To test this idea, a mathematical model of an acoustic shear wave sensor and corresponding software developed earlier for proteomic applications are used. In this case, the glycocalyx is treated as a layer homogenized over the thin polymer "villi". Its material characteristics depend on the density, thickness, and length of the villi and on the viscous properties of the surrounding liquid (blood plasma). It is proved that the model used has a good sensitivity to the above parameters of the villi and blood plasma. Numerical experiments performed using real data collected retrospectively from premature infants show that the use of acoustic shear wave sensors may be a promising approach to investigate properties of glycocalyx-like structures and their role in prematurity.

Modeling of the cerebral blood circulation in a capillary network accounting for the influence of the endothelial surface layer.

BACKGROUND AND OBJECTIVE: The paper describes a mathematical model of blood flow in capillaries with accounting for the endothelial surface layer (ESL). METHOD: The influence of ESL is modeled by a boundary layer with zero flow velocity. Finite element modeling and an analytical approach based on the homogenization of the core region of blood flow occupied by erythrocytes are developed to describe the resistance of a capillary. The reliability of the results obtained is verified for different values of the discharge hematocrit and vessel diameter using known in vivo data. RESULTS: The proposed approach is applied to the numerical simulation of blood circulation in a capillary network of the germinal matrix of infants born at 25 gestational weeks. The influence of the hematocrit level and effective thickness of ESL on the resistance of the capillary network of the germinal matrix of preterm infants is studied. It was found that a decrease in the effective thickness of ESL in the capillary network (and/or a decrease in the hematocrit) leads to reducing the resistance of the capillary network. CONCLUSION: A decrease in the effective thickness of ESL in the capillary network leads to an increase in the pressure drop in arterioles, which may be considered as an additional risk factor for hemorrhages in fragile blood vessels within the germinal matrix.

Accounting for arterial and capillary blood gases for calculation of cerebral blood flow in preterm infants.

One of the most feared neurological complications of premature birth is intraventricular hemorrhage, frequently triggered by fluctuations in cerebral blood flow (CBF). Although several techniques for CBF measurement have been developed, they are not part of clinical routine in neonatal intensive care. A promising tool for monitoring of CBF is its numerical assessment using standard clinical parameters such as mean arterial pressure, carbon dioxide partial pressure (pCO2) and oxygen partial pressure (pO2). A standard blood gas analysis is performed on arterial blood. In neonates, capillary blood is widely used for analysis of blood gas parameters. The purpose of this study was the assessment of differences between arterial and capillary analysis of blood gases and adjustment of the mathematical model for CBF calculation to capillary values. The statistical analysis of pCO2 and pO2 values collected from 254 preterm infants with a gestational age of 23-30 weeks revealed no significant differences between arterial and capillary pCO2 and significantly lower values for capillary pO2. The estimated mean differences between arterial and capillary pO2 of 15.15 mmHg (2.02 kPa) resulted in a significantly higher CBF calculated for capillary pO2 compared to CBF calculated for arterial pO2. Two methods for correction of capillary pO2 were proposed and compared, one based on the mean difference and another one based on a regression model. CONCLUSION: Capillary blood gas analysis with correction for pO2 as proposed in the present work is an acceptable alternative to arterial sampling for the assessment of CBF. WHAT IS KNOWN: • Arterial blood analysis is the gold standard in clinical practice. However, capillary blood is widely used for estimating blood gas parameters. • There is no significant difference between the arterial and capillary pCO2 values, but the capillary pO2 differs significantly from the arterial one. WHAT IS NEW: • The lower capillary pO2 values yield significantly higher values of calculated CBF compared to CBF computed from arterial pO2 measurements. • Two correction methods for the adjustment of capillary pO2 to arterial pO2 that made the difference in the calculated CBF insignificant have been proposed.

Mathematical modeling of the hematocrit influence on cerebral blood flow in preterm infants.

Premature birth is one of the most important factors increasing the risk for brain damage in newborns. Development of an intraventricular hemorrhage in the immature brain is often triggered by fluctuations of cerebral blood flow (CBF). Therefore, monitoring of CBF becomes an important task in clinical care of preterm infants. Mathematical modeling of CBF can be a complementary tool in addition to diagnostic tools in clinical practice and research. The purpose of the present study is an enhancement of the previously developed mathematical model for CBF by a detailed description of apparent blood viscosity and vessel resistance, accounting for inhomogeneous hematocrit distribution in multiscale blood vessel architectures. The enhanced model is applied to our medical database retrospectively collected from the 254 preterm infants with a gestational age of 23-30 weeks. It is shown that by including clinically measured hematocrit in the mathematical model, apparent blood viscosity, vessel resistance, and hence the CBF are strongly affected. Thus, a statistically significant decrease in hematocrit values observed in the group of preterm infants with intraventricular hemorrhage resulted in a statistically significant increase in calculated CBF values.

Assessing haemorrhage-critical values of cerebral blood flow by modelling biomechanical stresses on capillaries in the immature brain.

The development of intraventricular haemorrhages (IVH) in preterm newborns is triggered by a disruption of the vessels responsible for cerebral microcirculation. Analysis of the stresses exerted on vessel walls enables the identification of the critical values of cerebral blood flow (CBF) associated with the development of IVH in preterm infants. The purpose of the present study is the estimation of these critical CBF values using the biomechanical stresses obtained by the finite element modelling of immature brain capillaries. The properties of the endothelial cells and basement membranes employed were selected on the basis of published nanoindentation measurements using atomic force microscopes. The forces acting on individual capillaries were derived with a mathematical model that accounts for the peculiarities of microvascularity in the immature brain. Calculations were based on clinical measurements obtained from 254 preterm infants with the gestational age ranging from 23 to 30 weeks, with and without diagnosis of IVH. No distinction between the affected and control groups with the gestational age of 23 to 26 weeks was possible. For infants with the gestational age of 27 to 30 weeks, the CBF value of 17.03 ml/100 g/min was determined as the critical upper value, above which the likelihood of IVH increases.

Nonstationary Model of Oxygen Transport in Brain Tissue.

The paper addresses the mathematical study of a nonstationary continuum model describing oxygen propagation in cerebral substance. The model allows to estimate the rate of oxygen saturation and stabilization of oxygen concentration in relatively large parts of cerebral tissue. A theoretical and numerical analysis of the model is performed. The unique solvability of the underlying initial-boundary value problem for a system of coupled nonlinear parabolic equations is proved. In the numerical experiment, the tissue oxygen saturation after hypoxia is analyzed for the case when a sufficient amount of oxygen begins to flow into the capillary network. A fast stabilization of the tissue oxygen concentration is demonstrated. The reliability of the results of the numerical simulation is discussed.

Machine learning models for identifying preterm infants at risk of cerebral hemorrhage.

Intracerebral hemorrhage in preterm infants is a major cause of brain damage and cerebral palsy. The pathogenesis of cerebral hemorrhage is multifactorial. Among the risk factors are impaired cerebral autoregulation, infections, and coagulation disorders. Machine learning methods allow the identification of combinations of clinical factors to best differentiate preterm infants with intra-cerebral bleeding and the development of models for patients at risk of cerebral hemorrhage. In the current study, a Random Forest approach is applied to develop such models for extremely and very preterm infants (23-30 weeks gestation) based on data collected from a cohort of 229 individuals. The constructed models exhibit good prediction accuracy and might be used in clinical practice to reduce the risk of cerebral bleeding in prematurity.

Assessing key clinical parameters before and after intraventricular hemorrhage in very preterm infants.

Intraventricular cerebral hemorrhage (IVH) is one of the most severe complications of premature birth, potentially leading to lifelong disability. The purpose of this paper is the assessment of the evolution of three of the most relevant parameters, before and after IVH: mean arterial pressure (MAP), arterial carbon dioxide pressure (pCO2), and cerebral blood flow (CBF). Clinical records of 254 preterm infants with a gestational age of 23-30 weeks, with and without a diagnosis of IVH, were reviewed for MAP and arterial pCO2 in the period up to 7 days before and 3 days after IVH or during the first 10 days of life in cases without IVH.Conclusion: A statistically significant increase in pCO2 and decrease in MAP in patients with IVH compared with those without were detected. Both the mean values and the mean absolute deviations of CBF were computed in this study, and the latter was significantly higher than in control group. High deviations of CBF, as well as hypercapnia and hypotension, are likely to contribute to the rupture of cerebral blood vessels in preterm infants, and consequently, to the development of IVH.What is Known:• The origin of IVH is multifactorial, but mean arterial pressure, carbon dioxide partial pressure, and cerebral blood flow are recognized as the most important parameters.• In premature infants, the autoregulation mechanisms are still underdeveloped and cannot compensate for cerebral blood flow fluctuations.What is New:• The numerical simulation of CBF is shown to be a promising approach that may be useful in the care of preterm infants.• The mean values of CBF before and after IVH in the affected group were similar to those in the control group, but the mean absolute deviations of CBF in the affected group before and after IVH were significantly higher than that in the control group.

Accounting for Tube Hematocrit in Modeling of Blood Flow in Cerebral Capillary Networks.

The aim of this paper consists in the derivation of an analytic formula for the hydraulic resistance of capillaries, taking into account the tube hematocrit level. The consistency of the derived formula is verified using Finite Element simulations. Such an effective formula allows for assigning resistances, depending on the hematocrit level, to the edges of networks modeling biological capillary systems, which extends our earlier models of blood flow through large capillary networks. Numerical simulations conducted for large capillary networks with random topologies demonstrate the importance of accounting for the hematocrit level for obtaining consistent results.

Extended model of impaired cerebral autoregulation in preterm infants: Heuristic feedback control.

Cerebral autoregulation is the ability to keep almost constant cerebral blood flow (CBF) for some range of changing the mean arterial pressure (MAP). In preterm infants, this range is usually very small, even absent, and a passive (linear) dependence of CBF on MAP is observed. Also, variations of the partial CO2 pressure and intracranial/venous pressure result in fluctuations of CBF. The absence of cerebral autoregulation may be a cause of intracranial hemorrhages due to instability of cerebral blood vessels, especially in the so-called germinal matrix which exists in a developing brain from 22 to 32 weeks of gestation. In the current paper, a mathematical model of impaired cerebral autoregulation is extended compared with previous works of the authors, and a heuristic feedback control that is able to keep deviations from a nominal CBF within a reasonable range is proposed. Viability theory is used to prove that this control can successfully work against a wide range of disturbances.

Postnatal Paraclinical Parameters Associated to Occurrence of Intracerebral Hemorrhage in Preterm Infants.

Intracerebral hemorrhage (ICH) is the most frequent complication in postnatal development of preterm infants. The purpose of the present work is the statistical evaluation of seven standard paraclinical parameters and their association to the development of ICH. Clinical records of 265 preterm infants with gestational age (GA) 23 to 30 weeks were analyzed. According to ICH status, patients were divided into control (without ICH) and affected (with ICH) groups. Mean values of paraclinical parameters at each week of gestation were compared. Different ICH grades, periods before and after ICH were considered separately. Lower hematocrit, SaO2, and pH were statistically significant for preterm infants with 23 to 30 weeks GA and diagnosis of ICH relative to infants without ICH. Additionally, for preterm infants with 27 to 30 weeks GA, higher C-reactive protein, as well as lower values of thrombocytes were associated with the occurrence of ICH. Preterm infants with 23 to 26 weeks GA showed C-reactive protein values similar to those in the group without ICH and lower levels of thrombocytes after bleeding. Significant differences in paraclinical parameters between preterm infants with and without ICH may constitute useful indicators for closer clinical observation of preterm infants at risk of ICH.

Piano jacket for perceiving and playing music for patients with cerebral palsy.

PURPOSE: Patients with cerebral palsy with severe motor disabilities are limited not only in everyday life activities but also in choice of their hobbies. Playing a musical instrument is for the majority not possible, even though music constitutes a central component of many relaxation activities for people with disabilities. To give affected patients the opportunity to make music and to learn piano playing through somatosensory perception, a prototype of piano jacket was developed. METHOD: A cycling jacket was equipped with boxes, each representing a musical note, incorporated into the sleeves. Each box contains vibration motors and LEDs. These can be used to translate the sequences of piano key presses performed at an external E-piano. An additional operation mode allows the user to actively play a melody himself by touching the same boxes that also incorporate touch sensor components. RESULTS: A working prototype of the piano jacket was developed. CONCLUSION: The sensory piano jacket provides patients with cerebral palsy and contractures the possibility to develop sensorimotor skills, motor abilities and participation in music-related activities. The jacket is planned to be used in music lessons. Implications for Rehabilitation The system is suitable even for patients with severe motor disabilities and especially joint contractures. Excellent handling through large easily accessible communication buttons. All building blocks are held in a garment, which allows for easy portability and gripping comfort.

Modeling Cerebral Blood Flow Dependence on Carbon Dioxide and Mean Arterial Blood Pressure in the Immature Brain With Accounting for the Germinal Matrix.

Intraventricular hemorrhage (IVH) is one of the most critical complications in the development of preterm infants. The likelihood of IVH is strongly associated with disturbances in cerebral blood flow (CBF) and with microvascular fragility in the germinal matrix (GM). The CBF value and its reactivity to changes in arterial carbon dioxide pressure (pCO 2 ) and mean arterial blood pressure (MABP) are relevant indicators in the clinical assessment of preterm infants. The objective of the present study is mathematical modeling of the influence of pCO 2 and MABP on CBF in immature brain, based on clinical data collected from 265 preterm infants with 23-30 gestational weeks. The model was adapted to the peculiarities of immature brain by taking into account the morphological characteristics of the GM capillary network and vascular reactivity, according to gestational and postnatal age. An analysis of model based values of CBF and its reactivity to changes in MABP and pCO 2 was performed separately for each gestational week and for the first two days of life both for preterm infants with and without IVH. The developed model for the estimation of CBF was validated against equivalent experimental measurements taken from the literature. A good agreement between the estimated values of CBF, as well as its reaction on changes in MABP and pCO 2 and the equivalent values obtained in experimental studies was shown.

Mobile communication jacket for people with severe speech impairment.

PURPOSE: Cerebral palsy is a movement disorder caused by damage to motor control areas of the developing brain during early childhood. Motor disorders can also affect the ability to produce clear speech and to communicate. The aim of this study was to develop and to test a prototype of an assistive tool with an embedded mobile communication device to support patients with severe speech impairments. METHODS: A prototype was developed by equipping a cycling jacket with a display, a small keyboard, a LED and an alarm system, all controlled by a microcontroller. Functionality of the prototype was tested in six participants (aged 7-20 years) with cerebral palsy and global developmental disorder and three healthy persons. A patient questionnaire consisting of seven items was used as an evaluation tool. RESULTS: A working prototype of the communication jacket was developed and tested. The questionnaire elicited positive responses from participants. Improvements to correct revealed weaknesses were proposed. Enhancements like voice output of pre-selected phrases and enlarged display were implemented. CONCLUSIONS: Integration in a jacket makes the system mobile and continuously available to the user. The communication jacket may be of great benefit to patients with motor and speech impairments. Implications for Rehabilitation The communication jacket developed can be easily used by people with movement and speech impairment. All technical components are integrated in a garment and do not have to be held with the hands or transported separately. The system is adaptable to individual use. Both expected and unexpected events can be dealt with, which contributes to the quality of life and self-fulfilment.

Direct modeling of blood flow through the vascular network of the germinal matrix.

A premature birth, before completion of the 32nd pregnancy week, increases the risk of cerebral hemorrhage. The cause of brain bleeding is very often the germinal matrix of the immature brain. The germinal matrix consists of richly vascularized neuroepithelial cells and is located over the lower part of the head of the caudate nucleus. By 32-36 gestation weeks, the germinal matrix essentially disappears so that its hemorrhage is a disease of premature infants. The aim of this paper consists in developing a model of the brain vascular network and computing the pressure distribution in the germinal matrix, particularly near arterioles and venules, where cerebral hemorrhage may occur. Capillary networks consisting of several millions of vessels are directly simulated in the present study.

Effects of short-term piano training on measures of finger tapping, somatosensory perception and motor-related brain activity in patients with cerebral palsy.

Playing a musical instrument demands the integration of sensory and perceptual information with motor processes in order to produce a harmonic musical piece. The diversity of brain mechanisms involved and the joyful character of playing an instrument make musical instrument training a potential vehicle for neurorehabilitation of motor skills in patients with cerebral palsy (CP). This clinical condition is characterized by motor impairments that can affect, among others, manual function, and limit severely the execution of basic daily activities. In this study, adolescents and adult patients with CP, as well as a group of typically developing children learned to play piano for 4 consecutive weeks, having completed a total of 8 hours of training. For ten of the participants, learning was supported by a special technical system aimed at helping people with sensorimotor deficits to better discriminate fingers and orient themselves along the piano keyboard. Potential effects of piano training were assessed with tests of finger tapping at the piano and tests of perception of vibratory stimulation of fingers, and by measuring neuronal correlates of motor learning in the absence of and after piano training. Results were highly variable especially among participants with CP. Nevertheless, a significant effect of training on the ability to perceive the localization of vibrations over fingers was found. No effects of training on the performance of simple finger tapping sequences at the piano or on motor-associated brain responses were registered. Longer periods of training are likely required to produce detectable changes.

Implicit Learning of a Finger Motor Sequence by Patients with Cerebral Palsy After Neurofeedback.

Facilitation of implicit learning of a hand motor sequence after a single session of neurofeedback training of alpha power recorded from the motor cortex has been shown in healthy individuals (Ros et al., Biological Psychology 95:54-58, 2014). This facilitation effect could be potentially applied to improve the outcome of rehabilitation in patients with impaired hand motor function. In the current study a group of ten patients diagnosed with cerebral palsy trained reduction of alpha power derived from brain activity recorded from right and left motor areas. Training was distributed in three periods of 8 min each. In between, participants performed a serial reaction time task with their non-dominant hand, to a total of five runs. A similar procedure was repeated a week or more later but this time training was based on simulated brain activity. Reaction times pooled across participants decreased on each successive run faster after neurofeedback training than after the simulation training. Also recorded were two 3-min baseline conditions, once with the eyes open, another with the eyes closed, at the beginning and end of the experimental session. No significant changes in alpha power with neurofeedback or with simulation training were obtained and no correlation with the reductions in reaction time could be established. Contributions for this are discussed.

Development of congenital clubfoot during growth: a long-term study on the basis of pedobarography, biomechanics, and magnetic resonance imaging measurements of muscle volumes.

The aim of this study was to clarify the degree to which the operated congenital asymptomatic clubfoot still shows malpositions or whether it approaches a physiological development with increasing age. Clubfeet of 12 children were examined repeatedly over up to 10 years using pedobarography. The muscle volumes of the lower legs were investigated with MRI and compared with those of a healthy control group. Although some characteristics of clubfoot remained in the plantar pressure distribution, a gradual decrease in the heel and metatarsus load accompanied by an increase in the forefoot load could be registered as is typical for a developing healthy child's foot. The MRI showed a reduced volume of all muscles of the affected lower leg. A correlation was detected between the measured moments in the upper and lower ankle joints and the volumes of the muscles that move these joints. Even though a functional and anatomical separation between the two groups existed, the general developmental changes during growth were similar. The combination of pedobarographic data and derived joint moments with MRI-measured muscle volumes indicated that higher ankle joint moments in clubfoot were associated with smaller muscle volume and were therefore generated by higher joint rigidity.

The Case for Musical Instrument Training in Cerebral Palsy for Neurorehabilitation.

Recent imaging studies in cerebral palsy (CP) have described several brain structural changes, functional alterations, and neuroplastic processes that take place after brain injury during early development. These changes affect motor pathways as well as sensorimotor networks. Several of these changes correlate with behavioral measures of motor and sensory disability. It is now widely acknowledged that management of sensory deficits is relevant for rehabilitation in CP. Playing a musical instrument demands the coordination of hand movements with integrated auditory, visual, and tactile feedback, in a process that recruits multiple brain regions. These multiple demands during instrument playing, together with the entertaining character of music, have led to the development and investigation of music-supported therapies, especially for rehabilitation with motor disorders resulting from brain damage. We review scientific evidence that supports the use of musical instrument playing for rehabilitation in CP. We propose that active musical instrument playing may be an efficient means for triggering neuroplastic processes necessary for the development of sensorimotor skills in patients with early brain damage. We encourage experimental research on neuroplasticity and on its impact on the physical and personal development of individuals with CP.

Altered lower leg muscle activation patterns in patients with cerebral palsy during cycling on an ergometer.

OBJECTIVE: Cycling on a recumbent ergometer constitutes one of the most popular rehabilitation exercises in cerebral palsy (CP). However, no control is performed on how muscles are being used during training. Given that patients with CP present altered muscular activity patterns during cycling or walking, it is possible that an incorrect pattern of muscle activation is being promoted during rehabilitation cycling. This study investigated patterns of muscular activation during cycling on a recumbent ergometer in patients with CP and whether those patterns are determined by the degree of spasticity and of mobility. METHODS: Electromyographic (EMG) recordings of lower leg muscle activation during cycling on a recumbent ergometer were performed in 14 adult patients diagnosed with CP and five adult healthy participants. EMG recordings were done with an eight-channel EMG system built in the laboratory. The activity of the following muscles was recorded: Musculus rectus femoris, Musculus biceps femoris, Musculus tibialis anterior, and Musculus gastrocnemius. The degree of muscle spasticity and mobility was assessed using the Modified Ashworth Scale and the Gross Motor Function Classification System, respectively. Muscle activation patterns were described in terms of onset and duration of activation as well as duration of cocontractions. RESULTS: Muscle activation in CP was characterized by earlier onsets, longer periods of activation, a higher occurrence of agonist-antagonist cocontractions, and a more variable cycling tempo in comparison to healthy participants. The degree of altered muscle activation pattern correlated significantly with the degree of spasticity. CONCLUSION: This study confirmed the occurrence of altered lower leg muscle activation patterns in patients with CP during cycling on a recumbent ergometer. There is a need to develop feedback systems that can inform patients and therapists of an incorrect muscle activation during cycling and support the training of a more physiological activation pattern.