Daniel Haensse

Wireless miniaturized in-vivo near infrared imaging

Our group measures tissue oxygenation and the cortical hemodynamic response to sensory stimuli applying continuous wave near-infrared imaging (NIRI). To improve the methods quality and applicability and to explore new fields in clinical practice and research, we developed a miniaturized wireless NIRI system. It was validated by measuring muscle oxygenation in a blood-flow occlusion experiment and brain activity in adults.

Photonic textiles for pulse oximetry

Biomedical sensors, integrated into textiles would enable monitoring of many vitally important physiological parameters during our daily life. In this paper we demonstrate the design and performance of a textile based pulse oximeter, operating on the forefinger tip in transmission mode. The sensors consisted of plastic optical fibers integrated into common fabrics. To emit light to the human tissue and to collect transmitted light the fibers were either integrated into a textile substrate by embroidery (producing microbends with a nominal diameter of 0.5 to 2 mm) or the fibers inside woven patterns have been altered mechanically after fabric production. In our experiments we used a two-wavelength approach (690 and 830 nm) for pulse wave acquisition and arterial oxygen saturation calculation. We have fabricated different specimens to study signal yield and quality, and a cotton glove, equipped with textile based light emitter and detector, has been used to examine movement artifacts. Our results show that textile-based oximetry is feasible with sufficient data quality and its potential as a wearable health monitoring device is promising.

Hemodynamic response to visual stimulation in newborn infants using functional near-infrared spectroscopy

Brain activity is associated with physiological changes, which alter the optical properties of tissue. These changes can be detected by near‐infrared spectroscopy (NIRS). Aim of the study was to determine changes in cerebral oxygenation in response to stimulation in the visual cortex in newborn infants during spontaneous sleep in the first days of life. We used an in‐house developed multichannel NIRS imaging instrument, the MCP‐II, to measure changes in concentration of oxyhemoglobin (O2Hb) and deoxyhemoglobin (HHb) in specific brain areas. In 10 out of 15 subjects, a significant increase in O2Hb and/or a significant decrease in HHb were found in one or more channels over the occipital cortex. During stimulation, O2Hb increased by a mean of 0.98 μmol/l, HHb decreased by a mean 0.17 μmol/l, and total‐Hb increased by a mean of 0.81 μmol/l. The hemodynamic response to visual stimulation in the occipital cortex in newborn infants is similar to adults. The increase in O2Hb and the simultaneous decrease in HHb during stimulation suggest an increase in cerebral blood flow (CBF) that overcompensates for the increased oxygen consumption (CMRO2) in the activated cortical area. Hum Brain Mapp, 2008.

New multichannel near infrared spectrophotometry system for functional studies of the brain in adults and neonates

We have designed a versatile, multi-channel near-infrared spectrophotometry (NIRS) instrument for the purpose of mapping neuronal activation in the neonatal and adult brain in response to motor, tactile, and visual stimulation. The optical linearity, stability, and high signal to noise ratio (>70 dB) of the instrument were demonstrated using an in vitro validation procedure. In vivo measurements on the adult forearm were also performed. Changes in oxygenation, induced by arterial occlusion of the forearm, were recorded and were shown to compare well with measurements acquired using a conventional NIRS instrument. To demonstrate the capabilities of the instrument, functional measurements in adults and neonates were performed. The instrument exhibited the capability to differentiate with a spatial resolution in the order of cm, local activation patterns associated with a finger tapping sequence.

Liver tissue oxygenation as measured by near-infrared spectroscopy in the critically ill child in correlation with central venous oxygen saturation

Objective: To evaluate the clinical usefulness of near-infrared spatially resolved spectroscopic quantitative assessment of liver tissue oxygenation for simple, non-invasive estimation of global tissue oxygenation in critically ill neonates and children. Design: Prospective observational clinical study. Setting: A tertiary multidisciplinary neonatal and paediatric intensive care unit (23 beds). Patients: One hundred neonates and children consecutively admitted to the paediatric intensive care unit. Measurements and results: Near-infrared spectroscopic single-point assessment of liver tissue oxygenation index (TOILiver) was compared with global tissue oxygenation as measured by central venous oxygen saturation (SvO2) and derived haemodynamic parameters. Data were compared using linear and multiple regression analysis. Overall correlation between TOILiver and SvO2 was good (r=0.72, p<0.0001). Multivariable regression revealed that SvO2 alone explained 51% of the observed variance of TOILiver. However, our data demonstrated large inter-individual differences between SvO2 and TOILiver values. Conclusion: Near-infrared spatially resolved spectroscopic quantitative measurement of liver tissue oxygenation correlates well with SvO2 in critically ill neonates and children. Large inter-individual SvO2 to TOILiver differences may prevent its use for non-invasive single-point estimation of global tissue oxygenation. Further clinical studies are required to validate the method with other regional and global haemodynamic parameters and to evaluate its clinical use for continuous non-invasive haemodynamic monitoring.

Near-Infrared Spectroscopy Measurements of Cerebral Oxygenation in Newborns during Immediate Postnatal Adaptation

OBJECTIVE In view of growing concerns regarding the optimal supplementation of oxygen at birth, we measured cerebral oxygenation during the first minutes of life. STUDY DESIGN Using near-infrared spectroscopy, changes in cerebral oxygenated hemoglobin (O(2)Hb), dexoxygenated hemoglobin (HHb), and tissue oxygenation index (TOI) were measured during the first 15 minutes of life in 20 healthy newborn infants delivered at term by elective cesarean section. RESULTS O(2)Hb and TOI increased rapidly within the first minutes of life (median slope for O(2)Hb, 3.4 micromol/L/min; range, 1.4 to 20.6 micromol/L/min; median slope for TOI, 4.2 %/min; range, -0.4 to 27.3%/min), and cerebral HHb decreased (median slope, -4.8 micromol/L/min; range, -0.2 to -20.6 micromol/L/min). O(2)Hb, TOI, and HHb all reached a plateau within 8 minutes. CONCLUSIONS A significant increase in cerebral O(2)Hb and TOI and a significant decrease in HHb occur during immediate adaptation in healthy term newborns, reaching a steady plateau at around 8 minutes after birth.

Near infrared spectroscopy to study the brain: an overview

This paper gives an overview of principles, technologies, and applications using near infrared spectrometry and imaging (NIRS and NIRI) to study brain function. The physical background is reviewed and technologies and their properties are discussed. Advantages and limitations of NIRI are described. The basic functional signals obtained by NIRI, the neuronal and the hemodynamic signal are described and in particular publications about the former are reviewed. Applications in adults and neonates are reviewed, too.

Assessment of jaundice in preterm neonates: comparison between clinical assessment, two transcutaneous bilirubinometers and serum bilirubin values.

Aim: 1) To compare the clinical assessment of craniocaudal progression of jaundice and two transcutaneous bilirubinometers with serum bilirubin values in preterm neonates; 2) to identify factors affecting the difference between non‐invasive bilirubin estimation and serum bilirubin. Methods: Serum bilirubin was clinically estimated in healthy preterm newborn infants (34 to 36.9 gestational weeks) independently by a primary investigator and by nurses, and subsequently compared with separate measures of two transcutaneous bilirubinometers. Results: A total of 107 measurements were performed on 69 infants. Minolta JM‐102 showed the best performance, with ROC area under the curve of 0.96, followed by BiliCheck™ over the sternum (0.89) and over the forehead (0.88), clinical assessment by nurses (0.73) and by a physician (0.70). Serum bilirubin <190 μmol/l can be detected with 95% sensitivity with Minolta JM–102 ≫19 units, with BiliCheck™≫145 μmol/l over the sternum and ≫165 μmol/l over the forehead and with jaundice progression to the trunk or further (Kramer zone ≫2). Gestational age affects all non‐invasive methods in the estimation of serum bilirubin, whereas skin colour affects both BiliCheck™ and clinical assessment. Ambient light affects only clinical assessment.

Do GSM 900MHz signals affect cerebral blood circulation? A near-infrared spectrophotometry study

Effects of GSM 900MHz signals (EMF) typical for a handheld mobile phone on the cerebral blood circulation were investigated using near-infrared spectrophotometry (NIRS) in a three armed (12W/kg, 1.2W/kg, sham), double blind, randomized crossover trial in 16 healthy volunteers. During exposure we observed borderline significant short term responses of oxyhemoglobin and deoxyhemoglobin concentration, which correspond to a decrease of cerebral blood flow and volume and were smaller than regular physiological changes. Due to the relatively high number of statistical tests, these responses may be spurious and require further studies. There was no detectable dose-response relation or long term response within 20min. The detection limit was a fraction of the regular physiological changes elicited by functional activation. Compared to previous studies using PET, NIRS provides a much higher time resolution, which allowed investigating the short term effects efficiently, noninvasively, without the use of radioactive tracers and with high sensitivity.

A preliminary report of nursing in the three-stair-position to prevent apnoea of prematurity

Recurrent apnoea associated with hypoxaemia and brady-cardia is the most common monitor alarm situation inneonatal intensive care units. Previous studies have demon-stratedthatapnoeaeventsareassociatedwithacutechangesin cerebral perfusion and blood volume and may induceor aggravate pre-existing cerebral injuries (1). Therefore,apnoea should be prevented effectively. Interventions toreduce apnoea resulting in hypoxaemia and bradycardia in-clude continuous positive airway pressure (CPAP) (2) andmethylxanthines (3). Nursing in the prone, rather than inthe supine position has its proponents (4,5) as well as itsopponents (6,7).Jenni OG et al. 1997 showed in their study that nursingin the head elevated tilt position (HETP) placing the infantsprone reduces apnoea episodes significantly (8).In HETP the infant is placed on its underlay, which istilted until the infant is in an inclined position of 15