Smart Jacket Design for Neonatal Monitoring with Wearable ...dc-bdps.wikispaces.asu.edu/file/view/NeoNatalMonitoring.pdf · Smart Jacket Design for Neonatal Monitoring with Wearable

Smart Jacket Design for Neonatal Monitoring with Wearable Sensors

Sibrecht Bouwstra, Wei Chen, Loe Feijs Department of Industrial Design

Eindhoven University of Technology Den Dolech 2, 5612 AZ, Eindhoven, The Netherlands [email protected], [email protected], [email protected]

Sidarto Bambang Oetomo M.D. Neonatal Intensive Care Unit,

Máxima Medical Center 5500 MB, Veldhoven, The Netherlands

[email protected]

Abstract— Critically ill new born babies admitted at the Neonatal Intensive Care Unit (NICU) are extremely tiny and vulnerable to external disturbance. Smart Jacket proposed in this paper is the vision of a wearable unobtrusive continuous monitoring system realized by body sensor networks (BSN) and wireless communication. The smart jacket aims for providing reliable health monitoring as well as a comfortable clinical environment for neonatal care and parent-child interaction. We present the first version of the neonatal jacket that enables ECG measurement by textile electrodes. We also explore a new solution for skin-contact challenges that textile electrodes pose. The jacket is expandable with new wearable technologies and has aesthetics that appeal to parents and medical staff. An iterative design process in close contact with the users and experts lead to a balanced integration of technology, user focus and aesthetics. We demonstrate the prototype and the experimental results obtained in clinical setting.

Keywords-component; Neonatal Monitoring, Wearable Sensors, Textile Electrodes, ECG monitoring, wearability

I. INTRODUCTION When critically ill or premature neonates are admitted

to the NICU they are monitored and treated in an incubator. These neonates are extremely tiny and vulnerable. Round-the-clock health monitoring is crucial for early detection of medical problems (e.g. apnea, arrhythmias and hypoxemia) and potential complications (e.g. convulsions) [1]. The monitored vital signs include body temperature, electro-cardiogram (ECG), respiration and the degree of blood oxygen saturation (S02). Medical actions based on timely detection increases survival rate and results in a better developmental outcome. With appropriate monitoring and medical care at the NICU, neonates born after 25 weeks of pregnancy may survive [1]. Regular skin contact between the neonate and parent (Kangaroo mother care) establishes bonding and has a positive effect on the neonate’s development as well [2].

Improved neonatal care results in increased survival rates. However, the number of neonates at risk for poor developmental outcome also increases. The premature neonates with an immature central nervous center have to

develop in an extra uterine environment. This NICU environment is filled with bright light (e.g. phototherapy), noise (alarms) and medical procedures (examination, giving medication, feeding and cleaning). All interfere with the normal growth and development of neonates [3]. Preterm infants that have been admitted in a NICU show more long term neurodevelopmental problems compared to full term peers [4].

One of the structural causes of discomfort in the incubator is the monitoring system. The vital parameters are obtained with adhesive sensors on the fragile skin with individual wires running to external monitors. (Re)placement of the sensors and the large amount of tangling wires lead to discomfort, skin irritation and interruption of sleep of neonates. Furthermore, parents commonly feel detached from their baby who is barely recognizable between all the medical equipment, wires and patches. Currently, stimulatory efforts by medical staff are required to help parents overcome the technical hazards and engage in Kangaroo mother care. Therefore, the design of non-intrusive alternatives for monitoring of the vital signs is urgently needed.

Recent advances in sensor technologies and wireless

communication technologies enable the creation of a new generation of healthcare monitoring systems with wearable electronics and photonics [5, 6]. Smart textiles have already been integrated into a garment for electrocardiogram (ECG) and respiration monitoring with wireless transmission [7, 8]. Reflectance pulse oximeters attached on the forehead [9] have been developed. Embedding optical fiber into textiles for patient health monitoring are being developed [10].

In the neonatal monitoring area, some early efforts and developments have been made towards noninvasive neonatal monitoring. For example, some methodological options for technological integration and early design work of a future incubator have been reported [11]. A biosensor belt is described for monitoring the heart rate, breathing frequency, body movements and temperature of new born baby with embedded sensors [12]. Improvements on sensors, signal processing and integration are required for obtaining sufficiently reliable

2009 Body Sensor Networks

978-0-7695-3644-6/09 $25.00 © 2009 IEEE

DOI 10.1109/P3644.39

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2009 Body Sensor Networks

978-0-7695-3644-6/09 $25.00 © 2009 IEEE

DOI 10.1109/P3644.39

164

2009 Body Sensor Networks

978-0-7695-3644-6/09 $25.00 © 2009 IEEE

DOI 10.1109/P3644.39

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signals, combating movement artifacts, developing sensors with higher sensitivity, and optimizing the design and integration. The technical challenges for non-invasive neonatal monitoring encompass movement artifacts, miniaturized sensors, system modeling, power supply for wearable systems, design process from designing printed circuit board (PCB) to form giving, and clinical validation.

The Eindhoven University of Technology (TU/e) in the Netherlands has started a 10-year project in cooperation with the Máxima Medical Center (MMC) in Veldhoven, the Netherlands, for improving the healthcare of the pregnant woman and her child before, during and after delivery. The spear head of improving the healthcare of the neonates is to create a calm, natural and comfortable environment, by a carrier, such as a baby jacket or mattress, which has wearable sensors integrated for the monitoring of a neonates vital health functions. So far, various techniques have been developed in isolation. The collaboration between TU/e and MMC aims to bring together a multidisciplinary network of specialists in sensor technology, medical clinics and signal processing and develop revolutionary neonatal monitoring solutions.

The new approach can be foreseen to strongly improve comfort and reliability of neonatal monitoring systems, so as to improve the neonate’s comfort and quality of life later on, to enhance the parent-child interaction and to alleviate workload of clinical staff.

II. DESIGN PROCES AND DESIGN CONTEXT The Smart Jacket design aims to provide continuous

monitoring of vital functions when the neonate is inside the incubator or in the parents’ hug during Kangaroo mother care [2]. The first step towards the Smart Jacket is the design of a jacket that:

1. contains the integration of conductive textiles for ECG monitoring,

2. forms a platform for future research, in which wireless communication, power supply and sensors are developed,

3. obtains a sense of trust by parents. Methodologies from the field of Industrial Design are

applied in the design process of the Smart Jacket. Neonatal monitoring is a multi-disciplinary area which involves a unique integration of knowledge from medical science, design, technology and social study. The iterative process (“Fig. 1”) begins with an information search that includes user involvement and gathering of information on unobtrusive ECG monitoring, intelligent textiles and baby clothing design. Requirements were derived from the information search, forming a base for brainstorm sessions which resulted in ideas about technological challenges, functionality issues within NICU and about aesthetics. The ideas are placed in a morphological diagram and combined to several initial concepts. Design

choices are made through an iterative process in which technology and user tests provide clues for further development. The three aspects ‘Technology, User Focus and Design’, are strongly interwoven along the process and developed up to the same level of detail.

Figure 1. Design process model

With consideration of both user aspects and technical functions, the full design of the Smart Jacket should meet the following requirements:

• support the vital health monitoring functions • be safe to use in the NICU environment • be scalable to include more monitoring functions

such as wireless communication and local signal processing

• support continuous monitoring when the baby is inside the incubator or during Kangaroo mother care

• gain the feeling of trust by the parents and the medical staff through an attractive design

• be non-intrusive and avoid disturbance of the baby and avoid causes of stress

• provide appropriate feedback which is also interpretable for parents and hospital staff on whether the system’s components are correctly functioning

• non-washable parts must be easy to remove • look friendly, playful and familiar

III. PROTOTYPE AND ARCHITECTURE A prototype jacket is shown in “Fig. 2”. The jacket is

open at the front and has an open structure fabric on the back and hat, with the purpose of skin-on-skin contact, phototherapy and medical observation. The hat contains eye-protection and leaves room for future sensors. The aesthetics are designed to appear as regular baby clothing. The color combination of white and green with colorful happy animal heads is chosen because it is unisex while looking cheerful and clean.

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Figure 2. Prototype Smart Jacket

Based on these design requirements, the concept Diversity Textile Electrode Measurement (DTEM) is chosen. The neonate wears a baby jacket that contains six conductive patches that sense biopotential signals at different positions to perform diversity measurements. Depending on the way the baby lies or is held, there are always patches that are in close contact with the skin because of pressure. When one sensor becomes loose from the skin, another sensor can provide a better signal. The system continuously measures which leads of the suit have superior contact and chooses the strongest signal for further processing. The concept offers a solution for skin contact, without jeopardizing comfort by tightness. It might also solve the problem of searching optimal electrode positions in the jacket, which varies per baby.

Furthermore, the concept has a stress-less dressing process: (1) the baby is laid down on the open jacket, (2) the lower belt is closed, (3) the hat is put on, and (4) finally the chest straps are closed. See “Fig. 3”.

Several types of prototypes are built: test patches with

different versions of silver and gold textile electrodes and a blanket with large silver electrodes as shown in “Fig. 4”.

Figure 3. Stress-less dressing process

Figure 4. Test patches and blanket

The silver textile electrodes consist of silver plated nylons produced by Shieldex®. Construction details can be seen in “Fig. 5”. Three layers (1) of cotton are used and on the middle layer (2) the circuit is sewn with Shieldex® silver plated yarn. On the first layer the electrode is sewn, stitching through the circuit on the middle layer (3). The electrode’s connection to the monitor is realized by carbon wires obtained from regular disposable gel electrodes: the end of the carbon wires are stripped and sewn onto the circuit on the middle layer (4). (Carbon wire is a good alternative to metal buttons which are often applied, because it avoids the less stable soft-hard connection). Finally the third cotton layer for isolation is sewn to the others (5).

The gold printed electrodes consist of a thin smooth fiber with a metal print developed by TNO at Eindhoven, the Netherlands. The gold test patches are created in a similar way to the silver test patches, however in future application the circuit and electrode can be printed in one piece.

IV. CLINICAL TRIALS Several experiments were carried out, ranging from

experiments on adults as alternative subjects to neonates in the NICU at the MMC Veldhoven, the Netherlands. The goals are comparisons between the varies textile electrodes, verification of their functioning on a neonate and verification of the DTEM concept. Finally, a wearability test of the jacket was performed. An analysis of risks was performed before applying the prototypes to the NICU. Together with clinical physicists, a hospital hygiene and infection expert, and a neonatologist, the safety of the monitoring system and hygiene and allergy risks were analyzed. Precautions such as disinfection and allergy tests were taken. The ethical commission of the MMC Veldhoven approved the experiments.

Figure 5. Construction of textile electrodes

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A. Neonate’s ECG by textile electrodes In this test the quality of the ECG signals obtained by

textile electrodes varying in material and size and gel electrodes (3M™ 2282E) are qualitatively compared.

The electrodes were tested with two subjects: one neonate of 30 weeks and 5 days and one of 31 weeks and 6 days, both admitted in the NICU Veldhoven. The ECG is sensed by three textile electrodes in regular configuration and the data is acquired with a GE Heathcare Solar® 8000M (“Fig. 6”). The unprocessed digital data of derivation II was obtained from a network and imported and filtered in MATLAB. A notch, high pass and low pass filter are applied to remove the 50 Hz and higher harmonics, DC component and HF noise.

From “Fig. 7” we can see that the quality of ECG obtained by the golden printed textile electrodes is good and the QRS complex can be seen clearly. The ECG curve in “Fig. 7” is representative for the ECG quality by gold electrodes when the baby lies still.

B. Diversity Textile Electrode Measurement The goal is to find out whether the concept of DTEM

(Diversity Textile Electrode Measurement, see “paragraph III”) can improve the signal quality. Therefore, the ECG obtained by large silver textile electrodes in a blanket where the neonate lies on, is compared to the ECG obtained by large silver patches held on the back. This way the effect of pressure by body weight can be investigated. The test setup is equal to the setup in “paragraph A”.

Figure 6. Test setup

Figure 7. Gold printed electrodes D=15mm

From “Fig. 8” we can see that the quality of ECG obtained by the silver textile electrodes is good and the QRS complex can be seen clearly as well. The shape of the ECG complex looks different from “Fig. 7”, because the heart is monitored from another angle.

Figure 8. Silver Shieldex®, 50mmx60mm, blanket

C. Conclusions Textile Electrodes Due to the nature of conductive textiles, the quality of

the ECG signal obtained with textile electrodes cannot exceed the gel electrodes: they are ‘dry’ electrodes with relatively loose skin contact and have a flexible structure that causes artifacts. However, the specific application of ECG monitoring neonates offers new design opportunities:

• A premature has smoother skin, which results in better skin contact

• The premature moves relatively little, which results in less movement artifacts

• The premature always lies or is being held, which offers continuous pressure, which leads to better skin contact

Two textile electrode designs turn out very promising:

(1) large (±D=40mm) silver plated textile electrodes and (2) small (±D=15mm) gold printed electrodes. Both have different strengths and weaknesses. Large silver electrodes offer a stable ECG signal with low noise under the condition that pressure is applied. The silver seems hypoallergenic and does not change properties considerably after a few washing cycles.

The small gold printed electrodes, obtain a stable ECG signal with low noise, under the condition that pressure is applied in the beginning; once skin contact is established, little pressure is required. The gold print however is not hypoallergenic and looses conductivity after washing, due to corrosion of the metal layer beneath the gold. Although the silver electrodes could be applied without much adjustment, the gold prints are worth further development. They require less space due to higher conductivity, have a smoother surface that leads to better skin contact, are less flexible which leads to less artifacts and are seamless which leads to more comfort.

The monitoring of a neonate’s ECG by diversity measurements realized by textile electrodes in the jacket

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definitely is a useful idea. Through experimental verification it is found that the quality of the ECG signal improves significantly due to a neonate’s own body weight and is comparable to the quality of ECG signal obtained by gel electrodes.

D. Wearability Apart from reliable technology, the success of the

Smart Jacket largely depends on the wearable comfort of the jacket. Tightness is desirable for sensor contact, although it might be in conflict with wearable comfort. Therefore, extra caution is taken by performing a wearability test in an early design stage.

A stable neonate of 34 weeks was dressed in the first prototype of the Smart Jacket while being filmed. See “Fig. 9”. Compared to the stress that was caused when undressing the regular premature baby clothing, the dressing process of the Smart Jacket was very calm. Only when lifting the neonate, the legs and arms floundered, which can be a sign of distress or simply a search for boundaries. The dressing time is about one minute. The model needs to be more adjustable in size due to large variations in proportions and range of dimensions: in the NICU neonates can grow from 500g to 2000g and body proportions vary especially when caused by medical conditions. The straps on the chest cause discomfort because they move up to the neck. This information is valuable for the next design iteration.

Figure 9. Wearability test with first prototype

V. NEW PROPOSAL In “Fig. 10” the adapted Smart Jacket proposal is

displayed. It contains an extremely stretchable fabric that likely ensures adjustability to different sizes and proportions. The hat is kept separate for the same reasons. Furthermore, the straps are designed to prevent tightness around the neck.

This version of the suit is designed with the large silver textile electrodes. They are connected only on one of the four sides, in order to allow stretch of the jacket without stretch of the electrode itself. At present this prototype is ready for further clinical testing within the MMC Veldhoven.

Figure 10. Adapted prototype

VI. CONCLUSIONS AND OUTLOOK Based on interviews with parents and medical staff, the

conclusion can be drawn that the user groups are positive about the first results. They especially appreciate the freedom of movement, the aesthetic design, stress-less dressing process and integrated eye-protection. Through iteration steps most interference issues with current care are solved and users embrace the latest version of the Smart Jacket.

The Smart Jacket is already being used as a platform for further research. TU/e researchers from different departments are working on new wearable electronics/ photonics and wireless technology. PowerBoy [13] is the first step towards a wireless power supply.

The development of the Smart Jacket will be continued, initially by further development of the ECG sensors, wireless transmission and an adjustable size for different patients which enable clinical reliability tests.

ACKNOWLEDGMENT Our special thanks to Steven Schilthuizen from TNO,

who has supported this work and supplied the technology and materials to realize the gold printed electrodes. We also thank Statex® for supplying the Shieldex® silver coated textiles and yarns. Furthermore, our special thanks to prof. dr. ir. Lieva Van Langenhove from Ghent University, to the ‘Textile Management’ department at the Saxion Hogeschool Enschede and to the baby fashion magazine ‘Knippie Baby’, for sharing their knowledge on textiles and fashion. We also thank the medical staff at the MMC and the parents of babies in the NICU Veldhoven for all their support and input.

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