A wearable device to measure the palmar grasp reflex of neonates in neonatal intensive care unit

https://doi.org/10.1016/j.sna.2020.111905Get rights and content

Highlights

  • A wearable pressure sensor to measure the palmar grasp reflex of neonates was developed.

  • The device is compatible with the conventional diagnostic protocol used by pediatricians.

  • The device has a sensitivity of 0.13 kPa−1 in a pressure range up to 530 kPa.

  • The elicited palmar grasp strength of neonates was successfully examined in NICU.

Abstract

The examination of palmar grasp reflex is frequent in neonatal intensive care unit (NICU) to evaluate the neuro-sensorimotor developmental disorders and pathological abnormalities during the infancy period of clinically complicated neonates. In this study, we develop a wearable pressure sensing device to quantitatively measure the elicited palmar grasp strength of clinically complicated neonates aged 0–2 months. A capacitive pressure sensing device was fabricated using Ecoflex which acted as a dielectric material sandwiched between two copper electrodes, and further assembled with the coupling parts to provide comfort to neonates. The characterization of the fabricated device showed a linear sensitivity (0.13 kPa−1), a high pressure range up to 530 kPa, and excellent working stability. Clinical experiments were performed on 33 newborns by investigating the laterality and hand preferences in male and female neonates, the development of palmar grasp behavior in the first three days of life, the influence of weight loss on palmar grasp reflex, and difference in palmar grasp strength of term and preterm neonates. The developed device was capable of measuring the elicited grasping reflex of neonates reliably, mimicking the conventionally used diagnostic method in NICU.

Introduction

Palmar grasp reflex is one of the most important primitive reflexes with clinical significance in human neonates. Its examination is frequent in neonatal intensive care unit (NICU) to evaluate the neuro-sensorimotor developmental disorders and pathological abnormalities during the infancy period of clinically complicated neonates. The assessment of palmar grasp reflex is part of several neurological examination routines on neonates, associated with specific patterns of lesions [1,2]. This reflex emerges even during the first day after birth and its intensity becomes stronger during the first month and gradually decreases until it inhibits at around the fourth month [3,4]. The absence of grasping reflex during the first days after birth or aggravated presence after the fifth month is an important indication of neuro-sensorimotor disorders [[4], [5], [6]].

In clinical practice, to elicit the palmar grasp reflex, the examiner inserts his or her index finger into the palm of the neonate from the ulnar side and applies light pressure to the palm while the neonate is awake and lying on a flat surface in the symmetrical supine position [[7], [8], [9]]. In addition, to elicit the palmar grasp reflex, both of tactile stimulation without sufficient pressure and nociceptive stimulation are inadequate. A gentle pressure should be applied on the palm of the neonate for grasping reflex stimulation, which results in the flexion of all fingers around the examiner’s index finger [10,11]. However, this approach is subjective and non-quantitative as it is completely based on the examiner’s expertise, resulting in significant variations [12].

With technological advancement, there have been approaches to study the palmar grasp behavior and the relevant parameters that directly influence the palmar grasp reflex. Molina and Jouen [13] developed a sensorized cylindrical rod covered by a rubber pipette connected to pressure sensors to investigate the role of object texture on grasping pressure and frequency. Objects with smooth or soft texture can easily elicit the palmar grasp reflex than those with a rough surface. Rochat et al. [14] conducted a study on the palmar grasp behavior and suction of neonates using an air pressure transducer with a polygraphic recording of positive pressure variations. On the other hand, others verified the symmetry between limbs, the difference between genders, the level of testosterone, manual preferences, pH stressor from the umbilical arterial blood and predisposition to laterality by evaluating the palmar grasp strength [4,[15], [16], [17], [18]]. To satisfy the need to evaluate the palmar grasp strength using advanced technologies, Moraes et al. developed an instrument, M-FLEX™, capable of measuring the peak palmar grasp strength, the average strength and the grasping time. Similarly, Yamada & Watanabe [19,12] manufactured DataGrip, a bar grip with embedded pressure sensors to examine the development of palmar grasp strength in correspondence with physical development.

However, all previous experimental setups accompany bulky equipment, which occupies considerable space in hospitals and in turn results in high cost. Moreover, with such heavy equipment, point-of-care diagnostics become almost impossible in NICU. Equipment such as the ammeter, ohmmeter and polygraph recordings do not express the palmar grasp strength in physical quantities of force or pressure, and lack graphical or tabular data [4,[13], [14], [15], [16], [17], [18]]. Subsequently, although M-Flex [12] and DataGrip [19] employed advanced manufacturing techniques, they are inadequate to be used in NICU to adapt the conventional diagnostic method used by pediatricians and physiotherapists because of their tubular designs. In addition, using tube-shaped sensors, it’s hard to elicit the palmar grasp reflex in neonates, but only the measurement of spontaneous grasping reflex is possible. In case of M-Flex, a limitation of the device is associated with the inability to identify the palmar contact area with the M-Flex cuff held by neonates, which prevents the accurate calculation of the grasping strength.

In this study, we propose a wearable capacitive pressure sensing device to measure the elicited reflexive grasping power of neonates, which can be used in NICU. The objective was to measure the maximum elicited grasping power of neonates including term, preterm and clinically complicated neonates, following a clinical protocol that is identical to the conventional diagnostic method used by pediatricians as shown in Fig. 1(a). The device, with a small size and soft texture, was placed on the doctor’s index finger and provided comfortable feeling to neonates.

Section snippets

Design and working principle of the sensing device

The working principle of the proposed pressure sensor is based on the relationship between the change in capacitance and the applied pressure. When a pressure is applied, the elastic dielectric material deforms and the capacitance changes accordingly. The capacitance between two plates can be written asC=ε0εrAdwhere C is the capacitance, ε0isthepermittivityofvacuum(8.85×10-12F/m), εr is the relative permittivity of the dielectric material, A is the overlapping area of the electrodes and d

Results of device characterization

Several approaches were made to design and fabricate the optimized sensing device to get a high sensitivity, high pressure range, suitable ergonomics and repeatable results. To achieve the high sensitivity and pressure range, dielectric materials of PDMS and Ecoflex were tested, several electrode sizes and dielectric thicknesses were investigated, and the finger mold structures with curved and flat top surfaces were compared. After such iterative modifications, we finally optimized the device

Conclusion

We designed and fabricated a novel wearable pressure sensing device to measure the elicited grasping power of neonates in NICU, via time-efficient and low-cost manufacturing. The characterized pressure sensing device showed a sensitivity of 0.13 kPa−1 in a pressure range up to 530 kPa, excellent mechanical stability over 2000 repeated cycles and stable sensing performance over a month. To see the real-time performance and reliability of the pressure sensing device, we performed clinical

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This research was supported in part by the Basic Science Research Program (grant no. NRF-2017R1A2B2004598) through the National Research Foundation of Korea of Korea and in part by the DGIST R&D Program (grant no. 19-RT-01) supported by the Ministry of Science and ICT of Korea.

Tausif Muhammad received his BS degree in mechatronics engineering from University of Engineering and Technology (UET), Peshawar, Pakistan in 2015. He received his MS degree in robotics engineering from Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Korea in 2018. Currently, he is a PhD candidate in the Department of Robotics Engineering at DGIST. His research interests include wearable pressure sensors and polymer based soft MEMS for biomedical applications.

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  • Tausif Muhammad received his BS degree in mechatronics engineering from University of Engineering and Technology (UET), Peshawar, Pakistan in 2015. He received his MS degree in robotics engineering from Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, Korea in 2018. Currently, he is a PhD candidate in the Department of Robotics Engineering at DGIST. His research interests include wearable pressure sensors and polymer based soft MEMS for biomedical applications.

    Je Sang Lee graduated from Keimyung University School of Medicine, Daegu, Korea in 2010, and received her Master degree in medicine and PhD degree in rehabilitation medicine from Pusan National University School of Medicine in 2013 and 2018, respectively. She was an assistant professor in the Department of Rehabilitation Medicine at Pusan National University Hospital from 2016 to 2018. Since 2019, she is in the Department of Rehabilitation Medicine at Gimhae Hansol Rehabilitation and Convalescent Hospital in Gimhae, Korea. Her research interests include human brain development and pediatric rehabilitation.

    Yong Beom Shin received BS and MS degrees in medicine from Pusan National University School of Medicine, Busan, Korea in 1997 and 2000, respectively. He received his PhD degree in rehabilitation medicine from Graduate School of Pusan National University School of Medicine in 2004. He was a visiting associate professor in Neurosurgery Department at University of California in San Francisco, SF, California, USA from 2011 to 2013. Since 2014, he is professor in the Department of Rehabilitation Medicine at Pusan National University Hospital. His research interests include human brain development and pediatric rehabilitation.

    Sohee Kim received BS and MS degrees in mechanical engineering from Korea Advanced Institute of Science and Technology (KAIST), Daejon, Korea in 1998 and 2000, respectively. She received her Dr.-Ing. (PhD) degree in mechatronics from University of Saarland, Saarbruecken, Germany in 2005 while she worked at Fraunhofer Institute for Biomedical Engineering, St. Ingbert, Germany as researcher. She was a postdoctoral researcher in electrical and computer engineering at University of Utah, Salt Lake City, UT, USA. From 2009 to 2015, she was professor at Gwangju Institute of Science and Technology (GIST) in Gwangju, Korea, in both Departments of Medical System Engineering and Mechatronics. Since 2015, she is professor in the Department of Robotics Engineering at DGIST. Her research interests include neural interfaces for brain, retina and peripheral nerve applications as well as polymer-based soft MEMS technologies and flexible/wearable devices for biomedical applications.

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    Je Sang Lee was with the Department of Rehabilitation Medicine, Pusan National University School of Medicine and Pusan National University Hospital, Busan, Republic of Korea.

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