A Low-Cost Device for Measuring Non-Nutritive Sucking in Newborns

Abstract

Non-nutritive sucking (NNS) is an instinctive behavior in newborns, consisting of two stages: sucking and expression. It plays a critical role in preparing the infant for oral feeding. In neonatal and pediatric units, NNS assessment is routinely performed to determine feeding readiness. However, these evaluations are often subjective and rely heavily on the clinician's experience. While other medical devices that support the development of NNS skills exist, they are not specifically designed for the comprehensive assessment of NNS, and their high cost limits accessibility for many hospitals and tertiary care units globally. This paper presents the development and pilot testing of a low-cost, portable device and accompanying software for assessing NNS in newborns hospitalized in neonatal care units. Methods: The device uses force-sensitive resistors to capture expression pressure and a differential pressure sensor to measure NNS. Data were acquired through the analog-digital converter of a microcontroller and transmitted via Bluetooth for real-time graphical analysis. Pilot testing was conducted with six hospitalized preterm newborns, measuring intensity, number of bursts, and sucks per burst. Results demonstrated that the system reliably captures both stages of NNS. Significance: This device provides an affordable, portable solution to support clinical decision-making in clinical units, facilitating accurate, objective monitoring of feeding readiness and developmental progression.

Keywords: force sensing resistors; non-nutritive sucking; piezoresistive pressure sensors.

Figure 1

Sucking and expression measurement diagram. The voltage generated in the differential pressure sensor depends on the intensity of the sucking and is digitized and sent to the computer for graphic representation. The expression measurement consists of a voltage divider that changes the output voltage according to the force applied to the FSR sensors. The communication and transmission of data from the device to the computer were conducted through a wireless connection using a Bluetooth module. The upper section shows the power management and battery recharge system, which included a mini USB connector, an MCP73831 battery charger, a 3.7 V LiPo battery, and an LM3671 voltage regulator.

Figure 2

Graph of applied differential pressure versus output voltage. The green line corresponds to the sensor response when powered at 12 V, the red line when powered at 10 V, and, finally, the blue line when powered at 3.3 V.

Figure 3

Connections of the equipment developed to an industrial calibrated digital manometer and syringe to generate negative pressure. The three components are joined by a plastic hose, generating a closed circuit without any loss of pressure.

Figure 4

Measurement error (in mmHg) of the equipment developed with respect to the value delivered by the specialized equipment. The pressure was applied at 10 mmHg intervals.

Figure 5

Force sensor response at different pressures.

Figure 6

Pressure values obtained according to the voltage measured on the force sensor.

Figure 7

Designed prototype parts: (a) front cover, (b) main body, and (c) rear cover on the left. Prototype device ready to use on the right.

Figure 8

Internal components and assembly of the sensing device designed for intraoral pressure and force measurements. (a) Exploded view of the rigid conduit (internal diameter: 3 mm), connector elements, and custom-designed mounting piece. The rigid conduit maintains a direct connection to the atmosphere or to the infant’s oral cavity without deformation under external forces, ensuring unobstructed airflow and accurate intraoral pressure measurement. (b) Frontal view of the device assembled with the pacifier, illustrating the integration of the pressure sensor and FSR sensors and the connection of the teat (pacifier) to the device. A strategically positioned hole at the top of the pacifier enables a direct connection between the rigid conduit and the internal pressure sensor, ensuring precise transmission of intraoral pressure from the infant’s oral cavity. (c) Top view of the assembled system, showing the arrangement of the custom mounting component, which provides a flat surface for the FSR sensors and incorporates a mechanism that ensures a unique orientation and prevents assembly errors after sterilization. This architecture enables both physical and electrical isolation between the pressure sensor and the FSR sensors, allowing for independent and interference-free measurements from both sensor types while maintaining a reliable connection to the infant’s oral cavity. The cable is visible, featuring a polarized header connector for connection to the PCB. This connector mates with the vertical header on the PCB shown on the left in Figure 9.

Figure 9

Manufactured electronic board. The PCB dimension is 5 by 3.5 cm.

Figure 10

Graphic interface screen displaying the data received from the device. Start, stop, and save buttons are displayed at the bottom of the screen.

Figure 11

Patient record screen that allows clinicians/researchers to enter and save patients’ data and display infants’ NNS measurements.

Figure 12

Expanded segment of simultaneous recordings of suction (top) and expression (bottom) in a hospitalized preterm newborn, acquired with the developed device. The characteristic morphology, including distinct cycles, transients, peak amplitudes, frequency, and pauses between events, can be clearly observed. This level of signal fidelity enables accurate clinical classification of non-nutritive sucking skills according to the Lau and Kusnierczyk [4] scale.

Figure 13

Pilot data obtained from six premature newborns hospitalized in a neonatal care unit, illustrating suction and expression stage patterns measured by the developed device. Each plot (a–f) corresponds to an individual subject’s recorded data. Suction plots show negative amplitude values (mmHg), indicating the intensity of sucking bursts, while expression plots show positive amplitudes (mmHg), indicating compression movements.