Design, development and experimental validation of a non-invasive device for recording respiratory events during bottle feeding.

In newborns, a poor coordination between sucking, swallowing and breathing may undermine the effectiveness of oral feeding and signal immaturity of Central Nervous System. The aim of this work is to develop and validate a non-invasive device for recording respiratory events of newborns during bottle feeding. The proposed device working principle is based on the convective heat exchanged between two hot bodies and the infants' breathing. The sensing elements are inserted into a duct and the gas exchanged by infants is conveyed into this duct thanks to an ad hoc designed system to be mounted on a commercial feeding bottle. Two sets of experiments have been carried out in order to investigate the discrimination threshold of the device and characterize the sensor response at oscillating flows. The effect of distance and tilt between nostrils and device, and the breathing frequency, have been investigated simulating nostrils and neonatal respiratory pattern. The device has a discrimination threshold lower than 0.5 L/min at both 10° and 20° of tilt. Distance for these two settings does not affect the threshold in the investigated range (10-20 mm). Moreover, the device is able to detect breathing events, and to discriminate the onset of expiratory phase, during a neonatal respiratory task delivered by a lung simulator. The results foster the successful application of this device to the assessment of the temporal breathing pattern of newborns during bottle feeding with a non-invasive approach.

A transistors-based, bidirectional flowmeter for neonatal ventilation: design and experimental characterization.

A bidirectional, low cost flowmeter for neonatal artificial ventilation, suitable for application in mono-patient breathing circuits, is described here. The sensing element consists of two nominally identical bipolar junction transistors employed as hot bodies. The sensor working principle is based on the convective heat transfer between the transistors, heated by Joule phenomenon, and the colder hitting fluid which represents the measurand. The proposed design allows the sensor to discriminate flow direction. Static calibration has been carried out in a range of flowrate values (from -8 L·min(-1) up to +8 L L·min(-1)) covering the ones employed in neonatal ventilation, at different pipe diameters (ie., 10 mm and 30 mm) and collector currents (i.e., 500 mA, 300 mA, and 100 mA) in order to assess the influence of these two parameters on sensor's response. Results show that the configuration with a pipe diameter of 10 mm at the highest collector current guarantees the highest sensitivity (i.e., 763 mV/Lmin1 at low flowrate ± 1 L-min(-1)) and ensures the minimum dead space (2 mL vs 18 mL for 30 mm of diameter). On the other hand, the 30 mm pipe diameter allows extending the range of measurement (up to ±6 L-min 1 vs ±3.5 L· min(-1) at 10 mm), and improving both the discrimination threshold (<;0.1 L·min-(1)) and the symmetry of response. These characteristics together with the low dead space and low cost foster its application to neonatal ventilation.

An MR-compatible force sensor based on FBG technology for biomedical application.

Fiber Bragg Grating (FBG) technology is very attractive to develop sensors for the measurement of thermal and mechanical parameters in biological applications, particularly in presence of electromagnetic interferences. This work presents the design, working principle and experimental characterization of a force sensor based on two FBGs, with the feature of being compatible with Magnetic Resonance. Two prototypes based on different designs are considered and characterized: 1) the fiber with the FBGs is encapsulated in a polydimethylsiloxane (PDMS) sheet; 2) the fiber with the FBGs is free without the employment of any polymeric layer. Results show that the prototype which adopts the polymeric sheet has a wider range of measurement (4200 mN vs 250 mN) and good linearity; although it has lower sensitivity (≈0.1 nm-N(1) vs 7 nm-N(1)). The sensor without polymeric layer is also characterized by employing a differential configuration which allows neglecting the influence of temperature. This solution improves the linearity of the sensor, on the other hand the sensitivity decreases. The resulting good metrological properties of the prototypes here tested make them attractive for the intended application and in general for force measurement during biomedical applications in presence of electromagnetic interferences.

An automatized system for the assessment of nutritive sucking behavior in infants: a preliminary analysis on term neonates.

Nutritive Sucking (NS) is a highly organized process that can reflect infants' maturation during the early post-natal period. The assessment of NS may provide a sensitive means of evaluating early motor skills and their development. Thus, a reliable tool for assessing sucking behavior may benefit diagnostics and treatment of newborns since the first days of life. The aim of this work is to propose an automatized system to measure sucking ability and calculate a set of objective and quantitative indices for its assessment. We focused on the analysis of the Intraoral Pressure (IP) generated by infants while feeding: an ad-hoc designed software application was developed to analyze the signal obtained by a pressure transducer connected with a catheter placed through a standard bottle teat into the oral cavity during feeding. Automatic algorithms for suck and burst identification and for their characterization are described. We carried out a preliminary test of the system, analyzing data from two healthy term newborns, tested twice over time (1-2 days old and 6-10 weeks later). We calculated a set of different sucking parameters (e.g. sucking amplitude, frequency and area), and proposed some indices, that are typically used for the assessment of motor control, in order to assess the smoothness of IP. Results encourage further investigation of the proposed system for monitoring the development of early sucking skills.

An experimental protocol for the definition of upper limb anatomical frames on children using magneto-inertial sensors.

Motion capture based on magneto-inertial sensors is a technology enabling data collection in unstructured environments, allowing "out of the lab" motion analysis. This technology is a good candidate for motion analysis of children thanks to the reduced weight and size as well as the use of wireless communication that has improved its wearability and reduced its obtrusivity. A key issue in the application of such technology for motion analysis is its calibration, i.e. a process that allows mapping orientation information from each sensor to a physiological reference frame. To date, even if there are several calibration procedures available for adults, no specific calibration procedures have been developed for children. This work addresses this specific issue presenting a calibration procedure for motion capture of thorax and upper limbs on healthy children. Reported results suggest comparable performance with similar studies on adults and emphasize some critical issues, opening the way to further improvements.