Optical Identification of Parenteral Nutrition Solutions Exploiting Refractive Index Sensing

Abstract

Parenteral artificial nutrition (PAN) is a lifesaving treatment for a large population of patients affected by different diseases, and it consists of intravenous injection of nutritive fluids by means of infusion pumps. Wrong PAN solutions are, unfortunately, often administered, thus threatening the patients’ well-being. Here, we report an optofluidic label-free sensor that can distinguish PAN solutions on the basis of their volumetric refractive index (RI). In our system, a monochromatic light beam, generated by a laser diode, travels obliquely through a transparent, square-section polystyrene channel, is then back-reflected by a mirror, and finally exits the channel in a position that depends on the filling fluid RI. The displacement of the output light spot ΔXexperim is easily detected with a linear, 1-D position sensitive detector (PSD). We initially calibrated the sensor with water-glucose solutions demonstrating a sensitivity S = ΔXexperim/Δn = 13,960 µm/RIU. We then clearly distinguished six commercial PAN solutions, commonly administered to patients. To the best of our knowledge, this is the first reported healthcare sensing platform for remote contactless recognition of PAN fluids, which could be inserted into infusion pumps to improve treatment safety, by checking the compliance to the prescription of the fluid actually delivered to the patient.

Optical Multi-Parameter Measuring System for Fluid and Air Bubble Recognition

“…By converting the sum and difference signal, only considered when a fluid (not air) is in the cuvette, in spot displacement p PSD , using Equation (1), the linear calibration curve of the system, as volume RI sensor, was retrieved yielding a sensitivity of 13960 µm/RIU, in agreement with the detailed theoretical simulations presented in [ 23 ] describing the path traveled by the laser beam inside the cuvette. More details about a specific application of the RI measuring system for PAN recognition were reported in [ 23 ].…”

“…Moreover, it must be taken into account that the PSD response is not linear in a very wide range of RI values but the sensitivity tends to decrease as the RI variation increases. In view of all these considerations, the theoretical model described in [ 23 ] allowed to estimate a maximum range of measurable RI variation of the order of 1.67 RIU.…”

“…In this work, we have demonstrated a multi-parameter measuring system that can simultaneously detect air bubbles traveling in transparent fluids and distinguish fluids based on their refractive index by exploiting the same instrumental configuration, preliminary applied for the recognition of commercial solutions for parenteral artificial nutrition [ 23 ]. While recognition of solutions is carried out by measuring the light beam displacement on the PSD surface due to their different RI, simultaneous identification of air bubbles inside the cuvette is possible thanks to the fact that each of them interrupts twice the laser beam, providing a fingerprint signal.…”

“…In this work, the instrumental configuration that we originally designed only for the recognition of solutions for parenteral artificial nutrition (PAN) [ 23 ] is here upgraded to a multi-parameter measuring system able not only to identify transparent fluids through their refractive index (RI) but, at the same time, also able to recognize the presence of air bubbles in the fluidic circuit and measure their flow velocity. As in the previously reported scheme [ 23 ], a laser beam travels obliquely through a cuvette and is then back-reflected by a mirror toward a position that depends on the filling fluid RI.…”

“…In this work, the instrumental configuration that we originally designed only for the recognition of solutions for parenteral artificial nutrition (PAN) [ 23 ] is here upgraded to a multi-parameter measuring system able not only to identify transparent fluids through their refractive index (RI) but, at the same time, also able to recognize the presence of air bubbles in the fluidic circuit and measure their flow velocity. As in the previously reported scheme [ 23 ], a laser beam travels obliquely through a cuvette and is then back-reflected by a mirror toward a position that depends on the filling fluid RI. The fluid recognition function is accomplished by detecting the displacement of the transmitted spot due to the fluid under test, with respect to a reference fluid, with a 1-D linear position sensitive detector (PSD) [ 24 ], an optical detector typically employed, for example, in laser triangulation sensors.…”