title: Fiber Bragg Grating Measuring System for Simultaneous Monitoring of Temperature and Humidity in Mechanical Ventilation.
abstract: During mechanical ventilation, the humidification of the dry air delivered by the mechanical ventilator is recommended. Among several solutions, heated wire humidifiers (HWHs) have gained large acceptance to be used in this field. The aim of this work is to fabricate a measuring system based on fiber Bragg grating (FBG) for the simultaneous monitoring of gas relative humidity (RH) and temperature, intended to be used for providing feedback to the HWHs' control. This solution can be implemented using an array of two FBGs having a different center wavelength. Regarding RH monitoring, three sensors have been fabricated by coating an FBG with two different moisture-sensitive and biocompatible materials: the first two sensors were fabricated by coating the grating with a 3 mm × 3 mm layer of agar and agarose; to investigate the influence of the coating thickness to the sensor response, a third sensor was developed with a 5 mm × 5 mm layer of agar. The sensors have been assessed in a wide range of RH (up to 95%) during both an ascending and a subsequent descending phase. Only the response of the 3 mm × 3 mm-coated sensors were fast enough to follow the RH changes, showing a mean sensitivity of about 0.14 nm/% (agar-coated) and 0.12 nm/% (agarose-coated). The hysteresis error was about <10% in the two sensors. The contribution of temperature changes on these RH sensors was negligible. The temperature measurement was performed by a commercial FBG insensitive to RH changes. The small size of these FBG-based sensors, the use of biocompatible polymers, and the possibility to measure both temperature and RH by using the same fiber optic embedding an array of two FBGs make intriguing the use of this solution for application in the control of HWHs.
authors.affiliation: Unit of Measurements and Biomedical Instrumentation, Center for Integrated Research, Università Campus Bio-Medico di Roma, Via Álvaro del Portillo, 21, 00128 Rome, Italy. c.massaroni@unicampus.it.
authors.forename: Carlo
authors.initials: C
authors.lastname: Massaroni
authors.affiliation: Photonics Micro- and Nanostructures Laboratory Research Centre of Frascati, ENEA, Via Enrico Fermi, 45, Frascati, 00044 Rome, Italy. michele.caponero@enea.it.
authors.forename: Michele A
authors.initials: MA
authors.lastname: Caponero
authors.affiliation: Photonics Micro- and Nanostructures Laboratory Research Centre of Frascati, ENEA, Via Enrico Fermi, 45, Frascati, 00044 Rome, Italy. rosaria.damato@enea.it.
authors.forename: Rosaria
authors.initials: R
authors.lastname: D'Amato
authors.affiliation: Unit of Measurements and Biomedical Instrumentation, Center for Integrated Research, Università Campus Bio-Medico di Roma, Via Álvaro del Portillo, 21, 00128 Rome, Italy. lp.daniela@yahoo.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Lo Presti
authors.affiliation: Unit of Measurements and Biomedical Instrumentation, Center for Integrated Research, Università Campus Bio-Medico di Roma, Via Álvaro del Portillo, 21, 00128 Rome, Italy. e.schena@unicampus.it.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Schena
keywords: fiber Bragg grating sensors; fiber optic sensors; humidity measurement; mechanical ventilation; moisture-sensitive polymer; temperature measurement