OBJECTIVE: To develop a compact probe that can be used to monitor humidity in ventilator care equipment. A mesoporous film of alternate layers of Poly(allylamine hydrochloride) (PAH) and silica (SiO2) nanoparticles (bilayers), deposited onto an optical fibre was used. The sensing film behaves as a Fabry-Perot cavity of low-finesse where the absorption of water vapour changes the optical thickness and produces a change in reflection proportional to humidity. METHODS: The mesoporous film was deposited upon the cleaved tip of an optical fibre using the layer-by-layer method. The sensor was calibrated in a bench model against a commercially available capacitive sensor. The sensitivity and response time were assessed in the range from 5 % relative humidity (RH) to 95%RH for different numbers of bilayers up to a maximum of nine. RESULTS: The sensitivity increases with the number of bilayers deposited; sensitivity of 2.28 mV/%RH was obtained for nine bilayers. The time constant of the response was 1.13 s ± 0.30 s which is faster than the commercial device (measured as 158 s). After calibration, the optical fibre humidity sensor was utilised in a bench top study employing a mechanical ventilator. The fast response time enabled changes in humidity in individual breaths to be resolved. CONCLUSION: Optical fibre sensors have the potential to be used to monitor breath to breath humidity during ventilator care. SIGNIFICANCE: Control of humidity is an essential part of critical respiratory care and the developed sensor provides a sensitive, compact and fast method of humidity monitoring.
OBJECTIVE: To develop a compact probe that can be used to monitor humidity in ventilator care equipment. A mesoporous film of alternate layers of Poly(allylamine hydrochloride) (PAH) and silica (SiO2) nanoparticles (bilayers), deposited onto an optical fibre was used. The sensing film behaves as a Fabry-Perot cavity of low-finesse where the absorption of water vapour changes the optical thickness and produces a change in reflection proportional to humidity. METHODS: The mesoporous film was deposited upon the cleaved tip of an optical fibre using the layer-by-layer method. The sensor was calibrated in a bench model against a commercially available capacitive sensor. The sensitivity and response time were assessed in the range from 5 % relative humidity (RH) to 95%RH for different numbers of bilayers up to a maximum of nine. RESULTS: The sensitivity increases with the number of bilayers deposited; sensitivity of 2.28 mV/%RH was obtained for nine bilayers. The time constant of the response was 1.13 s ± 0.30 s which is faster than the commercial device (measured as 158 s). After calibration, the optical fibre humidity sensor was utilised in a bench top study employing a mechanical ventilator. The fast response time enabled changes in humidity in individual breaths to be resolved. CONCLUSION: Optical fibre sensors have the potential to be used to monitor breath to breath humidity during ventilator care. SIGNIFICANCE: Control of humidity is an essential part of critical respiratory care and the developed sensor provides a sensitive, compact and fast method of humidity monitoring.
Authors: Antonio M Esquinas Rodriguez; Raffaele Scala; Arie Soroksky; Ahmed BaHammam; Alan de Klerk; Arschang Valipour; Davide Chiumello; Claude Martin; Anne E Holland Journal: Crit Care Date: 2012-02-08 Impact factor: 9.097
Authors: J K Zuur; S H Muller; F H C de Jongh; M J van der Horst; M Shehata; J van Leeuwen; M Sinaasappel; F J M Hilgers Journal: Med Biol Eng Comput Date: 2007-07-13 Impact factor: 2.602
Authors: LiangLiang Liu; Serhiy Korposh; David Gomez; Ricardo Correia; Barrie R Hayes-Gill; Stephen P Morgan Journal: Sens Actuators B Chem Date: 2022-02-15 Impact factor: 7.460