Application of long-period-grating sensors to respiratory plethysmography

Abstract

Abstract.A series of in-line curvature sensors on a garment are used to monitor the thoracic and abdominal movements of a human during respiration. These results are used to obtain volumetric tidal changes of the human torso in agreement with a spirometer used simultaneously at the mouth. The curvature sensors are based on long-period gratings ͑LPGs͒ written in a progressive three-layered fiber to render the LPGs insensitive to the refractive index external to the fiber. A curvature sensor consists of the fiber long-period grating laid on a carbon fiber ribbon, which is then encapsulated in a low-temperature curing silicone rubber. The sensors have a spectral sensitivity to curvature, d / dR from ϳ7-nm m to ϳ9-nm m. The interrogation technique is borrowed from derivative spectroscopy and monitors the changes in the transmission spectral profile of the LPG's attenuation band due to curvature. The multiplexing of the sensors is achieved by spectrally matching a series of distributed feedback ͑DFB͒ lasers to the LPGs. The versatility of this sensing garment is confirmed by it being used on six other human subjects covering a wide range of body mass indices. Just six fully functional sensors are required to obtain a volumetric error of around 6%. © 2007 Society of Photo-Optical Instrumentation Engineers.

Fiber-optic sensors for monitoring patient physiological parameters: a review of applicable technologies and relevance to use during magnetic resonance imaging procedures

“…124,125 Preliminary studies of longperiod gratings (LPGs), a variation of Bragg gratings, for recording ventilatory movements and/or volumes have been performed because these gratings are particularly sensitive to any deformations in the LPG section. [126][127][128][129][130][131][132] Change in thorax curvature is sensed as bending of an LPG attached to the thorax. Bending induces strain and stress across the fiber and, in consequence, a change in its refractive index via the strain-optic effect, which manifests as a change in position, shape and amplitude of resonant bands in the transmission spectrum.…”

Long-period grating fiber-optic sensors of bending for applications in pulmonology

“…Kako kod ovog vlakna dominira sprezanje sa modovima unutrašnjeg omotača, mod je izolovan od okoline čime je eliminisana nepoželjna osetljivost rešetke na promene okolnog indeksa prelamanja [9]. Enkapsulacijom senzora u silikon znatno je umanjena i osetljivost rešetke na nagle promene temperature [13].…”

“…Sa stanovišta primene u svakodnevnoj bolničkoj praksi, činjenica da se u predloženoj tehnici postavlja samo jedna enkapsulirana rešetka prosečne veličine 10 cm x 2 cm x 0.5 cm na torzo pacijenta čini naš senzor praktičnijim od konkurentnih senzora sastavljenih od optičkih [13] ili električnih [18] elemenata ugrañenih u specijalne trake koje se postavljaju oko torza pacijenta.…”

Optical Fiber Gratings in Perspective of Their Applications in Biomedicine

“…Expansion of the thorax cage during respiration was accordingly transmitted to the sensor grating and caused it to deform under the strain. First application of a multiplexed LPG array on curvature sensing garment used to monitor the thoracic and abdominal movements of a human during respiration was reported by T. Allsop et al 2003Allsop et al , 2007. They have shown that, it is possible to generate a geometric profile of the chest and abdomen in three dimensions with an array of 20 sensors.…”