A fiber optic plethysmograph (FOP) has been redesigned and used to monitor cardiac activity in real time during apnoea. The device was tested using four healthy subjects aged between 23 and 31, and it is concluded that the device performs reliably. Advanced algorithms have been developed and implemented to perform the cardiac signal extraction. A strong correlation is noted between the signals derived using the FOP and the respiratory inductive plethysmograph (RIP) when the latter has also been applied to monitor cardiac activity. The approach developed for interpreting thoracocardiograms (TCGs) and abdominocardiograms (ACGs) derived from the RIP is therefore directly applicable to the interpretation of the corresponding FOP signals. The prospect of using the FOP system for real-time gating in a magnetic resonance (MR) scanner environment is discussed.
"Solutions supported in photonic systems are good ways due to its robustness and resilience when subjected to the former conditions . Optical fibers are good ways for achieving such measurement goal . The first set of tries to integrate optical fibers on textiles was done in the Georgia Tech's wearable motherboard (GTWM, also known as smart shirt), where the objective of the fibers was in the bullet wounds detection for soldiers acting on war scenarios . "
[Show abstract][Hide abstract] ABSTRACT: This paper presents a photonic system based on Fiber Bragg Gratings (FBGs) for application to wearable garments. The objective is spanning the FBGs over the whole area of the garments for acting as sensing elements. The FBGs are embedded on a polychloroethanediyl (polyvinyl chloride, commonly abbreviated as PVC) carrier in order to increase their sensitivity to strains and for improving the simultaneous acquisition of respiratory and cardiac frequencies with only one FBG sensor. The global structure comprising FBGs and carrier allow high strain cycles and at the same time present linear behavior with the temperature, 17 pm · °C<sup>-1</sup>. The measurements show a stable structure for temperatures up to 100°C. This brings excellent perspectives for measuring the temperature with high accuracy and range. A set of tests were done by subjecting the FBG/carrier structure (with FBG stretched and no curves) to strains up to 1.2 mm, and it was also observed a linear behaviour: e.g., displacements of 0.8 pm · με<sup>-1</sup>. Behind its sensing enhancement operation, the carrier makes easy to mount the sensing structures.
[Show abstract][Hide abstract] ABSTRACT: We present an optical non-contact method for heart beat monitoring, based on the measurement of chest wall movements induced by the pumping action of the heart, which is eligible as a surrogate of electrocardiogram (ECG) in assessing both cardiac rate and heart rate variability (HRV). The method is based on the optical recording of the movements of the chest wall by means of laser Doppler interferometry. To this aim, the ECG signal and the velocity of vibration of the chest wall, named optical vibrocardiography (VCG), were simultaneously recorded on 10 subjects. The time series built from the sequences of consecutive R waves (on ECG) and vibrocardiographic (VV) intervals were compared in terms of heart rate (HR). To evaluate the ability of VCG signals as quantitative marker of the autonomic activity, HRV descriptors were also calculated on both ECG and VCG time series. HR and HRV indices obtained from the proposed method agreed with the rate derived from ECG recordings (mean percent difference <3.1%). Our comparison concludes that optical VCG provides a reliable assessment of HR and HRV analysis, with no statistical differences in term of gender are present. Optical VCG appears promising as non-contact method to monitor the cardiac activity under specific conditions, e.g., in magnetic resonance environment, or to reduce exposure risks to workers subjected to hazardous conditions. The technique may be used also to monitor subjects, e.g., severely burned, for which contact with the skin needs to be minimized.
[Show abstract][Hide abstract] ABSTRACT: The aim of the present work is to establish a protocol for monitoring the cardiac activity measuring the skin surface vibrations of the main neck vessels, caused by vascular wall motion in carotid artery. The method is based on the optical recording of the movements of the neck by means of laser Doppler interferometry. The ECG signal and the velocity of vibration of the skin in correspondence of the carotid artery (named optical vibrocardiography: VCG) have been simultaneously recorded on five healthy subjects. Standard heart rate variability tests have been carried out. The capability of VCG signals to be used as a surrogate of the ECG in assessing both cardiac rate and heart rate variability (HRV) has been tested using time and spectral descriptors, and specific statistical analysis. Mean differences have been found lower than 3.13%. Optical vibrocardiography might be a simple approach to the clinical practice of cardiovascular screening, in particular in harsh environment, such as MR clinical practice, where ECG recordings are corrupted by artefacts and ECG cables might represent an hazard for the patients.
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