Desenvolvimento de cintas torácicas instrumentadas por sensores a fibra ótica para medidas cardíacas e respiratórias

Abstract

Human beings need oxygen to maintain their metabolic processes, which are essential to guaranteeing life. This makes heart and respiratory rates fundamental tools for detecting homeostatic alterations. Pulmonary respiration and heart rate are determined by rhythmic processes but are directly influenced by the age of the individual, physical exercise and even by some pathological conditions. The monitoring of cardiac and respiratory activity has been carried out and reported in the literature using different types of sensors, such as electrical and optical. The aim of this work is to develop, manufacture and characterize a belt instrumented with sensors based on optical fiber Bragg gratings (FBG) and use the device to monitor cardiac and respiratory measurements during in vivo tests. The proposed system was evaluated in a case study of a male volunteer, aged 25, during different stages of monitoring the cardiorespiratory cycle. The subject performed respiratory movements in apnea, rest, controlled breathing and during stationary running. The tests were carried out with the volunteer wearing the FBG belt covering the entire thoracic circumference, since the expansion of the chest cavity causes a change in the wavelength of the FBG. The results demonstrate the feasibility of using the belt instrumented by Bragg gratings to analyze thoracic movements by varying the wavelength of the optical spectrum reflected by the grating. Through a controlled prior characterization process, it is possible to establish a relationship between deformations and the variation in the wavelength of the optical spectrum. Thus, when the instrumented belt is attached to the patient, by analyzing the optical spectrum it will be possible to obtain the values of the thoracic deformations caused by cardiac and respiratory movements. Changes in the optical spectrum can be indicative of loss of oxygenation and fatigue of the respiratory muscles. For verification and comparison purposes, the tests carried out with the instrumented belt were also carried out using a cardiofrequency meter and manual reference counts. The frequencies estimated using the belt by the system developed showed a high correlation with the frequencies obtained manually, acquired by the cardiofrequency meter and estimated by statistical methods for all the tests carried out.