A long-period fibre grating monitor of respiratory volumes for the use in non-invasive mechanical ventilation

Abstract

The ventilators involved in mechanical ventilation are usually equipped with pneumatic sensor detecting patients own respiratory effort in order to assist spontaneous breathing. However, the interface of the mask with the patient promotes air leaks that affect the measurement of pneumatic variables and hence induces patient-ventilator asynchrony. In this paper we describe a new method and apparatus for continuous monitoring of the respiration based on the measurement of chest wall movements. The proposed solution uses a long-period fibre grating sensor attached to patients thorax and a simple and cost-effective monochromatic measurement scheme. On a set of healthy volunteers, we have established the linear correlation between the change in local torso curvature and the tidal volume during clinically relevant breathing patterns. The chest-wall movement measured by the grating advances with respect to the air-flow signal by about 200 ms, indicating the possibility to lead to more confidence triggering decision. The proposed scheme is non-invasive, simple, low-cost, and immune to air-leaks and drifts that are limiting factors in the currently standard pneumatic measurement techniques.