Preliminary evaluation of a simple optical fiber measurement system for monitoring respiratory pressure in mechanically ventilated infants

A novel fiber-optic pressure sensor is proposed for monitoring respiratory pressure in mechanically ventilated infants. The sensor principle is based on the measurement of the displacement of an emitting optical fiber cantilever due to the differential pressure applied on a capsule, performed by means of a photodiode array. The proposed fiber-optic sensing technique can reduce typical drawbacks affecting all biomedical fields, such as patient electrical safety and electromagnetic interference; moreover the device is not sensitive to optical power variations independent by pressure, because it is based on a detection of the illumination pattern of the emitting optical fiber. Two different arrangements of the fiber-optic pressure sensor have been examined: optimal configuration was found when the displacement of a capsule is amplified by means of an optical fiber cantilever, with a measurement range up to 15 cmH2O (i.e. the usual range of airway pressures encountered during tidal breathing of infants) and a high sensitivity (2.6 pixel/cmH2O) are obtained. The achieved metrological characteristics confirm that the proposed optical fiber pressure sensor is particularly suitable for monitoring respiratory pressure in mechanically ventilated infants and for detecting pressure drops due to infant’s inspiratory attempts. The proposed measurement system has been preliminarily verified through simple respiratory tests.