Measurement of respiration rate in preterm infants by laser Doppler vibrometry

The continuous monitoring of patients recovered in intensive care units is a mandatory tasks for clinicians in order to check conditions and effects of therapies. Among the many signals and quantities observable, the ones related to the heart and particularly the lung´s activity are of primary interest. Today the majority of the measurement methods used for the assessment of the respiration rate are based on invasive methods (spriometry) which are often included into mechanical ventilator to which the patients, in need of assisted breathing, are attached. In this paper an optical, non-contact measurement method for monitoring of the respiration rate in pre-term infants is reported. It is based on the assessment of abdominal wall movements detected by a laser Doppler vibrometer and can be operated at a distance from the patient and outside the incubator. A total of 9 preterm patients have been monitored; respiration rates measured by a reference instrument (BabyLog 8000 Draeger plus) and the proposed non-contact method have been measured for a period of time of 60s. Data have been compared using the Bland-Altman analysis and results demonstrate an optimal correlation (R=0.97) among data and an uncertainty of the proposed method of ± 0.13s (K=2).