P. Cappa, S.A. Sciuto, and S. Silvestri (Italy)
Pulmonary ventilation; Breathing circuit;Respiratory system parameters
Among many patient respiratory parameters, pulmonary ventilators for intensive care provide information on patient resistance, compliance and "work of breathing" values calculated from pressure and flow data patterns according to the widely utilized Mead and Whittenberger method. The effects induced by the breathing circuit and analogue filtering of the ventilator measuring system are experimentally investigated during controlled ventilation. Three main phenomena are observed: (a) errors in calculation of resistance and compliance due to filtering of pressure and flow waveforms; (b) the presence of pressure oscillations at the beginning of inspiration and expiration phases; and (c) the phase shift between pressure and flow waveforms. The experimental evaluation of the measuring system of a neonatal ventilator is then conducted and: (a) a delay in pressure and flow measurement synchronization equal to (22 2) ms is evaluated; moreover, (b) a difference between the values provided by the ventilator and those measured by the reference experimental setup on respiratory parameters such as the compliance, resistance and work of breathing that lies in the range of (7 16)% of reading is observed.
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