Portable instrument for the volume measurement of high-frequency percussive ventilators

In recent years, the usefulness of High Frequency Percussive Ventilation (HFPV) has been clinically valued as a suitable alternative to conventional mechanical ventilation especially in particularly conditions (for example in pulmonary resection [1]). It acquires the flow with a sampling rate of 2 KHz, computes the volume every 64 samples by numerical integration and sends the values to a visualization device (Hewlett Packard HP50g) that updates the numerical value and the volume plot every 32 milliseconds. The results show that the sampling frequency of the VT+ (50 Hz) is insufficient in the case of percussive ventilation, producing unacceptable errors (about 20%) in the volume evaluation; on the contrary, the sampling frequency of our system (2 KHz) allows to gain correct results. In conclusion, the suitable sampling frequency together with the system portability allow our device to realize a precise monitoring of respiratory parameters, during HFPV, of patients in surgery room or in intensive care unit.