Effect of the inspiratory flow pattern on inspiration/expiration transition of lung vibrations in mechanically ventilated patients
© BioMed Central Ltd 2008
Published: 13 March 2008
Mechanical ventilation can be performed using different inspiratory flow patterns. We used vibration response imaging (VRI) technology to ascertain the intensity of lung vibration with different inspiratory flow patterns during various modes of mechanical ventilation.
VRI was performed in succession during volume control ventilation with a square and decelerating inspiratory flow waveform, a pressure control waveform and a pressure support waveform. The total lung vibration energy transmitted to the posterior thorax (from 36 sensors) was plotted over time and the transition of vibrations from inspiration to expiration noted.
When the flow-time waveform recorded between the patient and the ventilator is compared with the vibration waveform summed from surface sensors, two patterns emerge: as the time between PIF and PEF increases, the separation of peak I and E lung vibration energy increases; and as end-inspiratory flow decreases, the valley between peak I and E vibration deepens. The decelerating flows that gradually diminish to zero will therefore produce the greatest separation in respiratory vibrations. There could be clinical relevance as to the effect of the inspiratory flow waveform on vibration transition in the chest.
This article is published under license to BioMed Central Ltd.