Secretion movement during manual lung inflation and mechanical ventilation

This project aimed to investigate the direction of artificial sputum movement during mechanical ventilation (MV) and bagging (MH) using a tube model. Three solutions of artificial sputum (ultrasonic gel, viscosity 100, 200 and 300 poise (P)) were prepared. About 1 ml of gel was placed in a glass tube connected to a test lung at one end and, via a pneumotachograph, to either a mechanical ventilator or a self-inflating bag, at the other. The position of the gel in the tube was recorded before and after 20 artificial breaths. Simultaneous breath-to-breath respiratory mechanics were measured. The procedure was repeated three times for each gel viscosity, with a fresh experimental set up for each measurement. Results showed that the distance travelled from the lung was significantly greater with MH compared with MV (P < 0.001). The lower the gel viscosity, the further the gel moved from the lung with both ventilatory modes (P < 0.001). MH was superior to MV for secretion mobilisation in a tube model.