Intratracheal pulmonary ventilation keeps tracheal tubes clean without impairing mucociliary transport

Intratracheal pulmonary ventilation (ITPV) is a form of tracheal gas insufflation through a reverse thrust catheter that facilitates expiration and enhances CO2 removal. Tracheas of sheep mechanically ventilated for 3 days with gas delivered through the reverse-thrust catheter remained free of secretions, without suctioning. It was hypothesized that: 1) The expiratory flow from the lungs, combined with continuous cephalad flow from the reverse-thrust catheter keeps endotracheal tubes clean; and 2) tracheal mucus velocity is not impaired by ITPV.

A model trachea connected to a test lung and to a ventilator, via an 8-mm endotracheal tube, was used. Inspiratory and expiratory peak flow velocities and the movement of mucus in the model trachea and in the endotracheal tube were measured during conventional mechanical ventilation and ITPV. Tracheal mucus velocity was measured radiographically, using tantalum discs as markers, in seven intubated sheep ventilated for one hour with volume-controlled ventilation, and with ITPV. One millilitre Evans Blue dye was introduced into the trachea, to visualize mucus transport into the endotracheal tube.

Peak expiratory flow velocity exceeded peak inspiratory flow velocity by 100% during ITPV. During volume-controlled ventilation, flow velocities were equal. During ITPV, there was slow, then rapid cephalad movement of mucus in the model trachea, 0.5 cm distal to the tip of the endotracheal tube, the velocity increasing once mucus entered the endotracheal tube. During volume-controlled ventilation, no movement of mucus was found. Baseline tracheal mucus velocity was equal during volume-controlled ventilation and ITPV. Secretions stained with Evans Blue dye entered the endotracheal tube and were rapidly expelled from within the endotracheal tubes during ITPV; only traces of mucus were found in two sheep during volume-controlled ventilation.

The enhanced expiratory flow during ITPV expels secretions from the endotracheal tube through entraining of mucus at the tip of the endotracheal tube. Tracheal mucus velocity is not influenced by ITPV.