Tracheal gas insufflation pressure control versus volume control ventilation - A lung model study

Tracheal gas insufflation (TCI) has been recommended as an adjunct to mechanical ventilation in the presence of elevated Pa-CO2. Based on our initial clinical experience with continuous flow TGI and pressure control ventilation (PCV), we were concerned about elevation in peak airway pressure as TCI was applied. In a lung model, we evaluated the effects of continuous flow TCI during both PCV and volume control ventilation (VCV). A single compartment lung model was configured with an artificial trachea into which an 8-mm endotracheal tube was positioned. TCI was established with a 16-G catheter positioned 2 cm beyond the tip of the endotracheal tube. Ventilation was provided by a Puritan-Bennett 7200ae ventilator with PCV 20 cm H2O or VCV with a tidal volume (VT) similar to that with PCV. A rate of 15 breaths/min and PEEP of 10 cm H2O were used throughout. Inspiratory times (TI) of 1.0, 1.5, 2.0, and 2.5 s were used with TCI of 0, 4, 8, and 12 L/min. Lung model compliance (ml/cm H2O) and resistance (cm H(2)0/L/s) combinations of 20/20, 20/5, and 50/20 were used. Auto-PEEP, VT, and peak alveolar and airway opening pressures increased as TCI and TI increased, regardless of lung mechanics settings (p < 0.01). All increases were greater with VCV than PCV (p < 0.05). Continuous flow TCI with both PCV and VT-uncorrected VCV may result in marked increases in VT and system pressures, especially at long TI.