Objective: To establish the method of continuous tracheal gas insufflation (CTGI) and investigate the role of pressure relief valve (PRV) in limiting high peak airway pressure induced by CTGI.
Methods: CTGI device was made by authors. Nine healthy mongrel dogs were mechanically ventilated by using Evita 2 (Drager Inc.). PRV was inserted into the ventilatory circuit for selected experiment steps and adjusted a threshold pressure equal to the preset inspiratory pressure. PCV, PCV + CTGI (TGI group) and PCV + CTGI + PRV (PRV group) were conducted in different inspiration/expiration (I/E) ratio of 1:2 and 2:1. Gas exchange, lung mechanics and hemodynamics status were monitored at the constant set inspiratory pressure of PCV.
Results: At the same I/E ratio, peak airway pressure in TGI group was higher than that of PRV and PCV group (P < 0.01), whereas PRV group maintained the preset inspiratory pressure as PCV group. At the different I/E ratio, peak airway pressure in TGI (2:1) group was higher than that of TGI (1:2) group(P < 0.01). PaCO2 in TGI and PRV group decreased significantly than that of PCV, TGI group was more lower than PRV group, PaO2, hemodynamics and oxygenation remained unchanged in all groups.
Conclusions: The CTGI device is effective in improving alveolar ventilation with no significant influence on hemodynamics and oxygenation; A pressure relief valve is necessary to ensure the safe use of CTGI.