Efficacy of continuous tracheal gas insufflation in spontaneously breathing canine with acute lung injury

Objective To investigate the effects of continuous tracheal gas insufflatio n (CTGI) combined with biphasic intermittent positive airway pressure (BIPA P) ventilation on dogs with spontaneous breathing. Methods Eight canine models with oleic acid induced lung injury and spontan eous breathing were ventilated in a random order by Evita 2 (Drager Inc., G ermany) in modes of BIPAP (BIPAP group) and BIPAP with CTGI flow rate of 3, 6 and 9 L/min (T3, T6 and T9 groups), respectively. The setting parameters of BIPAP were fiction of inspired oxygen 60%, inspiratory to expiratory ra tio 1:1, respiratory rate 20 and positive end expiratory pressure 5 cm H2O. Arterial and mixed venous blood gas, lung mechanics, systemic and pulmonar y hemodynamics status were monitored at the same level of PaCO2 obtained by adjusting peak inspiratory pressure of BIPAP. Results Peak inspiratory pressure in the T6 group (14 +/- 4 cm H2O) and in the T9 group (11 +/- 3 cm H2O) were significantly lower than that of BIPAP (20 +/- 5 cm H2O, P < 0.01), but there was no significant difference among the T3, T6 and T9 groups or between the T3 and BIPAP groups. PaO2, mean art ery blood pressure, mean pulmonary artery pressure, pulmonary artery wedge pressure, cardiac ouput, oxygen delivery and oxygen consumption all remaine d unchanged in four different conditions. Conclusions Using BIPAP combined with CTGI does not cause asynchrony betwee n ventilator and spontaneous breathing, but significantly decreases airway pressure with no influence on hemodynamics and oxygenation. Therefore, BIPA P with CTGI may be a useful support technique, especially in cases where th e airway pressure should be limited.