Experimental And Clinical Study Of Aspiration Of Dead Space In The Management Of Respiratory Failure

Objectives ASPIDS is a newly developed adjunct method to mechanical ventilation and is mainly used to decrease dead space, to improve ventilation efficiency, to resolve carbondioxide retention while undertaking small tidal ventilation and it can also be used to prevent or reduce the morbidity of ventilator-induced lung injury (VILI). The main objectives of this study are: (1) To manufacture a practical ASPIDS device and to confirm its efficacy and safety in experimental and clinical setting. (2) To induce a dog acute lung injury (ALl) model by massive saline lavage, to evaluate the effects of aspiration of dead space (ASPIDS) on the elimination of CO2 and the reduction of tidal volume (VT)^. airway peak pressure (Ppeak)N airway pause pressure (Ppause) while remain PaCO2 in the normal range during ALl dogs were permissive hypercapnia (PHC). We also observed the effects of ASPIDS on hemodynamics and oxygenation of dogs and compared with the effects of phasic tracheal gas insufflation (PTGI). (3) To induce a dog acute respiratory distress syndrome (ARDS) model by oleic acid , to evaluate the effects of ASPIDS on the elimination of CO2 and the reduction of V1 Ppe P_pause while remain PaCO2 in the normal range during model dogs were PHC. (4) To evaluate the effects of ASPIDS on the elimination of CO2. respiratory mechanics and hemodynamics during bronchial spasm model dogs were PHC. (5) Based on the animal study, we further investigated the CO2 removing effect of ASPIDS in COPD patients with respiratory failure and compared with the effects of PTGI. 6 Methods Using self-designed ASPIDS device, we observed some physiological paremeters such as PaCO2 Ppealc. Ppause? end expiratory carbondioxide pressure (PetCO2) and hemodynamics in the two animal groups of conventional mechanical I ventilation (CMV) and permissive hypercapnia (PHC) by applying TGI(4.OL/min) and ? ASPIDS (4.OL/min). The effects of ASPIDS and TGI were tested in normal dogs hypercapnia dogs as well as ALl dogs model of massive saline lavageN ARDS dogs model induced by oleic acid and bronchial spasm dogs model induced by methacholine. On the bases of animal study, 8 COPD patients with respiratory failure were applied to ASPIDS treatment using self-designed device, PaCO2 and PetCO2 as well as Ppause Paw were observed at the point while the patients received CMV and PHC. We also compared the effects of ASPIDS(4.OL/min) with PTGI(4.OL/min, 6.0 Llmin). Results The animal study showed that: (1) Both the normal dogs and diseased dogs model, ASPJDS significantly decreased the PaCO2 level, enhanced CO2 elimination and maintained PaCO2 in the normal range while decreased VT by 30%, the elimination of CO2 of ASPIDS was superior to that of TGI. (2) TGI elevated airway pressure in both animals groups, but the levels of Ppeajc and Ppause in PHC group were significantly lower than those of CMV group. ASPIDS significantly decreased airway pressure in both animals groups. (3) ASPIDS and TGI significantly decreased P^<sup>CO2 levels, but ASPIDS was superior to TGI . Re and VE levels were significantly increased after TGI , but Re level was significantly decreased after ASPIDS. ASPIDS and TGI showed no obvious influence on Cst. (4) ASPIDS and TGI have no obvious I...