OBJECTIVETo evaluate the effects of different interventional strategies, namely controlled high-concentration oxygen therapy, continuous positive airway pressure (CPAP) and bi-level positive airway pressure (BiPAP) ventilation, on respiratory response and work of breathing (WOB) in canine models of early-stage acute lung injury (ALI).

METHODSAfter successful duplication of ALI models with oleic acid (diagnostic criteria: Pa(O2)/Fi(O2)

RESULTSBiPAP resulted in the most significant effects in reducing the respiratory rate (RR) and f/V(T) (P<0.001), followed by CPAP and O2 interventions (P<0.001). None of the 3 treatments showed obvious effects on V(E) (P>0.05), which maintained the level of early ALI/ARDS stage. BiPAP greatly improved V(T) and V(T)/Ti, showing better effects than CPAP and O2. No significant differences were noted among the 3 groups in T(I)/T(tot) (P>0.05). BiPAP showed superior effect to CPAP in lowering the peak transdiaphragmatic pressure (Pdi). CPAP and BiPAP both effectively counteracted intrinsic positive end expiratory pressure (PEEPi) (P<0.01), while O2 produced no obvious such effects (P>0.05). BiPAP showed the most evident effects, followed by CPAP, in reducing WOB, but oxygen therapy produced no obvious effects. CPAP (P<0.01) and BiPAP (P>0.05) both effectively reduced the proportion of ingredients in WOB related to PEEPi.

CONCLUSIONBiPAP and CPAP can produce favorable effects in relieving dyspnea, reducing WOB and improving respiratory response to control the deterioration of ARDS. BiPAP has more significant therapeutic effects than CPAP and oxygen therapy.