EFFECT OF CPAP ON RESPIRATORY FUNCTION IN EXPERIMENTAL RABBITS WITH ACUTE LUNG INJURY

Cui W, Geng R, Chen XN, Wang Y

Beijing Children�s Hospital, Beijing, P. R. China

Objective: To evaluate the efficacy of treating oleic acid-induced acute lung injury (ALI) with different CPAP (5cmH₂O, 10cmH₂O).

Methods: Thirty-two healthy rabbits were anesthetized and surgically prepared for hemodynamic and gas exchange measurements. ALI was induced by oleic acid injection and was evidenced by PaO₂/FiO₂<300mmHg. Animals were randomized into three groups: a) Control; b) CPAP-5 (CPAP=5cmH₂O, FiO₂=0.4); c) CPAP-10 (CPAP=10cmH₂O, FiO₂=0.4). All groups were studied for 1.5hrs after the ALI.

Results: Compared with control, in CPAP-5 group, tidal volume (V_T) increased from 10.80�1.34 (mean�SD) to 13.80�1.01ml, functional residual capacity (FRC) increased from 6.93�0.40 to 17.46�0.73ml/kg, PaO₂/FiO₂ increased from 248.66�17.54 to 397.63�21.54mmHg, Qs/Qt decreased from 17.01�3.11 to 4.81�1.23% (P<.05); in CPAP-10 group, V_T increased from 10.88�1.53 to 14.79�0.97ml, FRC increased from 6.93�0.40 to 19.69�1.19ml/kg, PaO₂/FiO₂ increased from 244.64�19.38 to 435.31�27.00mmHg, Qs/Qt decreased from 18.09�3.34 to 4.39�2.39% (P<.05). Compared with those of CPAP-5 group, changes in FRC/Kg and PaO₂/FiO₂ were greater in CPAP-10 group (P<. 05). PaCO₂ was increased slightly in both groups of CPAP-5 and CPAP-10, not reaching statistical significance.

Conclusion: In the treatment of experimental ALI, 5 and 10cmH₂O CPAP can improve V_T, FRC and PaO₂/FiO₂ with no change in PaCO₂.

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