[Effects of lateral position and independent lung ventilation on unilateral acute lung injury in dogs].

OBJECTIVE: To investigate the effects of conventional ventilation, lateral position, asynchronous independent lung ventilation and synchronous independent lung ventilation on gas exchange, lung mechanics, hemodynamics, pulmonary perfusion and inflammatory mediators in dogs with a hydrochloric acid induced unilateral acute lung injury (ALI). METHODS: Twenty-eight dogs with hydrochloric acid induced unilateral ALI (the left lung) were ventilated with volume controlled ventilation. The animals were divided into four groups. The first group (group A, n = 7) received conventional ventilation in a supine position. The second group (group B, n = 7) received conventional ventilation in the healthy lung dependent position with the parameters as same as group A. The third group (group C, n = 7) received asynchronous independent lung ventilation. The fourth group (group D, n = 7) received synchronous independent lung ventilation with the parameters as same as group C. All the animals were observed for 4 h under the above described ventilation. Oxygenation, lung mechanics, hemodynamics and lung injury score were measured during the ventilation. The right and left pulmonary arterial blood flows were measured after 4 h ventilation. RESULTS: (1) After 30 min ventilation, PaO2/FiO2 in group A [(180 +/- 25) mm Hg, 1 mm Hg = 0.133 kPa] was significantly lower than those in group B, group C and group D [(277 +/- 23), (296 +/- 31), (299 +/- 22) mm Hg respectively, all P < 0.01]. PaO2/FiO2 in group C [(348 +/- 34) mm Hg] and group D [(343 +/- 29) mm Hg] was significantly increased when compared with that of group B [(314 +/- 33) mm Hg] after 60 min ventilation (P < 0.05), but there was no significant difference between group C and group D. (2) After 120 min ventilation, C(st) in group B [(23 +/- 4) ml/cm H2O] significantly increased when compared with that of group A [(19 +/- 2) ml/cm H2O, P < 0.05]. After 60 min ventilation, C(st)-L in group C and group D increased significantly as compared to the beginning of the ventilation. (3) The left lung pulmonary arterial flow in group B, group C and group D [(31.3 +/- 4.6)%, (27.5 +/- 1.3)% and (27.3 +/- 2.8)%, respectively] significantly decreased when compared with that of group A (38.3 +/- 2.2)% after 4 h ventilation (P < 0.05 and P < 0.01). CONCLUSIONS: Both lateral position and independent lung ventilation can improve gas exchange, while independent lung ventilation is better than lateral position ventilation. The improvement of oxygenation may be related to the effect on the distribution of pulmonary arterial flow.