COMPUTER TOMOGRAPHIC ASSESSMENT OF PERFLUOROCARBON AND GAS-DISTRIBUTION DURING PARTIAL LIQUID VENTILATION FOR ACUTE RESPIRATORY-FAILURE

The average in vivo chest computed tomographic (CT) attenuation number (air = -1,000, soft tissue = 0, perflubron = +2,300 Hounsfield units [HU]) of 10 ventrodorsal-oriented lung segments was calculated to asse ss the distribution of gas and perflubron in 14 oleic acid lung-injure d adult sheep during partial liquid ventilation (PLV, n = 7) or gas ve ntilation (CV, n = 7). Partial liquid ventilation was associated with a significant decrease in shunt fraction (PLV = 40 +/- 12%, GV = 76 +/ - 12%, p = 0.004). Computed tomographic attenuation data during expira tion (HUexp) demonstrated minimal gas aeration in CV animals in the de pendent (segments 6-10) lung zones (HUexp = -562 +/- 108 for segments 1-5, HUexp = -165 +/- 104 for segments 6-10, p = 0.015). During PLV, p erflubron was predominantly distributed to the dependent lung regions (HUexp = 579 +/- 338 for segments 1-5, HUexp = 790 +/- 149 for segment s 6-10, p = 0.04). The ratio of the inspiratory to expiratory HU (HUin sp/exp) was greater in dependent than nondependent regions (mean HUins p/exp segments 1-5 = 0.56, segments 6-10 = 0.81, p = 0.01), indicating that during inspiration relatively more gas than perflubron was distr ibuted to the nondependent lung regions. We conclude that during PLV i n this lung injury model, (1) gas exchange is improved when compared w ith gas ventilation, (2) perflubron is distributed predominantly to th e dependent regions of the lung, and (3) although gas is distributed t hroughout the lung with each inspiration, more gas than perflubron goe s to the nondependent lung regions.