Fig. 3. Regional distribution of amikacin (AMK) lung tissue concentrations measured in piglets with healthy lungs 60 min after the first (white bars), the second (gray bars), and the fourth (black bars) aerosol, showing a significant decrease (two-way analysis of variance) in tissue concentrations in the dependent pulmonary segments after the fourth aerosol. Data are expressed as mean ± SD. S2 = upper lobe; S4 = middle lobe; S6 = dependent segment of lower lobe; S8 = nondependent segment of lower lobe; S10 = caudal segment of lower lobe.