title: "First in, last out" in the lung.
mesh_terms: D001128:Argon; D006112:Gravitation; D006371:Helium; D006801:Humans; D011652:Pulmonary Circulation; D011868:Radioisotopes; D012129:Respiratory Function Tests; D012907:Smoking; D013147:Spirometry; D014978:Xenon
chemical_list: D011868:Radioisotopes; D006371:Helium; D014978:Xenon; D001128:Argon