the important influence of subtle localized changes or outliers. This was pointed out in much more difficult to measure and fraught with danger of bias if the airspace size is very variable. There are compelling arguments against abandoning Lm, although these views highlight that Lm may not be the most sensitive indicator for early emphysema diagnosis. Indeed, several studies have demonstrated that often cannot distinguish mild emphysema from healthy controls. Therefore, a histological method of measuring airspace enlargement that is specifically sensitive to the presence of the largest airspaces is NSC 601980 desirable for detecting such a disease state. Recently, Parameswaran introduced non-conventional metrics that could potentially be used as indicators of heterogeneously distributed airspace sizes characteristic of early lung disease. Briefly, these indexes, referred to as D1 and D2, utilize the equivalent airspace diameters and then incorporate higher moment factors from the airspace diameter distributions. Thus the largest airspaces potential indicators of early disease state are weighted more heavily than smaller ones. We stress that D1 and D2 do not provide conventional 3D stereological information about average airspace dimensions they simply emphasize the presence of a minority of enlarged airspaces. Nevertheless, as observed in Ref., these new indexes may prove useful as indicators of physiology expected in early or mild emphysema but require rigorous validation. Herein, as a validation effort, we have applied these indexes post factum to a study of airspace enlargement in smoke-exposed mice and compared the results to conventional Lm measurements on the same histological images. Lung tissue samples from 20 female AKR/J mice were used in this study, with 10 exposed to mainstream cigarette smoke for 24 weeks and 10 age-matched controls, as described previously. At the end of smoke exposure, the mice were sacrificed by CO2 asphyxiation and exsanguinated. Next, the chest cavity was Antibiotic-202 opened and the diaphragm incised. Lungs were then inflated to neutral buffered formalin for minutes, after which the trachea was tied off and the lungs excised and placed i
