VENTILATION INHOMOGENEITY USING MULTI-BREATH NITROGEN WASHOUT - COMPARISON OF MOMENT RATIOS AND OTHER INDEXES

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Abstract
Various indexes of ventilation inhomogeneity based on multibreath N washout of the lungs were compared. Forty subjects in 5 clinical groups were studied as follows: 6 normal subjects, 5 normal smokers, 6 subjects with asthma, 13 with diffuse interstitial lung disease (DILD) and 10 with chronic obstructive pulmonary disease (COPD). A moment ratio (.mu.1/.mu.0), which is a mean dilution number (or number of volume turnovers), is superior to other indexes studied with respect to minimal intrasubject variability and maximal diagnostic sensitivity. Minimal ventilation inhomogeneity could be detected in normal smokers, as evidenced by the difference in .mu.1/.mu.0 values from those found in normal nonsmokers. As a group, asthmatics showed mild ventilation inhomogeneity, with greater variation depending on their functional status at the time of testing. Subjects with DILD tended to have moderate ventilation inhomogeneity, which appeared to increase with age. The greatest ventilation inhomogeneity occurred in COPD.