Utility of Lung Clearance Index Score as a Noninvasive Marker of Deployment Lung Disease

LCI is determined by the number of lung volume turnovers necessary to clear the lungs of an inert tracer gas such as nitrogen that is inhaled at the beginning of the test. The LCI is calculated by determining the cumulative expired volume (CEV) and then dividing the CEV by the functional residual capacity. Values of less than7.0 indicate normal values while an LCI greater than 7.0 is associated with heterogeneity in ventilation and distal airway abnormalities. The ability to detect peripheral airway disease may make LCI a better modality for detecting distal airways abnormalities seen on lung histopathology but often missed on traditional pulmonary function testing.