Gravity effects on regional lung ventilation determined by functional EIT during parabolic flights

Gravity-dependent changes of regional lung function were studied during nor mogravity, hypergravity, and microgravity induced by parabolic flights. Sev en healthy subjects were followed in the right lateral and supine postures during tidal breathing, forced vital capacity, and slow expiratory vital ca pacity maneuvers. Regional 1) lung ventilation, 2) lung volumes, and 3) lun g emptying behavior were studied in a transverse thoracic plane by function al electrical impedance tomography (EIT). The results showed gravity-depend ent changes of regional lung ventilation parameters. A significant effect o f gravity on regional functional residual capacity with a rapid lung volume redistribution during the gravity transition phases was established. The m ost homogeneous functional residual capacity distribution was found at micr ogravity. During vital capacity and forced vital capacity in the right late ral posture, the decrease in lung volume on expiration was larger in the ri ght lung region at all gravity phases. During tidal breathing, the differen ces in ventilation magnitudes between the right and left lung regions were not significant in either posture or gravity phase. A significant nonlinear ity of lung emptying was determined at normogravity and hypergravity. The p attern of lung emptying was homogeneous during microgravity.