Contributions of lower limb and abdominal compression to ventilation inhomogeneity in hypergravity.
Gravito-inertial load in the head-to-foot direction (Gz) and compression of the lower body half by an anti-G suit (AGS) are both known to influence ventilation distribution in the lungs. To study the interaction of Gz and AGS and to asses the separate contributions from lower limbs and abdominal compressions to large and small-scale ventilation inhomogeneities nine males performed SF6/He vital capacity (VC) single-breath washouts at 1, 2, and 3 Gz in a centrifuge, with abdominal and/or lower limbs compressions. SF6/He and (SF6-He) phase III slopes were used for determination of overall and small-scale ventilation inhomogeneity. Closing volume and phase IV height were used as measures of large-scale inhomogeneity. VC decreased marginally with G-load but markedly with lower limbs compression. Small-scale ventilation inhomogeneity increased slightly with G-load, but substantially with AGS pressurization. Small-scale ventilation inhomogeneity increased with AGS pressurization. Large-scale inhomogeneity increased markedly with G-load. Translocation of blood to the lungs might be the key determinant for changes in small-scale ventilation inhomogeneity when pressurizing an AGS.
Swedish Defence Research Agency, Department of Defence Medicine, Aviation Medicine, P.O. Box 13400, S-580 13 Linköping, Sweden. mikgro@foi.se
Mikael J
MJ
Grönkvist
Eddie
E
Bergsten
Ola
O
Eiken
Per M
PM
Gustafsson
D000005:Abdomen / Q000502:physiology*; D000328:Adult; D003011:Closing Volume / Q000502:physiology; D005652:Functional Residual Capacity; D005676:Gravity Suits / Q000600:supply & distribution; D006801:Humans; D018471:Hypergravity; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D011187:Posture / Q000502:physiology*; D012119:Respiration; D014797:Vital Capacity / Q000502:physiology