title: Effects of hypergravity and anti-G suit pressure on intraregional ventilation distribution during VC breaths.
abstract: The effects of increased gravity in the head-to-foot direction (+G(z)) and pressurization of an anti-G suit (AGS) on total and intraregional intra-acinar ventilation inhomogeneity were explored in 10 healthy male subjects. They performed vital capacity (VC) single-breath washin/washouts of SF(6) and He in +1, +2, or +3 G(z) in a human centrifuge, with an AGS pressurized to 0, 6, or 12 kPa. The phase III slopes for SF(6) and He over 25-75% of the expired VC were used as markers of total ventilation inhomogeneity, and the (SF(6) -- He) slopes were used as indicators of intraregional intra-acinar inhomogeneity. SF(6) and He phase III slopes increased proportionally with increasing gravity, but the (SF(6) -- He) slopes remained unchanged. AGS pressurization did not change SF(6) or He slopes significantly but resulted in increased (SF(6) -- He) slope differences at 12 kPa. In conclusion, hypergravity increases overall but not intraregional intra-acinar inhomogeneity during VC breaths. AGS pressurization provokes increased intraregional intra-acinar ventilation inhomogeneity, presumably reflecting the consequences of basilar pulmonary vessel engorgement in combination with compression of the basilar lung regions.
authors.affiliation: Swedish Defense Research Agency, Aviation Medicine, S-580 13 Linköping, Sweden. pmgmed@artech.se
authors.forename: P M
authors.initials: PM
authors.lastname: Gustafsson
authors.forename: O
authors.initials: O
authors.lastname: Eiken
authors.forename: M
authors.initials: M
authors.lastname: Grönkvist
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005676:Gravity Suits; D006801:Humans; D018471:Hypergravity; D001239:Inhalation / Q000502:physiology; D008297:Male; D012016:Reference Values; D015656:Respiratory Mechanics / Q000502:physiology*; D013997:Time Factors; D014797:Vital Capacity / Q000502:physiology*