title: Inter- and intraregional ventilation inhomogeneity in hypergravity and after pressurization of an anti-G suit.
abstract: This study assessed the effects of increased gravity in the head-to-foot direction (+G(z)) and anti-G suit (AGS) pressurization on functional residual capacity (FRC), the volume of trapped gas (V(TG)), and ventilation distribution by using inert- gas washout. Normalized phase III slope (Sn(III)) analysis was used to determine the effects on inter- and intraregional ventilation inhomogeneity. Twelve men performed multiple-breath washouts of SF(6) and He in a human centrifuge at +1 to +3 G(z) wearing an AGS pressurized to 0, 6, or 12 kPa. Hypergravity produced moderately increased FRC, V(TG), and overall and inter- and intraregional inhomogeneities. In normogravity, AGS pressurization resulted in reduced FRC and increased V(TG), overall, and inter- and intraregional inhomogeneities. Inflation of the AGS to 12 kPa at +3 G(z) reduced FRC markedly and caused marked gas trapping and intraregional inhomogeneity, whereas interregional inhomogeneity decreased. In conclusion, increased +G(z) impairs ventilation distribution not only between widely separated lung regions, but also within small lung units. Pressurizing an AGS in hypergravity causes extensive gas trapping accompanied by reduced interregional inhomogeneity and, apparently, results in greater intraregional inhomogeneity.
authors.affiliation: Swedish Defence Research Agency, Defence Medicine, S-580 13 Linköping, and Karolinska Institutet, S-171 77 Stockholm, Sweden. mikgro@foi.se
authors.forename: Mikael
authors.initials: M
authors.lastname: Gronkvist
authors.forename: Eddie
authors.initials: E
authors.lastname: Bergsten
authors.forename: Ola
authors.initials: O
authors.lastname: Eiken
authors.forename: Per M
authors.initials: PM
authors.lastname: Gustafsson
mesh_terms: D000328:Adult; D005652:Functional Residual Capacity; D005676:Gravity Suits / Q000009:adverse effects*; D006371:Helium; D006801:Humans; D018471:Hypergravity; D008297:Male; D011312:Pressure; D012119:Respiration; D015656:Respiratory Mechanics; D013459:Sulfur Hexafluoride
chemical_list: D006371:Helium; D013459:Sulfur Hexafluoride