Journal of Applied Physiology
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J Appl Physiol (December 12, 2003). doi:10.1152/japplphysiol.00627.2003
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Submitted on June 17, 2003
Accepted on December 10, 2003

Effects of hypergravity on the distributions of lung ventilation and perfusion in sitting humans assessed with a simple two-step maneuver

Malin Rohdin1*, Patrik Sundblad1, and Dag Linnarsson1

1 Department of Physiology and Pharmacology, Karolinska Institutet, Section of Environmental Physiology, Stockholm, Sweden

* To whom correspondence should be addressed. E-mail: Malin.Rohdin{at}fyfa.ki.se.

Increased gravity (G) impairs pulmonary distributions of ventilation and perfusion. We sought to develop a method for rapid, simultaneous and non-invasive assessments of ventilation and perfusion distributions during a short-lasting hypergravity exposure. Nine sitting subjects were exposed to 1, 2 and 3 times normal gravity (1-3 G) in the head-to-feet direction and performed a rebreathing and single-breath washout maneuver with a gas mixture containing acetylene, oxygen and argon (Ar). Expirograms were analyzed for cardiogenic oscillations (COS) and for phase IV amplitude, in order to analyze inhomogeneities in ventilation (Ar) and perfusion (CO2/Ar) distribution, respectively. COS were normalized for changes in stroke volume (SV). COS for Ar increased from 1 G control to 128 ± 6% (means ±SE)at 2 G (P=0.02 for 1 vs. 2 G) and 165 ± 13% at 3 G (P=0.002 for 2 vs. 3 G). Corresponding values for CO2/Ar were 135 ± 12% (P=0.04) and 146 ± 13%. Phase IV amplitude for Ar increased to 193 ± 39% (P=0.008 for 1 vs. 2 G) at 2 G and 229 ± 51% at 3 G compared to 1 G. Corresponding values for CO2/Ar were 188 ± 29% (P=0.02) and 219 ± 18%. We conclude that not only large-scale ventilation and perfusion inhomogeneities, as reflected by phase IV amplitude, but also smaller-scale inhomogeneities, as reflected by COS/SV, increase with hypergravity. Except for small-scale ventilation distribution, most of the impairments observed at 3 G had been attained at 2 G. For some of the parameters and G levels there are previous comparable data which are in support of the present simplified method.




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