Effects of Partial Gravity on the Function and Particle Handling of the Human Lung

Abstract

Purpose of review: The challenges presented to the lung by the space environment are the effects of prolonged absence of gravity, the challenges of decompression stress associated with spacewalking, and the changes in the deposition of inhaled particulate matter.

Recent findings: Although there are substantial changes in the function of the lung in partial gravity, the lung is largely unaffected by sustained exposure, returning rapidly to a normal state after return to 1G. Provided there is adequate denitrogenation prior to a spacewalk, avoiding the development of venous gas emboli, the lung copes well with the low pressure environment of the spacesuit. Particulate deposition is reduced in partial gravity, but where that deposition occurs is likely in the more peripheral airspaces, with associated longer retention times, potentially raising the toxicological potential of toxic dusts.

Summary: Despite its delicate structure the lung performs well in partial gravity, with the greatest threat likely arising from inhaled particulate matter (extra-terrestrial dusts).

Keywords: Aerosol transport; Deposition; Gas exchange; Respiratory.

Figure 1:

The deposition of aerosol boluses of 1μm particles inhaled to different penetration depths in the airways in both 1G (green line) and in lunar gravity (~1/6G, blue line). Data were collected during parabolic flight. Partial gravity served to reduce deposition, however, as indicated by the red arrow, for an equivalent amount of deposition (say 25%), this occurred more peripherally in partial gravity, raising the potential of increased residence time in the lung of the particles once deposited. Modified from (62), with permission.