Thompson, Bruce R.

Abstract Technological advancements have increased the number of human spaceflights, including the advent of space tourism and deep space travel. The structure and function of the pulmonary system are gravitationally dependent, highlighting the importance of understanding functional changes within the pulmonary system during transient and sustained microgravity exposure. This systematic review and meta-analysis provide an overview of effects of microgravity (0G) on various functional outcome measures of the human lungs relative to Earth gravity (1G). Twenty-eight studies comprising parabolic flights (~20 seconds), short- (≤30 days) and long-duration spaceflight (>30 days) were assessed. Outcome measures reported in 1G (before flight) and 0G (in-flight) were extracted. Fixed effects models showed microgravity caused a reduction in elastic work and carbon dioxide production, and increases in pulmonary diffusion capacity, compliance, and pulmonary capillary blood volume. Despite this, the effect sizes were small and likely have little clinical significance in healthy individuals. However, they could impact space tourists who have lower health requirements for space travel, and those with underlying obstructive respiratory disorders. The results demonstrate how traditional functional pulmonary testing provides essential physiological benchmarks that complement high-throughput data collection methods, enabling an integrated understanding of how molecular changes translate into functional respiratory outcomes in microgravity.

Abstract Rationale Disability guidelines are often based on pulmonary function testing, but factors other than lung function influence how an individual experiences physiologic impairment. Age may impact the perception of impairment in adults with chronic lung disease. Objectives To determine if self-report of physical functional impairment differs between older adults with chronic lung disease compared with younger adults with similar degrees of lung function impairment. Methods The Lung Tissue Research Consortium provided data on 981 participants with chronic obstructive pulmonary disease and interstitial lung disease who were well characterized with clinical, radiological, and pathological diagnoses. We used multiple logistic regression to determine if responses to health status questions (from the Short Form-12 and St. George’s Respiratory Questionnaire) related to perception of impairment differed in older adults (age ≥ 65 yr, n = 427) compared with younger adults (age < 65 yr, n = 393). Measurements and Main Results Pulmonary function was higher in older adults (median FEV1 %, 70) compared with younger adults (median FEV1 %, 62) (P < 0.001), whereas the median 6-minute-walk distance was similar between groups (372 m vs. 388 m, P = 0.21). After adjusting for potential confounders, older adults were less likely to report that their health limited them significantly in performing moderate activities (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.22–0.58) or climbing several flights of stairs (OR, 0.51; 95% CI, 0.34–0.77). The odds of reporting that their physical health limited the kinds of activities they performed were reduced by 63% in older adults (OR, 0.37; 95% CI, 0.24–0.58), and, similarly, the odds of reporting that their health caused them to accomplish less than they would like were also lower in older adults (OR, 0.39; 95% CI, 0.25–0.60). The OR for reporting that their breathing problem stops them from doing most things or everything was 0.35 (95% CI, 0.22–0.55) in older adults versus younger adults. Conclusions Older adults with chronic lung disease were less likely to report significant impairment in their activities compared with younger adults, suggesting they may perceive less limitation.