Monitoring and maintaining cardiorespiratory health during long-term space flight

This application proposes: a) continued support of the experiment “Airway Monitoring 2 / Lung Health Monitoring” (see section 2.1), and b) support of a new ESA selected bedrest experiment “Artificial gravity and bedrest” (see section 2.2).Our over-all objectives are to use the unique microgravity and head-down tilt bedrest conditions (simulated microgravity) as tools to gain further insights into the normal physiological effects of gravity on the respiratory and circulatory systems of the human body, and to monitor and protect human health during space exploration.

The two modules will benefit mutually from being pursued in parallel, since exchange of blood-soluble gases (nitric oxide (NO) and carbon monoxide (CO) respectively) are central in both modules.

This is a well-established research area in our laboratory and among our collaborators.Lung Health Monitoring (LHM)Represents an extension of the previously supported and completed experiment “Airway Monitoring”.

Experiments will be made on the International Space Station (ISS) using equipment and procedures based on our previous space experiments along with additions.Background:In microgravity accidental inhalation of dust and toxic particles may cause airway inflammation.

Such inflammation can be diagnosed with analysis of elevated exhaled NO levels.Specific aims:To investigate how the normal levels of exhaled NO change with reduced gravity and gas density in combination.

Additionally, possible small-airway edema as a result of headward fluid shifts in microgravity is proposed to be studied.Research plan:In the previous “Airway Monitoring” experiment, the gas density was reduced 30% by decompression.

In this extension the experiments are proposed to be performed on ISS in an environment in which the gas density is reduced to half normal and to the level anticipated on future manned planetary habitats/space vehicles using a mixture of helium and oxygen (heliox) as a background gas instead of air.

This will result in more realistic predictions of the pulmonary NO turnover in a planetary habitat/space vehicles compared to the predecessor “Airway Monitoring”.Artificial Gravity (AG) and Bed Rest (Head-Down Tilt Bed Rest, (HDBR))Background:Reduced orthostatic tolerance (OT) and work capacity are commonly observed in astronauts returning to Earth, and a reduction of the blood volume (BV) is a likely common mechanism.

A 60 days HDBR study will be organized by the European Space Agency (ESA) in which three groups of subjects are studied during a) passive rest, b) a flight-like program of exercise (E) and c) in addition to E exposure to AG in a short-arm centrifuge.Specific aims:To determine the mechanism(s) by which AG and E mitigate OT after HDBR.To determine the changes in total hemoglobin (Hbmass), BV, plasma volume (PV) and related hormones before and after a 60-day HDBR with and without AG and E as countermeasures.To relate the observed changes in Hbmass, its key regulatory hormone erythropoietin (EPO), other fluid-controlling hormones/factors, PV and BV to concomitant changes in OT and work capacity.To assess whether AG provides significant benefits when added to E.Research plan:Hbmass is determined with an improved CO rebreathing method.

Having in addition data on hemoglobin concentration (Hb) and the % red cell volume (hematocrit, Hcr) in the blood, BV, PV and absolute red blood cell volume can be computed. Control measurements of Hbmass and associated variables are performed before the onset of HDBR. The end/post-bedrest measurements are done during the last days of HDBR.

If possible, duplicate measurements will be conducted on each occasion.

Blood samples for hematology, EPO and fluid-controlling hormones are to be taken coordinated with Hbmass, and at 3 occasions during the HDBR period.

Pre-HDBR and post-HDBR tilt test data and peak aerobic power (VO2 peak) will be related to our experimental data including those obtained with a novel sensor shirt (Hexoskin).