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Relationship Between Carbon Dioxide Levels and Reported Congestion and Headaches on the International Space StationCongestion is commonly reported during spaceflight, and most crewmembers have reported using medications for congestion during International Space Station (ISS) missions. Although congestion has been attributed to fluid shifts during spaceflight, fluid status reaches equilibrium during the first week after launch while congestion continues to be reported throughout long duration missions. Congestion complaints have anecdotally been reported in relation to ISS CO2 levels; this evaluation was undertaken to determine whether or not an association exists. METHODS: Reported headaches, congestion symptoms, and CO2 levels were obtained for ISS expeditions 2-31, and time-weighted means and single-point maxima were determined for 24-hour (24hr) and 7-day (7d) periods prior to each weekly private medical conference. Multiple imputation addressed missing data, and logistic regression modeled the relationship between probability of reported event of congestion or headache and CO2 levels, adjusted for possible confounding covariates. The first seven days of spaceflight were not included to control for fluid shifts. Data were evaluated to determine the concentration of CO2 required to maintain the risk of congestion below 1% to allow for direct comparison with a previously published evaluation of CO2 concentrations and headache. RESULTS: This study confirmed a previously identified significant association between CO2 and headache and also found a significant association between CO2 and congestion. For each 1-mm Hg increase in CO2, the odds of a crew member reporting congestion doubled. The average 7-day CO2 would need to be maintained below 1.5 mmHg to keep the risk of congestion below 1%. The predicted probability curves of ISS headache and congestion curves appear parallel when plotted against ppCO2 levels with congestion occurring at approximately 1mmHg lower than a headache would be reported. DISCUSSION: While the cause of congestion is multifactorial, this study showed congestion is associated with CO2 levels on ISS. Data from additional expeditions could be incorporated to further assess this finding. CO2 levels are also associated with reports of headaches on ISS. While it may be expected for astronauts with congestion to also complain of headaches, these two symptoms are commonly mutually exclusive. Furthermore, it is unknown if a temporal CO2 relationship exists between congestion and headache on ISS. CO2 levels were time-weighted for 24hr and 7d, and thus the time course of congestion leading to headache was not assessed; however, congestion could be an early CO2-related symptom when compared to headache. Future studies evaluating the association of CO2-related congestion leading to headache would be difficult due to the relatively stable daily CO2 levels on ISS currently, but a systematic study could be implemented on-orbit if desired.
Document ID
20160012725
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Cole, Robert (NASA Johnson Space Center Houston, TX, United States)
Wear, Mary (KBRWyle Aerospace Group Houston, TX, United States)
Young, Millennia (KBRWyle Aerospace Group Houston, TX, United States)
Cobel, Christopher (NASA Johnson Space Center Houston, TX, United States)
Mason, Sara (Mei Technology Corp. San Antonio, TX, United States)
Date Acquired
October 28, 2016
Publication Date
April 29, 2017
Subject Category
Aerospace Medicine
Report/Patent Number
JSC-CN-37736
Meeting Information
Meeting: Aerospace Medical Association Meeting
Location: Denver, CO
Country: United States
Start Date: April 29, 2017
End Date: May 4, 2017
Sponsors: Aerospace Medical Association
Distribution Limits
Public
Copyright
Public Use Permitted.

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