We have made significant progress over the past year in all dimensions of the Fluid Shifts (FS) experiment. To date the team has performed preflight baseline data collection on eleven crewmembers, completed all inflight sessions for 10 subjects with the exception of the final return minus 45 days (R-45) time points for the last three subjects. Eleven postflight tilt table sessions have been completed for the first six subjects, ranging from return plus 10 days (R+10) to R+180. Upright and 3 Tesla (3T) postflight MRI were also collected on these six subjects (ranging from R+1 to R+48). All training is now complete, and the last four Fluid Shifts subjects are currently on ISS.
The FS team has continued to collectively respond to changes in circumstances (inflight schedules, Russian travel limitations, hardware failures, etc.). The Cochlear and Cerebral Fluid Pressure (CCFP) Analyzer’s hard drive failed in August 2016 which resulted in the loss of inflight CCFP and tympanometry data until a replacement unit was delivered on orbit in November 2016. In January 2017 one of the otoacoustic emission analyzer’s probes became clogged with earwax so the backup probe is being used for continued data collection. Procedures were developed and successfully implemented in February 2017 to clean the primary probe. The Fluid Shifts team has also developed several alternate data collection plans based on changing crew schedules, most recently including the potential for an extended mission for the Expedition 51 Commander.
Supine and tilted 3T MRI data collections continued at the Victory Lakes facility (UTMB--University of Texas Medical Branch), taking advantage of the existing MRID (MED B) pulse sequences. Subjects continued to tolerate the procedure well and all early assessments of data quality gave satisfactory results. Since 2016, the team includes Dr. Larry Kramer (UTHSC-H) for general MRI advising and assistance with data analysis. Specifically, work is underway for CSF (cerebrospinal fluid) flow quantification in the Sylvian aqueduct and determination of pre- and postflight CSF production rates. Other MRI analysis methods continue to be refined to optimize data analysis in terms of quality and resources. Despite the decision by Medical Operations to use IV contrast during MED B MRI scans as the preferred version for venography, none of the Fluid Shifts subjects has received contrast injections and data collections are likely to continue with non-contrast techniques.
Since Russian and European Space Agency (ESA) subjects will “direct return” to their respective countries, immediate postflight testing in Houston will not be possible. We have been working to standardize the imaging procedure and protocol elements among UTMB, Research Center of Neurology in Moscow, Russia, and DLR/:envihab in Cologne, Germany. Both Partner facilities are equipped with -15 degree foam wedges and have prior experience with tilted MRI. A test run of all sequences was performed at DLR in a healthy volunteer (February 2017), and subsequent evaluation of data was performed. Additional testing may be conducted in March to complete standardization. A similar effort is underway with the Russian facility, which has demonstrated the ability to perform the protocol with satisfactory results. Additional efforts will be made to optimize the data in the 2 remaining postflight sessions.
The “free-floating” use of the OCT device for inflight Chibis sessions continues to work well for crewmembers, resulting in similar exam times and data quality when compared to the traditional chinrest method.
Similar to other measures, ultrasound data is collected in the inflight baseline state (Columbus module) and again during Chibis (Russian Service Module), which allows us to contrast space normal to the lower negative pressure state induced by the Chibis device. Transcranial Doppler, optic nerve sheath diameter, central retinal and ophthalmic artery Doppler, among other parameters, are being analyzed to compare conditions and individual subject variation.
Our team has continued to make advances in the analysis of otoacoustic emission (OAE) data over the past year. Dr. David Kemp continues to provide invaluable OAE expertise and has further automated his OAE processing software. Rozela Melgoza returned for a second summer audiology internship in 2016 and continued to be a major contributor for data processing and exploration of data nuances under Dr. Kemp’s guidance. We have focused our analysis on transient evoked OAE (TEOAE) phase shifts, which have been highly systematic in response to posture change and lower body negative pressure during preflight testing. TEOAE phase shifts are consistent with expected intracranial pressure changes due to HDT, and appear to be consistent across multiple subjects. The team was fortunate to host a second audiology summer intern in 2016 (Tyler Caldwell). Tyler preformed ground studies to define the effect of probe positioning, middle ear pressure, and head-down tilt on OAE stimulus and response signals, which resulted in two posters related to Fluid Shifts, one at the NASA Human Research Program (HRP) Investigators’ Workshop 2017 and one at the Texas Academy of Audiology. A third abstract related to this summer internship work has been submitted to the American Academy of Audiology meeting which will be held in April 2017.
Our team attended the NASA HRP Investigators’ Workshop in Galveston, TX in January 2017, presenting an overall project lecture for Fluid Shifts and participating in many Vision Impairment and Intracranial Pressure (VIIP)-related sessions and discussions. Our team also presented two otoacoustic emissions posters based on methods developed and data collected for the Fluid Shifts project.
Presentations (past year):
1) Caldwell T, Ebert DJ, Danielson R, Kemp D, Le Prell C. Assessing the Utility of Otoacoustic Emissions for Monitoring Intracranial Pressure in Microgravity through Analog Observations. Presented at the 17th Annual Texas Academy of Audiology Conference, Dallas, TX, October 20-22, 2016.
2) Caldwell T, Ebert D, Kemp D, Danielson R, Stenger M. Effects of Middle Ear Pressure and Intracranial Pressure on Transient-Evoked Otoacoustic Emissions. Human Research Program Investigators’ Workshop, Galveston, TX, January 23-26, 2017.
3) Kemp D, Melgoza R, Ebert D, Danielson R, Stenger M, Hargens A, Dulchavsky S. Otoacoustic Emissions in Fluid Shift Studies: Methodology and Confounding Factors. Human Research Program Investigators’ Workshop, Galveston, TX, January 23-26, 2017.
4) Melgoza R, Kemp D, Ebert D, Danielson R, Stenger M, Hargens A, Dulchavsky S. A Longitudinal Study of Transient Evoked Otoacoustic Emissions in Relation to Spaceflight (Fluid Shifts). Human Research Program Investigators’ Workshop, Galveston, TX, January 23-26, 2017.
5) Stenger MB, Hargens AR, Dulchavsky SA, Arbielle P, Danielson RW, Ebert DJ, Garcia KM, Johnston SL, Laurie SS, Lee SMC, Liu J, Macias B, Martin DS, Minkoff L, Ploutz-Snyder R, Ribeiro LC, Sargsyan A, Smith SM. Fluid Shifts. Human Research Program Investigators’ Workshop, Galveston, TX, January 23-26, 2017.
Abstracts for Journals and Proceedings
Stenger MB, Hargens AR, Dulchavsky SA, Arbielle P, Danielson RW, Ebert DJ, Garcia KM, Johnston SL, Laurie SS, Lee SMC, Liu J, Macias B, Martin DS, Minkoff L, Ploutz-Snyder R, Ribeiro LC, Sargsyan A, Smith SM. "Fluid Shifts." 2017 NASA Human Research Program Investigators’ Workshop, Galveston, TX, January 23-26, 2017.
2017 NASA Human Research Program Investigators’ Workshop, Galveston, TX, January 23-26, 2017. , Jan-2017