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Project Title:  Mechanical and Gravitational Countermeasures to Ocular Changes During Strict Head-Down Tilt Bedrest Reduce
Images: icon  Fiscal Year: FY 2024 
Division: Human Research 
Research Discipline/Element:
HRP HHC:Human Health Countermeasures
 Start Date: 08/26/2022  
End Date: 09/30/2025  
Task Last Updated: 05/29/2024 		 Download Task Book report in PDF pdf
Principal Investigator/Affiliation:   Macias, Brandon  Ph.D. / NASA Johnson Space Center 
Address:  Johnson Space Center Cardiovascular and Vision Laboratory 
2101 NASA Parkway, HAC/B21N-1207 
Houston , TX 77058 		 Email: brandon.r.macias@nasa.gov 
Phone: 281-483-2026  
Congressional District: 36 
Web:  
 Organization Type: NASA CENTER 
Organization Name: NASA Johnson Space Center 
Joint Agency:  
Comments: NOTE: Became civil servant fall 2020; previously KBR/NASA Johnson Space Center. Prior to that until 2016, was at the University of California, San Diego. 
Co-Investigator(s)
Affiliation: 
Brunstetter, Tyson  O.D., Ph.D. NASA Johnson Space Center 
Huang, Alex  M.D., Ph.D. Doheny Eye Institute 
Kramer, Larry  M.D. University of Texas Health Science Center at Houston 
Laurie, Steven  Ph.D. KBR/NASA Johnson Space Center 
Lee, Stuart  Ph.D. KBR/NASA Johnson Space Center 
Lovering, Andrew  Ph.D. University of Oregon 
Martin, Bryn  Ph.D. Alcyone Therapeutics Inc. 
Young, Millennia  Ph.D. NASA Johnson Space Center 
Lytle, Jason  KBR/NASA Johnson Space Center 
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA JSC 
Grant Monitor: Brocato, Becky  
Center Contact:  
becky.brocato@nasa.gov 
Unique ID: 15115  		Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: Ground 
Flight Program:  
TechPort: No  		No. of Post Docs: 1 
No. of PhD Candidates:  
No. of Master's Candidates:  
No. of Bachelor's Candidates:   		No. of PhD Degrees:  
No. of Master's Degrees:  
No. of Bachelor's Degrees:  
Human Research Program Elements: (1) HHC:Human Health Countermeasures
Human Research Program Risks: None
Human Research Program Gaps: None
Flight Assignment/Project Notes: NOTE: End date changed to 09/30/2025 per C. Ribeiro/NASA-JSC. (Ed., 11/27/23). Original end date was 08/20/2024.

NOTE: Project start date updated due to P.I. change to B. Macias. Information per C. Ribeiro/NASA-JSC. (Ed. 8/29/22).

Task Description: The Spaceflight Associated Neuro-ocular Syndrome (SANS) is associated with structural and functional ocular and brain changes and develops in ~2/3rds of astronauts during long-duration spaceflight. Although the etiology of SANS is unknown, a weightlessness-driven headward fluid redistribution relative to the upright position on Earth is hypothesized to be a primary initiating factor. A countermeasure that can successfully reverse this headward fluid shift for multiple hours per day may be needed to prevent SANS. Exposure to 30 days of the spaceflight analog strict 6 degree head-down tilt (HDT) bedrest induces the development of optic disc edema, a hallmark sign of SANS, in 2/3 of subjects; thus, NASA will utilize this platform to test the effectiveness of various countermeasures to prevent or reduce the development of SANS findings. This study will include a control group exposed to 30 days of strict 6 degree HDT. A second group of subjects will be exposed to 6 hours of 25 mmHg lower body negative pressure (LBNP), daily, during 30 days of strict 6 degree HDT bedrest. A third group of subjects will be exposed to 6 hours of upright posture per day, and 6 degree HDT for the remaining 18 h/day. This will help determine if daily exposure to 6 hours total of upright posture, fully reversing the headward fluid for the same duration of use as the LBNP group, is sufficient to prevent SANS findings, and thus can direct future countermeasure studies with respect to the duration needed to successfully prevent SANS. We will assess multiple cerebral, vascular, and ocular outcome measures to determine the effects of 30 days strict 6 degree HDT bedrest, and the ability of daily 6 hour exposure to LBNP or upright positioning to prevent these changes.

Specific Aims:

1. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents ocular and cerebral structural changes during 30 days of strict 6° head-down tilt bedrest.

2. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents ocular functional changes during 30 days of strict 6° head-down tilt bedrest.

3. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents vascular and cerebrospinal fluid changes during 30 days of strict 6° head-down tilt bedrest.

This bedrest study will be implemented in the :envihab facility at the German Aerospace Center (DLR) in Cologne, Germany.

Research Impact/Earth Benefits: Spaceflight associated neuro-ocular syndrome (SANS) develops in approximately 2/3 of astronauts during long-duration spaceflight. Although the etiology of SANS is unknown, a weightlessness-driven headward fluid redistribution relative to the upright position on Earth is hypothesized to be a primary initiating factor. A countermeasure that can successfully reverse this headward fluid shift for multiple hours per day may be needed to prevent SANS findings from developing. Exposure to 30 days of strict 6-degree head-down tilt (HDT) bedrest induces the development of optic disc edema, a hallmark sign of SANS, in approximately 2/3 of subjects; thus, NASA is utilizing this platform to test the effectiveness of various countermeasures to prevent or reduce the development of SANS findings.

Task Progress & Bibliography Information FY2024 
Task Progress: Summary of Key Updates This Period • Data collection was completed for campaigns 3 and 4. • All data were transferred to the NASA Johnson Space Center (JSC) Cardiovascular and Vision Laboratory and analyses have been completed. • A manuscript reporting on the effectiveness of the lower body negative pressure (LBNP) countermeasure (C1 and C2) will be submitted to J Appl Physiol in Spring 2024. • A manuscript reporting on the effectiveness of Exercise + Thigh Cuff countermeasure is being drafted also for submission to J Appl Physiol. • A manuscript summarizing eye findings across all campaigns is being led by Dr. Alex Huang and is in the early stages of development. • All equipment that was shipped to German Aerospace Center (DLR) to support data collection has been returned to NASA, except for certain equipment planned for use in upcoming NASA bedrest studies at DLR.

Bibliography: Description: (Last Updated: 06/30/2025) 

Show Cumulative Bibliography
 
Abstracts for Journals and Proceedings Marshall-Goebel K, Laurie SS, Pardon LP, Greenwald SH, Jasion J, Lytle J, Martin D, Lee SMC, Lovering AT, Huang AS, Martin BA, Brunstetter T, Young M, Kramer LA, Macias BR. "Mechanical and gravitational countermeasures to ocular changes during strict head-down tilt bedrest." 2022 NASA Human Research Program Investigators’ Workshop, Virtual, February 7-10, 2022.

Abstracts. 2022 NASA Human Research Program Investigators’ Workshop (2022), Virtual, February 7-10, 2022. , Feb-2022

Abstracts for Journals and Proceedings Marshall-Goebel K, Lytle JR, Laurie SS, Lee SMC, Pardon LP, Martin D, Young M, Hargens AR, Sargsyan A, Ebert D, Dulchavsky S, Macias BR. "Countermeasures targeting reversal of the weightlessness-induced headward fluid shift to mitigate spaceflight associated neuro-ocular syndrome." 2022 Aerospace Medical Association Annual Scientific Meeting, Reno, Nevada, May 22-26, 2022.

Abstracts. 2022 Aerospace Medical Association Annual Scientific Meeting, Reno, Nevada, May 22-26, 2022. , May-2022

Articles in Peer-reviewed Journals Moestl S, De Boni L, Hoenemann J-N, Kramer T, Schmitz J, Pesta D, Frett T, Bohmeier M, Frings-Meuthen P, Ewald AC, Nitsche A, Loehr P, Noppe A, Klischies N, Huang AS, Laurie SS, Marshall-Goebel K, Macias BR, Tank J, Jordan J, Mulder E. "Mechanical countermeasures for spaceflight-associated neuro-ocular syndrome during 30-days of head-down tilt bedrest: Design, implementation, and tolerability." Front Physiol. 2025 Feb 23;16:1530783. https://doi.org/10.3389/fphys.2025.1530783 ; PMID: 40066284; PMCID: PMC11891356 , Feb-2025
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Project Title:  Mechanical and Gravitational Countermeasures to Ocular Changes During Strict Head-Down Tilt Bedrest Reduce
Images: icon  Fiscal Year: FY 2023 
Division: Human Research 
Research Discipline/Element:
HRP HHC:Human Health Countermeasures
 Start Date: 08/26/2022  
End Date: 09/30/2025  
Task Last Updated: 08/30/2022 		 Download Task Book report in PDF pdf
Principal Investigator/Affiliation:   Macias, Brandon  Ph.D. / NASA Johnson Space Center 
Address:  Johnson Space Center Cardiovascular and Vision Laboratory 
2101 NASA Parkway, HAC/B21N-1207 
Houston , TX 77058 		 Email: brandon.r.macias@nasa.gov 
Phone: 281-483-2026  
Congressional District: 36 
Web:  
 Organization Type: NASA CENTER 
Organization Name: NASA Johnson Space Center 
Joint Agency:  
Comments: NOTE: Became civil servant fall 2020; previously KBR/NASA Johnson Space Center. Prior to that until 2016, was at the University of California, San Diego. 
Co-Investigator(s)
Affiliation: 
Brunstetter, Tyson  O.D., Ph.D. NASA Johnson Space Center 
Huang, Alex  M.D., Ph.D. Doheny Eye Institute 
Kramer, Larry  M.D. University of Texas Health Science Center at Houston 
Laurie, Steven  Ph.D. KBR/NASA Johnson Space Center 
Lee, Stuart  Ph.D. KBR/NASA Johnson Space Center 
Lovering, Andrew  Ph.D. University of Oregon 
Martin, Bryn  Ph.D. Alcyone Therapeutics Inc. 
Young, Millennia  Ph.D. NASA Johnson Space Center 
Lytle, Jason  KBR/NASA Johnson Space Center 
Key Personnel Changes / Previous PI: March 2023 Update: Laura Pardon, Ph.D. has left NASA and is no longer with the project (Ed., 1/3/24). August 2022 report: Scott Greenwald, Ph.D. has left NASA and is no longer with the project (Ed., 8/29/22). June 2022 report: CoInvestigators Alan Hargens, Jessica Jasien, and Benjamin Levine are no longer with the project (Ed., 7/22/22).
Project Information: Grant/Contract No. Directed Research 
Responsible Center: NASA JSC 
Grant Monitor: Brocato, Becky  
Center Contact:  
becky.brocato@nasa.gov 
Unique ID: 15115  		Solicitation / Funding Source: Directed Research 
Grant/Contract No.: Directed Research 
Project Type: Ground 
Flight Program:  
TechPort: No  		No. of Post Docs:  
No. of PhD Candidates:  
No. of Master's Candidates:  
No. of Bachelor's Candidates:   		No. of PhD Degrees:  
No. of Master's Degrees:  
No. of Bachelor's Degrees:  
Human Research Program Elements: (1) HHC:Human Health Countermeasures
Human Research Program Risks: None
Human Research Program Gaps: None
Flight Assignment/Project Notes: NOTE: End date changed to 09/30/2025 per C. Ribeiro/NASA-JSC. (Ed., 11/27/23). Original end date was 08/20/2024.

NOTE: Project start date updated due to P.I. change to B. Macias. Information per C. Ribeiro/NASA-JSC. (Ed. 8/29/22).

Task Description: The Spaceflight Associated Neuro-ocular Syndrome (SANS) is associated with structural and functional ocular and brain changes and develops in ~2/3rds of astronauts during long-duration spaceflight. Although the etiology of SANS is unknown, a weightlessness-driven headward fluid redistribution relative to the upright position on Earth is hypothesized to be a primary initiating factor. A countermeasure that can successfully reverse this headward fluid shift for multiple hours per day may be needed to prevent SANS. Exposure to 30 days of the spaceflight analog strict 6 degree head-down tilt (HDT) bedrest induces the development of optic disc edema, a hallmark sign of SANS, in 2/3 of subjects; thus, NASA will utilize this platform to test the effectiveness of various countermeasures to prevent or reduce the development of SANS findings. This study will include a control group exposed to 30 days of strict 6 degree HDT. A second group of subjects will be exposed to 6 hours of 25 mmHg lower body negative pressure (LBNP), daily, during 30 days of strict 6 degree HDT bedrest. A third group of subjects will be exposed to 6 hours of upright posture per day, and 6 degree HDT for the remaining 18 h/day. This will help determine if daily exposure to 6 hours total of upright posture, fully reversing the headward fluid for the same duration of use as the LBNP group, is sufficient to prevent SANS findings, and thus can direct future countermeasure studies with respect to the duration needed to successfully prevent SANS. We will assess multiple cerebral, vascular, and ocular outcome measures to determine the effects of 30 days strict 6 degree HDT bedrest, and the ability of daily 6 hour exposure to LBNP or upright positioning to prevent these changes.

Specific Aims:

1. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents ocular and cerebral structural changes during 30 days of strict 6° head-down tilt bedrest.

2. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents ocular functional changes during 30 days of strict 6° head-down tilt bedrest.

3. To determine if daily exposure to actual (upright posture) and simulated (LBNP) hydrostatic pressure gradients prevents vascular and cerebrospinal fluid changes during 30 days of strict 6° head-down tilt bedrest.

This bedrest study will be implemented in the :envihab facility at the German Aerospace Center (DLR) in Cologne, Germany.

Research Impact/Earth Benefits:

Task Progress & Bibliography Information FY2023 
Task Progress: Continuation of "Mechanical and Gravitational Countermeasures to Ocular Changes During Strict Head-Down Tilt Bedrest" with Dr. Macias as new Principal Investigator (PI). Former PI was Dr. Marshall-Goebel.

March 2023 Update on Task Status (Ed., 1/3/24)

Data collection has been completed for campaigns 3 (January-March 2023) and campaign 4 preparations are underway (planned data collection May-July 2023). In campaign 3, 6 subjects in each of the Control and Exercise plus thigh cuff groups completed data collection, with 12 additional subjects being planned for campaign 4. In this reporting period, personnel from the Cardiovascular and Vision Laboratory (CVL) traveled to the German Aerospace Center (DLR) to provide in-person training sessions to DLR staff and to oversee baseline data collection (BDC) on the 12 subjects who participated in campaign 3 of the study. Key aspects of training included countermeasure protocol development and new ultrasound targets of the femoral artery and vein related to the new thigh cuff countermeasure. The majority of data has been received by the CVL, with a few final pieces expected in the coming weeks. Data analysis was accelerated for optical coherence tomography (OCT) outcomes and the new ultrasound targets. Hand entry of multiple outcome variables has also been initiated.

Bibliography: Description: (Last Updated: 06/30/2025) 

Show Cumulative Bibliography
 
Abstracts for Journals and Proceedings Lytle JR, Laurie SS, Marshall-Goebel K, Lee SMC, Miller A, Martin D, Young M, Macias BR. "Cardiovascular responses to daily use of lower body negative pressure during 30 days of strict head-down tilt bedrest." American Physiology Summit, Long Beach, CA, April 20-23, 2023.

Abstracts. American Physiology Summit, Long Beach, CA, April 20-23, 2023. , Apr-2023

Abstracts for Journals and Proceedings Laurie SS, Pardon LP, Marshall-Goebel K, Lytle J, Martin D, Huang AS, Martin BA, Young M, Lee SMC, Lovering AT, Kramer LA, Macias BR. "Mechanical and gravitational countermeasures to ocular changes during strict head-down tilt bedrest: The SANS countermeasure bedrest study." 2023 NASA Human Research Program Investigators’ Workshop, “To the Moon: The Next Golden Age of Human Spaceflight”, Galveston, TX, February 7-9, 2023.

Abstracts. 2023 NASA Human Research Program Investigators’ Workshop, “To the Moon: The Next Golden Age of Human Spaceflight”, Galveston, TX, February 7-9, 2023. , Feb-2023

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