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Project Title:  Effects of Short-Term Hypercapnia During Head-Down Bed Rest on Ocular Structures and Cerebral Blood Flow in Healthy Human Subjects Reduce
Fiscal Year: FY 2016 
Division: Human Research 
Research Discipline/Element:
HRP HHC:Human Health Countermeasures
Start Date: 01/12/2015  
End Date: 03/10/2016  
Task Last Updated: 11/04/2016 
Download report in PDF pdf
Principal Investigator/Affiliation:   Vizzeri, Gianmarco  M.D. / The University of Texas Medical Branch 
Address:  Ophthalmology 
700 University Blvd 
Galveston , TX 77550-5552 
Email: givizzer@utmb.edu 
Phone: 409-747-5426  
Congressional District: 14 
Web:  
Organization Type: UNIVERSITY 
Organization Name: The University of Texas Medical Branch 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Stenger, Michael  Ph.D. Wyle Laboratories, Inc. 
Zanello, Susana  Ph.D. Universities Space Research Association 
Ploutz-Snyder, Robert  Ph.D. Universities Space Research Association 
Laurie, Steven  Ph.D. Wyle Laboratories, Inc. 
Project Information: Grant/Contract No. T72618 (subcontract) 
Responsible Center: NASA JSC 
Grant Monitor: Norsk, Peter  
Center Contact:  
Peter.norsk@nasa.gov 
Solicitation / Funding Source: 2013 HERO NNJ13ZSA002N-Crew Health OMNIBUS 
Grant/Contract No.: T72618 (subcontract) 
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: (1) Arrhythmia:Risk of Cardiac Rhythm Problems
(2) VIIP:Risk of Spaceflight-Induced Intracranial Hypertension/Vision Alterations (IRP Rev E)
Human Research Program Gaps: (1) CV07:How are fluids redistributed in flight?
(2) VIIP01:We do not know the etiological mechanisms and contributing risk factors for ocular structural and functional changes seen in-flight and postflight (IRP Rev E)
(3) VIIP12:We do not know whether ground-based analogs and/or models can simulate the spaceflight-associated VIIP syndrome (IRP Rev E)
Flight Assignment/Project Notes: NOTE: Extended to 3/10/2016 (original end date was 10/1/2015) per R. Brady/JSC HRP (Ed., 2/22/16)

Task Description: This proposal applies short-term hypercapnia to a head-down bed rest (HDBR) analog to more closely replicate the conditions characterizing a space exploration environment. The purpose of the study is to evaluate ocular structural and cerebral blood flow changes in healthy human subjects exposed to such environment. Commercially available sleeping cubicle provided with carbon dioxide (CO2) injection system will be used to produce hypercapnia (1% CO2). Intraocular pressure will be measured to evaluate the changes in response to a hypercarbic environment applied to HDBR. In addition, Spectral-domain optical coherence tomography (OCT) scans of the retina and the optic disc will be performed and compared to baseline conditions. Cerebral blood flow responses will be assessed using transcranial Doppler (TCD) ultrasonography. Noninvasive blood pressure waveforms and electrocardiogram will be obtained and correlated with TCD and ocular measures; in addition, they will be used with TCD to indirectly estimate the intracranial pressure by employing a novel algorithm (Non-invasive IntraCranial pressure Framework, or NICF). In conclusion, it is anticipated that this study will be able to assess a priority risk in the Human Research Program Roadmap and accelerate the understanding of the pathophysiology of the Visual Impairment and Intracranial Pressure syndrome.

Research Impact/Earth Benefits:

Task Progress & Bibliography Information FY2016 
Task Progress: Many astronauts experience ocular structural and functional changes including choroidal folds, optic disc edema, globe flattening, optic nerve sheath diameter (ONSD) distension, retinal nerve fiber layer thickening, and decreased visual acuity during long-duration spaceflight. The leading hypothesis suggests that weightlessness-induced cephalad fluid shifts may increase intracranial pressure (ICP) and contribute to these findings. An additional hypothesis implicates elevated ambient CO2 levels on the International Space Station. To investigate possible mechanisms for ocular changes we used the spaceflight analog of 6° head-down tilt (HDT) and studied eight male subjects during three 1-hour conditions: Seated, HDT, and HDT with 1% inspired CO2 (HDT+CO2). Non-invasive intracranial pressure (ICP), intraocular pressure (IOP; rebound tonometry), translaminar pressure difference (TLPD=IOP-ICP), ocular ultrasound, and optical coherence tomography (OCT) scans of the macula and the optic disc were obtained. Analysis of one-carbon pathway genetics were conducted to identify possible genetic risk factors. IOP and ICP increased and TLPD decreased during HDT, compared to Seated. Exposure to 1% CO2 during HDT+CO2 further increased IOP and decreased ICP compared to HDT, but there was no difference in TLPD between the HDT conditions. Compared to Seated, ONSD and subfoveal choroidal thickness increased during HDT, but there was no difference between HDT and HDT+CO2. There were no significant changes across conditions in visual acuity or ocular structures assessed with OCT imaging. ONSD and end-tidal PCO2 differed based on genetic polymorphisms. In conclusion, compared to Seated, acute HDT induced mild ocular changes, but acute mild-hypercapnia during HDT does not exacerbate these changes.

A manuscript (Laurie SS, Feiveson AH, Ferguson CR, Hu X, Lee SMC, May-Phillips T, Ploutz-Snyder R, Smith SM, Stenger MB, Taibbi G, Zwart SR, Vizzeri G. Effects of Short-Term Mild Hypercapnia during Head-Down Tilt on Ocular Structures, Visual Function, and Intracranial Pressure in Healthy Human Subjects) will soon be submitted to Journal of Applied Physiology.

Bibliography Type: Description: (Last Updated: 04/24/2019) 

Show Cumulative Bibliography Listing
 
Articles in Peer-reviewed Journals Laurie SS, Vizzeri G, Taibbi G, Ferguson CR, Hu X, Lee SMC, Ploutz-Snyder R, Smith SM, Zwart SR, Stenger MB. "Effects of short-term mild hypercapnia during head-down tilt on intracranial pressure and ocular structures in healthy human subjects." Physiol Rep. 2017 Jun;5(11):e13302. https://doi.org/10.14814/phy2.13302 ; PubMed PMID: 28611153; PubMed Central PMCID: PMC5471441 , Jun-2017
Project Title:  Effects of Short-Term Hypercapnia During Head-Down Bed Rest on Ocular Structures and Cerebral Blood Flow in Healthy Human Subjects Reduce
Fiscal Year: FY 2015 
Division: Human Research 
Research Discipline/Element:
HRP HHC:Human Health Countermeasures
Start Date: 01/12/2015  
End Date: 03/10/2016  
Task Last Updated: 04/27/2015 
Download report in PDF pdf
Principal Investigator/Affiliation:   Vizzeri, Gianmarco  M.D. / The University of Texas Medical Branch 
Address:  Ophthalmology 
700 University Blvd 
Galveston , TX 77550-5552 
Email: givizzer@utmb.edu 
Phone: 409-747-5426  
Congressional District: 14 
Web:  
Organization Type: UNIVERSITY 
Organization Name: The University of Texas Medical Branch 
Joint Agency:  
Comments:  
Co-Investigator(s)
Affiliation: 
Stenger, Michael  Ph.D. Wyle Laboratories, Inc. 
Zanello, Susana  Ph.D. Universities Space Research Association 
Ploutz-Snyder, Robert  Ph.D. Universities Space Research Association 
Project Information: Grant/Contract No. T72618 (subcontract) 
Responsible Center: NASA JSC 
Grant Monitor: Norsk, Peter  
Center Contact:  
Peter.norsk@nasa.gov 
Solicitation / Funding Source: 2013 HERO NNJ13ZSA002N-Crew Health OMNIBUS 
Grant/Contract No.: T72618 (subcontract) 
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: (1) Arrhythmia:Risk of Cardiac Rhythm Problems
(2) VIIP:Risk of Spaceflight-Induced Intracranial Hypertension/Vision Alterations (IRP Rev E)
Human Research Program Gaps: (1) CV07:How are fluids redistributed in flight?
(2) VIIP01:We do not know the etiological mechanisms and contributing risk factors for ocular structural and functional changes seen in-flight and postflight (IRP Rev E)
(3) VIIP12:We do not know whether ground-based analogs and/or models can simulate the spaceflight-associated VIIP syndrome (IRP Rev E)
Flight Assignment/Project Notes: NOTE: Extended to 3/10/2016 (original end date was 10/1/2015) per R. Brady/JSC HRP (Ed., 2/22/16)

Task Description: This proposal applies short-term hypercapnia to a head-down bed rest (HDBR) analog to more closely replicate the conditions characterizing a space exploration environment. The purpose of the study is to evaluate ocular structural and cerebral blood flow changes in healthy human subjects exposed to such environment. Commercially available sleeping cubicle provided with carbon dioxide (CO2) injection system will be used to produce hypercapnia (1% CO2). Intraocular pressure will be measured to evaluate the changes in response to a hypercarbic environment applied to HDBR. In addition, Spectral-domain OCT scans of the retina and the optic disc will be performed and compared to baseline conditions. Cerebral blood flow responses will be assessed using transcranial Doppler (TCD) ultrasonography. Noninvasive blood pressure waveforms and electrocardiogram will be obtained and correlated with TCD and ocular measures; in addition, they will be used with TCD to indirectly estimate the intracranial pressure by employing a novel algorithm (Non-invasive IntraCranial pressure Framework, or NICF). In conclusion, it is anticipated that this study will be able to assess a priority risk in the Human Research Program Roadmap and accelerate the understanding of the pathophysiology of the Visual Impairment and Intracranial Pressure syndrome.

Research Impact/Earth Benefits: 0

Task Progress & Bibliography Information FY2015 
Task Progress: New project for FY2015.

Bibliography Type: Description: (Last Updated: 04/24/2019) 

Show Cumulative Bibliography Listing
 
 None in FY 2015