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Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
Increased cerebral blood volume pulsatility during head-down tilt with elevated carbon dioxide: the SPACECOT Study
Gary E Strangman1,2,3, Quan Zhang4,2, Karina Marshall-Goebel4,5
1Neural Systems Group, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts; strang@nmr.mgh.harvard.edu.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 1, 2017
Summary
Astronauts experience vision changes due to spaceflight. This study found that head-down tilt and elevated carbon dioxide (CO2) increased cerebral blood volume pulsatility over time, potentially impacting intracranial pressure and leading to visual issues.
Area of Science:
- Space Medicine
- Neuroscience
- Ophthalmology
Background:
- Spaceflight causes ocular changes in astronauts, possibly linked to elevated intracranial pressure (ICP).
- Head-down tilt (HDT) and elevated carbon dioxide (CO2) in sealed environments like the ISS may influence ICP and cerebral blood flow.
Purpose of the Study:
- To investigate the physiological interaction between HDT and elevated CO2.
- To determine if cerebrovascular pulsatility relates to HDT and/or elevated CO2.
Main Methods:
- A double-blind crossover study with 6 participants.
- Measured cerebral blood volume (CBV) pulsatility using near-infrared spectroscopy.
- Monitored noninvasive ICP and intraocular pressure (IOP) during 28-hour -12° HDT at nominal and elevated CO2 levels.
Main Results:
- CBV pulsatility significantly increased over time at cardiac and Mayer wave frequencies during HDT.
- The interaction between HDT and CO2 on pulsatility was not robust, appearing driven by one individual.
- No significant differences in ICP or IOP were detected between atmospheres.
Conclusions:
- CBV pulsatility increases during HDT, with potential for greater increases under elevated CO2 in some individuals.
- These pulsatility changes may contribute to spaceflight-associated visual impairment.
- Further research is needed to link individual pulsatility responses to CO2 with visual changes in astronauts.
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