TY - JOUR
T1 - Reducing intracranial pressure by reducing central venous pressure
T2 - Assessment of potential countermeasures to spaceflight-associated neuroocular syndrome
AU - Hansen, Alexander B.
AU - Lawley, Justin S.
AU - Rickards, Caroline A.
AU - Howden, Erin J.
AU - Sarma, Satyam
AU - Cornwell, William K.
AU - Amin, Sachin B.
AU - Mugele, Hendrik
AU - Marume, Kyohei
AU - Possnig, Carmen
AU - Whitworth, Louis A.
AU - Williams, Michael A.
AU - Levine, Benjamin D.
N1 - Publisher Copyright:
© 2021 the American Physiological Society.
PY - 2021/2
Y1 - 2021/2
N2 - Spaceflight-associated neuro-ocular syndrome (SANS) involves unilateral or bilateral optic disc edema, widening of the optic nerve sheath, and posterior globe flattening. Owing to posterior globe flattening, it is hypothesized that microgravity causes a disproportionate change in intracranial pressure (ICP) relative to intraocular pressure. Countermeasures capable of reducing ICP include thigh cuffs and breathing against inspiratory resistance. Owing to the coupling of central venous pressure (CVP) and intracranial pressure, we hypothesized that both ICP and CVP will be reduced during both countermeasures. In four male participants (32 ± 13 yr) who were previously implanted with Ommaya reservoirs for treatment of unrelated clinical conditions, ICP was measured invasively through these ports. Subjects were healthy at the time of testing. CVP was measured invasively by a peripherally inserted central catheter. Participants breathed through an impedance threshold device (ITD, -7 cmH2O) to generate negative intrathoracic pressure for 5 min, and subsequently, wore bilateral thigh cuffs inflated to 30 mmHg for 2 min. Breathing through an ITD reduced both CVP (6 ± 2 vs. 3 ± 1mmHg; P = 0.02) and ICP (16 ± 3 vs. 12 ± 1mmHg; P = 0.04) compared to baseline, a result that was not observed during the free breathing condition (CVP, 6 ± 2 vs. 6 ± 2mmHg, P = 0.87; ICP, 15±3 vs. 15±4mmHg, P = 0.68). Inflation of the thigh cuffs to 30 mmHg caused no meaningful reduction in CVP in all four individuals (5 ± 4 vs. 5 ± 4mmHg; P = 0.1), coincident with minimal reduction in ICP (15 ± 3 vs. 14 ± 4mmHg; P = 0.13). The application of inspiratory resistance breathing resulted in reductions in both ICP and CVP, likely due to intrathoracic unloading.
AB - Spaceflight-associated neuro-ocular syndrome (SANS) involves unilateral or bilateral optic disc edema, widening of the optic nerve sheath, and posterior globe flattening. Owing to posterior globe flattening, it is hypothesized that microgravity causes a disproportionate change in intracranial pressure (ICP) relative to intraocular pressure. Countermeasures capable of reducing ICP include thigh cuffs and breathing against inspiratory resistance. Owing to the coupling of central venous pressure (CVP) and intracranial pressure, we hypothesized that both ICP and CVP will be reduced during both countermeasures. In four male participants (32 ± 13 yr) who were previously implanted with Ommaya reservoirs for treatment of unrelated clinical conditions, ICP was measured invasively through these ports. Subjects were healthy at the time of testing. CVP was measured invasively by a peripherally inserted central catheter. Participants breathed through an impedance threshold device (ITD, -7 cmH2O) to generate negative intrathoracic pressure for 5 min, and subsequently, wore bilateral thigh cuffs inflated to 30 mmHg for 2 min. Breathing through an ITD reduced both CVP (6 ± 2 vs. 3 ± 1mmHg; P = 0.02) and ICP (16 ± 3 vs. 12 ± 1mmHg; P = 0.04) compared to baseline, a result that was not observed during the free breathing condition (CVP, 6 ± 2 vs. 6 ± 2mmHg, P = 0.87; ICP, 15±3 vs. 15±4mmHg, P = 0.68). Inflation of the thigh cuffs to 30 mmHg caused no meaningful reduction in CVP in all four individuals (5 ± 4 vs. 5 ± 4mmHg; P = 0.1), coincident with minimal reduction in ICP (15 ± 3 vs. 14 ± 4mmHg; P = 0.13). The application of inspiratory resistance breathing resulted in reductions in both ICP and CVP, likely due to intrathoracic unloading.
KW - Central venous pressure
KW - Intracranial pressure
KW - Microgravity
KW - Spaceflight neuro-ocular syndrome
UR - http://www.scopus.com/inward/record.url?scp=85101716666&partnerID=8YFLogxK
U2 - 10.1152/JAPPLPHYSIOL.00786.2020
DO - 10.1152/JAPPLPHYSIOL.00786.2020
M3 - Article
C2 - 33270516
AN - SCOPUS:85101716666
SN - 8750-7587
VL - 130
SP - 283
EP - 289
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
IS - 2
ER -