Dose-dependent reduction of optic nerve sheath diameter during graded lower body negative pressure in healthy adults of both sexes

Bergauer, Andrej (avtor), Urevc, Janez (avtor), Steuber, Bianca (avtor), Schimd-Zalaudek, Karin (avtor), Pivec, Vid (avtor), Goswami, Nandu (avtor)

Background: Optic nerve sheath diameter (ONSD) measured by ultrasound provides a non-invasive surrogate of intracranial pressure. Although lower body negative pressure (LBNP) is widely used to simulate central hypovolemia, the dose-response relationship between graded LBNP and ONSD, and possible sex differences therein, are incompletely characterized.Methods: Forty-four healthy young adults (22 female, 22 male) underwent graded LBNP (−10 to −40 mmHg) in the supine position; valid ONSD data were available in 37 participants (18 female, 19 male) who constituted the analytical sample. ONSD was measured from transbulbar B-mode ultrasound images 3 mm posterior to the globe, with three representative frames averaged per condition. Relative changes from individual supine baseline were analyzed using a linear mixed-effects model with state, sex, and their interaction as fixed effects.Results: A progressive and statistically significant reduction in ONSD was observed at every LBNP level in both sexes. Female participants showed reductions of approximately −4.4 % (LBNP10, p = 0.001), −9.1 % (LBNP20, p < 0.001), −13.2 % (LBNP30, p < 0.001) and −15.9 % (LBNP40, p < 0.001) relative to supine baseline. Male-specific contrasts showed comparable reductions (LBNP10: −3.0 %, p = 0.022; LBNP20: −7.9 %, p < 0.001; LBNP30: −10.1 %, p < 0.001; LBNP40: −13.4 %, p < 0.001). The main effect of sex was not significant (p = 1.00), and no state × sex interaction reached significance (all p > 0.1). ONSD returned to baseline during recovery (female: p = 0.173; male: p = 0.059).Conclusion: Graded LBNP induces a progressive, dose-dependent reduction in ONSD that is detectable already at mild LBNP (−10 mmHg) and reaches approximately −15 % at −40 mmHg. No statistically significant sex-related differences in the ONSD response to graded LBNP were detected in the present study. These findings support the use of transbulbar ONSD ultrasound as a sensitive non-invasive marker consistent with intracranial-pressure reductions during simulated central hypovolemia. By linking a systemic cardiovascular perturbation to a cerebro-ocular pressure readout, the study offers a network-physiology view of central-hypovolemia responses relevant to spaceflight and orthostatic-stress research.

• Jezik: Angleški jezik
• Ključne besede: cardiovascular physiology, central hypovolemia, intracranial pressure, lower body negative pressure, network physiology, optic nerve sheath diameter, sex differences, ultrasound, microgravity
• Vrsta gradiva: Članek v reviji
• Tipologija: 1.01 - Izvirni znanstveni članek
• Organizacija: FS - Fakulteta za strojništvo
• Status publikacije: Objavljeno
• Različica publikacije: Objavljena publikacija
• Leto izida: 2026
• Št. strani: 11 str.
• Številčenje: Vol. 6, art. 1908460
• PID: 20.500.12556/RUL-185534
• UDK: 531.5:612.819
• ISSN pri članku: 2674-0109
• DOI: 10.3389/fnetp.2026.1908460
• COBISS.SI-ID: 287272195
• Datum objave v RUL: 07.08.2026

Gradivo je del revije

• Naslov: Frontiers in network physiology
• Skrajšan naslov: Front. netw. physiol.
• Založnik: Frontiers Media SA
• ISSN: 2674-0109
• COBISS.SI-ID: 75774211

Licence

• Licenca: CC BY 4.0, Creative Commons Priznanje avtorstva 4.0 Mednarodna
• Povezava: http://creativecommons.org/licenses/by/4.0/deed.sl
• Opis: To je standardna licenca Creative Commons, ki daje uporabnikom največ možnosti za nadaljnjo uporabo dela, pri čemer morajo navesti avtorja.

Sekundarni jezik

• Jezik: Slovenski jezik
• Ključne besede: kardiovaskularna fiziologija, centralna hipovolemija, intrakranialni tlak, negativni tlak spodnjega dela telesa, premer ovojnice vidnega živca, spolne razlike, transorbitalna ultrasonografija, mikrogravitacija

Projekti

• Financer: Drugi - Drug financer ali več financerjev
• Program financ.: European Space Agency
• Številka projekta: 4000137614/22/NL/SC
• Naslov: Prediction model of countermeasures efficiency on cardiovascular system and fluid shifting in simulated microgravity conditions

• Financer: Drugi - Drug financer ali več financerjev
• Številka projekta: MBRU-CM-RG2021-06