Physiological adaptation of the jugular venous pulse during long-duration spaceflight

Q: What are the key findings of this study?

Long-duration spaceflight significantly reduced mean internal jugular vein cross-sectional area and increased pulsatile excursion in three of four astronauts, with one astronaut developing thrombosis.

Q: What is the clinical evidence from this study?

Study design: Observational. Population: Microgravity exposure (n=4). Intervention: Long-duration spaceflight vs. Pre-flight baseline. Primary outcome: Mean internal jugular vein cross-sectional area (IJV-CSA) in ASTRO 0 (p=<0.001).

Q: What does this research mean for the field?

During long-duration spaceflight, the jugular venous pulse retains its terrestrial morphology but exhibits reduced mean cross-sectional area and markedly increased pulsatile excursion, suggesting enhanced transmission of cardiac pressure waves to the cerebral venous compartment. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.ESTABLISHES_NEW_DIRECTION.

Q: What question did this study set out to answer?

To characterize internal jugular vein cross-sectional area and serial jugular venous pulse waveforms before, during, and after long-duration spaceflight.

Paolo Zamboni; Anselmo Pagani; Alessandro Bertagnon; Gabriele Fanciulli; Antonino Proto; Matilde Zamboni; Rosa Brancaccio; Angelo Taibi

doi:10.1038/s41598-026-69054-9

September 3, 2026Scientific ReportsOpen Access

Physiological adaptation of the jugular venous pulse during long-duration spaceflight

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Key result

Long-duration spaceflight is linked to a ~37% reduction in IJV cross-sectional area and incident thrombosis.

P<0.001
n=4

Figures

Why the study?

The serial jugular venous pulse waveform during long-duration spaceflight in microgravity had never been characterised.

Does long-duration spaceflight alter internal jugular vein cross-sectional area and pulsatile excursion in astronauts?

Key Points

To characterize internal jugular vein cross-sectional area and serial jugular venous pulse waveforms before, during, and after long-duration spaceflight.
Evaluated 4 astronauts (sex ratio 1:1, mean age at launch 44.75 years, mean mission duration 166 days) using ECG-synchronized high-resolution ultrasound.
Acquired right internal jugular vein cross-sectional area (IJV-CSA) in the supine position 30 days before launch, within one week of splashdown (post-flight 1), and approximately 30 days after splashdown (post-flight 2).
Recorded in-flight IJV-CSA in a neutral body position at 5 days and 156 days after docking in one astronaut (ASTRO 0), analyzing 3855 frames via an automated convolutional neural network pipeline.
Mean IJV-CSA decreased significantly at early post-flight in three astronauts (ASTRO 0: from 0.723 ± 0.076 to 0.453 ± 0.061 cm2, -37.9%; ASTRO 2: -46.0%; ASTRO 3: -48.4%; all p < 0.0001).
Pulsatile excursion increased post-flight in ASTRO 0 (+105.0%, p < 0.0001) and ASTRO 2 (+337.1%, p < 0.0001), while trending upward in ASTRO 3 (+24.5%, p = 0.08).
ASTRO 1 showed increased mean IJV-CSA (+19.3%, p < 0.0001), increased minimum CSA (+42.5%, p < 0.0001), and decreased pulsatile excursion (-60.3%, p < 0.001), coinciding with right internal jugular vein thrombosis.

Study Design

Type

Observational (n=4)

Multicenter

No

Structured PICO

Does long-duration spaceflight alter internal jugular vein cross-sectional area and pulsatile excursion in astronauts?

P

Population

4 astronauts (mean age 44.8 years, 50% female) evaluated for physiological adaptations of the jugular venous pulse before, during, and after long-duration spaceflight averaging 166 days.

E

Exposure

Long-duration spaceflight (microgravity exposure for mean 166 days).

C

Comparator

Pre-flight baseline measurements on Earth (supine position, 30 days before launch).

O

Outcome

Internal jugular vein cross-sectional area (IJV-CSA) parameters (mean, minimum, maximum) and pulsatile excursion measured via ECG-synchronized high-resolution ultrasound.surrogate

Main Result

Absolute Event Rate: 0.453% vs 0.723%

p-value: p=<0.001

Long-duration spaceflight significantly alters jugular venous hemodynamics, reducing cross-sectional area and increasing pulsatile excursion, while highlighting a notable risk of internal jugular vein thrombosis.

Limitations

Small sample size of four astronauts, with in-flight acquisitions obtained in only one
Only the right internal jugular vein was examined, limiting extrapolation to global cerebral venous outflow
Breathing was not controlled, introducing respiratory variation into the area parameters
Operator differences between ground-based scans (trained operator) and in-flight scans (self-performed)
Lack of concurrent plasma volume, haematocrit, echocardiographic, or venous Doppler data
Right atrial pressure was not directly measured
Small sample size (n=4) with in-flight acquisitions obtained in only one astronaut.
Only the right internal jugular vein was examined.
Breathing was not controlled, introducing respiratory variation.
Operator difference between ground-based (trained operator) and in-flight (self-performed) acquisitions.
Lack of concurrent plasma volume, hematocrit, echocardiographic, or direct right atrial pressure data.

Implication

Spaceflight-associated jugular changes may elevate thrombosis risk in astronauts; leaves open whether monitoring or countermeasures are warranted pending larger studies.

Abstract

The jugular venous pulse (JVP) offers a non-invasive window into right atrial pressure. In microgravity, the serial JVP waveform during long-duration spaceflight had never been characterised. Using ECG-synchronised high-resolution ultrasound and a validated AI model, we quantified internal jugular vein cross-sectional area (IJV-CSA) throughout the cardiac cycle in four astronauts before and after flight, with in-flight measurements in one astronaut. Mean IJV-CSA fell significantly post-flight in three astronauts (ASTRO 0: from 0.723 ± 0.076 to 0.453 ± 0.061 cm 2 , ASTRO 2: − 46.0%, ASTRO 3: − 48.4%; p < 0.001). The reduction in ASTRO 0 developed between the first and fifth month in orbit. Maximum CSA declined consistently with reduced central venous pressure. Pulsatile excursion, an index never previously reported in spaceflight, increased markedly (ASTRO 0: + 105.0%, p < 0.001; ASTRO 2: + 337.1%, p < 0.001), suggesting enhanced transmission of cardiac pressure waves towards the cerebral venous compartment in the absence of hydrostatic gradients. ASTRO 1 showed the opposite pattern (minimum CSA + 42.5%, pulsatile excursion − 60.3%, p < 0.001), probably due to IJV thrombosis, representing the third documented case in space medicine. The JVP waveform retains terrestrial morphology and ECG timing in microgravity. Whether JVP parameters predict venous thrombosis or relate to glymphatic function in long-term spaceflight warrants further studies.

Discussion

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Cite This Study

Zamboni et al. (2026) conducted an observational in Microgravity exposure (n=4). Long-duration spaceflight vs. Pre-flight baseline was evaluated on Mean internal jugular vein cross-sectional area (IJV-CSA) in ASTRO 0 (p=<0.001). Long-duration spaceflight significantly reduced mean internal jugular vein cross-sectional area and increased pulsatile excursion in three of four astronauts, with one astronaut developing thrombosis.

synapsesocial.com/papers/6a9d1df228139818eab20baa https://doi.org/10.1038/s41598-026-69054-9

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Physiological adaptation of the jugular venous pulse during long-duration spaceflight

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

Physiological adaptation of the jugular venous pulse during long-duration spaceflight

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Implication

Abstract

Discussion

Cite This Study

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