Decompression-Induced Microbubble Choking in Blood: Acoustic Softening, Sanal Flow Choking, and Spaceflight Implications
AIAA 2026-0720
Session: Humans in Space Logistics, Medical issues, Bio-Research
Published Online:8 Jan 2026
Abstract:
Decompression-induced microbubble nucleation and the resulting multiphase flow instability in blood pose a significant but underrecognized risk to cardiovascular stability during extravehicular activity (EVA), rapid cabin depressurization, and emergency re-pressurization. This study provides experimental evidence that reduced ambient pressure can transform blood—typically considered incompressible under physiological conditions—into a compressible multiphase medium, enabling acoustic softening and Sanal Flow Choking (SFC). This thermo-acoustic, geometry-independent fluid-dynamic phenomenon can generate shock-like pressure waves and obstruct flow even at low physiological velocities. Fresh human venous blood was exposed to controlled vacuum conditions (760→100 mmHg, 37–40 °C). Microbubble nucleation consistently occurred between 650–350 mmHg, followed by vaporization and crust formation. Bubble rupture produced intense acoustic bursts, indicating rapid localized pressure transitions. These data suggest that a rupturing bubble behaves like a transient convergent–divergent nozzle capable of generating supersonic outflow and micro-shock events consistent with SFC onset. Using Wood’s multiphase acoustic model, effective sound speed was predicted to collapse from ~1500 m/s to <100 m/s, and in extreme void-fraction states toward 10 m/s. This supports the observation that even low bubble volume fractions can trigger early multiphase flow choking—well before classical decompression sickness thresholds. Surface-roughness experiments with water and plasma showed nucleation 60–80 mmHg earlier on rough than smooth interfaces, highlighting vulnerability near stents, vascular implants, and disturbed-geometry flow zones. In microgravity, impaired bubble clearance and absent buoyancy may amplify these effects, increasing risk of embolism, flow blockage, and endothelial injury. These findings introduce a physics-based framework linking decompression, acoustic softening, and SFC to circulatory instability, supporting development of pressure-adaptive EVA systems, real-time acoustic monitoring, thermophysical conditioning, and optimized biomedical interfaces for safer spaceflight.
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