What is it about?
This study shows how tiny air bubbles can form in blood when pressure drops below a certain level, such as during spaceflight or rapid decompression. These bubbles make blood more compressible, allowing sound waves to slow down and match the speed of flowing blood. When this happens, a choking effect called “Sanal flow choking” can occur, which blocks blood flow and creates dangerous pressure spikes or shock waves. Using analytical models, lab experiments, computer simulations, and animal studies, we confirm that this choking can happen in arteries—especially where there is a narrowing or bifurcation—leading to stroke-like events even without symptoms. This work helps us better understand cardiovascular risks in astronauts, patients with silent heart disease, and others exposed to decompression stress.
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Why is it important?
This research is important because it overturns the long-held assumption that blood is incompressible. We demonstrate that when blood pressure drops below the vapor pressure—such as during spaceflight, diving, or medical decompression—microbubbles form, making blood more compressible and prone to shock wave generation. This leads to a critical condition called Sanal flow choking, where blood flow is suddenly obstructed, potentially causing stroke, aneurysm, or silent heart attacks. Our work is the first to validate this phenomenon through analytical models, in vitro tests, simulations, and animal experiments. Importantly, this research builds on a connected Physics of Fluids article that confirmed, in accordance with the laws of thermodynamics, that all flowing fluids—including blood—are compressible. These findings offer a new predictive framework for cardiovascular risk, with implications for astronaut health, decompression safety, and next-generation medical diagnostics.
Perspectives
As the lead author, this publication represents a personal and scientific breakthrough that bridges aerospace fluid dynamics and cardiovascular medicine. Our research provides the first experimental evidence that decompression-induced microbubble formation in blood can reduce the local speed of sound to below 100 m/s—conditions under which Sanal flow choking occurs. This is a critical transition point where blood behaves as a compressible fluid, leading to sudden flow obstruction, shock wave generation, and hemodynamic instability. From a clinical perspective, these findings are highly relevant to procedures such as cardiopulmonary bypass (CPB), percutaneous coronary intervention (PCI), and coronary artery bypass grafting (CABG), where rapid decompression or flow redirection may inadvertently trigger such compressible flow behavior. Notably, we discovered that surface roughness—such as that found on stents—can enhance microbubble nucleation. This suggests that the texture of implanted devices directly influences the risk of bubble formation and downstream flow choking. Therefore, stent surface finish and graft design should not be considered trivial; they may play a significant role in patient outcomes. Personally, it is deeply rewarding to see how a theoretical fluid mechanics concept like Sanal flow choking now offers a unifying explanation for previously unexplained cardiovascular events—silent strokes, graft failures, or stent restenosis. Our study opens up a new translational frontier: acoustic softening–resistant interventional strategies that can be tailored for high-risk patients or environments, including aviation, diving, and space medicine. I believe this work will inspire future research into microbubble imaging, predictive diagnostics, and safer biomedical device engineering.
Dr. SANAL KUMAR VR
Amity University
Read the Original
This page is a summary of: In vitro prediction of the lower/upper-critical biofluid flow choking index and in vivo demonstration of flow choking in the stenosis artery of the animal with air embolism, Physics of Fluids, October 2022, American Institute of Physics,
DOI: 10.1063/5.0105407.
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