Occlusive Force as a Novel Parameter for Assessing Subclavian Vein Filling: A Feasibility Study of Body, Head, and Arm Positioning

Abstract Background Ultrasound-guided cannulation of the subclavian vein is a standard procedure. Venous cross-sectional area (CSA) is commonly used to assess changes in subclavian vein filling induced by patient positioning. However, CSA reflects only the geometric dimensions of the vein and does not quantify the mechanical force required for complete venous compression. We developed a simple device to measure the force required to fully compress the subclavian vein using a micro-convex ultrasound probe (occlusive force). Methods In this observational feasibility study, 10 healthy volunteers were examined under different body, head, and arm positions. Generalized Estimation Equations were used to analyze the influence of positioning maneuvers on occlusive force and CSA. Results Body and head positions showed strong effects on occlusive force. Compared to the neutral position, occlusive force increased by approximately 40% in Trendelenburg and decreased by about 20% in Anti-Trendelenburg position. Ipsilateral head rotation resulted in 20–30% higher forces, whereas contralateral rotation led to approximately 20% lower forces. Arm positioning showed inconclusive effects. CSA was similarly influenced by body and head position but with markedly smaller changes compared to occlusive force. Conclusion Occlusive force appears to be a sensitive parameter for detecting changes in subclavian vein filling induced by positioning maneuvers. As a novel parameter, it may complement conventional ultrasound measurements in the assessment of venous distension. Future studies are warranted to investigate its relationship with procedural success and complication rates during ultrasound-guided central venous cannulation. Trial registration: The study was approved by the Ethics Committee of the Saarland (Ethikkommission der Ärztekammer des Saarlandes; approval number: 234/23, 2024-02-19, study registration in the German Clinical Trials Register (DRKS00033551)).