The Current State of Studying Hemodynamics of Human Cavernous Veins in Different Phases of the Respiratory Cycle

Introduction and Objective. This article presents the results of a theoretical analysis of scientific literature concerning the hemodynamics of the human vena cava during different phases of the respiratory cycle, with a particular focus on the ultrasound method. Since the formulation of the Frank-Starling law and the recognition of the central role of venous return in cardiovascular physiology, researchers in various fields—including biology, physiology, and medicine—have sought effective methods to study central venous hemodynamics and the factors influencing it. Over time, and with the development of new technologies, several diagnostic tools have been introduced, including tetrapolar thoracic rheography, phlebography, plethysmography, computed tomography, magnetic resonance imaging, and pulmonary artery catheterization. Each has contributed significantly to the field, although many are limited by their invasiveness, cost, or complexity. In contrast, ultrasound imaging of the heart and great vessels has emerged as a non-invasive, safe, rapid, relatively accurate, and cost-effective method for evaluating cardiovascular status. Due to these advantages, the aim of this study was to analyze and summarize the current scientific knowledge on the use of ultrasound for assessing the inferior and superior vena cava, and to investigate the relationship between venous hemodynamic parameters and phases of the respiratory cycle. Materials and Methods. This study employed theoretical analysis, systematization, and generalization of modern scientific and methodological literature. Key Findings. Ultrasound evaluation of the vena cava is a highly effective, non-invasive, and safe method for assessing central hemodynamics. It is increasingly used in clinical practice due to its availability, lack of radiation exposure, applicability in emergency settings, and high diagnostic value for evaluating a patient’s fluid status. The review of literature highlights an urgent need for the development of a standardized ultrasound protocol for vena cava assessment, taking into account body position, respiratory phase, imaging window, and measurement site. A unified approach would significantly enhance the reliability, reproducibility, and clinical relevance of results. Future studies should aim to further clarify the physiological mechanisms linking respiration and venous return, compare the diagnostic potential of superior and inferior vena cava parameters in various clinical scenarios, and develop integrated assessment algorithms for routine use.