In vascular ultrasound, respiratory variation refers to changes in blood vessel diameter and flow dynamics in response to the respiratory cycle. This physiological phenomenon is particularly evident in veins, such as the inferior vena cava (IVC), where changes in intrathoracic and intra-abdominal pressures during inspiration and expiration affect venous return and vessel caliber. Assessing respiratory variation helps evaluate a patient’s fluid status and right heart function.
Understanding respiratory variation is crucial for accurate vascular assessments. For instance, a highly collapsible IVC with significant respiratory variation often suggests hypovolemia, whereas a plethoric, non-collapsing IVC can indicate fluid overload or elevated right atrial pressures. This diagnostic insight aids clinicians in guiding fluid management and identifying underlying cardiovascular conditions, enhancing patient care through precise ultrasound interpretation.