Influence of head-of-bed elevation on the measurement of inferior vena cava size using a pocket-sized ultrasound device in healthy male volunteers

Abstract

　During in-home healthcare and outpatient visits, most patients are in a head-of-bed elevated position instead of supine position. Therefore, the inferior vena cava (IVC) with echocardiography must be examined in this position. In this study, we clarified (1) the IVC diameter changes after head-of-bed elevation, and (2) the difference in IVC diameters in differing head-of-bed elevation positions in 10 healthy adult males. First, we examined the diameters of the IVC every minute for 10 minutes after elevation of the head of bed from the supine position using a pocket-sized ultrasound device. The maximum diameter of the IVC increased rapidly for 1 minute after elevation of the head of bed and was stable thereafter. Next, we measured the diameter of the IVC in the supine position and head-of-bed elevation of 30°, 45°, 60°, and 75°. In our results, the maximum IVC diameter has increased significantly at the head-of-bed elevation 75°vs. the supine position. The IVC collapsibility index of all elevations was less than 50%, except in the supine position. Thus, when examining a patient in the head-of-bed elevation position, it is better to wait one minute after the change in position, as the diameter of the IVC will expand.