Subclavian Versus Inferior Vena Cava Collapsibility Indices.

inferior vena cava diameters is obtained in the supine position with a convex probe .The probe is placed in the subxiphoid region or the right anterior midaxillary plane.The sagittal section of IVC is imaged. M-mode probe is used to identify the measurement of minimum and maximum venous dimensions over the respiratory cycle using the 3.5-5 MHz phased array probe. To standardize the measurements, measuring of the IVC diameter is performed at 2 cm caudal of the junction point of the right atrium and IVC. The difference between the maximum (D max) and minimum (D min)diameters of the target vein is normalized according to the standard formula to yield the collapsibility index (CI).

Right SCV diameters is checked in the supine position using a high frequency linear array probe (6-13 MHz) and M-mode. To standardize the measurements, the probe is placed beneath the proximal part of the middle part of the clavicle perpendicular to long-axis of the SCV to obtain the best cross-sectional view of the vien. After the target vein is localized , the dynamic diameter change is recorded using M-mode to identify and measure the minimum and maximum venous diameters.To calculate SCV collapsibility index, the standard formula is used.

ultrasound guided 7.5-F central venous catheter is introduced via right internal jugular vein under local analgesia with 2% lidocaine for measuring the CVP.