Relationship between inferior vena cava diameter ratio and central venous pressure

To explore the relationship between the shape of the inferior vena cava (IVC) lumen and central venous pressure (CVP).

In 60 patients undergoing mechanical ventilation and CVP monitoring in the Intensive Care Unit of Peking Union Medical College Hospital from July to October 2016, we measured with B-mode ultrasonography the transverse maximum (MXD) and minimum diameter (MID) of the IVC at end expiration, and calculated the diameter ratio (DR) as MXD/MID. Patients were divided into three groups according to CVP: low (CVP < 8 mm Hg), intermediate (8 mm Hg ≤ CVP ≤ 10 mm Hg), and high (CVP > 10 mm Hg).

MXD was 2.32 ± 0.41 cm, MID was 1.41 ± 0.40 cm, and DR was 1.76 ± 0.49. CVP was 9.27 ± 2.99 mm Hg. DR correlated with CVP (r = -0.527, P < .001). The low-CVP group had greater dispersion of DR values, with a large variety in IVC shape (elliptical, irregular, teardrop-shaped, partially collapsed…). The area under the ROC curve for predicting CVP with DR, with a CVP threshold of 8 mm Hg was 0.835 (95% CI, 0.726-0.945; P < .05). With a DR cutoff value of 1.76, sensitivity was 0.765 and specificity was 0.781.

DR above 1.7 is predictive of CVP < 8 mm Hg.