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# Distensibility Index of Inferior Vena Cava

## Purpose

The Distensibility Index of Inferior Vena Cava (dIVC) it’s the amount of increase of vena cava diameter after inspiration on a mechanical ventilated patient. This increase will rise when preload is reduced and so can be used to know when a patient its volume responsive[1]. It doesn’t give CVP or the preload of the right heart, but only if it is responsive to more volume.

## Measurement

1. On a subcostal window, measure the maximum IVC diameter on inspiration (dI) and the minimum IVC diameter on expiration (dE).
2. Calculate the dIVC using the following formula:

$dIVC=\dfrac{dI-dE}{dE}\times100$

## Conditions and caveats

• The patient must be on volume control ventilation, with tidal volume of about 8,5ml/Kg, breathing rate of 15 and PEEP of 4 mmHg[1].
• There shouldn’t be abdominal hypertension[1], cardiac arrhythmias or cardiopulmonary disease[2], pending more studies
• It must be possible to do a echocardiogram by subcostal approach, so it can’t be used on the very obese or after an laparotomy
• The first study[1] was done on a reduced number of patient. The followup studies were only done on patients with subarachnoid hemorrhage[3] and on renal replacement therapy[4]

## Reference Values

dIVC[1]
Fluid responsive >18%