IVC Collapse / Under-resuscitated (Caval Index 59%)

The IVC is measured about 2 cm from the entrance into the right atrium of the heart. Using M-mode, both inspiratory and expiratory diameters are measured. This patient has almost complete collapse of his IVC with respiration. His expiratory diameter is 1.63cm and his inspiratory diameter is 0.67cm. His caval index is 59%, which correlates to a CVP of 5-10mmHg and he is therefore under-volume resuscitated. He will need more IVF. Just a reminder that the IVC diameter chart is for spontaneously breathing, non-vented patients. If you want to measure IVC diameter in ventilated patients, you must remember that due to positive pressure ventilation, the IVC will be the largest diameter with inhalation. You should measure the IVC when the patient is sedated and not spontaneously breathing.