Collapsibility Index & Distensibility Index Calculator
- Collapsibility Index and Distensibility Index: Explanation and Clinical Context
The measurement of the inferior vena cava provides a noninvasive method to estimate right atrial pressure and to assess intravascular volume status. The collapsibility index compares the maximum diameter of the inferior vena cava during expiration with the minimum diameter during inspiration. A greater degree of collapse often reflects lower right atrial pressure in spontaneously breathing patients. The distensibility index compares the same measurements but uses the inspiratory diameter as the denominator. This index is frequently used in mechanically ventilated patients to evaluate potential fluid responsiveness. Larger values indicate a greater change in diameter with respiration, which may reflect preload dependence.
A collapsibility index greater than fifty percent in spontaneously breathing patients is commonly associated with a right atrial pressure between zero and five millimeters of mercury. A distensibility index greater than eighteen percent in mechanically ventilated patients has been associated with fluid responsiveness in several hemodynamic studies. Interpretation must be individualized because factors such as positive intrathoracic pressure, elevated intraabdominal pressure, mechanical ventilation settings, and underlying cardiopulmonary disease can influence the diameter and respiratory variation of the inferior vena cava.
References:
American Society of Echocardiography Guidelines for Evaluation of Right Heart Function. Journal of the American Society of Echocardiography. 2010.
Blehar DJ et al. Identification of congestive heart failure by inferior vena cava collapse index in emergency department dyspnea patients. Annals of Emergency Medicine. 2009.
Muller L et al. Respiratory variations of the inferior vena cava to predict fluid responsiveness in mechanically ventilated patients. Intensive Care Medicine. 2010.
Kircher BJ et al. Noninvasive estimation of right atrial pressure from the inspiratory collapse of the inferior vena cava. American Journal of Cardiology. 1990.
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