I:E ratio
The ratio of inspiratory time to expiratory time in mechanical ventilation cycles.
Full Definition
The inspiratory-to-expiratory (I:E) ratio describes the proportion of time spent in inspiration versus expiration during each ventilatory cycle. Normal spontaneous breathing typically has an I:E ratio of 1:2, meaning inspiration takes half as long as expiration. In mechanical ventilation, respiratory therapists adjust this ratio based on patient needs: shorter inspiratory times may improve comfort and cardiac output, while longer inspiratory times can enhance oxygenation in certain conditions. Inverse I:E ratios (such as 2:1) are sometimes used in severe respiratory failure to maximize oxygenation, though they require careful monitoring for adverse effects.
Usage
Usage note: Always express as a ratio (1:2) rather than a decimal (0.5) in clinical documentation.
In Context
- "Adjust the I:E ratio to 1:3 to allow more complete expiration in this COPD patient." — Ventilator management note
- "The inverse I:E ratio of 2:1 improved oxygenation but required sedation for patient comfort." — Critical care progress note