Calculate I:E ratio, inspiratory and expiratory times, breath cycle time, respiratory rate, and duty cycle from ventilator timing inputs for educational review.

Enter breaths per minute.

Seconds. Include any inspiratory pause when calculating the full mechanical breath timing.

I:E Ratio Formula

The I:E ratio compares inspiratory time to expiratory time in one breath cycle.

RR + Ti mode

T₍cycle) & = (60) / (RR)\ Tₑ & = T₍cycle) - Tᵢ\ I:E & = Tᵢ:Tₑ

Target ratio mode

T₍cycle) & = (60) / (RR)\ Tᵢ & = (T₍cycle)) / (1 + E)\ Tₑ & = T₍cycle) - Tᵢ

Direct times mode

T₍cycle) & = Tᵢ + Tₑ\ RR & = (60) / (T₍cycle))\ I:E & = Tᵢ:Tₑ
  • RR = respiratory rate, in breaths per minute
  • Tcycle = total breath cycle time, in seconds
  • Ti = total inspiratory time, in seconds
  • Te = total expiratory time, in seconds
  • E = expiratory part of a target ratio written as 1:E

The displayed ratio is normalized. If expiration is longer, the result is shown as 1:E. If inspiration is longer, it is shown as an inverse ratio such as 2:1. In RR + Ti mode, inspiratory time must be less than the total cycle time.

Useful I:E Ratio Tables

Common I:E ratio ranges

I:E result Meaning Typical note
1:2 to 1:4 Expiration is 2 to 4 times inspiration Common passive ventilation range
1:1 to 1:1.5 Shorter expiratory time May need review for air trapping risk
1:5 or higher Long expiratory time Can occur with lower rates or short Ti
2:1, 3:1 Inspiration is longer than expiration Inverse ratio pattern

Cycle time by respiratory rate

Respiratory rate Cycle time Ti for 1:2 Ti for 1:3
10 breaths/min 6.00 s 2.00 s 1.50 s
12 breaths/min 5.00 s 1.67 s 1.25 s
15 breaths/min 4.00 s 1.33 s 1.00 s
20 breaths/min 3.00 s 1.00 s 0.75 s
30 breaths/min 2.00 s 0.67 s 0.50 s

I:E Ratio Notes

Use total inspiratory time for Ti. If a ventilator setting separates flow time and inspiratory pause, include the pause when you want the full mechanical I:E ratio.

Example: if RR is 20 and Ti is 0.8 seconds, cycle time is 3.0 seconds. Te is 2.2 seconds, so the I:E ratio is about 1:2.75.

I:E ratio is only one part of ventilator assessment. Interpret it with the full ventilator mode, waveform, patient condition, and local protocol.