How this calculator works
Mean airway pressure is the area under the pressure-time curve divided by total cycle duration. For a square inspiratory pressure waveform, the area factor is 1 and the standard pressure-control estimate applies. A measured area factor can represent a different inspiratory shape, but the page does not infer that factor from a ventilator mode. Measured ventilator mean pressure is preferable when the waveform is complex or spontaneous efforts contribute. The result is an estimate for information only and is not medical advice.
Formula
MAP = PEEP + k x (PIP - PEEP) x Ti/Ttotal. Ttotal = 60/RR when RR is breaths/min. k is the inspiratory area above PEEP divided by (PIP - PEEP) x Ti. Each inverse mode rearranges this identity.
Worked example
For PIP 25 cmH2O, PEEP 5 cmH2O, Ti 1 second, cycle 4 seconds and k = 1, MAP = 5 + 20/4 = 10 cmH2O. The corresponding respiratory rate is 15/min.
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Frequently asked questions
What is the waveform factor?
It is a known geometric area fraction for the inspiratory pressure trace. It equals 1 for a square pressure waveform. Do not guess it for a complex breath.
Can inspiratory time equal the whole cycle?
This tool requires a positive expiratory interval, so Ti must be less than total cycle time.
Does estimated mean pressure replace the monitor?
No. Leaks, patient effort, flow shape and ventilator behaviour may make the actual measured mean pressure different.