Pneumatic triggering (traditional triggering – mechanism of action) – very oversimplified explanation.
Brain receives a multitude of inputs (ex: pH, PaO2, carotid body sensors, stretch receptors, etc.)
Brain sends a composite signal (final summation signal) down the phrenic nerve.
Diaphragm receives signal and starts contracting.
Diaphragmatic contraction results in an increased intrathoracic volume and a relative decrease in intrathoracic pressure.
The releative decrease in intrathoracic pressure results in the ventilator assuming a breath was taken and delivers the preset Vt (tidal volume).