Theory 07/Respiratory cycle/Onset phase

Onset Is a CO2 Threshold

The claim

Each breath is triggered above a threshold in arterial CO2 relative to the chemoreceptor gain, so the same CO2 drives different breathing in different people.

01Mechanism

Central chemoreceptors respond to pH; the threshold and gain set the trigger.

02Prediction

Breath timing should track the ratio.

03Refutation

Timing tracking O2 would remove the CO2 trigger.