Correct. Depth and frequency of breathing is regulated 90% by arterial CO2 level due to a direct, potent servo feedback based on a sensor in the brain stem. The

Correct. Depth and frequency of breathing is regulated 90% by arterial CO2 level due to a direct, potent servo feedback based on a sensor in the brain stem. The rest is due to O2 level. A fatal situation happens with low CO2 and low O2 that doesn't increase breathing. Pneumo doctors hate this and it's an absolute indication for intubation and mechanical breathing.