Oops, turns out I was wrong: it's the amount of CO² in the *blood* that determines how often you breathe. "[I]f the blood CO2 starts to rise, then your brain will drive you breathe more (either by increasing your breathing rate or breath size or both), and if your blood CO2 starts to fall, then your brain will cause you to breathe less s…
Oops, turns out I was wrong: it's the amount of CO² in the *blood* that determines how often you breathe. "[I]f the blood CO2 starts to rise, then your brain will drive you breathe more (either by increasing your breathing rate or breath size or both), and if your blood CO2 starts to fall, then your brain will cause you to breathe less so that CO2 levels rise again. All of this is happening at a completely subconscious level as you sit reading this. In most people the brain is ‘set’ to maintain a dissolved PCO2 of about 5 kilopascals (kPa) (or 0.05 ATA or 38mmHg depending on what units you prefer to use) in the arterial blood."
Oops, turns out I was wrong: it's the amount of CO² in the *blood* that determines how often you breathe. "[I]f the blood CO2 starts to rise, then your brain will drive you breathe more (either by increasing your breathing rate or breath size or both), and if your blood CO2 starts to fall, then your brain will cause you to breathe less so that CO2 levels rise again. All of this is happening at a completely subconscious level as you sit reading this. In most people the brain is ‘set’ to maintain a dissolved PCO2 of about 5 kilopascals (kPa) (or 0.05 ATA or 38mmHg depending on what units you prefer to use) in the arterial blood."
—https://www.divepacific.co.nz/post/carbon-dioxide-and-diving-basic-carbon-dioxide-physiology