Recently I tried holding my breath for as long as I could. I managed to hold it for almost 2 minutes, but after a bit more than 1 minute, I already felt a strong need to exhale some of the air. At the same time, I did not feel like I had to inhale again though. I ended up with two possible explanations:
1. At the beginning, I took a deep breath of air which was about 20 °C in temperature. After this one minute in my lungs, the air warmed up (I assumed it warmed up to 35 °C). For the sake of simplicity, I calculated with the ideal gas law
pV = nRT
that the pressure in the lung would increase by about 5%. Ok, this is why I had to release some air. But wait...
2. From what I learned about physiology, I know that our body has certain chemoreceptors to determine the oxygen saturation in our blood. And there are such chemoreceptors for carbon dioxide as well. The concentration of CO2 in my blood reached a certain threshold and I experienced this strong need to exhale.
Can anybody of you confirm one of these theories? Or are both of them wrong?