This just happened to me recently, I was trying to sleep with clogged nose, so I tried breathing through my mouth. As you can imagine it was hard, but I managed to sleep deeply.

So I became curious, how does our body know whether to breathe through the nose or the mouth especially when we have a clogged nose during the time when we are in deep sleep?

NOTE: I tried researching this, but most result just shows how to clear clogged nose before sleeping

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – AliceD
    Commented Feb 15, 2018 at 15:02

1 Answer 1


Most people with colds/allergies/stuffy noses don't die in the middle of the night. Why?

Prevention of oxygen deprivation is powerfully regulated. If insufficient air intake is possible through the nose, the mouth opens automatically (regulated by the autonomic nervous system. If you exercise, at some point, nasal breathing isn't enough, and you start mouth breathing. It's not conscious.

The autonomic nervous system (ANS)... is a division of the peripheral nervous system that supplies smooth muscle and glands, and thus influences the function of internal organs. The autonomic nervous system is a control system that acts largely unconsciously and regulates bodily functions such as the heart rate, digestion, respiratory rate, pupillary response, urination, and sexual arousal. This system is the primary mechanism in control of the fight-or-flight response.

Within the brain, the autonomic nervous system is regulated by the hypothalamus. Autonomic functions include control of respiration, cardiac regulation (the cardiac control center), vasomotor activity (the vasomotor center), and certain reflex actions such as coughing, sneezing, swallowing and vomiting. Those are then subdivided into other areas and are also linked to ANS subsystems and nervous systems external to the brain. The hypothalamus, just above the brain stem, acts as an integrator for autonomic functions, receiving ANS regulatory input from the limbic system to do so. (emphasis mine)

The answer is a complex interaction between blood pH and oxygen/CO2 receptors and the autonomic nevous system.

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    $\begingroup$ As a point of emphasis that I think is lost to novices of biology, the brain (and the rest of the nervous system) does a lot that you are not aware of - it seems that people often have some intuition about their "subconscious" and they think of all this high-order pseudo-Freudian stuff, but the nervous system is so good at just handling the day-to-day 'boring' nitty-gritty operation of the body that people take it for granted and it just seems magical... Respiration, circulation, digestion, all hardly noticed unless something is quite wrong. $\endgroup$
    – Bryan Krause
    Commented Feb 14, 2018 at 16:59

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