However some have problem breathing through their nose: here is the useful procedure from the Buteyko system
According to the argument reduced CO2 levels causes an increase in mucus secretion and constriction of the airways. and helps block it up.
The following, so it is claimed is a simple exercise which could unblock the nose (in as little as ﬁve minutes.)
The technique increases the carbon dioxide levels in the blood, which so its claimed, will open the nasal passages.
✦ Sit upright on a straight-backed chair.
✦ Calm your breathing. Take a small breath (two seconds) in through your nose, if possible, and a small breath out (three seconds). If you are unable to take a breath in through your nose, take a tiny breath in through the corner of your mouth.
✦ Pinch your nose and hold your breath. Keep your mouth closed.
✦ Gently nod your head or sway your body until you feel that you cannot hold your breath any longer. (Hold your nose until you feel a relatively strong need for air.)
✦ When you need to breathe in, let go of your nose and breathe gently through it, in and out, with your mouth closed. Avoid taking a deep breath when you breathe in, and calm your breathing as soon as possible by focusing on relaxation. Repeat to yourself ‘relax and breathe less’.
✦ Continue to do this exercise until you can breathe through your nose fully. If your nose does not become totally unblocked, wait about one minute and perform this exercise again. Initially you may need to do this a number of times before your nose is completely unblocked.
the basic aim is to improve your co2 tolerance. even during a hevy cold you should breat through your, presumably, snotty nose
Holding breath traps additional carbon dioxide which has been produced from the physical activity involved in moving the muscles. It is quite common for the nose to become blocked again shortly after doing this exercise. This is because the underlying breathing has not been changed and the body has not become accustomed to the increased carbon dioxide level. However, after some time, and with regular practice of breathing exercises, the body will adapt to a higher level of carbon dioxide and the nose will remain unblocked.
Give it a try