Role of nose in sleep-disordered breathing - Park (2014)
Nasal obstruction contributes to airway collapse through a nonlinear increase in airflow resistance
Mouth breathing at night mechanically narrows and increases pressure on the upper airways, predisposing to collapse
Nasal surgery won’t help unless you force yourself to breathe nasally at night
The Breathing Diabetic Summary
Undisrupted sleep is important for proper mental and physical function during the day. (Remember our awesome quote about mouth breathing and your brain?!) Thus, anything that affects normal breathing during sleep (that is, nasal breathing) will negatively affect many other aspects of life. Yet, according to a 2008 study, sleep-disordered breathing (SDB) is present in 0.9-13% of children. I can only imagine it’s gone up significantly since then. Can you imagine the role SDB might be playing in many aspects of their lives? A big part of the problem might be mouth breathing during sleep. Thus, this article reviews some of the key features of nasal breathing during sleep and how nasal obstruction and/or mouth breathing during sleep might cause SDB.
Let’s first look at how nasal obstruction might set the stage for airway collapse. Poiseuille’s law states that airflow resistance varies with the 4th power of the radius through which it is passing. Therefore, a small nasal obstruction might have a very large impact on resistance and airflow, setting up conditions for upper airway collapse. For example, many studies have shown that nasal obstructions are associated with, and can cause, sleep apnea.
The nasal passage also has receptors that are very important during sleep. One study (which we also highlighted in Lavie ) showed that if nasal receptors are anesthetized, SDB increased. This suggests that nasal receptors might play a critical role in regulating breathing rhythm during sleep.
There are also two aspects of mouth breathing that need to be considered for sleep. The first is mechanical. When you breathe through your mouth during sleep, it moves the jaw and tongue down and back. This narrows, increases resistance, and increases pressure on the upper airways, predisposing them for collapse.
There is also a chemical aspect of mouth breathing that we need to consider. When you mouth breath during sleep, you blow off more CO2. With low CO2, your urge to breathe is reduced. So, this could also contribute to SDB and apnea during sleep. Thus, keeping adequate concentrations of CO2 during sleep might be key to maintaining rhythmic breathing.
Finally, with all of this being said, it seems like having surgery to open up the nasal passages would correct SDB. But, the results are mixed. Some studies have shown positive improvements after nasal surgery, and some have shown no improvements. Why might this be? I have one answer, and it comes from a story Patrick McKeown told us during Oxygen Advantage training. When he was in his twenties (I think), he had surgery to open up his nasal passages. Yet, it didn’t seem to help his sleep or constant fatigue. He got the surgery, but no one told him he needed to start breathing through his nose! So, just because someone gets nasal surgery does not mean they will immediately start breathing through their nose. In fact, if you’ve been a mouth breather for a long time, it might be really difficult to break that habit. Luckily, we can simply tape our mouth shut at night to ensure we breathe nasally, reaping all of the above-mentioned benefits and getting deeper, more restorative sleep.
Abstract from Paper
The detailed pathophysiology and mechanisms of sleep-disordered breathing are not completely understood and the role of nose in sleep and obstructive sleep apnea has been still controversial. Considering that nasal obstruction has effects on anatomical factor, neuromuscular factor, and respiratory factor, nose may modulate upper airway collapsibility through anatomical, neuromuscular, and respiratory factors and play an important role of the pathogenesis of obstructive sleep apnea.
Park, C.-S., (2014) Role of nose in sleep-disordered breathing, Sleep Medicine Research, 5 (1), 1 – 4.