Every Breath You Take: a theory of Sleep Disordered Breathing

My introduction to Obstructive Sleep Apnea has been through the early orthodontic technique that recognizes that open mouth postures lead to deformation of the maxilla and, hence, crooked teeth.  Part of the deformity is poor forward growth of the mid-face leaving the airway smaller.  I've come to understand that these kids will be more susceptible to OSA since it will take less obstruction to stop the breath.

Mouth breathing has other effects as well.  

The theory is this: chronic open mouth posture allows  excess escape of  carbon dioxide (CO2) lowering both lung and blood CO2 levels.  Medullary breathing triggers (in the brain, stimulated by CO2)  are eventually lowered to accomodate these chronically lower levels.  Lower triggers are tripped sooner in a feedback cycle and in time breathing rate rises.  Hence, a state of chronic hyperventilation ensues.   Instead of 8-10 breaths/min, mouth breathers are 20 or more bpm.

Further, according to the Bohr phenomenon, lower blood CO2 raises blood pH and inhibits the release of O2 from hemoglobin lowering availability to tissues.

Finally, CO2 is responsible for regulating the tone of smooth muscle.  Lower levels lead to spasm in vessels and organs with multiple effects, including hypertension, behavioral effects, and more, too numerous to mention here.

 

Regarding sleep, open mouth postures are often at maximum during sleep, allowing even more CO2 escape.  Breathing may actually stop when blood levels are acutely low.  Breathing stoppage however allows a quick buildup of CO2 until the patient begins breathing with a start.  This is Centrally-mediated Sleep Apnea.

 

CPAP (continuous postive airway pressure), may be helping with OSA by physically opening the airway under pressure. But it may also be helping with CSA by preventing the excess release of CO2, allowing proper build-up and breathing triggering.  

It seems to me that this distinction has gone largely unrecognized by a burgeoning Sleep Medicine establishment.  You can see the relevance of this thinking is huge: to the extent mouth breathing is the cause of centrally mediated phenomenon, a transition to nasal breathing and a lowered breathing rate may be the FIRST line of defense against sleep disordered breathing, especially in the young.  Furthermore, mandibular advancement appliances,  airway clearing surgery, and even jaw surgery will be fruitless unless proper breathing is achieved simultaneously.

(I would like to thank Dr. John Flutter for helping me understand these concepts)

Sleep tight! (you lips, that is....)