breath-sinus-brain toxin removal?

Prana and apana are two of the types (out of total 5) of breath that works in ones body.  Prana is the breath that goes”upwards” and apana is the one that travels “downwards”. So says all our Yoga literatures.  Medical sciences have so far only identified the breath that goes down to the lungs .   It has not so far  registered that another branch of air actually travels upwards . http://en.wikipedia.org/wiki/Shiva_Swarodaya_/_Swara_Yoga#Introduction_to_Swaras_and_its_effects

http://www.swarayoga.org/Interviewwithcharan.htm

Just as we have two main lungs one on each side, we also have two sets of cavities behind the nose and eyes called sinuses.  The function of these “cavities have so far not been defined well by medical science and is still debated. http://en.wikipedia.org/wiki/Paranasal_sinuses All these cavities are connected to each other and to the nose. http://en.wikipedia.org/wiki/Nasal_cycle

All yogic lore including many siddhar’s songs,  refer to the Prana or the breath that travels up.   It is said that by increasing this flow one gets to a better state of mind , more awareness etc etc. Benefits listed by these literature is enormous.  Yet very few are able to discern that breath also travels upwards.  In Thirumoolar’s  Thirumandiram a higly respected text in tamil (http://www.thirumandiram.net/tirumandiram-about-the-book.html)  in 3^rd tantra, (song no 566)  there is a song that means  :

One who is able to control the prana and make it go upwards, he will get more pleasure than drinking , never fatigue, always be brisk, etc etc.  There are several other siddhars songs including avvayar’s songs on these lines hinting about the need for one to regulate the “ida” and pingala” breaths and take it to the agya chakra etc.

Until recently,  medical sciences did not believe that breath actually alternates between the two nostrils.  But now acknowledges this and say while the left nostril is working, the right brain hemisphere seems to be more active and vice versa.

There is also a concept of Blood Brain barrier which cuts of brain from all blood flow.  So drug developers actually have to test any drug, to see if it passes through this barrier for any drug aimed at the brain. http://en.wikipedia.org/wiki/Blood%E2%80%93brain_barrier

My conjecture is Like all tissues the brain also must be using up chemicals for its functions ( actually it works electro chemically)  and any imbalance of these neuro transmitters “ have known to affect the way a person thinks and acts. Most anti depressants target these chemicals.  It is also imperative that while doing so the brain must also be creating certain  “waste products”  requiring its systematic removal.  Since the blood cannot reach the brain,  Is it possible these toxins are actually removed by the Prana at the sinuses? ( atleast there seems to be no other really useful functions assigned to the sinus cavities.)