How to control breath for Meditation?

  Last experiment for breath, i.e Breath in 1, 2, 3, 4, 5.........upto 20 , hold for 8 to 10 sec. in lungs area and release . 

Now the experiment is same but holding time is 5 sec.

I.e Take breath In 1, 2, 3, 4, 5, 6,.................upto 20. Hold the breath for 5 sec. in the lungs area or overall and release sharpely Out. The suddenly breath out within 5 sec. due to this the head or brain will be go under jamming.   

Keep in mind in this exercise we are using both the nostrils, and this exercise should avoid those who having problems by Asthama or respiratory.