There is almost a complete exchange of gases between nasal passages and sinuses while humming in one exhalation vs. 4% without humming. If you have sinus problems, you should do a lot of humming. Chanting your mantra might do the same trick.
Humming Greatly Increases Nasal Nitric Oxide
Eddie Weitzberg and Jon O. N. Lundberg
Department of Anesthesiology and Intensive Care, Karolinska Hospital, and Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
American Journal of Respiratory and Critical Care Medicine Vol 166. pp. 144-145, (2002)
The paranasal sinuses are major producers of nitric oxide (NO). We hypothesized that oscillating airflow produced by humming would enhance sinus ventilation and thereby increase nasal NO levels. Ten healthy subjects took part in the study. Nasal NO was measured with a chemiluminescence technique during humming and quiet single-breath exhalations at a fixed flow rate. NO increased 15-fold during humming compared with quiet exhalation. In a two-compartment model of the nose and sinus, oscillating airflow caused a dramatic increase in gas exchange between the cavities. Obstruction of the sinus ostium is a central event in the pathogenesis of sinusitis. Nasal NO measurements during humming may be a useful noninvasive test of sinus NO production and ostial patency. In addition, any therapeutic effects of the improved sinus ventilation caused by humming should be investigated.