A number of procedures are available for objective evaluation of nasal passage. Our knowledge is still limited, however, with respect to the transition of ventilation from nasal to mouth breathing caused by increasing nasal obstruction.
We selected seven patients who had to breathe through the mouth besides the nose in unilateral nasal breathing because of severe nasal obstruction, measured nasal resistance, total and unilateral (right, left), as well as pulmonary resistance in nasal and mouth breathing among them, and analyzed the obtained data with Rohrer's formula.
The results were as follows:
1) The patient breathed through the nose when nasal resistance was equal to pulmonary resistance consistent with mouth breathing.
2) The patient complained of a suffocating sensation when unilateral nasal resistance exceeded pulmonary resistance consistent with bilateral nasal breathing, and began to breathe through the mouth.
3) In concomitant mouth breathing initiated to remove the suffocating sensation due to unilateral nasal breathing, pulmonary resistance was lower than that in bilateral nasal breathing.
4) Pulmonary resistance in simultaneous unilateral nasal and mouth breathings fell to 1.8 times that in mouth breathing.
The above findings indicate that the point of transition from nasal to mouth breathing lies where pulmonary resistance in nasal breathing becomes roughly twice as high as nasal resistance in that or pulmonary resistance in mouth breathing.
