Transition from Nasal to Mouth Breathing with Increasing Nasal Obstruction Estimated by Airflow Resistance Measurement

Abstract

There have been numerous attempts to evaluate the relationships between the upper and lower airways. However, there are no available data indicating when the shift from nasal to oral breathing takes place as a subject's nasal obstruction increases. In this experiment twenty-four subjects, each with varying degrees of nasal obstruction, were examined. Their nasal and pulmonary resistances were measured for both nasal and oral breathing. Each airflow resistance was analyzed according to the Rohrer's equation. The examination results of those subjects who fell into the fourth degree classification of nasal obstruction showed transition from nasal to oral breathing. The pressure-flow curves of the nasal passages and the pleural surface during oral breathing had a same pattern. For the fourth degree cases, the nasal resistance was approximately onehalf of the total pulmonary resistance. In these circumstances the results from our study indicated that at the flow rate of 0.5 liter/sec the nose contributes about 53 % of the total pulmonary resistance.