General Medical Information

Interpretation of Rhinomanometric Findings

Thomas V. Mccaffrey

Although rhinomanometry provides only one aspect of the clinical evaluation of nasal obstruction, the information obtained about the functional capacity of the nasal airway cannot be acquired with other methods of evaluation. In general, there are two major types of nasal obstruction: mucosal hypertrophy or congestion and structural deformity of the nasal airway. When nasal resistance is determined before and after maximum nasal decongestion with a topical decongestant, it is possible to determine the relative importance of mucosal and structural factors in producing nasal obstruction.

Calculated resistance can be compared with predetermined normal ranges found for persons without symptoms. Mucosal obstruction usually is expected to be corrected with topical decongestion. Structural abnormalities causing nasal obstruction are not expected to be in the normal range after decongestion. Normal nasal resistance values and ranges have been established. There is not an absolute upper limit of normal nasal resistance; however, a nasal resistance greater than 0.3 Pa/cm3 per second usually is symptomatic. The threshold for subjective obstruction, however, varies. Some persons with apparently normal or slightly elevated nasal resistance have obstructive symptoms at times. Several measurements obtained with rhinomanometry provide important information about the nasal airway. These are unilateral nasal resistance before decongestion, total nasal resistance before decongestion, the effect of decongestion on nasal resistance, and the presence of airway collapse.