Use of a portable spirometer for studies on the nasal cycle.

Studies based on the nasal cycle are difficult because multiple measurements of nasal patency need to be made over many hours. There is a great need for a simple portable instrument that can be used away from the clinical laboratory for studies on the nasal cycle. Our aim was to investigate the usefulness of a small portable spirometer in studying the nasal cycle. The Mir Spirobank spirometer was fitted with a nasal adapter to measure the volume of air expired from each nasal passage during a slow vital capacity (VC). The spirometer was used to measure the fractions of the slow VC volume of air expired through the right and left nasal passage in turn. Hourly measurements were made over a 5-hour period in six healthy volunteers. The spirometry measurements of the volume of air expired from each nasal passage were compared with nasal conductance of each nasal passage (airflow at 75 Pa) obtained by posterior rhinomanometry. The spirometer was found easy to use by both the investigator and the patients. Simple regression analysis of the spirometer and rhinomanometer measures of airflow partitioning found a correlation coefficient of r = 0.827 (p < 0.0001: n = 36). These results indicate that the partitioning of nasal expired volume measured by spirometry is directly comparable with partitioning of nasal airflow obtained with rhinomanometry. Spirometry has considerable advantages over rhinomanometry for studies on the nasal cycle because of portability and ease of use.