Use of a portable spirometer for studies on the nasal cycle

Studies based on the nasal cycle are difficult because multiple measurement s of nasal patency need to be made over many hours. There is a great need f or a simple portable instrument that can be used away from the clinical lab oratory for studies on the nasal cycle. Our aim was to investigate the usef ulness 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). T he spirometer was used to measure the fractions of the slow VC volume of ai r expired through the right and left nasal passage in turn. Hourly measurem ents were made over a 5-hour period in six healthy volunteers. The spiromet ry measurements of the volume of air expired from each nasal passage were c ompared with nasal conductance of each nasal passage (airflow at 75 Pa) obt ained by posterior rhinomanometry. The spirometer was found easy to use by both the investigator and the patients. Simple regression analysis of the s pirometer and rhinomanometer measures of airflow partitioning found a corre lation coefficient of r = 0.827 (p < 0.0001; n = 36). These results indicat e that the partitioning of nasal expired volume measured by spirometry is d irectly comparable with partitioning of nasal airflow obtained with rhinoma nometry. Spirometry has considerable advantages over rhinomanometry for stu dies on the nasal cycle because of portability and ease of use.