Abstract
Background: Conventional spirometry in which air flows through the mouth is used to detect obstructive airways disease. If air is made to flow through the nose only, obstructive disorders of nose-nasopharynx region may be detected. In this study, this was carried out by a simple modification at the patient end of the spirometer tube that enabled the patient to breathe out through the nose only or through the nose and mouth.

Aims and Objective: The main aim of the current study is to compare oronasal and nasal spirometry measurements in healthy individuals and establish normal values for nasal spirometry.

Materials and Methods: A total of 600 healthy individuals were divided into three groups based on age: Group 1: 6–15 years, Group 2: 16–35 years, and Group 3: 36–50 years. Each group contained 200 subjects. All subjects underwent two sets of measurements: (1) Oronasal spirometry and (2) nasal spirometry. Forced vital capacity (FVC), forced expiratory volume in first second (FEV1), FEV1/FVC%, Forced expiratory time (FET), peak expiratory flow rate, forced inspiratory flow at 50% of inspired volume during FVC test, forced expiratory flow at 50% of expired volume during FVC test, and peak inspiratory flow rate were evaluated in all groups.

Results: In the age group of 16–35 years, all the parameters are significantly less in nasal spirometry when compared to oronasal spirometry. In the 36–50 years group, the results were similar except for FET which did not differ significantly in females. In the age group of 6–15 years, differences in FET were not significant in both the sexes. In males, FVC, FEV1, and FEV1% were significantly less for nasal spirometry, but in females, there was no significant difference.

Conclusion: Significant differences were observed between many oronasal and nasal parameters. This indicates that there is a difference between airflow through the mouth and airflow only through the nose in healthy individuals. These differences could be exaggerated in persons with obstruction in the nose–nasopharynx region. Since the instrument is a portable one, many exciting possibilities are open to investigation.

Key words: Oronasal Spirometry; Nasal Spirometry; Nasopharynx; Nasal Obstruction