CHANGES IN THE AMPLITUDE OF THE NASAL CYCLE-ASSOCIATED WITH SYMPTOMS OF ACUTE UPPER RESPIRATORY-TRACT INFECTION

Nasal airflow is normally asymmetrical and subject to spontaneous reci procal changes which are often referred to as the 'nasal cycle'. The n ature of these spontaneous changes in nasal resistance is poorly under stood and little information is available about how they are affected by nasal disease. In order to understand the changes in nasal resistan ce in health and disease it is important to record unilateral resistan ce rather than express results as total nasal resistance. Unilateral r esistance is subject to continuous reciprocal changes and therefore ne w measurements were developed in this study in order to quantify the n asal resistance of each nasal passage. Twelve human subjects (age 19-3 8) with symptoms of acute respiratory tract infection (URTI) were recr uited for the study which involved serial measurements of unilateral n asal airway resistance using the technique of posterior rhinomanometry over a period of six hours. Measurements were made on one day when su bjects had symptoms of URTI and then repeated 6-8 weeks later when sub jects were healthy. The results of this study show that all of the sub jects exhibited spontaneous reciprocal changes in nasal airway resista nce on both study days but that there was a significant increase in th e amplitude of the changes in resistance when the subjects had symptom s of URTI with one nasal passage often becoming severely congested. In order to quantify the amplitude of the reciprocal changes in nasal re sistance two new measures were used. The minimum and maximum nasal air way resistance recorded for each nasal passage during the six hour rec ording period (MIN NAR and MAX NAR). Mean MIN NAR with URTI was 0.4 Pa cm(3)s +/- 0.07 which was not significantly different from mean MIN N AR in health which was 0.36 Pa cm(3)s +/- 0.05 (p = 0.22, n = 20). The mean MAX NAR during URTI was 2.44 Pa cm(3)s +/- 0.38 and this decreas ed significantly to 1.36 +/- 0.17 when recorded during healthy conditi ons (p = 0.01, n = 20). The increased amplitude of spontaneous recipro cal changes in nasal airway resistance associated with symptoms of URT I is proposed to be due to an increased filling pressure to the nasal venous sinusoids associated with a nasal inflammatory response. A mode l is proposed to explain the role of the nasal sympathetic vasoconstri ctor tone and nasal venous filling pressure in the control of nasal ai rway resistance and to help explain the periods of unilateral nasal ob struction often associated with allergic and infective rhinitis.