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 reciprocal changes which are often referred to as the 'nasal cycle'. The nature of these spontaneous changes in nasal resistance is poorly understood and little information is available about how they are affected by nasal disease. In order to understand the changes in nasal resistance in health and disease it is important to record unilateral resistance rather than express results as total nasal resistance. Unilateral resistance is subject to continuous reciprocal changes and therefore new measurements were developed in this study in order to quantify the nasal resistance of each nasal passage. Twelve human subjects (age 19-38) with symptoms of acute respiratory tract infection (URTI) were recruited for the study which involved serial measurements of unilateral nasal airway resistance using the technique of posterior rhinomanometry over a period of six hours. Measurements were made on one day when subjects had symptoms of URTI and then repeated 6-8 weeks later when subjects were healthy. The results of this study show that all of the subjects exhibited spontaneous reciprocal changes in nasal airway resistance on both study days but that there was a significant increase in the amplitude of the changes in resistance when the subjects had symptoms of URTI with one nasal passage often becoming severely congested. In order to quantify the amplitude of the reciprocal changes in nasal resistance two new measures were used. The minimum and maximum nasal airway resistance recorded for each nasal passage during the six hour recording period (MIN NAR and MAX NAR). Mean MIN NAR with URTI was 0.4 Pa cm3s +/- 0.07 which was not significantly different from mean MIN NAR in health which was 0.36 Pa cm3s +/- 0.05 (p = 0.22, n = 20). The mean MAX NAR during URTI was 2.44 Pa cm3s +/- 0.38 and this decreased significantly to 1.36 +/- 0.17 when recorded during healthy conditions (p = 0.01, n = 20). The increased amplitude of spontaneous reciprocal changes in nasal airway resistance associated with symptoms of URTI is proposed to be due to an increased filling pressure to the nasal venous sinusoids associated with a nasal inflammatory response. A model is proposed to explain the role of the nasal sympathetic vasoconstrictor tone and nasal venous filling pressure in the control of nasal airway resistance and to help explain the periods of unilateral nasal obstruction often associated with allergic and infective rhinitis.

Asymmetry in the autonomic nervous system with reference to the nasal cycle, migraine, anisocoria and Menière's syndrome.

Studies on the nasal cycle have demonstrated that the autonomic tone to the nose is asymmetrical and oscillates in a regular cycle. Autonomic tone may be regulated from a centre in the hypothalamus and normally there is a balance between he autonomic tone of the right and left halves of the body. However, under stress or with hypothalamic instability this balance may be disrupted and result in the marked autonomic asymmetry seen in migraine or Meniér's syndrome. Research on the nasal cycle in conditions where autonomic asymmetry is apparent could change the entire concept of autonomic control.

Sympathetic innervation of the nasal mucosa of the pig.

Nasal disorders such as atrophic rhinitis in the pig are widespread and are of economic importance in livestock production. A better understanding of the basic physiology of the nasal mucosa could help in the study and treatment of nasal disorders. This paper presents a simple method which may prove useful in studies on the autonomic innervation of the nasal blood vessels. The results demonstrate the great sensitivity of the nasal blood vessels to sympathetic activity and indicate that there may be a vascular connection between the two nasal passages.