Time Periods in the Nasal Cycle During Night Sleep

Abstract

The periodic congestion and decongestion of nasal venous sinuses and the alternation of airflow from one side of the nose to the other are referred to as a ‘nasal cycle’ in the literature. The aim of this study was to detect the nasal cycle during sleep in normal subjects and describe existing time periods and their sequence and patterns. We studied 58 records of the nasal cycle over 6–9 hours of sleep in six healthy volunteers and revealed that the cycle could be described as a combination of 1 to 4 discrete ultradian periods with various length: 1.0–1.5 h (mean 78.6min), 2.5–3.0 h (168.3 min), 4.0–4.5 h (260.3 min) or 5.5–6.0 h (347.5 min). The distribution of the discrete time periods was multi-modal and the mean lengths of periods were ‘multiples’ of a basic period of 85.4 min (˜1.5 h) which was very close to the mean length of the sleep cycle (˜1.5 h). In all subjects, during any of the REM stages of the sleep, an alternation of the airflow through the nostrils was observed. In about 75% of all cases, the switch of the flow between the nostrils occurred during the second or following REM stages of the sleep thus shaping a nasal cycle that contained mainly periods of 3.0 or 4.5 hours. We suggest a novel classification of the nocturnal nasal cyclicity and hypothesis that there is a relationship between the nasal cycle and the sleep cycle which, like other cyclic physiological phenomena with ultradian rhythmicity, expresses a pattern of ‘lateralisation’ that is synchronous with changes in the sleep cycle.