The effect of the nasal cycle on mucociliary clearance

The nasal cycle is a well-recognised physiological phenomenon where each si de of the nose alternates through phases of congestion and decongestion. Al though many physiological properties of the nose alternate with the nasal c ycle whether this has any effect on the nasal mucociliary clearance is less clear. As the nose is a potential site for the administration of pharmaceu ticals, it is essential that any factors that could affect clearance (and h ence absorption) are identified. This study set out to investigate if mucoc iliary clearance rates differed between the clear and obstructed airway at a morning peak of the nasal cycle in five healthy volunteers with normal na sal anatomy using a dual-radioisotope labelling procedure that allows both sides of the nose to be assessed simultaneously. The clearance of the radio pharmaceutical formulations from the nasal cavity was monitored using gamma scintigraphy and decay-adjusted 50%-clearance times were calculated for ea ch nostril. The ratios of clearance times from the patent nostril when comp ared to the obstructed nostril were statistically significant (two-tailed t -test; P = 0.039), the mean ratio being 2.5 : 1 (SEM +/-0.5). It can be con cluded that the nasal cycle has a marked effect on the mucociliary clearanc e patterns of the nose. This may have both theoretical and practical implic ations for the nasal delivery of drugs.