Abstract
Evidence has recently accumulated indicating that negative air ions are beneficial in certain cases of hay fever and asthma(2). Positive ions, on the other hand, are reported to produce nasal obstruction, dryness of the mucous membranes, and headaches (6,8). In order to test whether these clinical observations could be correlated with any measurable changes in the pulmonary clearing mechanism (including ciliary rate, rate of mucus flow, and smooth muscle tone), the following in vitro experiments were undertaken.
Methods. Pieces of fresh rabbit† trachea 2-3 cm long were cut along the anterior wall, spread open, and pinned to small blocks of wood. These blocks were then placed in glass-and-plastic chambers (Fig. 1) containing air of 80-100% relative humidity. By means of a 10X dissecting microscope and a Strobotac-Strobolux combination it was possible to observe the surface of the tissue and determine the ciliary rate ± 50 beats/min. Rate of mucus flow was determined by timing the progress of air-bubbles or of added grains of talc (averaging .01 mm in diameter) in the mucous layer. Clearing efficiency was gaged by the ability of a tissue to remove talc grains applied evenly over its surface with a medical powder blower. The experiments were conducted at room temperature, which varied from 21-23°C. Air ions were generated by beta radiation derived from tritium which was contained in sealed foils; a reversible rectifying circuit made it possible to select positive or negative air ions at will(5). Measurements made with the Beckett probe and Beckman micro-microammeter(3) established that 1 × 109 air ions of either charge impinged on each cm2 of exposed tissue/sec.
Results. 1. Effect on Ciliary Rate. Under conditions described above, the initial ciliary rate averaged between 1400 and 1500 beats/min.
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