Effects of normobaric oxygen on ciliary beat frequency of human respiratory epithelium

Respiratory infection is a major cause of morbidity after generalanaesthesia. Impairment of respiratory ciliary beat frequency (CBF) bydifferent stress factors causes a decrease in mucus transport rate (MTR).We have tested the effect of different concentrations of oxygen on CBF ofhuman respiratory epithelium in a prospective, randomized, in vitro study.Samples of superficial mucosa of the inferior nasal turbinates of 20non-smoking healthy volunteers were harvested and exposed to threedifferent oxygen environments (group I = 21% oxygen, group II = 60% oxygenand group III = 95% oxygen) for 2 h. In 50% of the samples, exposure timewas prolonged. At 30, 60, 90, 120 and 240 min, light microscopic images ofcilia activity were videotaped and CBF was later assessed in slow motion.Compared with baseline, group I showed no difference in CBF throughout thestudy. CBF was increased in group II from mean 9.7 (SD 0.4) to 11.2 (0.4)Hz (16%, P < 0.001) and in group III from 9.5 (0.6) to 12.1 (0.5) Hz(28%, P < 0.001) at 120 min. After 240 min of exposure to 95% oxygen,the CBF trend in group III was reduced to 11.8 (0.6) Hz but still remainedabove baseline. We conclude that oxygen appeared to have a dose- andtime-dependent accelerating effect on CBF. Prolonged exposure to highoxygen concentrations reversed this trend. Direct oxygen toxicity ("oxygenstress") is a possible explanation for this effect. These changes mayresult in impaired MTR.