Gong H, McManus M S, Linn W S
Environmental Health Service, Rancho Los Amigos Medical Center, Downey, California 90242, USA.
Arch Environ Health. 1997 Jan-Feb;52(1):34-41. doi: 10.1080/00039899709603797.
The development of attenuated response ("tolerance") to daily ozone (O3) exposures in the laboratory is well established in healthy adult volunteers. However, the capability of asthmatics to develop tolerance during multiday ozone exposures is unclear. We exposed 10 adult volunteers with mild asthma to 0.4 ppm O3 in filtered air for 3 h/d on 5 consecutive d. Two similar filtered-air exposures during the preceding week served as controls. Follow-up O3 exposures were performed 4 and 7 d after the most recent consecutive exposure. All exposures were performed in an environmental chamber at 31 degrees C and 35% relative humidity. The subjects performed moderate exercise (mean ventilation rate of 32 l/min) for 15 min of each half-hour. Responses were measured with spirometry and symptom evaluations before and after each exposure, and a bronchial reactivity test (methacholine challenge) was conducted after each exposure. All response measurements showed clinically and statistically significant day-to-day variation. Symptom and forced-expiratory-volume-in-1-s responses were similarly large on the 1st and 2nd O3 exposure days, after which they diminished progressively, approaching filtered air response levels by the 5th consecutive O3 day. This tolerance was partially lost 4 and 7 d later. Bronchial reactivity peaked after the first O3 exposure and remained somewhat elevated after all subsequent O3 exposures, relative to its control level following filtered-air exposures. Individual responses varied widely; more severe initial responses to O3 predicted less rapid attenuation. We concluded that asthmatics can develop tolerance to frequent high-level O3 exposures in much the same manner as normal subjects, although the process may be slower and less fully effective in asthmatics.
在健康成年志愿者中，实验室环境下对每日臭氧（O₃）暴露产生减弱反应（“耐受”）的现象已得到充分证实。然而，哮喘患者在多日臭氧暴露期间产生耐受的能力尚不清楚。我们让10名轻度哮喘成年志愿者在过滤空气中连续5天每天暴露于0.4 ppm的O₃中3小时。前一周进行的两次类似的过滤空气暴露作为对照。在最近一次连续暴露后的第4天和第7天进行后续的O₃暴露。所有暴露均在温度为31摄氏度、相对湿度为35%的环境舱中进行。受试者每半小时进行15分钟的适度运动（平均通气率为32升/分钟）。每次暴露前后通过肺活量测定和症状评估来测量反应，并在每次暴露后进行支气管反应性测试（乙酰甲胆碱激发试验）。所有反应测量结果均显示出临床和统计学上显著的每日变化。在第1天和第2天的O₃暴露日，症状和第1秒用力呼气量反应同样较大，此后逐渐减弱，到连续第5天的O₃暴露日接近过滤空气反应水平。这种耐受性在4天和7天后部分丧失。相对于过滤空气暴露后的对照水平，支气管反应性在首次O₃暴露后达到峰值，并且在所有后续O₃暴露后仍有所升高。个体反应差异很大；对O₃的初始反应越严重，预测其衰减速度越慢。我们得出结论，哮喘患者能够以与正常受试者大致相同的方式对频繁的高浓度O₃暴露产生耐受，尽管这一过程在哮喘患者中可能较慢且效果不太完全。
