Objective To investigate the application value of inspiratory phase CT scanning combined with expiratory phase HRCT scanning in evaluating HRCT image manifestations and related parameters in diagnosis of small airway lesions of patients with long-term smoking without symptoms .Methods Seventy patients with long-term smoking were served as smoking group,the other 30 patients without smoking were served as control group .The patients in both groups underwent chest deep inspiration end CT scanning with spiral CT combined with deep expiration end HRCT scanning to observe mainly air retention images at the end of expiration ,and to measure and calculate related parameters in order to analyze the correlation between these parameters and small airway diseases .Results The male smokers were significantly more than female smokers .There were significant differences in the parameters of lung volume between smoking group and control group ( P <0.05), and these parameters included inspiratory phase lung volume , expiratory phase lung volume , low attenuation area ratio in inspiratory phase, low attenuation area ratio in expiratory phase , average lung field density in inspiratory phase , average lung field density in expiratory phase , ratio of expiration lung volume/inspiration lung volume ,ratio of expiration average lung field density/inspiration average lung field density , the difference in lung volume between expiration and inspiration , the difference in average lung field density between expiration and inspiration .However except for inspiratory phase lung volume ,there were no significant differences in the other parameters of lung volume between mild smokers and heavy smokers ( P >0.05). Conclusion The chest expiratory phase HRCT scanning can show clearly the characteristic manifestations of air retention ,and chest expiratory phase HRCT scanning combined with inspiratory phase CT scanning and related parameters analysis plays an important role in early diagnosis of small airway diseases , with higher sensitivity, thus, which is a convenient and quick detection method and is worth using widely in clinical practice .%目的：探讨无症状长期吸烟者肺小气道损害的患者进行吸气相CT扫描，结合呼气相HRCT扫描，评价呼气相HRCT影像表现及相关参数在诊断小气道疾病方面应用价值。方法采用70例作为吸烟试验组，采用30例不吸烟对照组，均使用螺旋CT进行胸部深吸气末CT扫描，结合深呼气末HRCT扫描，重点观察呼气末的空气潴留影像，测量及计算相关参数，统计其与小气道病变的相关性。结果本研究从性别构成上显示男性吸烟者明显高于女性比例，吸烟组与对照组肺容积参数间差异均有统计学意义（ P ＜0．05），分别包括吸气相肺容积、呼气相肺容积、吸气相低衰减区比例、呼气相低衰减区比例、吸气相平均肺野密度、呼气相平均肺野密度、呼气－吸气肺容积比、呼气－吸气平均肺野密度比率、呼气－吸气肺容积差和呼气－吸气平均肺野密度差；轻度与重度吸烟组的肺容积参数比较显示除Ins－LV在2组间差异有统计学意义（ P ＜0．05），其余参数差异均无统计学意义（ P ＞0．05）。结论胸部呼气相HRCT扫描能够清晰的观察到空气潴留的特征表现，结合吸气相CT扫描，测量和计算相关参数等指标，对临床小气道病变的临床早期诊断具有重要意义，敏感性较高，是一种方便快捷，具有临床推广意义的的一种检查手段。
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