Influence of long-term cigarette smoking on changes of lung density by high-resolution computed tomography in asthmatics--4 years follow-up study

Background-The influence of cigarette smoking on the pathogenesis of asthma in the elderly remains controversial. This study attempts to estimate longitudinal changes in HRCT (high resolution computed tomography) parameters and pulmonary function parameters obtained for ex-smokers and never-smokers in asthmatics during 4-yr follow-up period. Methods-Fourteen asthmatics (6 ex-smokers and 8 never-smokers) were studied to determine the influence of aging and cigarette smoking on pulmonary function, and mean lung density (MLD) and the relative area of the lung showing attenuation values less than -950 HU (RA950) on HRCT scans. Results-The values of FVC and FEV1, were significantly more decreased in asthmatics without a smoking history during 4-yr follow-up period. The values of FVC, FEV1, FEV1/FVC and DLco/VA were significantly decreased and RV/TLC were significantly increased in asthmatics with a smoking history over 4 years, and annual decline in FEV1 ex-smokers was larger than that in never-smokers. In the upper lung field, inspiratory MLD was observed to shift in a negative direction and inspiratory RA950 was found to increase during 4-yr observation period in ex-smokers, but not in never-smokers. In the middle lung field, inspiratory RA950 was significantly enhanced in both two groups. Although expiratory MLD, expiratory RA950 and exp RA950/ins RA950 were observed to change significantly during the observation period in ex-smokers, no changes were observed in never-smokers. Conclusion-These results suggest that aging augments airspace enlargement predominantly in the middle lung field, while long term cigarette smoking further worsens emphysematous alterations in the upper lung field.

気管支喘息患者の肺高分解能CT所見に対する長期喫煙の影響を検討することを目的とした｡非喫煙喘息患者8名,喫煙歴を有する喘息患者6名を対象として,肺機能,肺平均CT値(MLD),-950HU以下のlow attenuation area(RA(950))について4年間の経過観察を行った｡ 4年間の観察中,非喫煙喘息患者では努力肺活量,1秒量の低下を認めた｡喫煙歴を有する喘息患者では努力肺活量,1秒量,1秒率,肺拡散能 の低下および残気率の増加を認めた｡喫煙歴を有する喘息患者では吸気において,上肺野MLDの有意の低下,RA(950)の有意の上昇を認めたが,非喫煙喘息患者では有意の変化は認めなかった｡中肺RA(950)は喫煙歴を有する喘息患者,非喫煙喘息患者ともに有意の上昇を認めた｡また,呼気において,喫煙歴を有する喘息患者でMLDの有意の低下,RA(950)の有意の上昇を認めたが,非喫煙喘息患者では有意の変化は認めなかった｡喘息患者において,加齢は主に中肺野のlow atenuation area,喫煙は上肺野のlow atenuation areaに影響を及ぼすことが示唆された｡