Analysis of respiratory function and respiratory impedance in elderly patients with fixed airflow obstruction

• Main Authors: Akiko Yamazaki, Mamoru Shiga, Arisa Ideguchi, Tatsuyoshi Yokoi, Kohki Horiguchi, Takazumi Yoshida, Keisuke Kato, Koichiro Takita, Takahiko Horiguchi
• Format: Article
• Language: English
• Published: Fujita Medical Society 2017-02-01
• Series: Fujita Medical Journal
• Subjects: bronchial asthma; chronic obstructive pulmonary syndrome; asthma–chronic obstructive pulmonary disease overlap syndrome; respiratory function; respiratory impedance
• Online Access: https://www.jstage.jst.go.jp/article/fmj/3/1/3_6/_pdf/-char/en

Objectives: Asthma and chronic obstructive pulmonary disease (COPD) are representative respiratory diseases characterized by obstructive ventilatory impairment. Asthma–COPD overlap syndrome (ACOS) has recently attracted attention. This study aimed to analyze the pathology of obstructive ventilatory impairment by assessment of respiratory function and impedance in smokers with fixed airflow obstruction, regardless of the disease entity. Methods: Thirty-eight elderly patients with a minimum of a 10 pack-year smoking history and fixed airflow obstruction with a forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) of <70% after bronchodilator administration were included. Respiratory function and impedance parameters were measured and compared across four phenotypes. Phenotypes were based on the pulmonary diffusing capacity and airway reactivity to inhaled bronchodilators. Groups 1 and 2 included carbon monoxide diffusion capacity (DLCO) <80% without and with positive airway reactivity, respectively. Groups 3 and 4 included DLCO ≥80% without and with positive airway reactivity, respectively. Results: FEV1 (% predicted) was significantly correlated with lung resistance at 5 Hz (R5), 20 Hz (R20), and R5−R20 in patients with fixed airflow obstruction. The correlation with R5 and R5−R20 was stronger than that with R20. These results are similar to those reported for patients with COPD, and suggest that small airways are primarily affected in patients with fixed airflow obstruction. Group 2 patients tended to show lower FEV1/FVC and higher ∆X5 values than patients in the other groups.. In some Group 2 patients, FEV1 and respiratory impedance values improved after addition of or a dose increase in inhaled corticosteroids, and this suggested the presence of ACOS. Conclusions: Evaluation of older patients with fixed airflow obstruction using various approaches is useful for determining the underlying pathology.