Accuracy of forced oscillation technique to assess lung function in geriatric COPD population

Hoi Nam Tse,1 Cee Zhung Steven Tseng,1 King Ying Wong,2 Kwok Sang Yee,2 Lai Yun Ng1 1Medical and Geriatric Department, Respiratory Unit, Kwong Wah Hospital, 2Department of Tuberculosis and Chest Unit, Wong Tai Sin Hospital, Hong Kong, People’s Republic of China Introduction: Performing lung function test in geriatric patients has never been an easy task. With well-established evidence indicating impaired small airway function and air trapping in patients with geriatric COPD, utilizing forced oscillation technique (FOT) as a supplementary tool may aid in the assessment of lung function in this population. Aims: To study the use of FOT in the assessment of airflow limitation and air trapping in geriatric COPD patients. Study design: A cross-sectional study in a public hospital in Hong Kong. ClinicalTrials.gov ID: NCT01553812. Methods: Geriatric patients who had spirometry-diagnosed COPD were recruited, with both FOT and plethysmography performed. “Resistance” and “reactance” FOT parameters were compared to plethysmography for the assessment of air trapping and airflow limitation. Results: In total, 158 COPD subjects with a mean age of 71.9±0.7 years and percentage of forced expiratory volume in 1 second of 53.4±1.7 L were recruited. FOT values had a good correlation (r=0.4–0.7) to spirometric data. In general, X values (reactance) were better than R values (resistance), showing a higher correlation with spirometric data in airflow limitation (r=0.07–0.49 vs 0.61–0.67), small airway (r=0.05–0.48 vs 0.56–0.65), and lung volume (r=0.12–0.29 vs 0.43–0.49). In addition, resonance frequency (Fres) and frequency dependence (FDep) could well identify the severe type (percentage of forced expiratory volume in 1 second