Model 2130

Pulmonary function was measured by clinical technicians using a dry rolling seal spirometer (model 2130; Sensor-Medics, Yorba Linda, CA, USA). Forced expiratory volume in 1 s (FEV1) and FVC measurements were performed according to the American Thoracic Society/European Respiratory Society guidelines and National Health and Nutrition Examination Survey (NHANES) method. Lung function measurements primarily included the FVC, FEV1, forced expiratory volume in 6 s (FEV6), forced expiratory flow between 25% and 75% of the FVC (FEV25–75%), and peak expiratory flow (PEF). Four criteria were applied to the spirometer data: (1) at least three acceptable spirometry curves for 6 s or more, (2) <150 mL inter-measurement variability in FVC and FEV1, (3) ≤10% inter-measurement variability in PEF, and (4) extra volume ≤5% of FVC (150 mL). Predicted spirometry values were calculated from the Korean reference equations, based on representative samples of the Korean population [15 (link)]. We used FVC, FEV1, the FEV1 to FVC ratio (FEV1/FVC), and the percentage of predicted values for FEV1 (%, FEV1p) and FVC (%, FVCp) to assess pulmonary function. A decline in the FVCp < 80% was regarded as a restrictive pattern of poor lung function [16 (link)].

Lung function was measured using a dry rolling seal spirometer (model 2130, SensorMedics, Yorba Linda, CA) according to the American Thoracic Society/European Respiratory Society criteria for standardization^{24 (link)}. Best forced expiratory volume in 1 second (FEV₁) and forced vital capacity (FVC) values were selected for data analysis. Spirometric data were obtained on site by clinical technicians. The percentage of predicted values for FEV₁ and FVC were calculated from the following equations obtained in a representative Korean population^{25 (link)}. $$\mathrm{Predicted}\mathrm{FVC}\mathrm{in}\mathrm{men}=-4.8434-(0.00008633\times {\mathrm{age}}^2\left[\mathrm{year}\right])+\left(0.05292\times \mathrm{height}\left[\mathrm{cm}\right]\right)+\left(0.01095\times \mathrm{weight}\left[\mathrm{kg}\right]\right)$$
$$\mathrm{Predicted}\mathrm{FVC}\mathrm{in}\mathrm{women}=-3.0006-(0.0001273\times {\mathrm{age}}^2\left[\mathrm{year}\right])+(0.03951\times \mathrm{height}\left[\mathrm{cm}\right])+(0.006892\times \mathrm{weight}\left[\mathrm{kg}\right])$$
$$\mathrm{Predicted}{\mathrm{FVC}}_1\mathrm{in}\mathrm{men}=-3.4132-(0.0002484\times {\mathrm{age}}^2\left[\mathrm{year}\right])+(0.04578\times \mathrm{height}\left[\mathrm{cm}\right])$$
$$\mathrm{Predicted}{\mathrm{FVC}}_1\mathrm{in}\mathrm{women}=-2.4114-(0.0001920\times {\mathrm{age}}^2\left[\mathrm{year}\right])+\left(0.03558\times \mathrm{height}\left[\mathrm{cm}\right]\right)$$

As described in detail previously [23 (link)], spirometry was performed using a dry rolling seal spirometer (Model 2130; Sensor Medics, Yorba Linda, CA, USA). Trained clinical technicians obtained spirometry data including FEV1, FVC, and FEV1/FVC on site and transferred them to an internet review center for processing. The data were compared against criteria metrics for acceptability, reproducibility, and quality control by a principal investigator to validate the data and to store them in a Korea Centers for Disease Control repository management system, in accordance with the ATS/ERS recommendations [1 (link)]. Two criteria were applied to the spirometry data: 1) two or more acceptable spirometry curves to ensure correct inspiration and 6s expiration and 2) 150-ml inter-measurement variability in FVC and FEV1. The spirometry tests were undertaken without the use of a bronchodilator. Age-, sex-, and height-adjusted normal predicted values of FVC and FEV1 in the general Korean population were used to calculate the values of percent-predicted FVC and FEV1.

Forced expiratory volume in one second (FEV₁) was measured in ECRHS II using a dry rolling‐seal spirometer (Model 2130; SensorMedics, Anaheim, Cal, USA). Up to five technically acceptable manoeuvres were measured. American Thoracic Society recommendations were followed.³³ The predicted values for FEV₁ were calculated on the basis of European Coal and Steel Union reference values.³⁴ Weight and height were measured, and body mass index (BMI) was calculated.