Table. 12—

Reported significant changes in forced vital capacity(FVC), forced expiratory volume in one second (FEV1), mid-expiratory flow (MEF25–75%) and carbon monoxide diffusing capacity (DL,CO) over time

Within a day
 Normal subjects≥5≥5≥13>7%
 COPD patients≥11≥13≥23
Week to week
 Normal subjects≥11≥12≥21>6 units
 COPD patients≥20≥20≥30>4 units
Year to year≥15≥15>10%
  • The variables are the same as in tables 6 and 8. Results for spirometry are rounded to the nearest integer 25, 128. The within-day DL,CO variability is from a study of diurnal variation in healthy nonsmokers 133. The week-to-week coefficient of repeatability (CR) is given for DL,CO in units of mL·min−1·mmHg−1, as calculated from CRs originally stated in units of mmol·min−1·kPa−1 138. The year-to-year variability of healthy adults is given using a 95% confidence interval 139. CRs from repeatability testing performed in your own laboratory should be substituted for the values in this table. COPD: chronic obstructive pulmonary disease.