1. Residual volume (RV) to total lung capacity (TLC) ratio versus FEV1 % predicted.
Residual volume (RV) to total lung capacity (TLC) ratio versus FEV1 % predicted. RV/TLC, expressed as a percent, is plotted against the % predicted FEV1 for 4,774 patients with asthma or COPD, with solid lines representing the best fit for each. The shaded area or gray zone represents the large degree of variability for subjects near the lower limit of normal for the FEV1. (From Reference 24, with permission.)‏
Gregg L Ruppel Respir Care 2012;57:26-38
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