ATS GUIDELINES Bundle

Routine Lung Function Tests

American Thoracic Society Quick-Reference GUIDELINES Apps

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12 Figures TLC <5th percentile? Possible hyperinflation TLC >95th percentile? Large lungs Hyperinflation Hyperinflation FRC/TLC or residual volume (RV)/TLC >95th percentile? Functional residual capacity (FRC)/TLC or RV/ TLC >95th percentile? a See Classification of Ventilatory Impairments Defined by Lung Volumes on pages 12–13. Beginning with the TLC, determine whether restriction is present based on whether the TLC is low (right side of figure). If restriction is present, then assess the relative size of FRC or RV to the TLC: if the FRC/TLC or RV/TLC are elevated, then determine if there is airflow obstruction based on the FEV 1 /FVC ratio. If obstruction is present, then this is a mixed disorder, but if not present, then it may be a form of "complex restriction," which implicates more than one process occurring to lower the FVC out of proportion to the reduction in TLC. Obesity or neuromuscular diseases are common causes of complex restriction. Figure 7. Approach to Interpretation of Lung Volumes a YES YES YES NO NO NO

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