What is indicated to rule out restrictive defects in spirometry for pulmonary function testing?

Updated: May 14, 2020
  • Author: Kevin McCarthy, RPFT; Chief Editor: Nader Kamangar, MD, FACP, FCCP, FCCM  more...
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Reduction in the FVC with a normal or elevated FEV1-to-FVC ratio should trigger further evaluation of total lung capacity (TLC) to rule out restrictive lung disease. Measuring the TLC and residual volume (RV) can confirm restriction suggested by spirometry (see Lung Volume Determination below). See the chart below.

This is a graph of lung volumes in health and in d This is a graph of lung volumes in health and in disease, showing the various lung subdivisions. Normal aging results in an increase in functional reserve capacity (FRC) and residual volume (RV) and a normal total lung capacity (TLC) percentage. Obstructive lung diseases cause hyperinflation (increase in RV and FRC) with a relatively normal forced vital capacity (FVC). In severe emphysema, the TLC percentage can exceed 150%, with the RV impinging on the FVC. Restrictive lung diseases exhibit reduced TLC percentage with relative preservation of the RV/TLC percentage in fibrosis, a reduced inspiratory capacity and expiratory reserve volume (ERV) in neuromuscular disease, and severe reduction of the ERV in extreme obesity.

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