Sarcoidosis is classified as a Restrictive lung disease and primarily affects the structure of the lung but since it can also affect the structure of the airways it can have an Obstructive component. It is characterized by an increased stiffness of the lung, a loss of functional alveolar surface area and occasionally by a narrowing of the airways. The increased stiffness acts to reduce lung capacity. The decrease in alveolar surface area reduces the ability of the lungs to transfer oxygen and carbon dioxide. The narrowed airways reduces the speed that air flow can flow in and out of the lung.

Sarcoid status is best monitored by FVC, FEV1, DLCO and Oximetry.

A typical PFT pattern for Sarcoidosis:

Spirometry FVC Reduced
  FEV1 Normal or Reduced
  FEV1/FVC Ratio Normal or Reduced
Lung Volumes TLC Reduced
  RV Reduced
Diffusing Capacity DLCO Reduced
Oximetry SpO2 Reduced

The severity of Sarcoidosis is determined by the decrease in TLC:

TLC >=60% and <80% of predicted Mild restriction
TLC >=40% and <60% of predicted Moderate restriction
TLC <40% of predicted Severe restriction

The severity of obstruction is determined by the reduction in FEV1. When the FEV1 or FEV1/FVC ratio are reduced:

FEV1 >= 70% of predicted Mild
FEV1 <70% and >=60% of predicted Moderate
FEV1 <60% and >=50% of predicted Moderately severe
FEV1 <50% and >=35% of predicted Severe
FEV1 <35% of predicted Very severe


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PFT Patient by Richard Johnston is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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