Obstructive vs Restrictive Lung Diseases

Disorders Affecting Our Ability to Exhale or Inhale

radiologist looking at lungs on chest x-rays
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When referring to lung disease, a doctor will often classify it as being either obstructive or restrictive. On the surface, the terms largely speak for themselves with one obstructing the airway passages and other restricting a person’s ability to fully inhale.

It’s a difference that might not be apparent at first but one that can be differentiated by a battery of tests which evaluate the capacity and forcefulness of person’s inhalation and exhalation.

Characteristics of an Obstructive Lung Disease

When a person has difficulty expelling all of the air from the lungs, he or she is said to have an obstructive lung disease. Obstruction is defined by exhalation which is slower and shallower than in a healthy person.

An obstruction can occur when inflammation and swelling cause the airways to become narrowed or blocked, making it difficult rid air from the lungs. This leaves an abnormally high volume of air which we refer to as "increased residual volume."

In obstructive lung disorders, increased residual volume leads both to the trapping of air and the hyperinflation of lungs—changes that contribute to a worsening of respiratory symptoms.

The following lung diseases are categorized as being obstructive:

Characteristics of Restrictive Lung Disease

Restrictive lung diseases are characterized by reduced total lung capacity (TLC).

As opposed to obstruction, restriction is defined by inhalation that fills the lungs far less than would be expected in a healthy person.

TLC represents the amount of air present in the lungs after taking the deepest breath possible. Measuring TLC is considered necessary to confirm the presence of a true restriction, categorized as being intrinsic, extrinsic, or neurological.

Intrinsic restrictive disorders are those which occur as a result of the lungs themselves and can include:

Extrinsic restrictive disorders refer to those that originate outside of the lungs. These include impairment caused by:

Neurological restrictive disorders are those caused by disorders of the central nervous system that prevent the lungs from working properly. Among the most common causes:

Tests Used to Diagnose Obstructive and Restrictive Disorders

Spirometry is a common office test used to evaluate how well your lungs function by measuring how much air you inhale, how much you exhale, and how quickly you exhale. The individual tests include:

  • Forced vital capacity (FVC) begins with the person taking as deep a breath as possible and then exhaling as forcibly for as long as possible. Because lung capacity is reduced in both obstructive and restrictive diseases, the FVC alone can not diagnose either disorder.
  • Forced expiratory volume in one second (FEV1) measures the total amount of air that can be forcibly exhaled in the first second of the FVC test. Healthy people generally expel around 75 to 85 percent in the first second of the test. The FEV1 is decreased in obstructive lung diseases and normal to minimally decreased in restrictive lung diseases.
  • Ratio of FEV1 to FVC represents the percentage of the total FVC expelled from the lungs during the first second of a forced exhalation. This ratio is decreased in obstructive lung disorders and normal to increased in restrictive lung disorders.
  • Total lung capacity (TLC) is calculated by adding the volume of air left in the lungs after exhalation (the residual volume) with the FVC. TLC is normal or increased in obstructive defects and decreased in restrictive defects.

    Obstructive and Restrictive Lung Patterns Chart
     

    Measurement

    Obstructive pattern

    Restrictive pattern

    Forced vital capacity (FVC)

    decreased or normal

    decreased

    Forced expiratory volume
    in one second (FEV1)

    decreased

    decreased or normal

    FEV1/FVC ratio

    decreased

    normal or increased

    Total lung capacity (TLC)

    normal or increased

    decreased

    Source:

    Pérez, L. "Office spirometry." Osteopathic Family Physician. March-April 2013; 5(2):65-69.

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