It is very difficult to understand what it feels like to breathe “abnormally.” However, individuals with either Restrictive or Obstructive Airway Disease do it every day. Some say that it feels like having an “elephant sit on their chest” while others claim they are “breathing through a straw.” Many get light-headed and have no strength due to the lack of oxygen in their systems.
Restrictive lung disease is characterized by a decrease in the total volume of air that the lungs are able to hold. It is often due to a decrease in the elasticity of the lungs themselves or caused by problems related to the expansion of the chest wall during inhalation. In restrictive lung disease, both the FEV1 and FVC are reduced, so the FEV1/FVC ratio is normal or even increased in contrast to obstructive lung disease where this ratio is reduced. Also, the values for residual volume and total lung capacity are generally decreased in restrictive lung disease. One definition for determining if someone is affected by a restrictive airway disease is that it requires a total lung capacity of 80% or less of the expected value. Examples of restrictive lung diseases include asbestosis, sarcoidosis and pulmonary fibrosis.
A bit different from restrictive lung disease, in obstructive lung diseases less air actually flows in and out of the airways because of one or more of the following:
- The airways and air sacs lose their elasticity
- The walls between the air sacs are destroyed
- The walls of the airways become thick and inflamed
- The airways make more mucus than usual, which clogs the tubing
In obstructive lung disease, there is an increase in airway resistance, shown by a decrease in FEV1. Obstructive lung disease is usually defined as having an FEV1/FVC ratio that is less than 0.7, or 70% of normal. The residual volume is often increased, as is the total lung capacity, while the vital capacity remains relatively normal. The increased total lung capacity, hyperinflation, can result in a “barrel chest” – a chest with a large front-to-back diameter that occurs in some individuals obstructive airway disease. Hyperinflation can also be seen on a chest x-ray showing a flattening of the diaphragm. The most common obstructive lung diseases are: asthma, emphysema, and bronchitis. These can also lead to chronic obstructive pulmonary disease (COPD), where the symptoms continue to worsen over time.
In this lab, students will learn some of the characteristics of both restrictive and obstructive airway diseases by mimicking the symptoms of these disorders. Using the iWorx system and a spirometer flow head, the breathing parameters at rest and while breathing through different resistance ports will be measured. It is important that the subjects be healthy, with no lung disorders, in order to participate in these exercises. If at any time the subject feel light- headed, the experiment should be discontinued and the subject should breathe normally.
Physiology in Action
Respiratory Resistance Set
Respiratory Resistance set with 2mm, 4mm, 6mm, 10mm and 14mm hole adaptors for the Flowhead