Restrictive versus Obstructive airway disease

#KYJ-  is it Obstructive Airway disease or Restrictive Airway disease?

We've all cared for a patient with a chronic lung disease. Words that we add to the jargon soup include chronic obstructive pulmonary disease or COPD, emphysema and asthma and chronic bronchitis and pulmonary fibrosis and pneumonia and pulmonary oedema.  All these are terms that we associate with both acute and chronic conditions that often manifest in shortness of breath.
At times we may confuse the terminology and when  nursing patients with respiratory diseases, two terms seem to dominate.
Obstructive airways disease and restrictive airways disease; these are different.

Obstructive Lung disease

An obstructive airways disease, as the name implies, is a disease characterised by a patient's inability to breathe out the predicted volume of air from the lungs.  Obstructive diseases also cause a restriction in the flow of air while breathing out, and as a result, are sometimes confused as restrictive airways disease.
Take a typical COPD patient, they tend to be able to draw breath but when they go to breathe out, the volume exhaled is less than normal (forced vital capacity (FVC) is diminished), and the outward flow of expired air is slower than normal.  This can be measured by a spirometry test called the Forced Expiratory Volume in one second or FEV1.
Say for example you were expected to be able to breathe out 4 litres, but when a spirometry test is performed, you can only breathe out  3 L; this would mean that you have only exhaled 75% of what was predicted.  Likewise you would expect to be able to breathe out a minimum of 70% of your entire lung volume in the first one second but on your test you might of only be capable of blowing 50% of your lung volume in that first second (ie 1500ml at 1 sec).  This would represent and obstructive picture, where you have both an obstruction to be able to blow your entire volume out (FVC 70% of normal) and an obstruction to the airflow, making exhalation slower (FEV1 50% of normal) .
Typically these are diseases like asthma, emphysema and chronic bronchitis, The three conditions that make up COPD.  The hallmark of these obstructive diseases is trapping of gas, altering diffusion and oxygen/CO2 exchange.

Restrictive Lung diseases
So what is a Restrictive lung disease?
People with restrictive lung disease are said to have a restriction preventing them from fully expanding their lungs.  They cant fill their lungs with air.

Have you ever munged out on a buffet so much, that you were so full you couldn't breathe?  Well imagine you did; that is an example of airway restriction.

With restricted airway diseases, there is a mismatch between ventilation and perfusion (VQ). Normally a adult lung will bring approximately 4 L of their into contact with 5 L of blood making a ratio of 4:5 displayed as a VQ=0.8 (4:5=4/5=0.8).  
When somebody has a restrictive lung disease, blood still circulates through the lungs in the same fashion, but it comes into contact with less air over a given point in time.  This reduction in VQ ratio, is often called a shunt, and results in poor gas exchange, and at its worst, respiratory failure
Restrictive lung diseases usually result from a condition causing stiffness in the lungs themselves, or in stiffness or weakness of the chest wall; think muscular dystrophy.

Other causes of restricted lung disease include the lungs physically filling with exudate or fluid such as ARDS, severe pneumonia, pulmonary oedema.

Physical body shape and chest architecture can have a restricting impact. Especially morbid obesity, severe kyphosis (hump back) and scoliosis (lateral spine curvature).

If a person suffers spinal cord injury between T2-T8 there may be poor neural control of the intercostal muscles which support chest expansion, deep breaths, sigh and yawning.

You can now probably think of a number of conditions that give rise to Restrictive pulmonary diseases.

Fibrosis causing diseases like post chemo, pulmonary fibrosis, cystic fibrosis, asbestosis, silicosis, anthracosis and its ugly spawn "Black lung or coal miners lung" (pneumoconiosis).

Space occupying lesions like cancerous tumours, will take up valuable thoracic realestate.  And another example could include a large pleural effusion, empyema, pneumothorax, or haemothorax.  They all take up space restricting a persons ability to fully filled the lung. These are just some examples of diseases that result in airway restriction.

In summary
Obstructive airways disease is characterised by not being able to empty a predicted volume of air
Restricting airways diseases are characterised by not being up to fill the lungs due to lung stiffness, poor muscle function or something occupying space.

Well that's it for this quick KYJ (Knowing your Jargon).

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~breath easy - Rob. Www.ect4health.com.au/courses