Normal Lung function on spirometry
- Note the shape of the graph:
- Fast rising in the first 1 second - FEV1>80% FVC
- Flat plateau
Obstructive lung disease
Characteristics
- ‘Obstructive pattern’ on PFT’s – see below
- Disease mechanisms affect the bronchi and bronchioles, usually in a diffuse pattern across the whole lung
Obstructive pattern lung disease
- Reduced FVC (<80% of normal)
- Reduced FEV1:FVC ratio (<70%)
- Reduced peak flow
Restrictive Lung Disease
This is caused by disease in the interstitium of the lung – and this is usually an increase in the amount of tissue in the interstitium of the lung.
- The lung x-ray will show increased density of the lung tissue
- The lung will be stiff with reduced compliance
Restrictive pattern of lung disease
- Reduced FVC
- Reduced FEV1
- Normal FEV1:FVC ratio
- Normal PEFR
Causes of restrictive lung disease
The underlying mechanism is usually
fibrosis of the lung. As the normal lung tissue is destroyed it is replaced by scar tissue, which is interspersed with
pockets of air. This often leads the lung to have a
honeycomb like appearance on x-ray.
The main symptoms are
SOB and cough.
Common causes
- Asbestosis
- Radiation fibrosis
- Drugs – common ones include amiodarone (anti-arrhythmic) and methotrexate (anti-folate and anti-metabolite drug – used in cancer and auto-immune diseases)
- Rheumatoid arthritis
- ARDS – acute respiratory distress syndrome
- this is an acute onset syndrome, which present with shortness of breath, bilateral infiltrates on the CXR and may occur within 48 hours of an acute illness
Mixed Pattern of Disease
Remember also you could see somebody who has both restrictive and obstructive disease – in which case they would have a mixed pattern of disease:
- See more at: http://almostadoctor.co.uk/content/systems/-respiratory-system/restrictive-vs-obstructive-lung-disease#sthash.jjplN6zy.dpuf
