Emphysema is essentially a progressive and destructive lung disease where there is formation of holes or bullae within the lungs.
Earliest detection of this disease was possible with the use of Gough whole-lung paper-mounted sections that are basically pathological tissue samples obtained from the lungs.
This same process of detecting pathological processes within the lungs caused by emphysema is now performed using very high resolution imaging studies like CT scan (computed tomography scan).
Types of emphysema
Based on the areas of the lungs affected there are two forms of emphysema detected on CT scan:-
Centriacinar emphysema also called centrilobular emphysema
Here the central portions of the lung lobule (section) are commonly affected. Centrilobular emphysema is usually more marked in the upper lung zones. On examination there is scanty wall tissue around the hole.
This affects nearly whole of a lung lobule leaving behind a gaping hole. This form is generally more severe in the lower lung zone. Panlobular emphysema is seen in alpha 1 protease deficiency.
A detailed history of smoking, exposure to chemicals, fumes, dust, air pollutants or passive smoke is taken. Smoking is one of the most important causes of emphysema and chronic obstructive pulmonary disease (COPD).
The patient is then examined. Anemia and cyanosis (bluing of the tips of the fingers, ears and nose due to lack of oxygen) and general physical health is assessed. The body mass index (BMI) is also assessed.
Spirometry involves testing breathing. The National Lung Health Education Program (NLHEP) Spirometry Committee recommends spirometry for:-
All smokers age 45 years or older
Anyone with chronic cough, excess mucus, breathlessness on exertion and wheeze. These are the major symptoms of COPD, which includes a spectrum of diseases: asthmatic bronchitis, chronic bronchitis, and emphysema.
Anyone with a family history of emphysema or chronic bronchitis
In this test the patient is asked to breathe into a machine called a spirometer. The spirometer takes two measurements – one is the volume of air a person can breathe out in 1 second (called Forced expiratory volume 1 or FEV1) and the other is the total amount of air a person can breathe out called the forced vital capacity or FVC.
This may be repeated several times before diagnosis may be confirmed. The readings are compared with normal measurements of the same age to reveal if there is airway obstruction.
Breathing test called post bronchodilator FEV1 / FVC. This test involves testing the Forced Expiratory Volume at 1 second (FEV1) and the Forced Vital Capacity (FVC) of the lungs in the patient.
Thereafter the patient is given an inhaled bronchodilator. When this ratio despite a bronchodilator that helps dilate the narrow airways remains less than 0.7 it signifies that the airflow obstruction not fully reversible with a bronchodilator and COPD is confirmed.
To rule out asthma FEV1 is compared. Asthmatic patients will have a 12% or greater improvement in FEV1 15 minutes after the use of an inhaled short-acting beta2 agonist or a bronchodilator.
Peak flow test
This is yet another breathing test. A peak flow meter can be used several times a day over several days to detect how fast the person can breathe out.
Routine blood tests
These may detect anemia and other abnormalities. White blood cell counts may be raised in case of infections.
Blood oxygen levels are also tested using a pulse oximeter. Airway obstruction may reduce the amount of oxygen in blood making it inadequate. This is detected using arterial blood gas assessment and blood oxygen measurements.
Chest X-ray and High resolution CT scan
This is one of the commonest imaging studies that is suggested to detect emphysema changes in the lungs. The most reliable finding is:-
Flat but horizontal diaphragm. The diaphragm is normally dome shaped and as the lung volume rises it becomes flattened and fails to perform its function. The flattening is clearly seen when X Ray is taken from the side.
The muscle slips of the costal insertions or rib attachments of the diaphragm may be thrown into prominence by the flattening leading to scalloping of the costophrenic angles (angles between ribs and diaphragm).
On sideways appearance the front to back diameter is usually increased.
The space just behind the breast bone or sternum is called the retrosternal space. It is increased to > 2.5 cm in front of the ascending aorta on side views.
There may be low prominence of blood vessels as well.
Blood test for alpha-1-antitrypsin deficiency – alpha 1 antityrpsin is a protein that protects the lungs. In its absence, as seen rarely in some genetically susceptible individuals, there is risk of emphysema. Emphysema and COPD in non-smokers below 35 is an indication towards alpha 1 antitrypsin deficiency.
Electrocardiogram (ECG) and echocardiogram – COPD and emphysema may co-exist with heart disease. These can be ruled out using ECG and echocardiograms.
Laboratory assessment of the sputum or phlegm. This may show presence of infective microorganisms in cases of chest infections.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)