Test and diagnosis of Chronic Obstructive Pulmonary Disease
In order to diagnose COPD the symptoms must be carefully evaluated, as well as the history of exposure to agents that irritate the lungs (such as smoking), and family history. Furthermore, a physical examination must be carried out and, which is more important, tests to examine lung function and a simple chest x-ray.
Chest X-Ray. The chest x-ray provides us with the simplest image of the lungs, but it indirectly gives us a bearing on the impact of obstruction of airflow or the presence of other diseases that could contribute to the worsening of the clinical situation.
Spirometry. Is the key element in the diagnosis, as well as the assessment of the severity of the COPD, and is based on the study of the degree of airflow obstruction. In forced spirometry, a volume of air that is measured when a person is capable of moving on exhaling with all their effort (as if they wanted to blow out a candle at the other end of a table). The most important value is the volume of air expired in the first second (FEV1).
Although spirometry is essential to make the diagnosis of COPD, by itself it is unable to describe the complexity of the disease, and has to be complemented by other methods of evaluation.
New combined assessment methods. They involve other variables, such as the symptoms, the airflow limitation, the decompensation risk, and the presence of other diseases (comorbidities).
In some cases, in order to assess the severity of the disease, more complex lung function tests need to be performed:
Lung volume measurements. A method employed to study lung function through the air volume that goes in and out of the lungs.
Arterial blood gases. Measures the oxygen (PaO2) and carbon dioxide (PaCO2) pressure in an arterial blood specimen. To measure arterial blood gases it is necessary to obtain specimen of blood from an artery (to perform routine analyses a specimen of venous blood is used). Arterial puncture is more complex than the puncture of a vein, given that the artery is pulsatile, that is, it beats. The blood specimen is often obtained by puncture of the radial artery (in the wrist). Local anaesthesia is administered before performing the puncture and then compression has to be applied to the artery for a few minutes afterwards.
The other tests that may be considered once the diagnosis of COPD is made, and which may be used to characterise the disease and help to stratify patients, are:
Thorax CT Scan. Enables the situation of the lung to be studied with greater precision. The multiple images provided by the CT scan makes it possible to see if there are dilations in the bronchial tubes or areas with greater air entrapment.
The 6-minute walk test. It is a test that measures the maximum distance that a person can travel in 6 minutes. As well as the distance, it measures the degree of breathlessness or shortness of breath (dyspnoea) and the modification in gas exchange, taking into account the oxygen saturation value.
Cardiac function study. In some cases it is difficult to diagnose the origin of the shortness of breath (dyspnoea), and to decide whether it is due to a respiratory or cardiac problem. In these cases it is necessary to perform an echocardiogram or more complex exertion tests.
Blood analysis. A full laboratory analysis with biochemistry and a full blood count including white cell counts.
What is spirometry?
Spirometry is a rapid and painless test in which a manual device called a “spirometer” is used to measure the amount of air that a person’s lungs can retain (air volume) and the velocity of the inhalations and exhalations during respiration (airflow velocity).
How do I prepare myself for the test?
It is recommended to wear comfortable clothes, and avoid eating abundant food or smoking in the 2 hours before the test. You should take into account that you must notify before taking the test, whether you have had a recent injury or surgery of the chest, eyes, ears, or abdomen.
How is the test performed?
The health professional takes down details, such as height and weight. Before performing the test the patient’s nose is blocked using pegs to prevent air coming out. The patient carries a small airflow measuring device that has a mouthpiece attached at one end. This is placed in the mouth clenching the teeth and the lips closed around the mouthpiece preventing the tongue blocking the orifice.
You can breathe normally and easily through the mouth piece, but to perform the test you should breathe and follow the instructions of the professional.
Steps to perform
- Keep the mouthpiece well sealed between your lips throughout the whole time the test is being performed.
- Breathe in normally.
- Exhale gently until the lungs are completely empty. Take a long and deep breath, filling the lungs.
- Exhale with force and continue until instructed to stop doing so. More or less for 6 seconds. Although you might have the sensation that you cannot exhale any more air, you have to continue exhaling so that each small air exhalation can be measured.
- When you are instructed to stop, remove the mouthpiece and rest. These steps will be repeated at least 3 times, but it could be more.
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