How to Prepare for Your Lung Function Test: A Simple Guide

05 Sep 2024

Introduction

Lung function tests are highly useful for assessing a broad range of respiratory factors. This guide will help you understand the different methods, procedures, risks, and benefits associated with lung function tests.

What is a lung function test?

The primary purpose of a lung function test is to assess the functioning of your lungs, examining how effectively they are working. Lung function tests are also known as pulmonary function tests (PFTs). They are not only useful for diagnosis but also for monitoring various lung problems and pulmonary diseases.

Most lung function tests involve using a mouthpiece to assess the patient’s breathing. These tests measure different lung parameters, such as the amount of air your lungs can hold, how efficiently you breathe in and out, and how well your lungs absorb oxygen from the air. In short, lung function tests help to evaluate the status of your airways, including the trachea (windpipe), bronchial tubes, throat, and nose.

Why do I need a lung function test?

You may need a lung function test if you are experiencing difficulties in breathing. Symptoms such as wheezing or breathlessness can make it difficult to determine whether the problem originates from your lungs or your heart.

Issues like chest tightness, persistent coughing, or the possibility of lung damage from radiation, asbestos, or certain medications may also necessitate a lung function test. In some cases, doctors may recommend this test before cardiac surgeries to check whether your lungs can cope with the operation.

What is the use of a lung function test?

A lung function test has several applications, including:

Diagnosing various lung problems and pulmonary diseases such as COPD, asthma, emphysema, pulmonary fibrosis, sarcoidosis, or scleroderma.
Checking the proper functioning of your lungs.
Monitoring the current status of your lungs by comparing results to normal ranges.
Evaluating improvements in your lung function in response to different treatments.
Assessing your fitness or health status before a biopsy or surgery.
Detecting lung damage from exposure to chemical substances.

Different Methods of Lung Function Tests

Here are some common procedures used in lung function testing. Read on to learn about the processes involved and the duration of each test.

Spirometry Test

The spirometry test measures how quickly your lungs can expel air. This test compares your results with healthy benchmarks and can identify any constriction in your airways. The steps involved in a spirometry test are as follows:

Your healthcare provider will clip your nose to prevent air from escaping.
You will then breathe into the lung function machine, ensuring your lips are tightly sealed around the mouthpiece.
Take a deep breath and exhale as hard and fast as possible.
The spirometer will measure the volume of air you breathe out and how quickly you do so.

This test takes about 15 minutes. If necessary, your healthcare professional may suggest a reversibility test, which takes an additional 20 minutes on average.

For the reversibility test:

Use your salbutamol inhaler after the initial spirometry test.
Take the lung function test readings again to check for any differences.

Other Approaches to Lung Function Testing

Additional methods for assessing lung function include:

Peak Flow: This test evaluates how effectively your lungs can expel air. Pulmonary conditions like asthma can cause airway constriction. The peak flow test measures your peak expiratory flow (PEF) score using a peak flow meter.
Imaging and Scanning Techniques: Imaging tests, such as chest X-rays, help to examine the interior of your chest, including the lungs, heart, ribs, and diaphragm.
Bronchoscopy: In this procedure, a bronchoscope (a thin, flexible tube with a camera) is inserted through your nose or mouth and down the windpipe to provide a visual examination of your airways.
Lung Biopsy: This involves taking a small sample of lung tissue to examine for abnormalities. If an abnormality is detected, your healthcare professional may proceed with further pulmonary treatment.
Exhaled Carbon Monoxide Test: This test measures the amount of carbon monoxide in your body, which can come from sources such as cigarette smoke or exhaust fumes. The primary aim of this test is to monitor the carbon monoxide level you exhale with each breath.
Testing Oxygen Levels: Pulse oximetry measures your blood oxygen level (oxygen saturation) using a sensor placed on your earlobe or fingertip. This is a simple, painless test.
Respiratory Muscle Tests: These tests assess the functioning of the muscles surrounding your lungs. They can be performed using either a sniff pressure test or a mouth pressure test.
Sleep Breathing Test: If you experience symptoms such as waking up unrefreshed, daytime tiredness, loud snoring, morning headaches, disturbed sleep, or breathing difficulties with high CO2 and low O2 levels, you may have sleep-disordered breathing (SDB). This test can help detect such conditions.
Blood Test: Blood tests are fundamental in examining inflammation or allergic reactions in your lungs.
Six-Minute Walk Test: This test measures your blood pressure, shortness of breath, and fatigue before and after walking for six minutes. The doctor will also monitor your blood oxygen and heart rate during the walk to assess your lung fitness.

Where can I get a lung function test?

Lung function tests are available in the outpatient departments of hospitals and general healthcare organisations. Many private GPs also offer these services.

How should I prepare for the lung function test?

To prepare for a lung function test, follow these guidelines:

Wear loose and comfortable clothing.
Avoid smoking for 24 hours before the test.
Refrain from alcohol for at least 4 hours before the test.
Do not eat a heavy meal for at least 2 hours before the test.
Avoid strenuous exercise for 30 minutes before the test.
Stop using any inhalers 4 hours before the test.
Consult your doctor about whether you need to stop any medications before the test.

Getting Results of the Lung Function Test

If you have your lung function test performed by a private GP, you may receive your results within a day. However, tests conducted by the NHS may take longer to produce results. You can report these results to your respiratory doctor or any other doctor you are seeing. Based on the results, your doctor will schedule follow-up appointments if necessary.

Significance of the Test Results

To obtain accurate lung function test results, doctors will compare your results with standard reference tables that match your age, height, sex, and lung size. Abnormal results usually indicate some form of underlying lung condition.

Lung function tests cannot identify the exact lung disease but can provide an indication of the type of lung condition you might have:

Obstructive Lung Diseases: Conditions such as bronchitis, asthma, or emphysema, where the airways narrow, making it difficult for air to flow smoothly through the lungs.
Restrictive Lung Diseases: Conditions such as pulmonary fibrosis, sarcoidosis, scleroderma, or some interstitial lung diseases, where there is a reduction in the volume of air your lungs can hold, usually due to difficulty in lung expansion.

Risks of Lung Function Tests

Lung function tests are generally safe, but there may be minor risks, such as:

Feeling dizzy
Coughing
Shortness of breath
Fatigue due to repeat testing

Who is not eligible for a lung function test?

In general, most individuals can undergo lung function tests. However, certain conditions may make someone unfit for the test, including:

Recent eye surgery
A recent heart attack
Aortic aneurysm
Pulmonary embolism
Recent surgeries involving the heart, abdomen, or chest

Summary

Lung function tests offer numerous benefits for assessing and monitoring respiratory health. Ongoing scientific research aims to improve the accuracy and effectiveness of these tests. Regular lung function testing should be considered a crucial part of your routine health screenings to maintain optimal respiratory health and overall well-being.