Overview of Spirometry
Spirometry is a handy and commonly used test to check the health of your lungs. It does this by measuring how much air you can exhale forcefully after taking a deep breath in.
Three main aspects are reported in the test results:
1) The total volume of exhaled air, termed as Forced Vital Capacity (FVC).
2) The volume of air exhaled in the first second, known as Forced Expiratory Volume in one second (FEV1).
3) The ratio between the two (FEV1/FVC).
The results come in the form of a graph showing volumes and combinations of these volumes, which doctors refer to as “capacities”. These results help doctors diagnose and monitor lung diseases. Some studies also suggest that they can encourage people to quit smoking.
Anatomy and Physiology of Spirometry
The lungs are incredibly important organs in our body that help keep us alive by enabling the exchange of gases. When we breathe in, they take in oxygen that our body needs to function. And when we breathe out, they get rid of carbon dioxide, which is a waste product produced by our body. The process starts when we breathe in air, which travels down our throat and into a tube called the trachea.
This trachea is a flexible tube studded with rings of cartilage for support, and it splits into two tubes at a point called the carina, which is roughly at the same level as the sixth cervical vertebra in your neck. From there, the air goes into the two main branches or ‘bronchi’ that lead to each lung.
These branches split to form millions of smaller tubes called bronchioles, which end in tiny, air-filled sacs known as alveoli. It’s in these alveoli that the real magic happens. The alveoli are surrounded by a mesh of tiny blood vessels, and it’s across this thin barrier that oxygen enters the bloodstream, and carbon dioxide leaves it, allowing the crucial exchange of gases to happen.
Why do People Need Spirometry
Spirometry is a type of lung function test often used to diagnose conditions like asthma and chronic obstructive pulmonary disease (COPD), which are illnesses that affect your breathing. However, this test doesn’t just serve to diagnose these conditions. It can be used in other circumstances as well:
For example, doctors might use spirometry to:
- Assess symptoms or abnormal results from other medical tests
- Understand how a certain disease might be impacting how well your lungs work
- Find out early if you have a chance of developing lung disease, especially if you are at high risk
- Check how well your lungs are working before you have surgery
- Measure how severe a lung disease is, or what might happen in the future because of it
Beyond diagnosis, spirometry is also useful for monitoring:
- Checking if treatments for lung problems, like medicines to help your airways stay open, are working well
- Tracking changes or progression in a lung disease over time, for instance, diseases affecting the tissue and space around the air sacs in your lungs or diseases causing your airways to be blocked or narrowed
- Keeping an eye on lung function in people who have jobs that might put their lungs at risk
- Gathering data for studies that look at diseases and health in large groups of people
When a Person Should Avoid Spirometry
Spirometry is a common method used to check how well your lungs are working, but it might not be suitable for everyone. There are certain conditions that may make it unsafe or ineffective for some patients. These are known as ‘contraindications’, which are situations where a particular treatment or procedure could be harmful.
Absolute contraindications are situations when you absolutely cannot use spirometry for testing. These include:
- If you are dealing with a severe heart concern such as a recent heart attack or acute coronary syndrome
- If you have an unstable condition, meaning your vital signs such as blood pressure or heart rate are extremely high or low
- If you have a lung infection, a recent lung collapse, or a clot in the lungs
- If you have a large or growing aneurysm, which is a bulging blood vessel, in your chest or abdomen
- If you’re coughing up blood
- If you have high pressure inside your skull
- If your retina, which is a part of your eye, has detached
Relative contraindications, on the other hand, are situations where spirometry should be used with caution or it may need to be postponed. These include:
- If the person has trouble understanding how to use the device properly, such as young children or people with dementia, who might misuse the device
- If the person has conditions that make it difficult to hold the mouthpiece, like facial pain
- If the person had a recent surgery in their abdomen, chest, brain, eye, ear, nose, or throat
- If the person is dealing with a hypertensive crisis, which is a severe increase in blood pressure
Equipment used for Spirometry
The first thing needed to perform a spirometry test, which measures your lung function, is enough room. You should be in a room around the size of a small bedroom (2.5 by 3 meters) with fairly large side doors (120 cm wide) to ensure you’re comfortable.
Spirometers, devices used in this test, come in two types: closed-circuit and open-circuit. Closed-circuit spirometers can be either wet or dry and use a piston or bellow system to gather and measure your breath. Meanwhile, they have a recording system that tracks the rate of your breathing.
Open-circuit spirometers, which are more common now, work a bit differently. They don’t collect air, but instead measure the speed and volume of your breath. The turbine flow meter is a popular type of open-circuit spirometer. It measures the breath by monitoring the rate of spinning turbines. Pneumotachographs are another type. They measure your breath by checking how much the pressure changes when your breath passes through a resistance.
Hotwire spirometers, another example of open-circuit spirometers, use a heated metal wire. The air from your breath cools this wire and the device uses this cooling effect to calculate your airflow. Ultrasound spirometers can be based on any of these open-circuit principles.
A good spirometer should be able to measure a volume of 8 liters with an accuracy of plus or minus 3% or plus or minus 50ml. It should have a flow measurement range of plus or minus 141 and a sensitivity of 200ml/s. Also, it should be able to record 15 seconds of the breath-release time to properly assess lung function.
Who is needed to perform Spirometry?
The people working on the procedures, such as a medical operation or test, need to be familiar with signs of breathing problems. They need proper training to understand the technical and physiological aspects, which are the scientific and body-based reasons behind the tests. These trained professionals need to be skilled enough to carry out the operation of any medical equipment used for the procedure.
They should also know how to apply generalized safety precautions, make sure the patients understand what to do to prevent problems, and be ready to take immediate action if any issues arise during the procedure. The medical staff should be able to tell how a patient is responding to any treatment, if therapy should be started or if it’s not working and needs to be stopped.
Maintaining up-to-date knowledge through ongoing training and retraining is very important for these staff, especially those in charge of a breathing test called spirometry. Spirometry is a common medical test that measures how much and how quickly a person can move air out of their lungs.
Preparing for Spirometry
Patients need to be aware that before going into their medical procedure, they should avoid smoking and physical activity. If they take any bronchodilator medication (medicine that helps open up the airways in your lungs), it also needs to be stopped for some time before the procedure.
The doctor will provide details about the procedure to the patients. This is important, because when patients understand and cooperate, it leads to the best results. It’s also important for the doctor to measure the patient’s height and weight while they’re barefoot and in light clothes. If the patient has a chest condition like kyphoscoliosis (an abnormal curve in the spine), different measurements should be taken. In such cases, to ascertain the height, the distance between the tips of the middle fingers when the arms are crossed is measured. This measure is then divided by 1.06 to estimate the height.
During the procedure, patients will be asked to sit up straight in light clothing, with uncrossed legs. For children, they may be asked to either sit or stand, but it should be consistent each time they come for the procedure. While sitting, the patient’s back needs to be against a backrest, and they should not lean forward. If they wear dentures, these may need to be removed if they interfere with the process.
Nose clips could be used to avoid air escaping through the nose, although it’s not absolutely necessary. The spirometer (a device used to assess lung function) needs to be calibrated correctly, which will be checked on the day of the test.
Any existing conditions or infections that need special precautions to take, could cause the procedure to be delayed.
How is Spirometry performed
The patient will be asked to put a special device, called a mouthpiece, into their mouth. The healthcare professional will then make sure there are no leaks and that the patient isn’t blocking the device. This procedure is done as follows:
1. The patient will need to take the deepest breath possible, and hold it for less than 1 second.
2. The mouthpiece is placed just inside the mouth between the teeth shortly after the deep breath. The lips should be tightly sealed around the mouthpiece to prevent any air from escaping. The patient is then asked to breathe out at least for 6 seconds, or as long as the healthcare professional suggests. If only the amount of air that can be exhaled at a forced pace is to be measured, the patient should insert the mouthpiece only after taking the deep breath and should not breathe in through it.
3. If the maneuvers are not done correctly, the healthcare professional will stop the patient to avoid them getting tired and will explain the procedure again.
The procedure is repeated with rests of 1 minute in between until two matching acceptable results are obtained.
Possible Complications of Spirometry
Spirometry, a test to measure your lung function, has very few complications. But, if they happen, they can make the test results inaccurate. Here are some potential issues:
* Respiratory alkalosis: This can occur due to too much breathing, causing an imbalance in the body’s acid levels.
* Hypoxemia: This is a condition where the oxygen level in your blood gets too low because oxygen therapy got interrupted.
* Chest pain: You might experience discomfort or pain in your chest during or after the test.
* Fatigue: The test might make you feel extra-tired or worn out.
* Paroxysmal coughing: This is a sudden, intense bout of coughing that can happen during the test.
* Bronchospasm: This is tightening of the muscles that line your airways, which can make it harder to breathe.
* Dizziness: You might feel lightheaded or lose your balance.
* Urinary incontinence: This is a lack of control over urination.
* Increased intracranial pressure: The pressure inside your skull might go up, which can lead to headaches or other problems.
* Syncopal symptoms: These are things like fainting or feeling like you’re about to faint.
What Else Should I Know About Spirometry?
Spirometry is a type of test that’s critical in diagnosing lung diseases. It measures how well your lungs are working and assesses your health before a surgery. It may also be potentially valuable for helping people quit smoking.
Spirometry isn’t typically used for patients having surgery that doesn’t involve the chest, unless the patient has lung conditions such as asthma or Chronic Obstructive Pulmonary Disease (COPD). However, some studies have shown that spirometry could be useful for predicting problems after surgery in other parts of the body as well, like the abdomen. More research is needed to confirm this.
Understanding your lungs’ capacity and function is important when preparing for surgery or if you have a pre-existing lung condition. The key components of lung volume include tidal volume, which measures the amount of air you inhale and exhale normally. Inspiratory reserve volume is the extra amount of air you can inhale forcefully after a normal breath, and expiratory reserve volume is the additional air you can exhale forcefully. Residual volume is the air left in your lungs after you’ve exhaled as much as possible.
Total lung capacity is the combination of all the components of lung volume, showing how much air your lungs can hold at maximum. Vital capacity is the total air exhaled after deepest possible inhalation.
Understanding these lung capacities helps in diagnosing certain lung issues. For example, the patterns of obstructive or restrictive lung diseases can be identified based on these lung volume values.
In restrictive lung diseases, lung compliance is reduced and results in lower lung volumes and capacities. Obesity is one of the common causes of this type of lung disease because it reduces the leftover air in the lungs after normal exhalation. Other causes include diseases affecting the chest wall or neuromuscular disorders.
Obstructive lung diseases involve a greater reduction in the airflow speed from the lungs compared to the volume of air displaced from the lungs.
Finally, spirometry exams provide various measurements for evaluating lung function, one of which is FEV1—a measure of how much air can forcibly be exhaled in one second. It’s often used to assess the risk of postoperative complications, specifically in chest surgeries. In particular, those with predicted postoperative FEV1 less than 30% are likely to have a higher risk of complications after chest surgery.
