Have you ever wondered how much air you take in when you inhale? Or the amount of air you expel when you exhale? Spirometry is all about assessing the volumes of air inhaled and exhaled and the ease/ rate at which it is done. A physiological test measures the maximum amount of air volume that an individual can expire and inspire with maximal effort. Spirometry is an important biology concept for those studying human respiration. NEET aspirants must go through every minute detail related to the respiratory system in humans, its disorders, and their diagnosis to score more marks in the upcoming NEET exam in 2022. Read on to learn about spirometry and why it is done.
NEET 2022 Syllabus includes the following topics related to human respiration:
- Breathing and respiration
- Respiratory system in humans
- Mechanism of breathing and its regulation in humans
- Disorders related to respiration- Asthma, Emphysema, and other occupational respiratory disorders
It is important for students studying respiratory disorders to understand the basic concept of spirometry, its procedure, side effects, and uses as spirometry results help diagnose and monitor respiratory disorders.
What do you understand about spirometry?
Spirometry is a common pulmonary function test that measures the amount of air you breathe in and breathe out of your lungs. Thus, it allows the evaluation of the pulmonary volumes and pulmonary capacities. It is also your ease of breathing and the rate at which you can blow the air out of your lungs.
Spirometer: It is a diagnostic instrument used in spirometry that allows you to measure the capacity of the lungs.
Spirograph: It is an apparatus that you can use to record lungs’ movement.
Spirograph: It is the graphic measurement of breathing movements and lung capacities. It is also called pneumography.
Spirogram: A diagrammatic representation that allows tracing the relationship between maximal expiratory airflow and time is a spirogram. It is a measure of ventilatory lung function. A spirogram helps identify abnormal ventilation patterns: obstructive and restrictive.
If you want to learn more about spirometry and spirometry in practicality, then learn how a spirometer is different from a respirometer by clicking here!
Why is spirometry done?
A doctor can ask a patient to have spirometry done if the patient complains of cough, wheezing, or shortness of breath. He can also suggest spirometry for patients to check their lung function before surgery.
Spirometry results help diagnose the following diseases:
- Chronic obstructive pulmonary disease or COPD
- Pulmonary fibrosis
- Other conditions that hinder normal breathing
Furthermore, spirometry is also done for patients receiving treatments for chronic lung disease, asthma, COPD, and others. The test helps determine whether the disease under treatment is improving or worsening.
What precautions should be taken before the test?
A person who has to undergo spirometry must take the following precautions before the test (on the doctor’s advice):
- Patients should take their daily medications before the test.
- They should not smoke before the test.
- Follow the doctor’s instructions regarding medications.
- Opt for loose and comfortable clothing to minimise interference while taking a deep breath.
- The patient must avoid taking a large meal before the test.
What happens in the spirometry test?
In the course of the test, a patient will be required to sit upright. The technician or doctor conducting the test places a clip on the nose of the patient being examined. Also, they provide a plastic mouthpiece to the patient that stays connected to the spirometer.
Next, the patient will be asked to place the mouthpiece tightly to the lips, take a deep breath (as deep as possible), and breathe out hard (as hard and fast as possible). It is crucial to put maximum effort, and the process is repeated at least three times to obtain optimal results.
The doctor might also give the patient some medication (bronchodilator) that helps open airways and then perform the test again to see if the medication improves breathing.
The complete spirometry process can take up to 15 to 30 minutes.
The after-effects of the spirometry test
The after-effects of the test are short-lived, usually for a minute or two. They can be:
- A dizzy feeling
- Shortness of breath
Doctors do not recommend this test to a person who has recently had a heart attack or some other severe heart condition, as the test procedure requires the patient to exert some force.
What does spirometry measure?
Spirometry measures the following:
Forced vital capacity (FVC)
FVC is the maximum amount of air that a patient can forcefully exhale after taking as deep a breath as possible. If you find the reading lower than what the normal reading shows, that indicates restricted breathing.
Forced expiratory volume (FEV)
FEV is the amount of air that a patient can exhale from their lungs in one second. It helps a doctor estimate the degree of bronchial obstruction and the severity of the patient’s breathing issue. A lower FEV-1 reading is an indication of a more pronounced pulmonary obstruction.
Understanding some important concepts related to respiration and spirometry
Students often find it challenging to understand various volumes and capacities related to spirometry and respiration. Here is a simplified version in an easy to understand and remember format.
Respiratory Cycle: One inhalation plus one exhalation constitutes a respiratory cycle.
Respiratory rate: The number of respiratory cycles completed per minute is called the respiratory rate. The normal rate is 12-16 per minute.
Tidal volume: Suppose you are sitting in a relaxed position. Now you take in a breath and breathe out once. This volume of air you take in or breathe out is called tidal volume.
Inspiratory Reserve Volume or IRV: The maximum amount of air you can inhale in addition to the tidal volume.
Expiratory Reserve Volume or ERV: The maximum amount of air that a person can exhale in addition to the tidal volume.
Residual Volume or RV: The amount of air left in the lungs after maximum exhalation.
Capacities are additions of different lung volumes.
Inspiratory Capacity: TV + IRV
Expiratory Capacity: TV + ERV
Total Lung Capacity: TV + IRV + ERV + RV
You can understand total lung capacity as follows:
- Suppose you just exhaled up to your maximum. So, you exhaled out ERV.
- Now your lung has residual volume.
- You will first fill up ERV, then TV, and finally IRV when you breathe in.
- So, a total of RV, ERV, TV, and your total lung capacity. Normally it is up to 5.8 to 6 litres.
Functional Residual Capacity: You do not exhale ERV nor inhale IRV when you breathe normally. So, your lungs carry RV and ERV, i.e., the functional residual capacity.
Vital Capacity: TLC – RV
Image source: researchgate
Spirometry Results: Normal Values
The normal values are as follows:
Tidal Volume-TV = 500 mL
Inspiratory Reserve Volume (TRV) = 3000 mL
Expiratory Reserve Volume (ERV) = 1100 mL
Residual Volume (RV) = 1200 mL
Inspiratory Capacity (IC) = 3500 mL
Functional Residual Capacity (FRC) = 2300 mL
Vital Capacity (VC) = 4600 mL
Total Lung Capacity-TLC = 5800 mL
Spirometry has become a modern way to test the presence of various lung diseases. If these diseases are diagnosed in time, they can be cured with the help of medication and, in worst cases, surgeries. If your spirometry score is above 70%, you are healthy. These are FEV1% values for adults. Whereas in the case of children, the healthy FEV1% values must be 80-85%.
If you have concerns regarding breathing, coughing, chest pain, or any other related symptoms, you must visit the doctor immediately. Do not forget to abide by the preventive measures before going for spirometry. After the test is done, don’t be careless and follow the instructions given to you by the doctor. Take the medication dosage on time till the course is completed. Please do not skip any meal/dosage as it can worsen your situation.
Preparing for these minute topics for NEET UG 2022 can boost your scores. It will help if you do not stress while learning new topics. Reading them regularly will stuff them in your subconscious mind that you will recall while attempting the NEET exam. So, read and learn as much as you can till the exam day.