Lung Function Test: All You Need To Know

What Is A Lung Function Test?

Lung function tests are used to identify different lung conditions like asthma, chronic obstructive pulmonary disease (COPD), and pulmonary fibrosis. They provide insights into ventilation and gas exchange within the airways, crucial for a comprehensive health assessment. [2]

When Should The Lung Function Be Tested?

Lung function tests are usually recommended when symptoms such as coughing, shortness of breath, or difficulty breathing arise. They are used to detect lung conditions, assess lung function, prepare for surgeries, and evaluate the effects of factors like smoking and occupational exposure on lung health. [3]

How Do Lung Function Tests Work?

Lung function tests are conducted by trained medical professionals. For instance, spirometry, one of the most common tests, involves taking a deep breath and forcefully exhaling into a device. This records the volume and speed of exhaled air. [4]

What Lung Function Tests Exist And What Is Measured?

Various types of lung function tests assess airway and lung function. These include spirometry, body plethysmography (measuring static lung volumes), diffusion tests, stress tests, and exercise tests. These tests measure specific parameters that aid in diagnosing lung diseases, assessing disease severity, and evaluating treatment efficacy.

Spirometry

Spirometry forms the foundation of lung function diagnostics. This test assesses crucial parameters such as vital capacity, maximum inspiratory volume, and peak flow rate.

Vital capacity is the maximum air volume you can exhale after a deep inhalation. It indicates how much air your lungs can take in and release. This is a significant indicator of your lung function. [9]

Maximum inspiratory volume is the amount of air you can inhale deeply. It measures your lung's ability to take in air, which is essential for supplying your body with sufficient oxygen.

Peak flow rate measures the maximum speed at which you can exhale air from your lungs. It is especially crucial in assessing respiratory conditions like asthma, as it can detect changes in respiratory function early on. [11]

In summary, the results of spirometry provide essential insights into how your lungs function in terms of air quantity and speed (known as dynamic lung volumes). These results can aid in diagnosing lung diseases or monitoring the progression of existing conditions like asthma, COPD, or pulmonary fibrosis. [5]

Body Plethysmography

Body plethysmography, also known as whole-body plethysmography, provides insights into total lung capacity and the volume of air remaining in the lungs even after maximal exhalation. During the test, you sit in a sealed chamber and breathe through a specialized mouthpiece. This process measures and calculates parameters such as pressure differentials, airway resistances, and air volumes. This test yields information on parameters like airway resistance and functional residual volume. [14]

Airway resistance describes the level of resistance offered by the airways as air flows through them. When the airways are narrowed or obstructed, as is the case with respiratory conditions like asthma or COPD, airway resistance increases. This can make breathing difficult and lead to respiratory issues. A low airway resistance indicates open and healthy airways and lungs. [12]

Functional residual volume refers to the amount of air that remains in the lungs after a normal exhalation. This maintains the openness of the airways or lungs and ensures optimal air exchange. A healthy functional residual volume is crucial for maintaining lung function and ensuring adequate oxygen supply.

These parameters provide essential information to the doctor regarding the health of the airways and the lung's functionality in terms of air quantity. They are used to identify potential respiratory conditions, monitor the progression of lung diseases, and plan the best possible treatment for affected airways. [6]

Diffusion Test

Another lung function test is the diffusion test, also known as the DLCO test (Diffusion Carbon Monoxide Lung Test). The diffusion test provides information about how well your lungs take in oxygen and release carbon dioxide. For this test, you will first inhale and exhale a special mixture of carbon monoxide. The concentration of carbon monoxide is then measured in the exhaled air. This process assesses the lung's gas exchange function and identifies potential issues.

Gas exchange function describes the lung's ability to absorb oxygen from inhaled air into the blood and release carbon dioxide from the blood through exhalation. This ability is crucial for the human body and its adequate oxygen supply. When the lungs are healthy, this gas exchange occurs efficiently, allowing the body to receive sufficient oxygen while effectively eliminating excess carbon dioxide. If this is not the case, it may indicate lung diseases or other health problems that require treatment. This test is used in the diagnosis and assessment of various lung conditions such as pulmonary fibrosis or emphysema. Pulmonary fibrosis involves scarring and stiffening of lung tissue, while emphysema is a condition in which the lung's air sacs are damaged and destroyed, leading to a loss of elasticity in the lung.

Overall, efficient gas exchange function contributes to ensuring the body is well supplied with oxygen, receives the necessary energy, and efficiently manages metabolism. [7] [13]

Stress And Performance Tests

Stress tests are employed to assess lung function during exercise or physical exertion in individuals with asthma, COPD, or respiratory issues. These tests include the 6-minute walk test and the exercise spirometry test. In the latter, respiratory gases are measured using a mask, and cardiopulmonary performance is evaluated during physical activities like cycling. These tests aid in monitoring stress levels and devising individualized therapy and training plans. They are also relevant for individuals undergoing respiratory therapy or lung transplantation. [8]

What Are Normal Lung Function Values?

Lung function tests measure various values to assess airway and lung function. There are general reference ranges considered as normal. The normal values in lung function tests vary depending on age, gender, height, and ethnic background. The specific normal values depend on the test type and individual parameters of the tested person.

Below you will find descriptions of some important values and their “normal ranges”:

Vital Capacity (VC)

Vital capacity is the volume of air you can exhale after a deep inhalation. For an individual, with healthy lungs, this ranges from 3 to 5 liters.

Forced Expiratory Volume In 1 Second (FEV1)

FEV1 is a measure of the maximum amount of air you can exhale in one second. This means you inhale until you can't inhale anymore, and then exhale as forcefully as possible – the volume of air you can exhale within one second is FEV1. Normal FEV1 values depend on age, gender, ethnicity, and height. Values of 80% or more are generally considered normal. Peak Flow Meter: Typical peak flow meter values vary based on age, gender, and height. For adults, the normal range is between 400 and 700 liters per minute. [10]

Airway Resistance

Normal airway resistance is usually less than 2.5 cmH2O/L/s (centimeters of water per liter per second). Increased airway resistance may indicate a narrow or obstructed airway.

Diffusion Capacity (DLCO)

Normal DLCO is typically about 80–100% of the predicted value, depending on age, gender, and height.

Please note that these reference ranges are general guidelines and can vary due to other factors. The interpretation of lung function test results should always be conducted by a doctor or qualified medical professional, taking into consideration individual circumstances.

Where Can I Get My Lung Function Tested?

You can have your lung function tested at various medical facilities. These include hospitals, clinics, pulmonary practices, as well as diagnostic and treatment centers. Lung function tests are typically conducted by medical professionals, such as pulmonary doctors, also known as pulmonologists. It's advisable to inquire about the test requirements beforehand.

At CARE, as part of the preventive health check, a lung function test is conducted using a spirometry device.

In Conclusion

In summary, the lung function test is a valuable tool for assessing respiratory function and lung capacity. It's a vital part of medical diagnostics, enabling timely treatment and care for individuals with respiratory and lung conditions. A healthy respiratory system is crucial for quality of life and physical performance, making regular lung function assessments essential for long-term well-being.