The Tiffeneau index is a measurement used in lung function testing. It shows how well and how quickly air can be breathed out again after taking a deep breath in.
What is behind the term?
The Tiffeneau index, sometimes called the Tiffeneau-Pinelli index, is an important value in lung function tests. It comes from the ratio of two measurements: the so-called one-second capacity (FEV1) and the total amount of air that can be breathed out after breathing in as deeply as possible (VC or FVC). This sounds complicated at first, but it can be explained simply. After breathing in deeply, you breathe out as hard and as fast as you can. The amount of air that comes out in the first second is the FEV1 value. The total amount of air breathed out is the vital capacity (VC).
The Tiffeneau index is calculated like this: FEV1 divided by VC (or FVC). The result is usually given as a percentage. A value of 80% means, for example, that 80 per cent of the total air was already breathed out in the first second.
What is the Tiffeneau index measured for?
The Tiffeneau index is a key part of assessing how well the airways are working. It is used most often when lung conditions such as bronchial asthma or chronic obstructive pulmonary disease (COPD) are suspected. A low value can suggest that the airways are narrowed and air can no longer escape as quickly as it would in healthy lungs.
Values below around 70 per cent are seen as a sign that an obstruction, meaning a narrowing of the airways, may be present. This can have various causes, such as chronic bronchitis, asthma, or other conditions that affect the bronchial tubes.
Normal values are usually above 75 to 80 per cent. In children, values can be a little higher, and they tend to decrease slightly with age.
What does an unusual Tiffeneau index mean?
Many people are worried when they see a low value in a doctor's letter. But not every unusual Tiffeneau index automatically means a serious illness. Sometimes the value is only temporarily low, for example during an acute infection, an allergic reaction, or if the measurement was not carried out under ideal conditions.
A persistently low value, however, often points to a chronic narrowing of the airways. This can be the case with asthma or COPD, for example. Symptoms can range from a lasting cough and breathlessness to a wheezing sound when breathing. The overall picture is always what matters most: symptoms, other test results, and medical history.
When is a low Tiffeneau index dangerous?
Whether a low value is serious depends on how much the airways are actually restricted and what symptoms are present. Many people with slightly low values have very few limitations in daily life. It only becomes truly relevant when there is a clear deviation alongside symptoms such as severe breathlessness, coughing, or difficulty with physical activity.
A lasting and significant narrowing of the airways can affect oxygen supply over time and lead to further health problems. That is why it is important to get a thorough assessment from a lung specialist if values are unusual and symptoms are present.
What happens next?
If the Tiffeneau index is unusual, further tests are usually carried out. These may include repeated lung function tests, sometimes special provocation tests, or imaging of the lungs. The aim is to find the cause of the narrowing and treat it in a targeted way. Depending on the diagnosis, such as asthma, COPD, or another cause, different treatment options may be considered. These range from inhaled medicines and breathing therapy through to lifestyle changes.
Sometimes a one-off low value can result from an inaccurate measurement or an infection and does not necessarily mean that a chronic condition is present.
Why is the Tiffeneau index so important?
The Tiffeneau index helps to distinguish between different types of lung problems. When the bronchial tubes are narrowed, as happens in asthma or COPD, the value drops noticeably. With other problems, for example reduced elasticity of the lung tissue (as in pulmonary fibrosis), the value usually stays normal or only slightly changed, even if the lungs can take in less air overall.
In this way, the Tiffeneau index helps to reach the right diagnosis and begin the most suitable treatment.
