Why spirometry?

Assessing lung function is a particular task. Lung functions are pending on many variables like integrity of the constituents tissues, viability of the airways, effective wrapping system, strenght of the individual body, gender, height, weigh…

Facilitating lung evaluation

However, in terms of lung function it tends to be restricted to the patency of airways. If airways are open, lungs will receive oxygen and the respiration itself is eased. Although the airways in some lung diseases are working appropriately, the tissues beyond may be damaged and lung function will be altered anyway.

What’s spirometry for?

Spirometry is a tool that helps to determine if airways are patent or not, and if lungs have enough elasticity or space to hold air enough to catch oxygen and release carbon dioxide.

With spirometry, the physician may give numeric values to the respiratory exam. Spirometry allows to get objective measurements as the sphygmomanometer provides us with real numbers on blood pressure and electrocardiogram shows the rythm of the heart.

Comparing spirometry with other methods in other diseases

With spirometry there is an almost good picture of lung volumes managed by a patient as well as flows through the airways. The big difference of spirometry when compared to sphygmomanometry or electrocardiography is that the former requires patient effort: an active participation. It requires pre-training, repetitions, and good will to get a good maneuver.

Spirometry and its 2 key values

Spirometry records several values related to the air expelled during a forced expiration. The first key value is the maximal amount of air the patient can exhale; it is called Forced Vital Capacity. The second value will be the amount of that air exhaled during the first second in the Forced Vital Capacity maneuver: Forced Expiratory Volumen in second 1. The importance of this value rely on the maximal effort to expell air which is easy at the begining.

Force Vital Capacity (FVC) may be diminished as an alternative to the normal. When it occurs it talks about restrictions in space. The FVC may be reduced due to a tigh (rigid) lung, a hard wrapping system, fluid around the lungs, thoracic deformities or pain.

Forced expiratory volumen in the first second (FEV₁) may be reduced due to changes and reductions in the caliber of the airways like in COPD, asthma, bronchiectasis.

Obstructive - Restrictive - Mixed

When the ratio FEV₁/FVC is reduced is the same to say: from the air exhaled from lungs forcedly, a small amount is released during the first second (which is not normal). This reduction allows pulmonologists to clasify the abnormality as Obstructive. When it is increased and most probably due to a reduced FVC, the category is Restrictive. And there are mixed patterns too.

Asthma and COPD

When the obstruction is reversible after administration of bronchodilators, it’s more likely a diagnosis of asthma. When the obstruction is always present with a partial response of bronchodilators, it’s more likely COPD (chronic obstructive pulmonary disease) although in some asthmatics it may be hard to revert the obstruction with bronchodilators either.

Can you ask for a spirometry?

Although these are not all the values obtainable from a spirometry, they are key to address a diagnosis. Spirometry with the resultant spirogram is fundamental to assess or confirm most of the respiratory diseases related to breathlessness. Smokers should encourage their physicians to get a spirometry as well as they want to know the blood pressure values.

In a near future…

When patients feel more empowered into the management of their health, particularly the respiratory patients, they will want to know the FEV₁and FEV₁/FVC values to understand what’s happening inside their bodies. Perhaps, in a near future, a patient will remember that their FEV₁/FVC was 0.7  while their FEV₁was 65% of the predicted value to help their physician adressing decision process.