A spirometer is a device used for the measuring of air volume that enters and leaves the lungs during breathing. This is important because any gases that enter the body can be accounted for. It is also an important indicator of accessing the respiratory system of medicine patients. It provides an insight on how clear the airway is and the state of lung tissues therefore forming a basis for diagnosis of diseases like as asthma which occurs when the airways are obstructed.

The first attempt to discover an instrument that would be able to measure the volume of air that the lung can hold was by a Greek philosopher and doctor called Claudius Galen in around 200A. D. In his experiment where he instructed a young boy who was his patient to breathe into a bladder, he noted that the total volume after a full breathing cycle did not change. His results were not well received by his peers who considered the experiment inconclusive.

Sometime later a guy by the name Borelli tried also tried to measure the volume inspired in a single breathe, he used the principle of water displacement to access the volume inspired. This technique was accepted by many other researchers and has been the basis of the modern day apparatus. Since then specialist have refined the device to be able to measure volumes more accurately to diagnose both lung and heart conditions.

As technology and knowledge increases, many different varieties have come into place. Today the devices are more specific in the results they give and the test they do. An example includes the whole body plethysmograph which is considered to be very accurate in measurement unlike the other types. It is the standard of reference for the other devices when measuring lung function. The patient doing this test must be kept in an enclosed small space for best results.

Another type is the Pneumotachometer that measures the rate of flow of gases by using a fine mesh that is able to detect differences in pressure. It is very useful and of advantage to very ill patient because the patient breath fresh air during the process.

There are also electronic forms of these devices that do not require moving parts or meshes but they utilize ultrasonic transducers that are able to accurately determine the rate of flow and volumes. These types are more accurate and reliable because they are automated and thus not likely to having mistakes. They also have a disposable portion of air channels that patients use and discard immediately after. This makes them very good in terms of hygiene and safe from transmission of infections.

There is a specialized types which is the best for patient who need respiratory lung support called incentive spirometers. These devices have a unique ability of supporting the pulmonary function in addition to obtaining lung volumes. Where there is need to determine the ability of a patient to breathe out properly a special type called a peak expiratory device is used.

The latest type is the Tilt-compensated spirometer which can be held in a horizontal position as the process of measurement continues. This is more comfortable in that the patient takes the position that best suits him. There are many other types that are still not very well understood but generally the use of these devices has made the practice of medicine very efficient.