Spirometers are part of medical equipments that are used by clinicians in identifying breathing problems in patients. They record the flow rate and volume of air in lungs and can therefore be used to diagnose lung diseases or other related conditions. There are several different subtypes of spirometers the majority of which will be explained here.

The use of spirometers was an idea that began a very long time ago by a Greek doctor at around 200A. D. The medical doctor found it necessary to be able to measure and understand lung volumes and speed of flow in order to diagnose respiratory conditions. In his experiment where he used the bladder to estimate volume he opened up the world of research into this matter. From that time with the increase in knowledge and technology the current devices have arose.

The plethysmograph is one variety of these devises that record the volume of an organ or that of the whole body. The device is able to detect the amount of blood or air flowing into an organ. The pulmonary plethysmograph is specifically preferred for measuring functional residual capacity which is the volume of air that remains in the lungs after a normal expiration. The only short coming with this type of equipment is that is that it must be used in a small space that is enclosed.

The pneumotachometer spirometers measure the rate of flow of air entering or leaving the lungs by using a specially designed fine mesh. The mesh is sensitive to changes in pressure of air within the lungs and that from the outside environment. The main advantage with this form of instrument is that the patient is able to breathe natural air as normal as the experiment is being done.

The incentive spirometers are a very special group of devices which in addition to the normal measuring of lung volumes, they have the additional ability of being able to support the functioning of the lungs. They therefore mostly used in those patients that are very sick or patient who have had surgeries involving the chest and heart. The equipments will help reduce build up of fluids in the lungs.

A peak expiratory device is small hand held equipment that is used when determining the maximum speed with which an individual can breathe out. It helps monitor the ability of a person to expire and thus monitoring recovery in people undergoing treatment for obstructive lung conditions. It can also be used to determine the degree of obstruction of the airway.

There are other called electric spirometers that are able to measure air passing through channels without the need of any moving parts or meshes. They measure speed of flow of air using ultrasonic transducers able to determine pressure differences in the channels. They are therefore very accurate and reliable because they are automated. These have fewer chances of errors and are better preferred for hygiene purposes because the channels are disposable.

A windmill-type is another special variety that is mainly used to determine forced vital capacity. It employs a principle of volume and water displacement in reaching to the volume results. Care should be taken in the used of this type because wrong positioning can displace rotating disks that make the device to work properly.

The final groups of these instruments are the Tilt-compensated spirometers which were the latest to be discovered. Their greatest merit is that they are very flexible and can easily be tilted to a position that best accommodates the patient.