Spirometry is a medical procedure used to measure lung functions, specifically the volume and speed of the air one breathes in and out. It is one of pulmonary function tests and it is also referred to as measuring of breath. Spirometry is performed using pieces of equipment called spirometers. There are many version and models of these apparatus in the market, giving a buyer a wide range of options to choose from.

The work of this equipment is to determine abnormal ventilation patterns and how air moves in and out of the lungs. This device is normally able to detect two kinds of abnormal ventilation patterns. The first abnormal pattern is restrictive while the second one is obstructive. Different device models use different measurement methods to achieve their functions. Some of most common methods include use of water gauge, ultrasonic, and pressure transducers.

These gadgets continue getting better as technology improves. At the present time several makes are in utilization in different around the globe. Among the key models are windmill-type, incentive, whole body plethymograph, pneumotachometer, peak flow type, fully electronic, and tilt compensated model. Of all the models body plethymograph has the highest accuracy with high precision in values taken. The great precision is partially because patients get enclosed in small spaces during the process.

The pneumotachometer employs a fine mesh which is used to measure the flow rate of gasses. As the gases flow over the fine mesh, their pressure is detected making it possible to measure their rate of flow. The patient under assessment has the freedom to breath in fresh air during the process. This is an advantage that other models do not have.

Previous models have been improved to come up with the fully electronic version, which does not use moving parts or fine meshes. In fully improved models, techniques like ultrasonic transudcers and pressure difference are used to gauge rate of air flow. Accuracy is greatly improved because no friction due to resistance is experienced since no moving parts are present. Disposable air flow channels in the products improve hygiene.

The most commonly used type is the incentive model. These models improve gaseous exchange in the lung of patient when used for a long time. In hospitals they are placed on benches or tables next to beds. Doctors instruct patients to breathe through them for a given number of times daily. Any improvements the patient makes in their breathing habits can be observed on the calibrations on the apparatus.

Windmill-type version is used to measure forced vital capacity without using water. It is lighter and more portable in comparison to water-tank model. The measurements in this device are broad running from 1000 to 7000 ml. The presence of rotating discs in the apparatus requires it to be held in a horizontal position when recording measurements. Tilt-compensated type has 3D sensing mechanics that allow patients to lean backwards or forwards while in use.

The testing process is highly dependent on the cooperation of the patient. The values from one recording cannot be used because they may contain errors. That is the reason why the procedure is normally repeated at least three times. That is also the reason it cannot be used on small children who cannot follow instructions.