Spirometry is the gold standard for measuring lung function in both clinical support and research roles. Modern spirometers are high precision, reliable instruments enabling a large numbers of parameters relating to lung volumes and the rate of emptying the lungs during a forced expiration to be measured. The most common and accurate method to measure the patient's forced expiration is via pneumotachograph which measures the flow of air through a mouthpiece and integrates the signal to derive the volume expired.