Fig. 1.

Real examples of flow volume loops received from our paediatric patients using home spirometry. A – Normal flow volume curve. A deep breath to maximal inspiration has been taken with maximum expiration. B – Delayed start. There is a slight pause/delay prior to expiration after total inspiration. C – Submaximal effort. Total inspiration has not been achieved and expiration is a poor effort, as seen by lack of peak in the flow volume curve. D – Early termination. Maximal expiration has not been achieved as seen by the sharp cut off in the flow volume curve. E – Multiple blows. Following inspiration, there is more than a single blow during expiration as shown with multiple peaks, a common way some children try to ‘cheat’ to get a better result. F – Incorrect mouthpiece position. The end of the mouthpiece must be behind the teeth with lips sealed around it, as the tongue or teeth can obstruct air flow during maximal expiration. In this example, the malposition is causing higher expiratory volumes.