. Lung function test. A boy breathes out through a peak flow meter, a device used to monitor breathing in asthmatics. The peak flow meter measures the maximum rate that air can flow out of the lungs. The patient first zeros the black notch on the calibrated scale, takes a deep breath, and then breathes out as hard as possible through the tube. The black notch slides down the scale, giving a reading in litres of air per min- ute. Asthma causes constriction of airways in the lungs (bronchospasm), making breathing difficult. The peak flow meter measures the severity of bron- chospasm and monitors the patient's response to bronchodilator drugs. MODEL RELEASED

Photo website with Rights Managed and Royalty Free stock photos, images, illustrations and footage available for download immediately for commercial and editorial uses. Aflo is a leading independent supplier and producer of stock pictures and visual content. Search and find high quality images and video for design, print, web-use and publishing. Buy photos from our extensive collection of model released and property released sports images. Search some of the most beautiful travel and landscape pictures from our own photographers and license from our large collection of content, modern and archive, focusing on Japan. We provide free research. Register for personal account management and for full use of our Stock Photography website and start to download images now.