MARK CLARKE / SCIENCE PHOTO LIBRARY MARK CLARKE / SCIENCE PHOTO LIBRARY
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 release not available. Property release not required.