Question

An elderly man has a chest infection and a history of asthma. How would you expect his chest infection to affect the peak flow meter results?

Answer 1

In asthma the airways constricts when the air is exhaled out. This causes congestion in the airway and air gets trapped in the lungs. Peak flow meter measures the air flow rate when the air is breathed out and hence this measures any problem in the lung during exhalation. Chest infection with asthma further deteriorates the function of lungs and in such condition peak flow rate will decrease. Normally peak flow rate is 400 to 600 litres/min. A reading of 80% to 100% of normal peak flow rate indicates that asthma is under control. Any drop of 20% in peak flow rate from normal is a matter of concern and a drop of 50% or more in peak flow rate is an emergency which requires immediate medical care.