To establish a diagnosis when either asthma or COPD is suspected. Both asthma and COPD are characterized by an obstructive pattern of dysfunction, so the PEFR is the index that will be abnormal. To distinguish between asthma and COPD, the obstruction is assessed to see whether it is reversible or not. This can be done by repeating the peak flow meter test after administering a bronchodilator and a steroid inhaler or nebulizer. If the PEFR becomes normal after taking the medicine, then the condition is asthma.
If it remains the same then it is COPD.
After beginning therapy with asthma medication like bronchodilators and steroids to assess the response to the drug regimen and the adequacy of treatment. Although bronchodilators and steroids are the mainstay of treatment in asthma, there are many different types that vary in potency and duration of action(and thus in side effects ), also the dosage is variable according to the severity of the condition. The peak flow meter helps to titrate the potency of the regimen until the best outcome is achieved.
Serial measurements on a regular basis are used to get an idea about the general course of the illness i.e. whether improving, stable or deteriorating. If a patient keeps deteriorating in spite of treatment this might indicate a concomitant exacerbating condition.
After hospital admissions and stays to decide when it is appropriate to release patient. In severe attacks of asthma, hospitalization is frequently required to administer oxygen therapy and intravenous medications etc. The patient is subsequently weaned off gradually and released when it is possible to achieve good PEFR readings with only the usual treatment, for example only bronchodilator and steroid inhalers.