Asthma peak expiratory flow measurement

Peak flow measurement of peak expiratory flow rate (PEFR) on waking, before bed, before and after bronchodilator medication is useful to assess the extent of airflow limitation and the characteristic of the disease in terms of reversibility. There is some evidence of diurnal variability. PEFR is also useful in assessing the disease progression longer term and the response to therapy. Patients are advised to keep an asthma diary and record regularly the peak flows to ascertain their diurnal pattern. 

Q5 Measurement of peak expiratory flow this is a simple measure of expiratory function. The peak flow meter measures the velocity of expired airflow and is suitable for both adults and children. The patient breathes out a short blast of air, as fast as possible, into the device. Normal individuals can achieve airflow velocity of 450-6501 min-1. The peak flow meter is a cheap device which is used by patients at home to monitor their asthma. If a patient s peak flow diminishes below a certain level which has been set by their nurse practitioner or family doctor, they can adjust their own treatment, within specified limits, and control their condition better. 

In clinical practice, pulmonary function testing is the primary measurement used to assess disease and monitor asthma pharmacotherapy. Pulmonary function testing methods vary. The two most common measures of lung function include forced expiratory volume exhaled in one second (FEVi) and peak expiratory flow rate (PEE). FEV], measured in milliliters, represents the amount of air that patients can forcibly blow out in 1 second. 

Analytic or individual-level studies have been directed either at the effect of air pollution exposure on respiratory health generally, or on the status of persons with conditions (e.g., asthma) that make them more susceptible to air pollution than the population in general. The Six-Cities Study, a prospective cohort study, and the 24-Cities Study, a cross-sectional study, were of the general design. The panel study, a short-term cohort study involving relatively intensive assessment of outcome, has been used to assess the effects of air pollution on susceptible persons. Typically, a panel of participants is enrolled and asked to maintain a diary of symptom status and medication use, and physiological measurements, such as peak expiratory flow rate (PEFR) may be made. New methods for data analysis have also made this design more informative than previously (7,8). 

Clinical Trials In controlled clinical trials in patients with asthma, the onset of improvement in pulmonary function, as measured by maximum midexpiratory flow rate (MMEF), was within 30 minutes after a dose of albuterol tablets, with peak improvement occurring between 2 and 3 hours. In controlled clinical trials in which measurements were conducted for 6 hours, clinically significant improvement (defined as maintaining a 15% or more increase in forced expiratory volume in 1 second [FEVj] and a 20% or more increase in MMEF over baseline values) was observed in 60% of patients at 4 hours and in 40% at 6 hours. In other single-dose, controlled clinical trials, clinically significant improvement was observed in at least 40% of the patients at 8 hours. No decrease in the effectiveness of albuterol tablets was reported in patients who received long-term treatment with the drug in uncontrolled studies for periods up to 6 months. 

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