Peak expiratory flow rate , obstructive

Obstructive disease reduces peak expiratory flow rate (PEFR) and increases RV via gas trapping. The TLC may also be higher although this is difficult to demonstrate without values on the x axis. The important point to demonstrate is reduced flow rates during all of expiration, with increased concavity of the expiratory limb owing to airway obstruction. The inspiratory limb is less affected and can be drawn as for the normal curve but with slightly lower flow rates. 

Abbreviations QOAD, chronic obstructive airway disease FEFM, forced expiratory flow rate at 50% vital capacity FEFJSJ forced expiratory flow rate at 25% vital capacity FE V forced expiratory volume at Is NR, not reported PEFR, peak expiratory flow rate Raw, airway resistance TLC, total lung capacity. 

Q8 Brad s FEVi and peak expiratory flow rate are a little lower than expected for a person of his age and height. The FVC is just a little higher than expected. The low peak flow and FEVi suggests that he may now be experiencing some obstruction to expiration. 

Salmeterol 42 micrograms bd has been compared with inhaled ipratropium bromide 36 micrograms/day and inhaled placebo in a randomized, double-blind study for 12 weeks in 405 patients with chronic obstructive pulmonary disease (6). Both salmeterol and ipratropium bromide significantly increased the peak expiratory flow rate compared with placebo. Non-specific ear, nose, and throat symptoms (for example sore throat and upper respiratory tract infections) were more common with salmeterol and ipratropium than placebo. There were no significant differences between the groups in the total number of ventricular and supraventricular extra beats. There was no tolerance to the bronchodilating effects of salmeterol. 

The approach most commonly used to evaluate effects on distal airways in clinical and occupational medicine is the maximum forced expiratory maneuver, which allows measurement of airflows as a function of lung volume from total lung capacity to residual volume. Typically, the forced vital capacity (FVC) and the forced expiratory volume at 1 s (as a % of FVC) (FEVi) are measured. Peak expiratory flow is a frequently used measure since simple portable devices permit self-evaluation by patients with obstructive disease. Decreased airflow rates are seen with emphysema, chronic bronchitis, and following... 

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