Which measurement is more accurate/appropriate in patients with COPD; spirometry or peak flow?
A. Many doctors and nurses have become used to measuring serial peak flow measurements as part of asthma care. PEF is a more simple measure than FEV1 and repeat measurements can be easily performed at home by the patient using a hand held peak flow meter. As such, they might appear of immediate value in COPD. However, there are important physiological differences between COPD and asthma which limit the value of PEF in COPD. In asthma there is a reasonably good correlation between PEF and FEV1 which allows the use of PEF as a surrogate for FEV1. In COPD this relationship breaks down. Because the amount of airway collapsibihty varies between COPD patients, the relationship between PEF and FEV1 will also vary. PEF can be misleadingly optimistic and therefore it may be severely limited as a diagnostic tool. In addition, PEF is not a sensitive measure for detecting the small treatment changes typical of COPD.
