Can peak expiratory flow be measured accurately during a forced vital capacity manoeuvre?

Spirometry and peak flow measurements traditionally depend on different for ced expiratory manoeuvres and have usually been performed on separate, dedi cated equipment. As spirometry becomes more widely used in primary care set tings, the authors wished to determine whether there was a systematic diffe rence between peak expiratory flow (PEF) derived from a short sharp exhalat ion (PEF manoeuvre) and from a full forced vital capacity (FVC) manoeuvre, using the same turbine spirometer (Microloop, Micro Medical, Kent, UK), Eighty children (38 with current asthma) aged 7-16 yrs were asked to perfor m 2 blocks of PEF and FVC manoeuvres, the order being randomly assigned. PEF obtained from a peak flow manoeuvre (EFPF) was significantly greater th an that from a forced vital capacity manoeuvre (PEFVC) in both healthy (gro up mean difference 20 L.min(-1): p<0.001) and asthmatic children (group mea n difference 9 L.min(-1); p<0.004), For clinical purposes, a mean difference of about 3% for children with asth ma is of no practical significance, and peak expiratory flow data can usefu lly be obtained during spirometric recordings.