A comparison of peak expiratory flow measured from forced vital capacity and peak flow meter manoeuvres in healthy volunteers

BACKGROUND: Spirometry measures the mechanical function of lungs, chest wall and respiratory muscles by assessing the total volume of air exhaled from total lung capacity to residual volume. Spirometry and peak flow measurements have usually been carried out on separate equipments using different expiratory maneuvers. AIMS: The present study was carried out to determine whether there is a significant difference between peak expiratory flow (PEF) derived from a short sharp exhalation (PEF maneuver) and that derived from a full forced vital capacity (FVC) maneuver in healthy volunteers. SETTINGS: A medical college and tertiary level hospital. MATERIALS AND METHODS: The present study was carried out during the period from January 2006 to July 2006. The study included 80 healthy volunteers with no coexisting illnesses, who were in the 15-45 years age group and belonging to either sex. They were asked to perform two sets of PEF and FVC maneuvers using the same turbine spirometer; the order was randomly assigned. STATISTICAL ANALYSIS: The difference between PEF obtained from a peak flow maneuver (PEFPF) and that obtained from a forced vital capacity maneuver (PEFVC) in healthy volunteers was analyzed separately for males and females, as well as for both groups combined, and statistical significance of its correlations with study data parameters was analyzed. RESULTS: The difference between PEF obtained from a peak flow maneuver (PEFPF) and that obtained from a forced vital capacity maneuver (PEFVC) was statistically significant (P < 0.001) in males and in females separately and also for both groups combined. PEFPF (517.25 ± 83.22 liters/min) was significantly greater than PEFVC (511.09 ± 83.54 liters/min), as found on combined group mean analysis. However, the difference was small (6.16 + 7.09 liters/min). CONCLUSIONS: FVC maneuver can be used over spirometers to detect the PEF; and on follow-up subsequently, the same maneuver should be used to derive PEF. If we are using a peak flow maneuver subsequently, corrections are required to compensate for the difference due to the different maneuver.