Comparison of four types of portable peak flow meters (Mini-Wright, Assess, Pulmo-graph and Wright Pocket meters)

Ambulatory peak flow monitoring plays an important role in the diagnosis and management of patients with bronchial asthma. Today several kinds of portable peak flow meters (PFMs) are available for this purpose and sometimes comparisons between the readings of different kinds of PFMs are necessary in clinical setting. We compared four types of PFMs in patients with various respiratory diseases. The study population consisted of 294 patients with asthma, chronic obstructive pulmonary disease, diffuse panbronchiolitis and other respiratory systems, and 15 healthy volunteers. Initially, subjects underwent a spirometry until at least three acceptable forced expiratory curves were obtained. Thereafter each subject blew into a Mini-Wright meter, Assess meter, Pulmo-graph meter and Wright Pocket meter, three times in a random order, with an interval of 4 min. The highest value of three blows was recorded in each PFM measurement. Finally, a second set of spirometric measurements were obtained. Spirometric peak flow rates (PEFRs) were obtained from the best single test which gave the largest sum of forced vital capacity and forced expiratory volume in 1 s (FEV1). In cases when FEV1 in the first spirometry examination was less than 11 or the readings of the PFM were less than 3501 min-1, low-range PFMs were used. The second spirometric PEFR was used as a standard against which the reading of the PFM was compared. The correlation coefficients between the readings of each PFM and spirometric PEFR did not differ significantly from each other. The limits of agreement between each PFM were very wide. In both low- and standard-range PFM, the Assess meter had a significantly greater absolute difference from the spirometric PEFR than other PFMs. In the standard range, the Wright Pocket meter also had a greater difference than the Pulmo-graph meter. The standard-range Assess meter tended to lose its strength of correlation with the spirometric measurement at higher flow rates as did the low-range Pulmo-graph and Mini-Wright meters at the lower and higher flow rates, respectively. All four types of standard-range PFMs gave similarly valid values when spirometric PEFR was used as a reference. However, the limit of agreement between each PFM is so wide that we do not recommend the use of the readings of each meter interchangeably.