Background: The home monitoring of peak expiratory flow rate (PEFR), although recommended in current asthma guidelines, remains seriously underutilized by both patients and physicians. Our assessment is that this is more a statement regarding the inability of current charting methods to fulfill the promises made for PEFR monitoring, rather than a commentary regarding the usefulness of peak expiratory flow rate monitoring per se. We have adapted the theory and charting tool of the discipline of statistical process control to the daily monitoring of PEFR in the care of patients with asthma. Statistical process control charts integrate the actual PEFR values and their day-to-day variation in a manner that permits more informed decision-making. This article introduces our adaptation of statistical process control theory and charts via three case presentations.
Objective: Report our experience in the use of statistical process control theory and charting to the monitoring of peak expiratory flow in the care of patients with asthma.
Methods: Discussion of methodology and case reports.
Conclusion: This is the first report of the application of statistical process control (SPC) theory and charting to the home monitoring of peak expiratory flow rate and the clinical decision-making processes involved in the day-to-day care of patients with asthma. SPC charts integrate knowledge of actual serial PEFR measurements with knowledge of their associated serial variation. Our adaptation of this theory and its charting methodology results in a tool that loses nothing provided by the charting methods suggested in current guidelines and, at the same time, provides patient specific, statistically driven signals of significant change; facilitates identification of the reason(s) for the change in PEFR; predicts the range in which future function will occur; permits decision-making and care to be provided in an anticipatory manner; and, importantly, permits the early identification of the functionally at-risk patient. This report demonstrates that home monitoring of peak expiratory flow is a robust tool whose usefulness in the care of patients with asthma has been limited more by the paradigm in which we have required it be used than by any of the limitations of the measurement per se.