The absence of canister dumping in the feedback group may be due to the participants knowledge that the NC printout would expose this practice. In related research, Petranyi et al studied blood glucose level monitoring of diabetics using an electronic device which internally recorded the date and time of glucose monitoring, as well as the actual blood glucose level. Participants were asked to keep a diary of glucose monitoring, including the date, time, and glucose level. For the first two months, participants were unaware of the memory capability of the device. A majority of participants turned in deceptive diary reports which included blood glucose levels lower than those that were objectively monitored and nonexistent monitoring sessions. In contrast, after the initial blinded trial, when the same patients were made aware that the blood glucose monitor could record the exact date and time of glucose testing and actual glucose levels, subsequent concordance between diary entries of both glucose levels and the time of monitoring with those recorded by the monitoring device was almost perfect.
The greater accuracy of self-reporting by the feedback group was probably due to a combination of the monitoring and feedback. Participants in this group were aware that deception would be detected and also realized through the initial feedback sessions that they tended to overestimate their usage.
In addition to its utility in clinical trials for accurately monitoring and enhancing compliance to regularly scheduled inhaler use, the NC also can be used to monitor as-needed beta-agonist MDI use as an outcome variable related to the level of disease control. The NC potentially could be used to assist physicians in monitoring patients with poorly controlled obstructive pulmonary disease.