Background: Patients often experience problems using metered dose inhalers (MDIs), particularly poor coordination between inhalation start and dose actuation (TsIn: time difference between the start of an inhalation and the actuation of a dose), and fast peak inspiratory flow (PIF). We investigated if a coordination cap (CAP), with instruction to prolong inhalation, solved these problems.
Methods: Inhalation profiles [PIF, TsIn, inhalation volume (Vi), inhalation time (Ti)] of patients with stable asthma prescribed an MDI were measured using their real-life technique (MDI). Inhalation profiles were then measured with the cap fitted (MDI+CAP). These patients were then instructed to inhale through the MDI+CAP for 5 sec, and inhalation profiles measured (MDI+CAP+TRAIN). TsIn was only measured for the MDI.
Results: Resistances of MDI and MDI+CAP were 0.0135 and 0.0243 (cm H2O)(½)/(L/min), respectively. Seventy-one patients were evaluated, with mean [standard deviation (SD)] forced expiratory volume over 1 sec % predicted normal of 78.3% (21.0). Following MDI, MDI+CAP, and MDI+CAP+TRAIN: mean (SD) PIF was 155.6 (61.5), 112.3 (48.4), and 73.8 (34.9) L/min, respectively (p<0.001); mean (SD) Ti was 1.60 (0.60), 1.92 (0.80), and 2.99 (1.03) sec, respectively (p<0.001); and Vi was similar between stages. Twelve patients used a slow flow with the MDI alone, but only two of these patients demonstrated good coordination. With the cap in place (which ensures good coordination), the number of patients using a slow flow increased to 25 for MDI+CAP and to 50 following MDI+CAP+TRAIN.
Conclusions: The cap with its effect of increasing resistance to airflow combined with the instruction to prolong inhalation time significantly decreased the inhalation flow.
Keywords: I-Breathe; asthma; device; inhalation flow.