Apparatus for the Control of Breathing Patterns During Aerosol Inhalation

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Abstract
A computerized breathing circuit for monitoring, recording and controlling aerosol inhalation patterns is described. A target pattern, using sine functions derived from previous recording of breathing, is displayed on the computer screen. The reproducibility of tidal breathing patterns of nine normal volunteers was compared using: (i) no target, (ii) a metronome and tidal volume (Vt) target and (iii) the full control provided by this system. Each subject breathed for 2 minutes using each method on separate days. The breath-by-breath variability was found to be similar for all methods. The day-to-day variation was greatest for the 'no control' method with the exception of inspiratory pause (Pi). The inspiratory flow rate (Fi) and Pi had a greater variation using the metronome than the full control. The Vt and breathing frequency were equally well controlled using these two methods. This system provides better control with an easy to follow target display of the subject's own, or pre-set inhalation pattern. Glossary of symbols: fi = 2 × time of inspiration (Ti) [s] fe = 2 × time of expiration (Te) [s] Pi = Inspiratory pause [s] Pe = Expiratory pause [s] Vt = Tidal volume [ml] Fi = Inspiratory flow rate [l/min] Fe = Expiratory flow rate [l/min] Trc = Time of respiratory cycle [s]