Micro Medical's unique design has taken a hitherto specialised measurement out of the pulmonary function laboratory and into the clinic or home. MicroRint enables airway resistance to be measured with the same ease as peak flow but without effort or technique from the patient. The subject simply breathes passively through a mouthpiece or face mask. A rapidly occluding valve automatically interrupts the airway for a period so brief as to be imperceptible to the patient.
The airway resistance result is automatically computed and displayed. The whole procedure takes only a few minutes and can be performed on all age ranges from neonates to adults. With the transducer weighing only 350g, the instrument is palm sized, easy to use and comes complete with all accessories in a sturdy carrying case.
Wheeziness is a common problem in pre-school children. Objective assessment of this is difficult because such children cannot usually co-operate with conventional test of pulmonary function such as peak expiratory flow (PEF), or spirometry (FEV1 - FVC). This has hindered both the diagnosis of respiratory tract conditions and assessment of the response to therapy.
Airway resistance is determined by the calibre of the airways, the same factor which determines PEF. Airway resistance may be determined by momentary interruption of the airflow. During interruption alveolar pressure equilibrates with airway pressure allowing airway resistance (Rint) to be determined from airway pressure immediately after interruption and flow(Q) immediately before interruption (Rint - pressure/flow).