| 摘要 |
<p>A flowhead for use in expiratory flow measuring equipment is designed to be disposable and to fit on the casing of a unit containing pressure transducers and associated measurement electronics. When the flowhead is fitted to the casing, the pressure transducers are coupled with ports (8 and 9) in the wall of the main tube, which connect the transducers to the measurement chambers. Each port is surrounded by a cylindrical sealing collar (12 and 13). The measurement chambers are upstream and downstream of a central perforated wall (5) which constitutes a passage restriction and across which a pressure drop is accordingly generated if breath is exhaled through the tube, via the mouthpiece (15). Measurement of the pressure drop allows determination of parameters such as peak expiratory flow and forced expiratory volume at one second. Low pressure drop hydrophilic filters may be used to damp high frequency pressure oscillations and to protect the instrument from ingress of condensed water vapour.</p> |
