Wet-wedge spirometer for the accurate continuous measurement of ventilation under anaesthesia

  • S. A. O'Connor
  • D. J. Wilkinson
  • G. R. Dickson
  • B. J. Ashley


A wet-wedge spirometer which continuously and accurately measures tidal volume in the spontaneously breathing anaesthetised patient has been developed. This spirometer may be adapted for use with any anaesthetic system which employs a reservoir bag and expiratory-relief valve. The performance of this apparatus both in the laboratory and in the operating theatre has shown the device to be linear, sensitive and suitable for routine anaesthetic use. Measurement of tidal volume was accurate within ±3·5 per cent of reading up to respiratory frequencies of 60 breaths per minute independent of the fresh gas flow. The resistance of the anaesthetic circuit remained within normally accepted limits when used with this spirometer.


Anaesthesia Bag-in bottle principle Respiratory depression Ventilation Wet-wedge spirometer 


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Copyright information

© IFMBE 1985

Authors and Affiliations

  • S. A. O'Connor
    • 1
  • D. J. Wilkinson
    • 1
  • G. R. Dickson
    • 1
  • B. J. Ashley
    • 1
  1. 1.Departments of Medical Electronics and AnaesthesiaSt. Bartholomew's HospitalLondonEngland

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