Continuous spirometry: an aid to monitoring ventilation during operation.

We present six case-reports of patients who experienced inadequate ventilation as a result of endobronchial or oesophageal intubation, or obstruction to the tracheal tube or airway and were monitored with on-line spirometry. The continuously displayed pressure-volume or flow-volume loops may be compared with previously recorded baseline loops. The changing configuration of the curves offers additional and instantaneous information about the cause of increased inspiratory airway pressure, decreased compliance or increased airway resistance. Monitoring flow-volume and pressure-volume loops in conjunction with currently available techniques provides a comprehensive method of monitoring ventilation.