Functionally crossed pipelines. An intermittent condition by a faulty ventilator.

Unexpectedly high blood oxygen tension in intensive care patients occurring over a 5-year period were found to have been caused by an apparently normally functioning ventilator which was intermittently acting as a conduit between the oxygen and air pipelines. Responses to a circular letter sent to Quality Control Pharmacists in England and Wales suggest that similar faults may have occurred at least five times in the past 10 years. Recommendations are given for the prevention of this problem, including monitoring of gas pipeline composition.