• Pieter A Bothma, Andreas Brodbeck, and Uday Bapat.
• Consultant in Anaesthesia and Intensive Care and lead consultant of the East of England Hyperbaric Unit, James Paget University Hospitals NHS Foundation Trust, Lowestoft Road, Gorleston, Norfolk NR31 6LA, United Kingdom, Phone: +44-(0)1493-452475, Fax: +44-(0)1493-452753, E-mail: pabothma@dsl.pipex.com.
• Diving Hyperb Med. 2009 Mar 1; 39 (1): 45-7.

IntroductionPatient ventilators for use in the hyperbaric chamber need to be of special design; any malfunction could have disastrous consequences. We report two serious problems with a recently purchased Siaretron 1000 Iper™ ventilator.MethodsThe ventilator was tested with a Biotek VT-Plus™ gas flow analyzer, which also measures O2 concentration. The changes in fraction of inspiratory oxygen (FiO2) were verified with a Teledyne Electronic Devices™ O2 analyzer.ResultsIn volume control ventilation (VCV) mode: excessively large tidal volumes were delivered when the fraction of inspiratory oxygen (FiO2) was changed. In pressure control ventilation (PCV) mode: changing the FiO2 setting did not change the FiO2 delivered by the ventilator. The ventilator also exhibited an irregular flow pattern in PCV.ConclusionsThese problems may cause serious diagnostic and clinical consequences if not identified as equipment malfunction issues. A malfunction of the integrated memory in the microchip on the main board was said to cause the PCV malfunction. The manufacturer replaced the main board, which corrected the problem. The solution offered for the VCV problem was to change FiO2 in steps of 0.1 per breath, which eliminates the tidal volume surges. We feel it is extremely important that all users of the Siaretron 1000 Iper™ are made aware of these problems as they are not described in the user manual or elsewhere.

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