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Monoplace Delivery System

Monthly Hyperbaric Safety Notice: July  2006

Calibrating the TCM-3 Transcutaneous Oxygen Monitor for In-Chamber Testing

In this notice, the process by which the TCM-3 monitor is calibrated to allow the recording of values in excess of 1,000 mmHg is reviewed.

Background

Tissue oxygen determinations represent an important component of the hyperbaric case management process. Increasing scientific and clinical interest is being directed at the value of in-chamber assessment, in order to better determine the suitability and adequacy of hyperbaric oxygenation. Three such monitors are in use within many organizations, all of which are manufactured by Radiometer. They are the TCM-3, the TCM-30, and the TCM-400.

Safety Issue

The TCM-30 was specifically designed with hyperbaric medicine in mind. It has the capacity to record values across the full range of anticipated patient states. It requires no special calibration process. The TCM-400 can likewise record across this range. The monitor of interest of interest of this Notice is the TCM-3. Under normal calibration steps, it will only record up to 1,000 mmHg. To enable this monitor to record beyond 1,000 mmHg, the following process is followed:

  1. To be able to record a value of 2,000 mmHg it is necessary to "half-scale" the calibration value. This is achieved by dividing the normal calibration value (160 mmHg at sea level) by two and calibrating to this value (80 mmHg).
  2. During hyperbaric treatment, whenever an in-chamber reading is taken, the value recorded on the monitor is doubled.

Some may prefer to "one-third" scale at higher pressures (3.0 ATA), and multiply each observed value by three.

Bottom Line 

The TCM-3 can be utilized for in-chamber transcutaneous monitoring. It will be necessary to undertake the above steps, however, in order to record values in excess of 1,000 mmHg.

Contributing Author: Dick Clarke, CHT

Dick ClarkeDick is President of National Baromedical Services, which he founded in 1986. His previous background included service in the British Royal Navy, diving instructor and underwater photographer, assistant director of the seabed habitat 'HydroLab' and several years in the offshore commercial diving industry. Dick heads the Baromedical Research Foundation where he serves as Principal Investigator for several international clinical trials. He is course director for 'Primary Training in Hyperbaric Medicine' and the 'HBO 2000' series of advanced hyperbaric symposia. Dick has been a NOAA Diving Medical Officer Training Course faculty member since 1983. He pioneered the Certification in Hyperbaric Technology (CHT) program, is a past president of the National Board of Diving and Hyperbaric Medical Technology and remains active at the committee level within the Undersea and Hyperbaric Medical Society.

Full Panel of Safety and Technical Correspondents

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