Multiplace Delivery System

Monthly Hyperbaric Safety Notice: November 2005

Chamber Pressure Gauge/Depth Gauge

In this notice, the hyperbaric chamber pressure gauge/depth gauge will be discussed.

Background

Pressure gauges indicating the internal pressure of the chamber are critical for the safe and accurate operation of the chamber. This is reflected in both code and in good practice. Redundant gauges, shut off valves, calibration, piping and pressure (depth) markings are all important considerations.

Safety Issue

The hazards of operating a chamber without adequate gauges are very real. Decompression sickness, over pressure accidents and mechanical failure are some examples. There is also the consideration that your patients receive the correct treatment pressure.

Each chamber compartment should be equipped with a minimum of two dedicated pressure gauges. An internal pressure gauge for the inside attendants use and an external gauge for the chamber operator. The internal gauge should be protected to ensure that the sensing port is not blocked which would lead to incorrect pressure readings. Dedicated lines and shut-off valves must be employed on the gauges located at the chamber hull. These gauges and piping are to be installed and maintained under an ‘oxygen clean’ process. The system will have a means to attach a master reference gauge to check the chamber gauges while they are in place. All gauges should be clearly marked to indicate which chamber they address. Consideration should also be given to what units of pressure are appropriate for your service. All of the gauges should use the same units of pressure and the markings fully understood by the staff. Where remote chamber control systems exist redundant gauges are necessary. Chamber pressure gauges should be calibrated or tested against a master reference gauge on a regular basis. The Undersea and Hyperbaric Medical Society and the United States Navy have annual calibration and maintenance standards. The o ccupational Safety & Health Administration requires calibration every six months or when there is a discrepancy of greater than 2% between any two gauges. A 2% discrepancy for a pressure gauge reading 0 psig / 0 fsw – 100 psig / 225 fsw would have a 2 psig / 4.5 fsw allowance. This may not be acceptable in your practice, however. There should be a policy agreed on by the Medical Director and the Safety Director for what degree of tolerance is acceptable. The test gauge/master reference gauge should be of high quality, kept in a secure location and calibrated on a regular basis. Calibration, testing and maintenance results are recorded in the equipment log.

Bottom Line

Hyperbaric chamber pressure gauges must be tested/calibrated and maintained at a minimum of once a year and at any time there is a discrepancy between two gauges. In the clinical hyperbaric setting chamber gauges are, by definition, in a protected environment and expected to be part of a well-designed system. They require very little maintenance. Regular testing and documentation, however, is critical for their safe and effective functioning.

Reading Assignment

Chapter III, Hyperbaric Facility, Chamber Pressure Gauge, Guidelines For Clinical Multiplace Facilities, UHMS
ASME PVHO-1, 4-7.4 Depth Gauges
29 CFR XVII 1910.427 (g)(2), OSHA
USN Diving Manual, 4.6 Diving Gauges, Revision 4, change A, I March, 2001

Contributing Author: James Bell, CHT, EMT

James Bell Jim has over 25 years experience in the operation and maintenance of multiplace hyperbaric chambers. He serves as safety director and lead hyperbaric technologist at Hennepin County Medical Center, in Minneapolis, Minnesota, USA. Jim is a certified hyperbaric technologist, and an Undersea and Hyperbaric Medical Society facility accreditation surveyor.

Full Panel of Safety and Technical Correspondents

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