Volume 10, No. 1 • Spring 1995

What do Anesthesiologists Know About Medical Gas and Vacuum Systems?

Todd G. Peterson, M.D.

Daily, anesthesiologists depend on their Medical Gas Vacuum System (or ‘MGVS’) to continuously deliver an adequate supply of ‘medical grade” gases for patient care. Because these systems seldom appear to have problems and are hidden behind the walls, little thought is given to the complexity of the MGVS and its potential safety hazards.

To educate anesthesiologists regarding the potential problems in the design, construction, maintenance, and certification of the MGVS, the APSF Subcommittee on the MGVS was formed, and, at the 1994 ASA Annual Meeting in San Francisco, presented a scientific exhibit ‘Beyond the Walls” which demonstrated many problems encountered in MGVS. As part of this exhibit, a survey was conducted to define what practitioners know about the MGVS they use and the problems that they have encountered.

One hundred and two visitors to the exhibit participated in the survey and their demographic makeup is summarized in Table 1.

Table 1: Survey Demographics


Anesthesiologists at Academic Institutions: 53

Anesthesiologists at Nonacademic Institutions: 32

Other: (CRNA, residents, engineers, technologists):17

Years of Experience

0 to 5 years 22

6 to 10 years 18

11 to 15 years 29

16 to 20 years 10

Greater than 20 years 23

Primary Site of Practice

Hospital with more than 500 beds 42

Hospital with 100 to 500 beds 41

Other (Small hospital, Outpatient Surgery center) 7

Anesthesiology Residency Training site 58

CRNA Training site 16

Knowledge of the MGVS was assessed in a series of seven questions which ranged from site specific questions such as “Do you know who is responsible for and maintains your MGVS?’ and ‘Is it certified?’ to general questions of prior awareness of MGVS problems and education experience. Only 55% of those surveyed knew who was responsible at their institution for the MGVS; a mere 25% knew that their system had been certified. Of those having medical air in their facility (31 of 93), only 50% had checked that the compressor was medical grade, 35% the outside air purity, and 25% the locations of the intake for the compressor.

Most sites had bulk liquid oxygen supplies (87 of 97), but only 51% knew that the bulk site was the responsibility of the supplier. Though 73% of those responding knew the location of the zone cut-off valves (a question frequently asked on JCAHO surveys), only 27% knew where the bulk supply or main line cutoff valve was located. Of those responding, 40% were aware of the complexity of a MGVS shutdown, but only 25% knew of the requirements for piping and brazing in construction. Thirty percent of respondents knew of the potential contaminants to be found in medical gas systems, and this correlated significantly with those having experienced problems with their MGVS (p=.005). In addition, only 24 of 99 had received any teaching about the MGVS as part of their training, yet 83 of 92 felt that it should be covered as part of training. Overall knowledge of the MGVS correlated positively with three factors: being an academic anesthesiologist (p=.02), years of practice (p=.005), and having experienced a MG-VS problem (p=.017).

Five questions dealt with first hand experience with MGVS problems, failures and shutdowns. Sixty-one problems were reported by 39 of 102 respondents. The most common problems encountered were:

  • Contaminants (liquid, particulate, infectious, and gaseous) 28%
  • Components failures (valves, regulators, etc.) 18%
  • Bulk supply problems 18%
  • Pipeline leaks 15%
  • Design and construction problems 15%

Fifty-five respondents (54%) reported having had a shutdown of the MGVS at their institution; there were no significant differences between institutions either in size or whether they were a training site or not. Most shutdowns (58%) occurred to expand the MGVS, though 18% were to upgrade systems to meet standards and 9% were to clean systems of contaminants. For these shutdowns, less than half of the anesthesia departments represented actively participated in the planning process (45%); the rest (except for one case in which no warning was given) were only informed when the shutdown was to occur. Two patient deaths were reported that resulted from MGVS shutdowns or failures (one resulted from a crossed pipeline and no data were given on the second).

This survey shows that there is a significant knowledge deficit among anesthesiologists regarding the MGVS and its potential hazards. Nearly 30% of those surveyed acknowledged that they had little knowledge of their MGVS. Few (25%) were taught about the MGVS during their training (yet, over 90% of respondents felt that lectures about the MGVS should be included as part of the residency program). These survey results suggest that one way many anesthesiologists may learn about their MGVS is through experiencing problems or failures (a very strong correlation between problems experienced and knowledge of the MGVS). Extrapolating from the survey data, an anesthesiologist might expect a failure or shutdown of the MGVS (that would directly affect him/her and clinical care) about once every 10 years.

The APSF Subcommittee on the MGVS has been working to help educate the practitioner through a continuing series of articles in the APSF Newsletter and through presentation of the ‘Beyond the Walls’ scientific exhibit at the 1994 ASA and NYPGA conferences. Clearly though, there is a need for these topics to be covered as part of residency training. Strong support was expressed in the survey results for the development of training aids such as videotapes, reprints, exhibits, and a general outline of the issues. Efforts are underway to organize and fund a videotape that could be used in training programs. Further, the Subcommittee has proposed creation of a ‘MGVS Hotline’ to answer questions about the MGVS and assist with MGVS problems. When available, details will appear in the APSF Newsletter.

Dr. Peterson, an active member of the APSF subcommittee on MGVS, is Assistant Professor of Anesthesiology, University 0 Arizona, Phoenix