[Survey and budgetary impact of anaesthesia machines failures]

OBJECTIVE

To assess the incidence and the causes of failures of anaesthesia machines in relation to aging. Study design. - Prospective survey from january 1996 to july 2000.

MATERIAL AND METHODS

The causes (mechanical or electronic), the moment of identification (checklist, maintenance operation or quality-control operation) of each anaesthetic machine failure, the repair cost and the maintenance cost of 14 anaesthetic machines have been collected and entered into a database.

RESULTS

Over 31,948 anaesthesia delivered during the period of the study, 614 failures have been declared: 53% were related both to mechanical problems or monitoring failure and 40% were identified during the pre-operative checklist. In half of the cases, a specially trained anaesthetic nurse was able to correct the failure in the operating theatre. The annual rate of anaesthetic machine failure remained stable over the study period and the annual maintenance cost is approximatively 10% of the initial machine value. No procedure was cancelled because of a machine technical failure.

CONCLUSION

Anaesthetic machine failure rate change according to the time should not be criteria for remplacement if rigorous quality control and maintenance operation are used.

[The breakdown of anesthesia equipment survey]

OBJECTIVE

To assess the incidence and the causes of failures of anaesthesia machines.

STUDY DESIGN

Prospective survey from August 1995 to September 1997.

MATERIAL

Check-list and machine failure forms.

METHODS

Failures of anaesthetic machines have been collected and entered into a database. Causes and treatment of each failure have been analysed.

RESULTS

Of 5,096 foreseen forms, 3,926 (77%) have been completed after check-list or anaesthesia machine failure. Overall, 233 incidents have been declared (4.5%). Failures identified during the preoperative check-list (n = 96) were mainly related to mechanical problems, especially the gas proportioning device (35%). Perioperative failures (n = 137) were mostly related to electronic problems (ventilator: 27% and monitor: 57%). In more than half of the cases, a specially trained anaesthetic nurse was able to correct the failure in the operating theatre. Using 14 anaesthetic machines for 12 operating rooms, no procedure was cancelled because of a technical failure of a machine.

CONCLUSIONS

This study emphasizes the value of the check-list and the failure report. The presence of a specially trained anaesthetic nurse allows immediate correction of the majority of technical problems.

[Pressure control in medical gas distribution systems]

OBJECTIVE

To assess whether the pressure gauges at the downstream part of pressure regulators are accurate enough to ensure that pressure in O2 pipeline is always higher than in Air pipeline and that pressure in the latter is higher than pressure in N2O pipeline. A pressure difference of at least 0.4 bar between two medical gas supply systems is recommended to avoid the reflow of either N2O or Air into the O2 pipeline, through a faulty mixer or proportioning device.

STUDY DESIGN

Prospective technical comparative study.

MATERIAL AND METHODS

Readings of 32 Bourdon gauges were compared with data obtained with a calibrated reference transducer. Two sets of measurements were performed at a one month interval.

RESULTS

Pressure differences between Bourdon gauges and reference transducer were 8% (0.28 bar) in average for a theoretical maximal error less than 2.5%. During the first set of measurements, Air pressure was higher than O2 pressure in one place and N2O pressure higher than Air pressure in another. After an increase in the O2 pipeline pressure and careful setting of pressure regulators, this problem was not observed at the second set of measurements.

DISCUSSION

Actual accuracy of Bourdon gauges was not convenient enough to ensure that O2 pressure was always above Air pressure. Regular controls of these pressure gauges are therefore essential. Replacement of the faulty Bourdon gauges by more accurate transducers should be considered. As an alternative, the increase in pressure difference between O2 and Air pipelines to at least 0.6 bar is recommended.

[Quality control of anesthesia equipment after maintenance procedure]

OBJECTIVE

To assess the value of quality control tests after routine maintenance procedures of anaesthesia machines.

STUDY DESIGN

Prospective laboratory study.

MATERIAL AND METHODS

Over a 4-year-period, anaesthesia machines were checked after regular maintenance procedures, in order to detect unrecognized dysfunctions before clinical use.

RESULTS

Overall 106 tests were performed on 14 machines and five dysfunctions were identified. Three of them concerned gas proportioning devices, which delivered a hypoxic gas mixture (FO2 < 15%). This defect was recognized by gas analysis at their outlet, whereas mechanical controls were satisfactory. The last two concerned pressure relief valve linearity and gas leak at PEEP valve.

CONCLUSIONS

This study underlines the necessity of both postmaintenance controls and gas analysis at the outlet of the gas proportioning device. These controls should be performed by hospital technicians, independent from those involved in regular maintenance procedures.