1Département dAnaesthésie, CHU dAngers, F-49033 Angers Cedex 01, France. 2Département dAnaesthésie, Hôpital Necker, F-75015 Paris et Commission Nationale de Matériovigilance, France 3Département dAnaesthésie, Hôpital Laennec, Rue de Sèvres, F-75007 Paris, France*Corresponding author
J. Ancellin, B. Bacchi, J. M. Bedicam, V. Billard, M. A. Dauphin, S. Fougère, G. Freys, F. Fries, C. Itty, G. Krim, J. Labrousse, G. Laguenie, R. Leroyer, P. Lever, M. A. Lochet, M. P. Macquet, D. Meunier, S. Molliex, J. F. Muir, Y. Nivoche, J. C. Otteni, E. Salgues, F. Saulnier, D. Thiveaud and J. P. Viale
Accepted for publication: November 7, 2000
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Abstract |
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Br J Anaesth 2001; 86: 3827
Keywords: equipment, anaesthesia machines; equipment, failure; monitoring, intensive care
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Introduction |
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Materials and methods |
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Results |
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Twenty reports (2%) were associated with patient death. The failure of the device itself accounted for 12 accidents: two ventilators of the same type caused massive pneumothorax when they failed; this led to changes in the design of the apparatus. The devices involved in all the other cases of device failure were different in each case. In four cases the monitors did not sound an alarm in response to ventricular fibrillation or asystole. In two other cases, the monitors mistook the activity of a pacemaker for that of the heart, and produced no alarm even when the patient was already dead. Two cases of gas supply failure each killed one patient through contamination of the oxygen line with nitrous oxide. In two cases an isoflurane vaporizer gave an overdose, resulting in the death of one patient. Incorrect use was the second most common cause of death (n=7). One user failed to make proper use of an oxygen tank for home ventilation and died from anoxia. Another death was attributed to a heat and moisture exchanger (HME), which was attached to a one-way Ambu valve in the wrong direction; ventilation became impossible and the patient died from anoxia. This problem with one-way valves prompted an order from the French authorities for design changes to make such mistakes impossible. The four deaths involving infusion equipment were associated with catheter fracture and migration, cardiac tamponade and embolism, usually resulting from technical errors made during insertion of catheters. One patient died because all alarms had been turned off to make life more comfortable for the nursing staff. We encountered one death in which the device did not seem to be faulty. The clinician using a pulse oximeter failed to identify as false a very low SpO2 value during extracorporeal circulation for repair of a congenital defect, although pulse oximetry is known to be unreliable in this context. However, this problem was not the main cause of death.
While 98% of the accidents were not fatal, several of them warrant further examination. Some of these cases involve the same problems as the fatal ones described above.
The rupture of epidural catheters in the epidural space was the most significant problem in regional anaesthesia. The most significant catheter port incident was catheter fracture (44% of reports for catheter ports), leading to their migration into the heart and pulmonary veins in 36% of cases.
Defibrillation equipment caused burns to patient or doctor in three cases (11%). A shock could not be delivered in four cases. Three cases were the result of incorrect use. For example, synchronization to the ECG requires a delay before the shock can be triggered and delivered. This function was not understood by the user, who thought the device had failed. Other problems included the unexpected failure of batteries or components. Checking procedures had often not been performed properly or at the correct time.
Incidents involving systems for medical gas delivery and gas analysers were mostly minor, such as leaks, simple failure of gas analysers or rotameter inaccuracies. However, serious errors involved the misconnection of medical gas lines; these occurred in four cases and were possibly caused by defects in the sockets. Still more seriously, there were four cases of ignition of aluminum oxygen pressure regulators after the oxygen high pressure valve, upstream of the regulator, was opened rapidly, causing major burns to users. Two non-fatal cases of contamination of the oxygen lines with nitrous oxide were noted.
For infusion equipment (excluding catheter ports) there were few severe accidents. These included the migration of catheters inside vessels, air embolism and infusion rate errors with syringe pumps. Minor problems were numerous and mainly caused by errors of use and/or failures of quality assurance during manufacture.
The extent of problems with monitors varied according to the type. Haemodynamic monitors (45%) headed the list, followed by SpO2 monitors, including their accessories (15%). Monitors failed mainly because of component breakdown and errors in design, including software (Table 3).
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The database was then analysed to assess the mode of investigation used, and the causes of failure, classified by category of equipment (Tables 2 and 3). Table 2 shows the number of reports that required a formal analysis of the faulty device by the manufacturer or an independent laboratory. Such a formal analysis was possible in only 40% of cases involving perfusion catheters, catheter ports and equipment for regional anaesthesia. This was because most users, having declared the problem, discarded the device, either by accident or on the grounds that it was contaminated with blood and thus not safe to send to a laboratory. Thus, effective laboratory investigations were performed in fewer than 33% of cases. This was due to the large number of component breakdowns that were easily recognized without specific expertise.
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Considering the whole database, it is clear that this post-marketing survey led to design changes in 1244% of cases. These reports led the French health authorities to issue 11 directives demanding the withdrawal from the market or restricted use of the problematic devices. In almost all cases there was a design fault.
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Discussion |
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Vigilance is important in anaesthesia as failure of devices used in this field may place the patient at high risk.13 Hart and colleagues6 categorized 22% of incidents reported in ICUs as severe (this category included those in which patients died and other severe incidents). The duration of injuries was permanent or long-lasting in 6%. Equipment featured in 41% of cases. Gilron14 in Canada noted that, although anaesthetic devices accounted for only 2.3% of newly marketed medical devices, they accounted for 8.6% of all problems and recalls and 37% of alerts. Similarly, anaesthesia accounted for 32% of all reports in France.
Infusion equipment and catheter ports
All the incidents we encountered in this field involved known problems. Errors during insertion and failure to check the catheter position radiologically accounted for the majority of problems with catheters. This led to vein perforation and to catheter rupture with migration and leaks. Catheter ports failed and migrated because of unnoticed pinch-offs.15 16 Like others, we found many errors in the use of infusion pumps.17 This highlights the fact that further education and safety measures are required, even with simple and commonly used devices such as catheters and pumps.
Monitors
Monitors, especially pulse oximeters and capnometers, are important for detecting anaesthetic mishaps, so increasing their reliability is a key issue.18 19 Short and colleagues20 noted that, of the 125 critical incidents reported during a quality assurance programme, 50% were detected by the anesthetist and 34% by monitoring equipment. This highlights the potential risk posed by monitor failures, especially if there is no built-in alarm system.
Defibrillators
Defibrillator failure because of defective batteries is the major cause of failure in published reports.21 The systematic use of checklists and tests has been advocated in response to incidents, especially for defibrillators that are seldom used. Errors of operation were also frequent, especially in devices linked to the patients ECG. Users did not know how these differed in function from more classical devices. This highlights a need to educate users and to label the front panel clearly with instructions for fast, error-free operation.
Ventilation and medical gas supply
In most cases, problems arising from ventilation devices were caused by device failure or human error. There were two main problems with medical gas supply: (i) contamination of oxygen lines with nitrous oxide or air due to a valve failure2224 and (ii) ignition of oxygen flow regulators made of aluminium alloy, which can melt at a low temperature, causing serious burns to users. These devices are liable to blow their fuses, which may ignite any inflammable equipment. This has encouraged the French authorities to forbid the use and sale of regulators including parts made of aluminium.
Incubators
Several devices were not sufficiently protected against possible errors of use. Serious burns arose from errors in incubator settings, or in placing the temperature probe on the child. Another was caused by incorrectly placed surgical drapes directing a hot air stream towards the baby. This risk was mentioned in the user manual, but the manufacturers had not gone on to reinforce it with an alarm. A warning from health authorities, an information campaign and the addition of warning labels on the canopy did not prevent another accident of the same type from occurring a year later. This highlights the fact that manufacturers should consider how people actually use their devices in practice, e.g. performing surgical operations in closed incubators instead of open ones.
Human errors were very frequent: they involved 1471% of the reports, depending on the category of the device. Most of these incidents were caused by negligence or inadequate knowledge, despite clear instruction manuals. It seems that medical device-orientated culture is not sufficiently widespread and does not keep up with industrial progress. Williamson and colleagues25 reported in the Australian Incident Monitoring Study that errors of judgement when using medical devices, a failure to check and technical errors represented 16%, 13% and 13% of human errors, respectively. Clayton26 showed that 55% of residents were not able to check anaesthesia machines according to the standards of the New Zealand College of Anaesthetists and that only 16% of them could use defibrillators properly and solve problems involving this device. Reducing errors of this kind will require more education. For this reason, the German authorities have requested users to undergo specific training on each new medical device introduced in a clinical department before they use them on patients.
Another study identified a failure of regular checking in 33% of the reports.21 This was taken up as a major regulatory issue by the French authorities, who require by law that all devices used in the operating theatre should be checked daily before use and according to formal checklists. This recommendation also imposes a between case simplified check.27
We found incidents of equipment failure that differed from those reported by Webb and colleagues5 Equipment failures represented only 9% of all incidents reported in their study. Ventilation equipment accounted for 44%. These were due to one-way valve failures in 43% of cases and to leaks of various kinds in 13%. The remaining causes were miscellaneous. Forty per cent of incidents involving ventilators were actually or potentially life-threatening. Monitors were involved in 24% of incidents, of which arterial pressure monitors accounted for 26%. All were described as potentially life-threatening. Oximeters, oxygen analysers, capnographs and pulse oximeters each accounted for about 20%. Surprisingly, infusion pumps accounted for fewer than 2% of all incidents. This pattern of incidents is strikingly different from ours. It may be that the types of event reported in the two studies differed. In the study of Webb and colleagues,5 all consecutive events occurring during anaesthesia were reported, including malpractice and probably also numerous trivial problems resulting from human error. Under these circumstances, equipment failures were likely to be underestimated. Conversely, our data featured equipment failures specifically. However, both studies relied on voluntary reporting. This underestimates the true occurrence of incidents. For example, a study by Sandborn and colleagues28 showed that only 4% of electronically detected incidents had led to a voluntary report. To exploit equipment failures in improving safety and reliability, and to further the education of users, incident reporting must become mandatory. Since ECRI (Emergency Care Research Institute, 19462-1298 Plymouth Meeting, Pennsylvania, USA) and a systematic survey and analysis of medical device failures was introduced in the USA, this reporting has been shown to be successful.29
We conclude that vigilance leads to a better understanding of the problems involving medical devices. The French experience is positive, and may help to improve safety.
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Acknowledgements |
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References |
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