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Editorial Comment: Mask Induction Despite Circuit Obstruction An Unrecognized Hazard of Relying on Automated Machine Check Technology

Eisenkraft, James B. MD

doi: 10.1213/XAA.0000000000000035
Case Reports: Case Report

Department of Anesthesiology, Icahn School of Medicine at Mount Sinai, New York, New York,

Many studies have shown that anesthesia caregivers are poor at performing a thorough preuse checkout of, and trouble-shooting faults in, their anesthesia delivery systems.1,2 Contemporary computerized electronic anesthesia workstations incorporate many features designed to optimize function and further patient safety. Among these features is automation of many of the components of the manufacturer’s recommended preuse checkout. Some steps, however, cannot be automated and must be performed by the caregiver him/herself, usually following instructional prompts displayed on the workstation screen. It is therefore important to understand which checks are automated and essential to understand and to correctly perform those that are not.3

In this issue of A & A Case Reports, Yang and Lewis4 describe how their institution’s protocol for preanesthesia checkout of the GE Aisys Carestation® (GE Healthcare, Madison, WI), which included automated checks, failed to detect an almost complete breathing circuit obstruction distal to the Y-piece. Several important lessons can be learned from this case report.

First, a critical step in the preuse checkout is confirming that gas flows properly and unimpeded through a correctly configured breathing circuit into a “test lung” (second reservoir bag) connected at the Y-piece during both inspiration and exhalation (the so-called flow test). This procedure cannot be reliably automated. Indeed, this component of the preuse checkout is essentially unchanged between the 1993 Food and Drug Administration Anesthesia Apparatus Checkout Recommendations and the American Society of Anesthesiologists’ 2008 Recommendations for Preanesthesia Checkout.5 The automated checkouts of the breathing system are performed with the Y-piece occluded and are designed to detect leaks and to measure compliance.

Second, with the circuit open at the Y-piece and the adjustable pressure limit valve closed, operation of the oxygen flush should normally produce a minimal increase in breathing circuit pressure and distension of the reservoir bag. Such a test, seeking an increase in pressure and greater distension of the reservoir bag, might be too insensitive to detect a partial obstruction at the Y-piece. It is noteworthy that, despite the “near total obstruction” of the lumen in this case, the authors were able to perform a successful mask induction in an 11-year-old, 38 kg patient using oxygen, nitrous oxide, and sevoflurane.

Third, the evolution of each model of electronic workstation usually involves software changes and, sometimes, updates to the User’s Reference manual. In the case reported, the authors refer to “more recent versions (Software Revision 3.x) of the User’s Reference manual” which included manual checkout instructions that might have detected a significant obstruction at the Y-piece. A Google search (on 11.3.2013) returned the User’s Manual for Software Revision 7.x. It is therefore important that users of anesthesia workstations be updated when any clinically relevant changes are made to their anesthesia workstations. Manufacturers of workstations inform the purchasers of their equipment (i.e., institution, hospital, and surgicenter) of updates, but the institution must have a mechanism for passing such information on to those who use the equipment clinically. A hard copy of the User’s Instruction Manual is supplied with each new workstation, but the manual usually “disappears” after a few days and is often hard to find when reference to it needs to be made. Currently, those seeking any type of information usually turn first to an Internet search. At present, workstation manufacturers have not made their user’s manuals readily available electronically on their own Web sites. Some user manuals are available on the Internet only because they have been uploaded by other interested parties. I believe that it would be very helpful if all user’s reference manuals were made available electronically for immediate reference. Alternatively, the pertinent user’s manual could be loaded into the memory of each workstation and be available via a “Help” screen.

Fourth, as workstations become more sophisticated so must the caregivers who use them. It is generally agreed that improvements in education concerning the use of new technologies are required.6 This was the subject of an Anesthesia Patient Safety Foundation 1-day conference held in September 2013.7

Fifth, and as concluded by Yang and Lewis, visual inspection is the most reliable method for identifying obstructions distal to the Y-piece. This inspection should include the facemask that is also a possible source of obstruction if the plastic wrapper in which the mask is supplied is not totally removed before being attached to the circuit.8

This case report should encourage the reader to critically review the preuse checkout of his/her own anesthesia workstation and appreciate the purpose and the limitations of any automated steps.

James B. Eisenkraft, MD

Department of Anesthesiology

Icahn School of Medicine at Mount Sinai

New York, New York

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