The value of audible clinical alarm signals is widely recognized.1 As of January 1, 2004, all Joint Commission on Accreditation of Healthcare Organizations (JCAHO) health care facilities are required to comply with a set of 7 National Patient Safety Goals.2 Goal #6 is to “improve the effectiveness of clinical alarm systems” and requires that alarms are “activated” and “are sufficiently audible.” Integral to the ongoing national analysis of the JCAHO requirements is a question regarding the applicability of goal #6 when an “operator” (clinician) is present—such as in the OR.3,4 Similarly, there is a long-standing debate among anesthesiologists about the utility of audible clinical alarm signals in the operating room.
The argument supporting the use of audible alarm signals is straightforward: Audible alarm signals can enhance vigilance by directing the clinician’s attention to out-of-bounds parameters. Undoubtedly, we have all experienced the benefits of timely and effective audible clinical alarm signals in the OR.The argument against the mandated use of audible clinical alarm signals in the OR is based on a subjective risk-benefit analysis of the alarms. Yes, alarms might be useful, the argument goes, but the cacophony of alarm signals during critical periods of anesthetic management may distract and overwhelm the clinician.5 As a result of cognitive overload, vigilance may be diminished, not enhanced.6 These perceptions of the performance of extant clinical alarm systems appear to be universally held. Thus, many anesthesiologists silence physiologic alarms.7 Unfortunately, unlike machines, we are not eternally vigilant,8,9 and the silencing of intraoperative physiologic alarm signals has resulted in clinical disasters.
To be clear, the debate about the usage of audible clinical alarms applies primarily to physiologic alarm conditions (e.g., ECG rhythm, blood pressure) and not to some of the “equipment” technical alarm conditions that are integral to medical devices. For example, the US national safety and performance standard for anesthesia workstations requires an audible alarm signal to indicate failure of the oxygen supply and the presence of sub-atmospheric breathing system pressure, among other conditions.10
The complexity of deploying effective clinical alarm systems that have adequate sensitivity and specificity for the detection of clinically significant events is becoming widely recognized.11 Various “intelligent” alarm systems have been considered for years.12-14 In fact, the newly published international alarm system standard has a section (201.2) dedicated to intelligent alarm systems.15 However, the intelligence of alarm systems is hampered by their inability to be “aware” of the context of clinical management.16 For example, absence of contextual awareness may prevent an “intelligent” alarm system from correctly displaying the alarm message generated by a hypotensive non-pulsatile arterial blood pressure tracing. For this situation, is the appropriate alarm urgency “high priority” to direct our attention to unexpected cardiac arrest; “medium priority” for a partially occluded arterial catheter; or is no alarm necessary since the changes are due to the initiation of cardiopulmonary bypass?
Despite the limitations of current clinical alarm systems, anesthesiologists have enthusiastically embraced one clinical alarm sound that isn’t strictly an alarm: it is an information signal. The audible “pulse tone,” “saturation tone,” or “beep tone” of the pulse oximeters has become indispensable for modern anesthetic practice. According to the requirements of the US national standard for pulse oximeters, the variable pitch tone (if present) must parallel the SpO2 reading.17 Thus, the pulse tone conveys pulse rate, pulse regularity, and changes in SpO2. The matching of changes in pulse tone to changes in SpO2 seems to be based on an intuitive relationship that appeals to “clinical sense.” And, by virtue of conveying this information, the pulse oximeter fulfills the definition of an alarm, which is “communicating information that requires a response or awareness by the operator.”18 The pulse oximeter’s values can be affected by a variety of physiological changes, so the high-level information conveyed by the instrument must be interpreted with other data to provide a diagnosis and guide corrective action. Nevertheless, it is precisely the real-time, high-level assessment of general cardio- pulmonary performance that underlies the instrument’s value. Consequently, as anesthesia providers, we are not the only clinicians in the OR to respond to the pulse tone. Surgeons routinely use the tone to guide interventions.
With due respect to the long-standing debate about the “limited proven clinical value” of pulse oximetry for intraoperative management, the jury of clinicians has spoken: pulse oximetry has become the de-facto standard of care for intraoperative monitoring of oxygenation, and the pulse tone is the one monitor that is always heard in almost every operating room. Isn’t it time that we mandate the use of the pulse oximeter pulse tone for the monitoring of all patients undergoing general anesthesia and incorporate this requirement in the ASA Standards for Basic Anesthetic Monitoring?19 If so, we must explore related issues, such as the necessity of standardizing the pulse oximeter’s pitch-saturation values.
Dr. Goldman is an Instructor at the Harvard Medical School (Departments of Anesthesia and Biomedical Engineering, Massachusetts General Hospital) and is an Adjoint Associate Professor of Anesthesiology at the University of Colorado School of Medicine.
Dr. Robertson is an Assistant Professor of Anesthesiology at the Medical College of Wisconsin.
- Morris RW, Montano SR. Response times to visual and auditory alarms during anesthesia. Anaesth Intensive Care 1996;24:682-4.
- 2004 National Patient Safety Goals. Joint Commission on Accreditation of Healthcare Organizations. Available on the web at: http://www.jcaho.org/accredited+organizations/patient+safety/04+npsg/index.htm. Accessed on June 30, 2004.
- The Patient Safety Discussion Forum. National Patient Safety Foundation. Available on the web at: http://listserv.npsf.org/SCRIPTS/WA-NPSF.EXE?A1=ind0405& L=patientsafety-l&D =0&F=P&H=0&O=T&T=1#12. Accessed June 30, 2004.
- JCAHO Goal #6. Improve the effectiveness of clinical alarm systems (Powerpoint presentation). Available on the web at: http://www.bmets.org/pages/news/ jcaho/JCAHO%20Goal%206.ppt. Accessed June 30, 2004.
- Quinn ML. Semipractical alarms: a parable. J Clin Monit 1989;5:196-200.
- Coiera EW, Tombs VJ, Clutton-Brock TH. Attentional overload as a fundamental cause of human error in monitoring. August, 1996. Available on the web at: http://www.coiera.com/papers/attention.pdf. Accessed on June 30, 2004.
- Block FE Jr, Nuutinen L, Ballast B. Optimization of alarms: a study on alarm limits, alarm sounds, and false alarms, intended to reduce annoyance. J Clin Monit Comput 1999;15:75-83.
- Denisco RA, Drummond JN, Gravenstein JS. The effect of fatigue on the performance of a simulated anesthetic monitoring task. J Clin Monit 1987;3:22-4.
- Loeb RG. A measure of intraoperative attention to monitor displays. Anesth Analg 1993;76:337-41.
- ASTM International, F1850-00 Standard Specification for Particular Requirements for Anesthesia Workstations and Their Components. Available from most hospital biomedical engineering departments or on the web at: http://www.astm.org/cgi-bin/SoftCart.exe/ STORE/filtrexx40.cgi?U+mystore+smpn0109+L+ANESTHESIA+/usr6/htdocs/astm.org/DATABASE.CART/REDLINE_PAGES/F1850.htm. Accessed June 30, 2004.
- Medical Equipment Management Manual, R. H. Stiefel, AAMI, Arlington, VA, 2004, pp 47-49.
- Westenskow DR, Orr JA, Simon FH, et al. Intelligent alarms reduce anesthesiologist’s response time to critical faults. Anesthesiology 1992;77:1074-9.
- Navabi MJ, Watt RC, Hameroff ST, Mylrea KC. Integrated monitoring can detect critical events and improve alarm accuracy. J Clin Eng 1991;16:295-306.
- Goldman JM, Cordova MJ. Advanced clinical monitoring: considerations for real-time hemodynamic diagnostics. Proc Annu Symp Comput Appl Med Care 1994;:752-5.
- International Electrotechnical Commission (IEC) Standard 60601-1-8. Medical electrical equipment – Part 1-8: General requirements for safety – Collateral standard: General requirements, tests and guidance for alarm systems in medical electrical equipment and medical electrical systems. Available on the web at: http://domino.iec.ch/webstore/webstore.nsf/artnum/031024. Accessed June 30, 2004.
- Phelps EB, Goldman JM. Automated situational analysis for operating room anesthesia monitoring. Biomed Sci Instrum 1992;28:111-16.
- ASTM International. F1415-92 (2000) Standard Specification for Pulse Oximeters. Available on the web at: http://www.astm.org. Accessed June 30, 2004.
- International standard IEC 60601-1-8, section AAA.0.2
- Standards for Basic Anesthetic Monitoring. American Society of Anesthesiologists, Inc. Available on the web at: http://www.asahq.org/publicationsAndServices/standards/02.pdf#2. Accessed June 30, 2004.