Patient Safety Tip of the Week

February 22, 2011          Rethinking Alarms


We have written multiple columns on problems related to alarms. One year ago we did an extensive update after an alarm-related death in Boston (see our February 23, 2010 Patient Safety Tip of the Week “Alarm Issues in the News Again”). Last week the Boston Globe ran an excellent series (Kowalczyk 2011a, Kowalczyk 2011b) on problems related to alarms and especially the problem of alarm fatigue.


The Globe series focuses on alarm fatigue and efforts to reduce the number of alarms and, hence, the number of false alarms. It describes efforts that hospitals are implementing to prevent purposeful disabling of alarms and staffing changes to ensure alarms are heeded. It also discusses nascent efforts to develop alarm systems (“smart” alarms) that integrate multiple types of physiologic measurements to help better differentiate true emergencies from artifact.


But it is important to keep in mind that alarm fatigue is not the only problem that leads to patient harm when alarm systems are misused. Equally important is overreliance on alarms. All too often the critical clinical observation of patients takes a backseat because physicians and staff think “the alarm will alert me if there is a problem”.


A provocative article (Lynn 2011) on alarms and their failure to identify deteriorating patients early was also just published. The authors describe 3 patterns of unexpected in-hospital deaths and demonstrate the problems with threshold-based alarms (almost all currently used alarm systems use threshold-based principles) in detecting early deterioration. Indeed, they posit that threshold-based alarms themselves often cause us to miss signs of early deterioration. This is a fascinating perspective on identifying deteriorating patients early and, though it is a hard read at times, is well worth your time.


The first pattern of unexpected death is the most common and is typical of the deterioration seen in conditions like sepsis, CHF, and pulmonary embolism. Respiratory alkalosis develops. While this is usually due to an increase in respiratory rate, it is also due to an increase in tidal volume and seldom does the respiratory rate exceed common thresholds set (such as rates of 30/minute) for triggering alarms. Also, the changes in minute volume and the respiratory alkalosis shifting the oxyhemoglobin curve tend to keep oxygen saturations at high levels until late in the course. Hence, even continuous pulse oximetry may fail to alert providers to deteriorating clinical conditions and may lead to a false sense of security.


The authors also have a good discussion of how the commonly used, but arbitrary, threshold of 90% for oxygen saturation came about and became perpetuated.


The second pattern of deterioration they note is the classic CO2 narcosis. As CO2 rises one sees further central depression of respiration and a vicious cycle. However, as we have pointed out previously, it is not just respiratory rate that slows and it is notoriously difficult at the bedside to predict who is hypoventilating. The authors also note that in some cases benzodiazepines may suppress tidal volumes and respiratory rates may actually increase. This is a pattern for which we have advocated using a combination of sedation scales and capnography. However, the authors point out that such monitoring may be inadequate because many of these cases are complicated by the third pattern described below. The important point is that there may be a huge difference when the patient is awake and when he/she is asleep.


The third pattern is one that is typically seen in sleep apnea. In this pattern one sees repetitive reductions in airflow and oxygen saturation during sleep followed by arousals. The arousals rescue the patient but eventually the capacity or reserve of the patient to recover with arousals becomes impaired (often in response to narcotics or sedatives) and the patient may experience sudden death during sleep. The authors discuss the inability of currently used oximeters to recognize this pattern. They even imply that this pattern may give rise to oximeters alarming and being interpreted as “false” alarms attributed to motion artifact, etc. because when staff respond to the alarm the patient is now awake, breathing normally and has a normal oxygen saturation.


Warnings about this third pattern become even more concerning given the significant percentage of patients being admitted who are at risk for sleep apnea (see our What’s New in the Patient Safety World columns for November 2010 “More on Preoperative Screening for Obstructive Sleep Apnea” and July 2010 “Obstructive Sleep Apnea in the General Inpatient Population”).


In both the second and third patterns, use of supplemental oxygen may mask the deterioration, provide a false sense of security, and delay critical responses to a deteriorating clinical situation. Hence, it’s important not to use oxygen unless there is a legitimate indication for its use (see our January 4, 2011 Patient Safety Tip of the Week “Safer Use of PCA”).


The authors go on to discuss the flaws in current threshold-based alarm systems and the need for true “smart” alarms that integrate multiple physiological parameters and respond to patterns of changes in these. This article provides tremendous insight into why the concept of rapid response teams has proven disappointing to date. As we have mentioned in several of our own columns on rapid response teams, the problem is not with the response teams. Rather it is with our poor recognition of early clinical deterioration.




Checking alarms should be a regular component of your Patient Safety Walk Rounds. More importantly, it should be something your staff does daily on every unit that utilizes alarms of any type. Some units even do it on every shift. You should at least include alarm status as part of your structured handoff tool used at changes of shift. We also strongly recommend that any time you set up a new piece of equipment on a patient you use a checklist specific to that piece of equipment that forces you to verify that all alarms are appropriately set and functional and that parameters chosen are appropriate. We also recommend you review some of the useful tips we’ve included in our February 23, 2010 Patient Safety Tip of the Week “Alarm Issues in the News Again” and the several other columns noted below.



And if you are considering doing a FMEA (Failure Mode and Effects Analysis) on one or more of your alarm systems, an excellent resource is “Fault Tree Analysis of Clinical Alarms” (Hyman 2008). This is a great way of looking at the potential things that can go wrong, both technical and human, in each of multiple facets of any alarm system.




Prior Patient Safety Tips of the Week pertaining to alarm-related issues:




Prior Patient Safety Tips of the Week pertaining to early recognition of clinical deterioration:




Prior Patient Safety Tips of the Week pertaining to PCA and postoperative respiratory depression:








Kowalczyk L. For nurses, it’s a constant dash to respond to alarms. (first of two parts)

Boston Globe February 13, 2011



Kowalczyk L. No easy solutions for alarm fatigue. (second of two parts).

Boston Globe February 14, 2011



Lynn LA, Curry JP. Patterns of unexpected in-hospital deaths: a root cause analysis. Patient Safety in Surgery 2011, 5:3 (11 February 2011)



Hyman WA, Johnson E. Fault Tree Analysis of Clinical Alarms. Journal of Clinical Engineering 2008; 33(2) 85-94














Patient Safety Tip of the Week Archive


What’s New in the Patient Safety World Archive