Frequency and reliability of alarms in the monitoring of cardiac postoperative patients

Postoperative monitoring of cardiac operated patients requires appropriately functioning monitor alarms as well as intensive nursing activity. The limit alarms can be used for detection of life-threatening situations and monitoring of physiological changes in the patient's state. We studied the significance and the frequency of audible alarms during the postoperative intensive care of ten cardiac patients. Of 1307 occasions when such an alarm was activated during the study period of approximately 26 hours per patient, only 139 (10.6%) were significant. The highest proportion of significant audible limit alarms was found during the immediate postoperative period. Heart rate alarms were more reliable than alarms of the other parameters monitored in the study. Possibilities for improving the physiological monitoring and alarm system are discussed.     

Clinicians' opinions on alarm limits and urgency of therapeutic responses

To survey the routine use of bedside multivariable monitors in monitoring cardiac postoperative patients, 23 experienced anesthesiologists and cardiac surgeons were first asked to list which variables and what limit alarms they used. Then they defined to what extent the variables' values were allowed to deviate before therapeutic actions were needed. Typically, limit alarms were applied to heart rate and end-tidal CO₂. For clinical assessment of a patient's state, the clinicians usually observed the heart rate and the systemic arterial blood pressures, but placed less emphasis on the pulmonary arterial pressures. Clinicians had similar opinions on alert limits for monitoring less extensive physiological deviations and on alarm limits for warning of a critical situation. Person-to-person tolerance of suboptimal monitored values varied.No correlation was found between the limit values and how long these values were tolerated without therapeutic response. However, the inquiry provided information on setting limits for alerts and alarms, and on experienced clinicians' decision-making during postoperative intensive care of cardiac patients.     

A knowledge-based alarm system for monitoring cardiac operated patients-assessment of clinical performance

An intelligent alarm system for the postoperative monitoring of cardiac surgery patients, which did not require any manual data entries, was tested in two phases. A clinician monitored at bedside the patients' recovery and verified clinically abnormal physiological states. After the first test with ten patients, the system's rulebase was upgraded and then tested with an additional 15 patients. The alarm system employed two PC/ATs and was programmed to give notive of four pathological states (hyperdynamic state, hypovolemic state, hypoventilation and left ventricular failure) at two levels of urgency (alarm and alert levels). The monitoring lasted 5.4±1.7 hours per patient (mean ±S.D.), totalling 134.7 hours. The system alarmed 27 times during the first and 73 times during the second phase of the testing. The sensitivity of the alarms was 100% in both phases, and the specificities increased from 20.0% to 73.9% and from 59.1% to 70.0% for the alarms and the alerts, respectively. This computerized decision support system based exclusively on data available in the automatically collected data base had a low false positive rate and gave early warnings about pathological states in the homogeneous group of adult postoperative cardiac patients.     

The Application of a Modified Proportional-Derivative Control Algorithm to Arterial Pressure Alarms in Anesthesiology

Objective. We have developed an arterial pressure alarm system based on a modified proportional-derivative (PD) controller algorithm, and prospectively tested its ability to predict significant hypotensive episodes, defined as systolic arterial pressure <80 mmHg, in comparison to conventional limit alarms. Methods. The alarm algorithm was tuned to detect hypotension using selected invasive arterial pressure traces taken from ten patients who had large intra-operative arterial pressure changes. The algorithm's performance was then tested prospectively in comparison to conventional limit alarms and median filtered limit alarms, set at 85 mmHg and 90 mmHg, for its ability to predict hypotensive episodes in a further 100 patients who required invasive arterial pressure monitoring. Results. For the PD alarm algorithm, onset times for significant hypotensive episodes were between those of limit alarms set at 85 mmHg and 90 mmHg. Offset times were similar to the 85 mmHg limit alarms. The false positive rate was 34% compared with 45–64% for the other alarms (p < 0.01). Using our definitions, there was one false negative in the PD group, being a 15 second drop in observed arterial pressure, when a non invasive blood pressure cuff was inflated above the arterial line. Conclusions. An arterial pressure alarm system design based on a closed loop control algorithm offered improved performance over conventional limit alarms and in addition provided a graded output of severity of the hypotension.     

Effect of bundle set interventions on physiologic alarms and alarm fatigue in an intensive care unit: A quality improvement project

ObjectiveTo determine if the implementation of an evidence-based bundle designed to reduce the number of physiologic monitor alarms reduces alarm fatigue in intensive care nurses.DesignThis quality improvement project retrospectively reviewed alarm data rates, types, and frequency to identify the top three problematic physiologic alarms in an intensive care unit. An alarm management bundle was implemented to reduce the number of alarms. The Nurses’ Alarm Fatigue Questionnaire was used to measure nurses’ alarms fatigue pre- and post-implementation of the bundle.SettingA combined medical surgical intensive care unit at an accredited hospital in the United States.ResultsThe top three problematic alarms identified during the pre-implementation phase were arrhythmia, invasive blood pressure, and respiration alarms. All three identified problematic physiologic alarms had a reduction in frequency with arrhythmia alarms demonstrating the largest decrease in frequency (46.82%). When measuring alarm fatigue, the overall total scores increased from pre- (M = 30.59, SD = 5.56) to post-implementation (M = 32.60, SD = 4.84) indicating no significant difference between the two periods.ConclusionAfter implementing an alarm management bundle, all three identified problematic physiologic alarms decreased in frequency. Despite the reduction in these alarms, there was not a reduction in nurses’ alarm fatigue.     

Whats that noise? Bedside monitoring in the Emergency Department

ObjectiveTo determine the frequency, duration and type of audible monitor alarms in an ED, utilising the standard manufacturer’s classification.MethodsThe audible monitor alarms and the timing of any intervention related to the patient monitoring was observed and recorded.Results110 Patients admitted to the Majors area or Resuscitation Room were observed for a total of 93 hours. One monitor was observed at a time. Alarm noise was generated 29% of the observation time. Overall, 429 alarms lasting 21 hours 27 minutes were judged to be positive and 143 alarms lasting 5 hours 47 minutes, negative. 74% of Resuscitation Room and 47% of Majors alarms were silenced or paused. Alarm limit parameters were only adjusted after 5% of alarms in Resuscitation Room and 6% of alarms in Majors.ConclusionsWhilst high level monitoring is desired from a patient safety perspective, it contributes to a significant ambient noise level, which is recognised by all who pass through an ED, and can be detrimental to patients, relatives and staff. We have demonstrated that there is a high probability of near-continuous alarm noise from patient monitoring in a 10-bedded Majors area. We make suggestions for methods of noise reduction and intend to implement some of these within our own ED.     

Respiratory monitoring during postoperative analgesia

Respiratory monitoring, using a novel flow sensor based on an acoustic principle, has been investigated in 30 patients during postoperative analgesia. Each patient was subjected to monitoring and human observation for 8 hr. The study was performed by independent observers at three clinics. Significant correlation was noted between respiratory rate (RR) determined by the sensor and the observers. Recordings of respiratory duration index (RDI), breathing time intervals (BTIs) indicated high sensitivity of the instrument to respiratory depression and perturbations in the breathing rhythm. More than 800 apnea alarms were noted, using an alarm setting of 30 sec; 61% of the categorized alarms were noted by the observers as true apneas. From the recordings it was shown that the number of alarms can be reduced by a factor of four if the alarm setting is changed to 45 sec. We conclude that the suggested technique, with slight modifications, provides adequate respiratory monitoring of patients during post-operative analgesia.     

An expert system for monitor alarm integration

Objective. Intensive care and operating room monitors generate data that are not fully utilized. False alarms are so frequent that attending personnel tends to disconnect them. We developed an expert system that could select and validate alarms by integration of seven vital signs monitored on-line from cardiac surgical patients. Methods. The system uses fuzzy logic and is able to work under incomplete or noisy information conditions. Patient status is inferred every 2 seconds from the analysis and integration of the variables and a unified alarm message is displayed on the screen. The proposed structure was implemented on a personal computer for simultaneous automatic surveillance of up to 9 patients. The system was compared with standard monitors (SpaceLabsTM PC2), using their default alarm settings. Twenty patients undergoing cardiac surgery were studied, while we ran our system and the standard monitor simultaneously. The number of alarms triggered by each system and their accuracy and relevance were compared. Two expert observers (one physician, one engineer) ascertained each alarm reported by each system as true or false. Results. Seventy-five percent of the alarms reported by the standard monitors were false, while less than 1% of those reported by the expert system were false. Sensitivity of the standard monitors was 79% and sensitivity of the expert system was 92%. Positive predictive value was 31% for the standard monitors and 97% for the expert system. Conclusions. Integration of information from several sources improved the reliability of alarms and markedly decreased the frequency of false alarms. Fuzzy logic may become a powerful tool for integration of physiological data.     

品管圈管理工具在减少ICU床旁监护仪误报警应用效果

目的 探讨品管圈管理工具在减少重症加强护理病房(ICU)床旁监护仪误报警应用效果.方法 纳入2018年1月—2019年12月98例ICU患者,其中2018年1—12月实施品管圈管理前共48例为对照组,2019年1—12月实施品管圈管理共50例为观察组,参与品管圈活动护士共7名.设定品管圈名为"HOPE圈",以"采用品管...     

Are auditory warnings in the intensive care unit properly adjusted?

The purpose of this study was to determine whether auditory warnings in the intensive care unit (ICU) were properly adjusted. An intervention study (before- and-after assessment) was conducted in a 12-bed medical-surgical ICU of an acute-care teaching hospital in Barcelona, Spain. A total of 100 patients with stable haemodynamic and respiratory parameters were included. In the first 3-month phase of the study, minimum and maximum alarm parameters of breathing rate, expired volume/min, airway pressure, SaO(2), arterial blood pressure and heart rate were recorded. In the second 12-month phase of the study, the same alarm parameters were recorded every 4 hours in the patient's medical record. In the third 3-month phase of the study, alarm readings were recorded again as in the first phase. The change throughout coefficient of variation (CV) and the 95% confidence interval (CI) for each alarm were calculated. Following the intervention, there was a statistically significant improvement in alarm readings for expired volume, heart rate and systolic blood pressure, so that alarms had been more properly adjusted to the patient's real value. Nursing staff should be aware that auditory warnings in ICU stable patients are frequently set very far from suitable values. Recording of alarm parameters in the patient's medical record as a routine daily activity was an effective intervention for improving adjustment of auditory warnings.     

Carbon monoxide … the silent killer with an audible solution

Carbon monoxide (CO) is responsible for more poisoning fatalities each year than any other toxic agent. The often insidious nature of the symptom progression and its ability to imitate many common illnesses may result in the failure to diagnose a potentially fatal outcome. CO detectors equipped with an audible alarm can alert potential victims of CO poisoning before toxic sequelae develop. A study was conducted in which all calls to 911 concerning a CO detector in alarm or regarding possible CO poisoning were investigated by a paramedic crew; 101 possible CO exposures were investigated. CO detectors with audible alarms were the genesis of 59.4% of the calls. Detectable CO levels were found in 69.3% of the investigations, and 80% of the homes with detectors had verifiable CO concentrations. The mean CO concentration in homes with detectors was 18.6 ppm, compared with 96.6 ppm when no detector was available; 63.4% of the victims with no alarm were symptomatic, compared with 13.3% of victims with alarms. CO detectors with audible alarms were effective in alerting the potential victims of CO poisoning to its presence. Persons with CO detectors were less likely to become symptomatic from a CO exposure than those who did not have CO detectors.     

Influence of Pulse Oximeter Settings on the Frequency of Alarms and Detection of Hypoxemia

Objective. The potential benefit of a reduced frequency of false pulse oximeter low oxyhemoglobin saturation (SpO₂) alarms is that the attention of personnel is only directed to patients who experience hypoxemia. The present study was undertaken to better understand the effects of different settings of the pulse oximeter on false (artifact) and true (hypoxemia) alarms. Methods. Using the original SpO₂ data of 200 postoperative patients, we calculated off-line the effects of five methods (artifact rejection, alarm delay (2–44 s, 2 s increments), averaging (10–90 s), median filtering (10–90 s) and decreasing the alarm limit from 90% to 85%) on the number of (true- and false) alarms. Results. 830 episodes of hypoxemia (SpO₂ 90%) and 73 episodes of severe hypoxemia (SpO₂ 85%) occurred. With a SpO₂ alarm limit of 90%, the alarm was triggered 1535 times (830 true, 705 false). Artifact rejection reduced alarms by almost 50%. An alarm delay of 6 s or an averaging or median filtering epoch of 10 s resulted in an alarm reduction of almost 50%. No differences were found in the reduction of alarms between averaging and median filtering. Changing the alarm limit to 85% reduced the number of alarms by 82%. A similar reduction of alarms was obtained with either an alarm delay of 18 s or an averaging or median filtering epoch of 42 s. However, an alarm limit of 85% reduced the number of false alarms less than the other three algorithms (p < 0.01). Conclusions. The data from the present study suggest that in order to effectively suppress false alarms caused by pulse oximeter artifacts, it may be preferable to use a longer filtering epoch of approximately 40 s, rather than to decrease the lower alarm limit.     

Clinical alarms: improving efficiency and effectiveness

The clinical environment contains a plethora of bells, beeps, and buzzers. As clinicians, each audible disruption in the care environment must be analyzed to decide if the sound or visual is clinically significant. Alarms may signal a clinically significant change in a patient's condition (true positive), an alarm violation that is clinically insignificant (false positive), or a reflection of poorly set monitoring parameters. Our challenge is to develop monitors that are sensitive and specific. This coupled with protocols that are designed for a specific population, and customized for each individual patient, enable the caregiver to maximize the use of monitoring systems and ensure patient safety. This article guides the critical care nurse through an assessment of alarms in the critical care environment, beyond the cardiorespiratory alarms, assessing the impact of clinical and environmental alarms.     

Preliminary clinical trials of a computer-based cardiac arrest alarm

The use of a high reliability cardiac arrest alarm utilising the continuously monitored values of patient heart rate and mean arterial blood pressure is described, based on a sample of 167 patients monitored for a total of 5116h. The analogue heart rate and mean blood pressure signals are sampled at 1 s intervals, and a smoothing algorithm is applied to each of the resulting series which rejects artefacts, and identifies slope and step changes in each. Certain combinations of events in the 2 series, occurring within a preset time window, determine whether a cardiac arrest alarm or warning signal should be activated by the system. A total of 30 acute events occurring in 14 patients during the course of the study were each identified within 10s. No cardiac arrest event was misdiagnosed by the algorithm during the period of the study. The algorithm also generates warnings which may have predictive value, and which will be the subject of further research. A final false alarm rate of about 1/200 h of monitoring was observed in adults (1/50 h in children), with evidence that these rates could be substantially improved.     

The Problem of Alarm Fatigue

Up to 99 percent of alarms sounding on hospital units are false alarms signaling no real danger to patients. These false alarms can lead to alarm fatigue and alarm burden, and may divert health care providers’ attention away from significant alarms heralding actual or impending harm. As the health care environment continues to become more dependent upon technological monitoring devices used for patient care, nurses must become aware of the possibility and consequences of alarm fatigue and ways to prevent it from negatively affecting their practice, as well as the possible consequences for patient care.