Post-CABG Smart Alarm

The Intensive Care Unit of most major hospitals is a noisy environment. In order to monitor patients, healthcare practitioners set threshold alarms on each of many individual vital sign monitors. While nurses themselves rarely consider one vital sign in isolation, the current alarm algorithms elicit numerous false positive alarms by only examining each vital sign individually. The lack of clinical relevancy in a majority of these alarms produces an inefficient healthcare system, where nurses habitually ignore low level alarms due to their overabundance.

This Smart Alarms project consists of an alarm algorithm that considers multiple vital signs when monitoring a post coronary artery bypass graft (post-CABG) surgery patient. The nature of this condition enables the algorithm to focus on monitoring four vital signs: blood pressure, heart rate, respiration rate, and oxygen saturation rate. This solution constructs a new, three level alarm priority system that more efficiently communicates the clinical severity of the problem based on the needs and requests of current healthcare practitioners. As a result, this multivariate approach decreases clinical false alarms.

The algorithm takes the input of four vital signs from three monitors and employs a Fuzzy Expert System to mimic the decision processes of nurses. In addition, the algorithm includes a Clinical Decision Support tool that employs Bayesian theory to display the possible CABG-related complications the patient might be undergoing at any point in time, as well as the most relevant risk factors.

Objectives

  • Develop an alarm algorithm that considers multiple vital signs when monitoring a post coronary artery bypass graft patient.
  • Decrease the number of total alarms and of false alarms by vital sign monitors by 25% without creating additional false negatives. For the purposes of system validation in this project, false alarms are defined as those resulting in no clinical intervention.
  • Create a new, three level alarm priority system that more efficiently communicates the clinical severity of the problem.

Clinical Background

Coronary Artery Bypass Graft (CABG) surgery is a common surgical procedure in which arteries from elsewhere in a patient's body are grafted to the coronary arteries to bypass narrowings and improve blood supply to the heart. A common surgery, 427,000 CABG surgeries are performed every year in the United States. Following surgery, patients are moved to the ICU for observation. During this period, due to the large amount of movement, changes in the patient's position, etc, there are often hundreds of false alarms.

As these patients are common, their demographics fairly uniform, and their false alarm rate notably high, they were targeted for a smart alarm effort.

Data Collection

Penn Presbyterian Medical Center

The smart alarm manager was initially tested using retrospective vital sign and contextual data from de-identified PMC surgical ICU patients. The data was obtained with IRB approval (Protocol #811401). This process involved identifying patients who had had CABG surgery, collecting their vital signs retrospectively, and having clinicians annotate the data when alarms occurred.

PhysioNet

Further primary validation on a larger cohort was performed on clinical data obtained from the PhysioNet.org online databank.

Further Validation

Further validation is being performed on prospective patient data, including observation of nurse behavior to determine whether individual threshold alarms are considered false alarms (not useful) during care.

Results

The original monitor interface.

The Smart Alarm Monitor improves upon existing patient monitors by including color-coded alarm message boxes and by adding a clinical decision support tool that displays, in order of likelihood, the possible complications and the underlying risk factors present in the patient’s medical history.

A graph of alarm reduction.

Results from both the PMC data and Physionet show a substancial decrease in the number of false alarms with no change in false negatives, or missed alarms.