<p><strong>AIM AND OBJECTIVE: </strong>The purpose of this study was to explore clinical reasoning about alarm customization among nurses in intensive care units.</p>

<p><strong>BACKGROUND: </strong>Critical care nurses are responsible for detecting and rapidly acting upon changes in patients' clinical condition. Nurses use medical devices including bedside physiologic monitors to assist them in their practice. Customizing alarm settings on these devices can help nurses better monitor their patients and reduce the number of clinically irrelevant alarms. As a result, customization may also help address the problem of alarm fatigue. However, little is known about nurses' clinical reasoning with respect to customizing physiologic monitor alarm settings.</p>

<p><strong>DESIGN: </strong>This article is an in-depth report of the qualitative arm of a mixed methods study conducted using an interpretive descriptive methodological approach.</p>

<p><strong>METHODS: </strong>Twenty-seven nurses were purposively sampled from three intensive care units in an academic medical center. Semi-structured interviews were conducted by telephone and were analyzed using thematic analysis. Consolidated Criteria for Reporting Qualitative Research (COREQ) reporting guidelines were used.</p>

<p><strong>RESULTS: </strong>Four themes were identified from the interview data: unit alarm culture and context, nurse attributes, motivation to customize, and customization "know-how." A conceptual model demonstrating the relationship of these themes was developed to portray the factors that affect nurses' customization of alarms.</p>

<p><strong>CONCLUSIONS: </strong>In addition to drawing on clinical data, nurses customized physiologic monitor alarms based on their level of clinical expertise and comfort. Nurses were influenced by the alarm culture on their clinical unit and colleagues' and patients' responses to alarms, as well as their own technical understanding of the physiologic monitors.</p>

<p><strong>RELEVANCE TO CLINICAL PRACTICE: </strong>The results of this study can be used to design strategies to support the application of clinical reasoning to alarm management, which may contribute to more appropriate alarm customization practices and improvements in safety. This article is protected by copyright. All rights reserved.</p>

<p><strong>BACKGROUND: </strong>Customizing monitor alarm settings to individual patients can reduce alarm fatigue in intensive care units (ICUs), but has not been widely studied.</p>

<p><strong>OBJECTIVES: </strong>To understand ICU nurses' approaches to customization of electrocardiographic (ECG) monitor alarms.</p>

<p><strong>METHODS: </strong>A convergent mixed methods study was conducted in 3 ICUs in 1 hospital. Data on the type and frequency of ECG alarm customization were collected from patient monitors (n=298). Nurses' customization clinical reasoning was explored through semi-structured interviews (n=27).</p>

<p><strong>RESULTS: </strong>Of the 298 patients, 58.7% had ≥1 alarm(s) customized. Heart rate limits, irregular heart rate, and atrial fibrillation were the most commonly customized alarms. Interviews revealed that customization practices varied widely and were influenced by factors including clinical expertise, lack of customization education, and negative experiences.</p>

<p><strong>CONCLUSION: </strong>Alarm customization is nuanced and requires adequate support to develop safe and effective practices. The challenges identified can inform development of strategies to improve alarm customization.</p>