A visual alert level in CUSUM analysis is a predefined horizontal line drawn on the chart that serves as a trigger point for clinical or educational attention.

It does not always correspond to formal statistical thresholds but is used as a practical tool to:

• Highlight when performance may be deteriorating
• Prompt early review or feedback
• Enhance interpretability for supervisors, trainees, or quality officers

In the CUSUM chart:

• The y-axis represents the cumulative deviation from expected performance.
• The x-axis represents sequential cases.
• A horizontal dashed line (e.g., at 2.5) indicates the alert threshold.

When the CUSUM curve crosses this level, it visually suggests that the number or magnitude of complications exceeds the acceptable trend.

• Offers a quick and intuitive signal for clinical educators and QA teams
• Simplifies decision-making during resident supervision
• Acts as a communication tool in performance reviews and morbidity & mortality (M&M) meetings
• Encourages proactive action rather than reactive analysis

In our ICP monitor placement example:

• Target complication rate: k = 0.1
• Visual alert level: CUSUM ≥ 2.5
• The CUSUM curve approached this line during the first 12 cases but remained below it, suggesting early variability followed by stabilization.

Visual alert levels can be adjusted based on:

• Procedure risk profile
• Surgeon experience level
• Institutional quality standards

They serve not as punitive thresholds, but as safety-oriented prompts to reflect and improve.