Which statement best describes the Swiss cheese model in patient safety?

• A. Errors occur due to a single point of failure.
• B. Safety barriers are not necessary in preventing harm.
• C. Errors occur due to multiple latent and active failures; safety barriers must align to prevent harm.
• D. Active failures are always the sole cause of harm.

Answer: (C)

The Swiss cheese model focuses on how harm happens when multiple weaknesses in different defenses line up. Each safety layer—policies, procedures, equipment, training, teamwork, and so on—has holes or gaps. An error by a clinician is an active failure, but it often sits atop latent conditions like flawed design, communication problems, or staffing issues. When the holes across these layers align, a path through all defenses opens and harm can occur. Preventing harm means maintaining multiple safety barriers and addressing both the active errors and the underlying latent conditions so that a single mistake is unlikely to pass through all layers.

Single points of failure ignore how defenses stack and why failures are multifactorial. Saying safety barriers aren’t necessary is false because barriers reduce risk and catch mistakes. Saying active failures are the sole cause ignores the role of latent conditions and how barriers interact.