Patient Safety

Reliability: The Next Frontier in Patient Safety

by Dev Raheja, MS, CSP

Author: Safer Hospital Care 

Reliability is the next frontier in patient safety according to Dr. Carolyn Clancy, the former Director of the Agency for Healthcare Research and Quality (AHRQ) and current Assistant Deputy Undersecretary for Health, Quality, Safety and Value, veterans Health Administration. She gave this message as a keynote speaker at the Sixth Annual Forum and Gala of the Lucian Leape Institute of the National Patient Safety Foundation, held in Boston on September 12, 2013.

Hospitals are still far from being highly reliable is a similar high level warning from the Joint Commission, the premier hospital accreditation agency. In an article High-Reliability Health Care: Getting There from Here” written by The Joint Commission President and CEO Mark R. Chassin, M.D., M.P.H., and executive vice president for healthcare quality evaluation Jerod M. Loeb, Ph.D., they urge hospitals to make the substantial changes that will be needed to achieve the ultimate goal of zero patient harm by adapting lessons from high-risk industries. They report that “too many hospitals and health care leaders currently experience serious safety failures as routine and inevitable parts of daily work. To prevent the harm that results from these failures, which affects millions of Americans each year, the article specifies a framework for major changes involving leadership, safety culture and robust process improvement. This framework is designed to help hospitals make progress toward high reliability, which is the achievement of extremely high levels of safety that are maintained over long periods of time —safety comparable to that demonstrated by the commercial air travel, nuclear power, and amusement park industries.”

Reliability Theory Missing in Healthcare

Medical education usually does not cover the theory of reliability. One cannot blame hospitals to be going in different directions. The Institute of Healthcare Improvement (IHI) has taken the initiative to apply industry methods of system reliability to healthcare systems. It defines reliability as “failure-free performance over time. This is simple enough to be understood by anyone. The aim is to have no failures over an extended time period in spite of variability in the patient environment. This is in line with the technical definition of reliability as the probability of successful performance of intended functions for a specified length of time under a specified user (patient) environment. In a system where the severity of consequences is high, such as in hospitals, the goal is to achieve reliability as close to 100% as possible. This is called failure-free performance. Some hospitals have achieved this goal for specific medical procedures for several quarters. Can they extend this performance over years instead of quarters? That depends on many factors such as understanding reliability at senior management level, culture of innovation, effective teamwork, etc.

Roadblocks to Use of Reliability

The failures of the U.S. healthcare system are enormous considering the severity of failures. As much as 100,000 patients die each year from hospital mistakes. Another 2.1 million patients are harmed from nosocomial infections (infections acquired during hospital stay). The cost is in billions. There is very little incentive use reliability measures because the variability in healthcare is enormous compared to the aviation and industrial fields. Each customer (patient) is different and each illness is unique in its own way. Then there are interconnecting systems such as cardiology, gynecology, gastroenterology, emergency medicine, oncology, and patient data from various doctors, pagers, computers, vendor software, and intensive care, each operating independently most of the time.

Good Solutions are Available

We like to offer a good solution hoping that it will be good beginning to improve patient outcomes significantly. A good solution may be to apply system reliability methods to each critical intervention so that the variability is known. For example, if a protocol requires that a patient coming to the ED (emergency department) must get attention within ten minutes of arrival, then the performance can be defined as “patient must be registered with the triage nurse within 10 minutes.” A failure can be defined as “patient waiting longer than 10 minutes”. A woman in a New York hospital died while waiting for an hour in the emergency department. A blood clot in her leg traveled all the way to her brain. All 24 hours were recorded on the hospital video.

The time dimension for reliability can be defined in terms of calendar time such as every three months (quarterly) or every 1000 patients. Then reliability can be measured as the percentage of patients receiving service within 10 minutes during the quarter, or per 1000 patients. IHI is taking a similar approach for patients who need antibiotics within an hour after a surgical procedure; then reliability is measured as the ratio of number of patients receiving the antibiotic within an hour and the number of patients requiring this treatment.

Before we define system reliability, we need to define a medical system. It is a composite, at any level of complexity, of medical equipment, caregivers, medical procedures, lab work, environment, communications, and patients with a specified system mission.  Medical equipment includes CT, MRI, ventilators, artificial hearts, and dialysis machines. People include physicians, residents, interns, attendings, nursing staff, med techs, support associates, administrative personnel, patients, visitors.  Medical procedures include diagnosis, surgery, intensive care, intermediate care, lab procedures, intubations, intra-venous fluid infusions, patient visits, admittance, discharge, emergency patient processing, and trauma support. Communications include patient handoffs, verbal communications and communication among pharmacists, doctors, nurses, residents, patients, pagers, telephones, and computer screens.

Obviously, the mission is a safe and positive experience for patients. Therefore system reliability is the function of the integrated performance of all these. This model is pictorially shown in illustration below and is called a series system.  If any block in the system fails, the whole mission fails.

The chain shows that if any subsystem fails, the mission fails.

We can write the system reliability as the multiplication of all the subsystem reliabilities:

System Reliability = R(patient admittance) x R(diagnosis) x R(treatment) x R(post-discharge follow-up)

In this equation R stands for reliability. A hospital may modify the model if this model is not comprehensive. This model assumes that each of these four subsystems is independent of each other and each must work right. If not, the laws of conditional probability apply. For a calculation of conditional probability, please click here. Numerically, the system reliability in the above model for a defined time (yearly, over 3 years, etc) will then be:

System Reliability = (Percent patients admitted without harm or inconvenience) x (percent patients receiving the right diagnosis the first time) x (percent patients receiving satisfactory treatment) x (percent patients who follow the treatment regimen after discharge)

If the reliability of each of these four subsystems is 90 percent, the system reliability (chance that all of these will perform as intended) would be:

            .90 x .90 x .90 x .90 = .656 or 65.6 percent

To our knowledge no hospital is measuring reliability at the system level. Most of them are applying to a component of a system. The IHI is applying reliability measurements to components such as diagnoses, community acquired pneumonia, heart failure, acute myocardial infraction, hip/knee replacements, and bypass graft surgery. The reliability for each is simply the ratio of patients receiving the right care and the number of patients requiring the care. It may be noted that the system reliability model can be applied at the component level also as long as the components are functions of equipment, people, procedures, environments, and communications. The mission is still the same, safe and positive patient experience.

Contact the Author: Dev Raheja can be contacted at

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