Focus on systems not people

In a medical diagnostics company, an engineering manager was charged with the task of improving the reliability of a blood gas analyzer which broke down too often. He kept asserting that failures were due to customer misuse. This was somewhat convenient since if this were accepted by management, then no action was required by the engineering manager. However, management asserted that an improved design focusing on ease of use and better instruction manuals (these documents were provided by engineering) would reduce customer misuse.

In a similar fashion, if a person in a hospital has committed an error that leads to patient injury or death, one could argue that better people and / or more training is needed. This is the “people” solution which may at times be valid. However the systems solution may be more appropriate. Consider a real example.

“A hospitalized patient was connected to a portable blood pressure (BP) monitoring device was transported to radiology for an MRI.. A length of tubing that led from the monitor’s BP cuff inflator had a male Luer connector. This fit into a female connector on a shorter length of white tubing that was integrated with a Critikon disposable BP cuff. The tubing and cuff were disconnected before the MRI since the Luer connector on the monitor’s tubing was metal. After the test, a radiology employee reconnected the tubing and transported the patient back to his room. Upon arrival, a family member immediately noticed that the tubing from the monitor was attached incorrectly to a needleless Y-injection port on the patient’s IV line! A nurse was contacted and she quickly disconnected the tubing. Normally, the device cycles at preset intervals, inflating the cuff with more than 500 mL of air at pressures up to 300 mm Hg. If no resistance is met with an inflated cuff, two additional cycles quickly occur. Thus, more than 1,500 mL of air might have entered the patient’s vascular system. Fortunately, this did not happen, as the machine had not yet cycled to take a BP reading. Another patient was not as lucky. In that case, the patient died from an air embolism after a nurse mistakenly connected the monitor tubing to his IV line.” (1) Reproduced with permission from ISMP Medication Safety Alert! June 12, 2003.

Some potential mitigations to prevent this error include:

  1. provide training to all relevant staff to make them aware of the issue
  2. label all BP and IV connectors with a warning message
  3. change all BP connectors, making it impossible for them to be connected to an IV line

These mitigations illustrate the spectrum from focusing on a people solution (1) to a systems solution (3). Solution 2 can be thought of as a combination of people and systems. Solution 3 follows Ralph Evans advice of make it easy to do the right thing and hard to do the wrong thing but is probably more expensive since it would involve replacement or modification of existing equipment.


  1. From the Institute of Safe Medication web site, accessed 4/29/04

Addition reading (References based discussion with Michael Astion, MD, Ph.D., University of Washington) 3/12/2005

  1. Reason, J. Human error: Models and management BMJ 2000;320:768-770
  2. Marx, D. Patient Safety and the “Just Culture”: A Primer for Health Care Executives

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: