# Table 1

Interpretation of the Swiss cheese model of medical error by 85 professionals who claimed to be fairly or very familiar with the model.

Compatibility with Swiss cheese model

N (%) endorsing statement

In your opinion, what does a slice of cheese represent?

A health care professional

Sometimes3

14 (16.5)

-

A barrier that protects patients from harm

yes

61 (71.8)

71.8

A root cause of an error

no

9 (10.6)

89.4

A procedure that alleviates the consequences of an error

yes

14 (16.5)

16.5

A defence that prevents the occurrence of an error

yes

52 (61.2)

61.2

In your opinion, what does a hole represent?

A latent error1

yes

28 (32.9)

32.9

A loss (in terms of health or money) due to an error

no

5 (5.9)

94.1

An opportunity for error

yes

53 (62.4)

62.4

A weakness in defences against error

yes

54 (63.5)

63.5

An unsafe act

yes

17 (20.0)

20.0

What does the arrow represent?

The patient's trajectory through the health care system

no

29 (34.1)

65.9

A transfer of energy that injures a patient

no

2 (2.4)

97.6

The transformation of a latent error1 into an active error2

no

24 (28.2)

71.8

The series of events leading to a medical error

Sometimes4

51 (60.0)

-

The path from hazard to patient harm

yes

41 (48.2)

48.2

How or where is an active error represented on this figure?

At the base (origin) of the arrow

no

10 (11.8)

88.2

At the tip of the arrow

no

24 (28.2)

71.8

As one of the holes

yes

26 (30.6)

30.6

As the arrow itself

no

24 (28.2)

71.8

As the alignment of holes

no

28 (32.9)

67.1

How can we make the health care system safer, using the "Swiss cheese" metaphor?

By adding a slice of cheese

yes

27 (31.8)

31.8

By removing a slice of cheese

no

6 (7.1)

92.9

By plugging a hole

yes

76 (89.4)

89.4

no

1 (1.2)

98.8

By making all slices thinner

no

6 (7.1)

92.9

1 Latent error: Failure of system design that increases the probability of harmful events. Loosely equivalent to causal factor or contributing factor.

2 Active error: Error (of commission or omission) committed at the interface between a human and a complex system.

3 A professional whose role is to make the process of care safer may be thought of as a protective barrier

4 This would be true if the error equates with patient harm, as in the case of wrong site surgery

Perneger BMC Health Services Research 2005 5:71   doi:10.1186/1472-6963-5-71