Further discussion of the roles of each phase is outside the remit of this text. It is sufficient to note that all are needed for basic psychological well being. Interruptions, such as those encountered during an on-call shift, will impact differently depending on where they occur in the cycle. It is also important to note that, during an on-call period, an individual’s ability to resume good cognitive function varies significantly. This ability is usually regained promptly when waking from light sleep, but will take several minutes if deep sleep is interrupted.
Many external factors affect the quality of sleep we achieve. The best quality sleep will be achieved in a quiet, dark, cool room, without interruption. However, even under ideal conditions, insomnia or more minor disturbance may occur, secondarily to stress. Stress can be negative or positive in nature, that is both excitement and apprehension regarding a forthcoming event may impact on wakefulness. It is also well known that clinical depression can result in reduced sleep. Perhaps less well known is that disturbance may occur from sleeping with a restless, depressed partner. It is important to note that intoxicating substances that appear to promote sleep, such as alcohol, have a significant impact on the normal cycles described above and frequently result in poor-quality sleep.
Fatigue
A useful definition of fatigue is difficult to capture. Other authors have made reference to Caldwell and Caldwell’s (2003) definition, which is, ‘The state of tiredness that is associated with long hours of work, prolonged periods without sleep, or requirements to work at times that are ‘out of synch’ with the body’s biological or circadian rhythm.’ The effects of fatigue are shown in Box 8.1.
- adverse effect on innovative thinking and flexible decision making
- reduced ability to cope with unforeseen rapid changes
- reduced ability to adjust plans when new information becomes available
- tendency to adopt more rigid thinking and previous solutions
- lower standards of performance become acceptable
- less effective coordination
- poor timing
- difficulty in finding and delivering the correct word
- speech is less expressive
- increasingly withdrawn
- more acceptance of own errors
- less tolerant of others
- neglect smaller tasks
- less likely to converse
- increasingly irritable
- increasingly distracted by discomfort
Stress
Stress is a familiar concept; we will describe it as, ‘the effects of subjective emotion upon human physiology and performance,’ for the purpose of this discussion. The term ‘stress’ is generally utilised in a negative context. However, it can be both a positive and negative phenomenon. The degree of stress that an individual experiences is a product of the balance between the stressors an individual is exposed to and the resources they have to deal with those stressors. It is important to note that the degree of stress is entirely subjective. One person presented with a set of stressors and resources may not experience the same reaction compared with another faced with exactly the same scenario. Strictly speaking, this difference is due to an individual’s personality, since any differences in training or experience between two people would mean that their resources were not matched.
The ‘balance’ model of stress is useful as it is conceptually simple, illustrating both the positive and negative effects of stress. It has been presented graphically by Flin et al. (2008) and a modified version is shown in Figure 8.2 overleaf.
Figure 8.2 Balance model of stress
(modified from Flin et al. 2008).
(a) All in balance. (b) All in balance in those who thrive in challenging situations. (c) All in balance for those who struggle in challenging situations. (d) Out of balance – too much to cope with.
In the balanced diagrams, the individual’s perception of the balance of stressors and resources is such that they feel comfortable and their performance is optimal. For some, this balance might be represented by a position that feels challenging but achievable. For others, the balance will only be achieved where stressors and resources are in equipoise. In the final diagram, the individual perceives an excess of stressors over resources. If this is sustained, a negative attitude develops that itself feeds back into the stressor pool and effectively initiates a downward spiral. At the other extreme (not shown), resources are in abundance. Here the task becomes too easy and a feeling of boredom ensues. At either end of the scale, an individual may lose their situation awareness because of unfocused panic or inattention.
An individual can experience stress in either acute or chronic scenarios. While the balance model works for both, it is important to recognise that the impact on the individual may be different. Acute stress is short term, occurring secondarily to a sudden, unexpected event. It may interfere with normal functioning, resulting in non-ideal or even dangerous decisions being made in response to an unravelling scenario. However, it is also a time where some will find hidden depths and perform exceptionally. Once the situation resolves, the individual returns to their normal functioning level. By contrast, chronic stress arises from an array of long-term stressors that the individual feels they have insufficient resources to address. This person is likely to have their performance compromised on a daily basis. The deficit may be quite insidious and pervade all aspects of their life.
A major component of the application of human factors principles is to try to prevent acutely stressful events occurring or, where they are inevitable, to provide training in order to minimise the negative effects on the individuals involved.
Some of the commonest manifestations of chronic stress are shown in Box 8.2. Their appearance in either oneself or one’s colleagues should promote a search for the causal factors so that, where possible, they can be mitigated.
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