FAST™ ANALYSIS OF CURRENT AND PROPOSED RNZN WATCH KEEPING ROUTINES HELEN KILDING.

FAST™ ANALYSIS OF CURRENT AND PROPOSED RNZN WATCH KEEPING ROUTINES

HELEN KILDING

Only soft people sleep!

Captain Johnny WalkerStayed awake for days on end in his relentless pursuit of U boats

Died aged 48 of overstrain, overwork and war weariness….a hero but a dead one!

The Officer of the Watch

• Responsible for the safety of the ship and it’s company 24/7

• Must maintain vigilance, efficiency and alertness while on watch….

• …..and then do their normal ‘day’ job.

Fatigue at Sea

• Paul et al. (2012) evaluated fleet watch schedules on board a Royal Canadian Navy patrol frigate and found “worrisome levels of modelled cognitive performance equivalent to intoxicated levels of blood alcohol (BAC > 0.05%)”

• The consequences of fatigue are not only felt in terms of impaired performance and reduced safety, but decreased wellbeing and increased risk of ill health (Spurgeon et al. 1997).

Fatigue Mitigation

• To better forecast and thus mitigate fatigue, various models have been developed.

• The Fatigue Avoidance Scheduling Tool (FAST™) is a commercially available Windows program based upon the SAFTE applied model originally developed for USAF.

• FAST™ estimates the average effects of a work-rest schedule on human cognitive performance, based on information supplied about an individual’s work and sleep patterns.

Example FAST™ output

Dashed blue line = the predicted 10th percentile response.

Thick blue sections = sleep

Thick black sections = work periods

Overall trace is predicted cognitive effectiveness

Example FAST™ output

Dashed black line is the criterion line for acceptable performance - 77.5% (BAC of 0.05%)

Red zone is the danger zone representing <65% effectiveness

Green zone = ideal performance. Under normal circumstances, performance only dips in to the yellow zone during normal sleep hours.

Fatigue Mitigation in the NZDF

• RNZAF currently utilises FAST™ to help plan flight schedules and work shifts for its aircrew and maintenance teams, with positive results.

• RNZN approached DTA to provide an objective evaluation of current versus alternate watch keeping strategies to:

1) Predict the % performance effectiveness and equivalent blood alcohol level of watch keepers employed in one of six watch keeping routines over a 6 day period

2) Establish the efficacy of strategies such as naps and extended sleep periods on % performance effectiveness.

Thank you

[email protected]

0000 0200 0400 0600 0800 1000 1200 1400 1600 1800 2000 2200

1ST DOG LAST DOG

Day 1Day 2Day 3Day 4Day 5Day 6

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1ST DOG LAST DOG


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1ST DOG LAST DOG


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1ST DOG LAST DOG


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1ST DOG LAST DOG


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1ST DOG LAST DOG


Schedule 2: 1 in 3 Split Dogs

Schedule 3: 1 in 3 West Country

Schedule 1: Standing 1 in 3


MIDDLE MORNING FORENOON AFTERNOON FIRST

AFTERNOON FIRST

FIRST MIDDLE MORNING FORENOON AFTERNOON

MIDDLE MORNING FORENOON

Thank you

[email protected]

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1ST DOG LAST DOG


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1ST DOG LAST DOG


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1ST DOG LAST DOG


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1ST DOG LAST DOG


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1ST DOG LAST DOG


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1ST DOG LAST DOG


Schedule 5: Circadian 1 in 3 (proposed)

Schedule 6: Circadian 1 in 4 (proposed)


MIDDLE MORNING FORENOON AFTERNOON



FIRST

Schedule Analysis

• Each schedule was entered in to the FAST™ software (along with likely wake and sleep times and sleep quality).

• FAST™ outputs for each schedule were compared based on:

Time spent below an acceptable fatigue threshold* while on watch

Number of watches with time spent below an acceptable fatigue threshold

Minimum effectiveness score while on watch

Average sleep per day.

*Acceptable Fatigue Threshold

An Acceptable Fatigue Threshold (AFT) of 77.5% was selected as it has been shown to represent an equivalent blood alcohol level of 0.05% (Dawson & Reid 1997) and is the default value employed by the USAF and RNZAF for

acceptable performance on flying operations.

Results

1st watch 2nd watch 3rd watch 4th watch Schedule Total

Day watches below AFT

Night watches below AFT









1 in 3 2 6 5 3 2 14

1 in 3 SD 2 2 2 4 2 4 6 10

1 in 3 WC 1 4 3 4 1 11

1 in 4 4 3 2 3 0 12

1 in 3 Circ 5 4 4 0 13

1 in 4 Circ 2 3 3 3 0 11

AFT = Acceptable Fatigue Threshold (77.5% performance effectiveness or 0.05% BAL)

% of Time spent operating below the AFT

Yellow = 1st watch, Green = 2nd watch, Pink = 3rd watch, Blue = 4th watch, Black = Schedule Average

1 in 3 1 in 3 SD 1 in 3 WC 1 in 4 1 in 3 Circ 1 in 4 Circ

Minimum Effectiveness Score


1 in 3 1 in 3 SD 1 in 3 WC 1 in 4 1 in 3 Circ 1 in 4 Circ

Sleep duration and time continuously awake

• Actual available sleep duration does not vary substantially between the different watch keeping schedules.

• However, the time continuously awake prior to a night shift is a concern in most schedules.

• Some watch keepers are awake for >18 hours prior to the start of their shift. This would be compounded further by chronic sleep debt and circadian dysfunction.

• Importantly, although the opportunity to sleep may be available, actual sleep may not be possible due to excessive noise, vibration and sea state.

Summary points

• All schedules affected to some degree by lack of recent sleep, poor sleep quality, chronic sleep debt, prolonged hours awake, circadian phase and circadian dysfunction.

• Worst performances are always associated with night watches (down to 52%), with 100% of one or more night watches performed below the criteria for some schedules.

So what next?

• Initial analysis revealed a need to mitigate fatigue levels for most watch keepers within a schedule.

• Sleep deprivation was identified as the primary cause of very high levels of fatigue during night shifts.

• As such, the impact of extended sleep periods and a daytime nap (for individuals who had completed a night watch) was predicted…..

Results of Mitigation

• By manipulating sleep duration, substantial improvements were observed for the 1 in 3, 1 in 4 and 1 in 4 Circ Schedules.

• While small improvements to the other schedules were possible, they were generally more complex to manipulate and did not facilitate the same reduction in fatigue.

Time on watch operating below AFT - before and after mitigation


1 in 3 1 in 4 1 in 4 Circ1 in 3 mitigated

1 in 4 mitigated

1 in 4 Circ mitigated

Standing 1 in 3 – Fatigue Mitigation

1) Yellow and green watch keepers given an extra 2 hours sleep in the morning following a night shift.

2) Pink watch keeper scheduled a short afternoon sleep between 1630 and 1800.

Total time below 77.5% reduced from 2461 to 508 minutes

Lowest minimum effectiveness score improved from 59 to 73%

Schedule minimum average improved from 67% to 75%

Schedule could be extended out to 21 days with only minimal increases in fatigue forecasted

Before mitigation

After mitigation

Recommendations

1. Discontinue the use of current watch schedules (without fatigue mitigation) due to the excessive fatigue they induce…..cognitive performance decrement and lapses in attention.

2. Implement the use of a modified Standing 1 in 3 watch.

3. Introduce an “in shift” nap requirement for night watchkeepers.

4. Encourage night watch personnel to extend their sleep hours at the start of the day whenever possible

5. Provide cover for later start times and naps.

6. Minimise the use of caffeine during the day and prior to sleep.

Recommendations

6. Develop specific policy, training and guidance covering:Utilisation of the FAST™ software to aid in the scheduling of Navy

duties and work patterns both at sea and on land

Fatigue SOPs and working practices that either stimulate and optimise performance or reduce the likelihood of errors

Appropriate use of stimulants and light exposure to optimise work environment, in particular during night watches

Sleep hygiene, optimal health strategy advice, including nutrition/diet, exercise and lifestyle

Advice for family members and those who share accommodation.

7. Finally, compare predicted sleep and performance to actual sleep and performance measured at sea.

Thank you

[email protected]

Study limitations

• Simulation of forecasted fatigue based on expected sleep outcomes and utilising a fatigue model. Actual fatigue could be either greater or less than forecasted in this study.

• Generally limited to 6 days in duration.

• Did not investigate the effects of individuals cycling through different watch keeper shifts within the watchkeeper schedules.

• Model does not account for fatigue induced by environmental conditions, physical fatigue, noise or vibration - highly likely that these factors would induce greater deficits in fatigue than is forecasted.

FAST™ ANALYSIS OF CURRENT AND PROPOSED RNZN WATCH KEEPING ROUTINES HELEN KILDING.

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