Raghu Upender, MD Assistant Professor in Neurology Medical Director

1. Fatigue Science & Safety Occupational Sleep Medicine Raghu Upender, MD Assistant Professor in Neurology Medical Director Vanderbilt Sleep Disorders Center

2. Disclosures • None

9. EXXON VALDEZ

13. DRIVING WHEN DROWSY • 71,000 non-fatal injuries occur per year • 1,550 fatal injures occur per year • $12.5 billion in monetary losses

14. How can we mitigate the risk of human error in future disasters?

15. Outline • Define fatigue and sleep • Review effects of Sleep loss • Review sleep physiology • Describe fatigue modeling • Fatigue risk management

16. Fatigue Definition Physical or mental “exhaustion arising from labor, exertion, or stress” -Merriam-Webster Dictionary

17. Fatigue Severity Scale

18. Fatigue in the Work Place Fatigue ≈ performance degradation

19. Psychomotor Vigilance Test • PVT is relatively brief, easy to administer, and can be repeated multiple times through the day. • The PVT measures simple reaction time to a visual stimulus • PVT reaction times correlate well with other cognitive tests.

20. PVT Reaction Times Doran SM, Van DongenHPA, Dinges DF. Arch ItalBiol 2001;139:253-267.

21. Ascending Arousal System Saper CB et al. Nature437, 1257-1263 (27 October 2005)

22. Sleep Promoting VLPO Saper CB et al. Nature437, 1257-1263 (27 October 2005)

23. Flip Flop Switch Saper CB et al. Nature437, 1257-1263 (27 October 2005)

24. Clinical Examples • Narcolepsy Sleepiness intrudes into wakefulness due to • Loss of orexin producing neurons leads to loss of orexin’s stabilizing effect on arousal • Insomnia in the elderly Wakefulness intrudes into sleep due to • age related loss of VLPO neurons leads to less effective suppression of arousal system.

25. Flip-Flop Switch and Fatigue • During prolonged arousal • Arousal system weakens due to exhaustion • Sleep pressure accumulates • Wake promoting circuits are overwhelmed and abrupt transition to sleep occurs causing momentary lapse

26. PVT Speed and Sleep Deprivation Wesensten NJ, Thorne DR, et. Al. Aviat Space Environ med 2004;75:520-525

27. Sleep – Wake regulation • Process S • Process C

28. Process S • Sleep homeostatic drive • Increases during the wake period • Declines during sleep • Quantified by slow wave sleep

29. Cerebral Blood Flow across Sleep States Taber KH et al. The Journal of Neuropsychiatry and Clinical Neurosciences 2006

30. Performance Reservoir http://dnr.wi.gov/org/water/wm/dsfm/dams/gallery.html

31. Process C • Master Circadian oscillator • Provides alerting signal

32. The two-process model of sleep regulation Richardson GS: The human circadian system in normal and disordered sleep. The Journal of Clinical Psychiatry 2005; 66(Suppl 9):3—9.

33. Process WProcess of Awakening Balkin, TJ et al. Brain 2002;125:2308-2319

34. Basis for Fatigue Modeling • Human error due to fatigue is fundamentally stochastic, i.e. random. • Performance lapses that occur due to wake state instability are also stochastic. • Though the individual performance lapses in attention occur randomly, the probability at which they occur is predictable.

35. Fatigue Model

36. PVT Speed and Sleep Time Belenky, G et. al. J Sleep Res. 2003 Mar;12(1):1-12.

37. Hursh SR. Aviat Space Environ Med 2004; 75:A44-53

38. Fatigue vs. Accident Risk Hursh SR et al. SAE Trans 2004;113:111-119.

39. “I’m too tired to listen to a story right now, mom. Just e-mail something and I will read it tomorrow.”

40. Sleep Loss • Approximately 21% of adults average ≤ 6 hours of sleep • 70 million American experience chronic sleep loss on a daily basis • Both acute and chronic sleep loss can have detrimental effects on performance • Deficits in executive functions can lead to critical errors in the work place

41. “If you don’t think fatigue wreaks havoc, take a look at some of the laws we write around here at 1 a.m.” -Rep. James Oberstar (D-MN)

42. Fatigue Risk management • Coast Guard • Federal Rail Road Administration • Federal Motor Carrier Administration • Federal Aviation Administration • Health Care- ACGME

44. Rail Road • No specific Regulations at this time • Rail Safety Improvement Act of 2008 (RSIA) requires railroads to develop • Risk Reduction Program • Fatigue Management Plan

45. Truck Drivers • Total hours of service (HOS) per week = 70 • Daily driving limit = 11 • Continuous driving limit = 8 (30 minute break) • Two nights’ rest (1:00 am to 5:00 am)/week • 34 consecutive hours of rest to restart • Company penalties- $11,000 per offence • Driver Penalty- $2,75 per offence.

46. Aviation • Varying flight and duty requirements based on what time the pilot’s day begins. • Flight duty period • Flight time limits of 8-9 hours • 10-hour minimum rest period • Cumulative Flight duty and flight Time limits • Fitness for duty • Fatigue risk management system

47. Resident Duty Hours • 16 hr duty hour limit for 1st year of residency • 24 hr limit for subsequent years of residency • Strategic napping encouraged • 10 hrs off in between duty periods • 24 hrs off per 7-day period • 80 hour limit per week • Flexibility depending on specialty

48. Fatigue Modeling • Predicts risk of impairment in a given schedule • Function as a component of fatigue risk management systems that are mandated by law • Guide the effective implementation of fatigue countermeasures • Allow more flexible and more effective scheduling then hours of service regulation

49. Potential Applications • Military • Health Care • Manufacturing • First Responders (EMS, Police, Fire Fighters) • Education • Sports

50. Future Goals • Develop non-intrusive tools to measure performance in the operational environment • Develop inexpensive tools to measure sleep quality and quantity over sequential sleep periods • Develop personalized fatigue management programs to reduce occupational risk and improve individual performance and well being.