Kathe G. Henke, PhD

Sleep Disorders Center of Virginia

Henrico, VA

NTSB Safety Recommendation Reports

July 26, 2000 - Tractor trailer in Tennessee rear ends a highway patrol car.

Sept. 27, 2008 – Evacuation helicopter crash in Maryland

Feb. 13, 2008 - Airliner overflies airport in Hawaii

June 23, 1995 - a cruise ship grounded near Alaska

NTSB Safety Recommendation Reports

In each of these cases untreated sleep apnea (suspected or diagnosed) was felt to be a contributing factor.

Sleep apnea was suspected to have contributed to:

Sleepiness

Poor reaction

Poor judgment

Why Blame Sleep Apnea?

Sleep apnea causes daytime sleepiness

and impairs neuropsychological

functioning.

•Engleman 1999 •Guilleminault 1988 •Brzecka 2003 •Roehrs 1989 •Cheshire 1992 •Peceta 1992 •Gottlieb 1999 •Johns 1993 •Rosenthal 1997 •Furuta 1999 •Kingshott 2000 •Banks 2004 •Stepanski 1987 •Martin 1996 •Verstraeten 1996

•Kanbayashi 2003 •Montplaisir 1992 •Munoz 2000 •Bedard 1991 •Verstraeten 2004 •Mazza 2005 •Adams 2001 •Findley 1995 •Barbe 1998 •Munoz 2000 •Risser 2000 •Juniper 2000 •George 1987 •Findley 1992 •Fulda 2003

•Bardwell 1999 •Kim 2007 •Ayalon 2008 •Beebe 2002 •Kim 1997 •Boland 2002 •Ferini-Strambi 2003 •Kotterba 1998 •Naegel 1998 •Bennett 1998 •Yokoe 2003 •Vgontzas 1997 •Vgontzas 2004 •Alberti 2003 •Ciftci 2004

Some Studies on Daytime Impairment and Sleep Apnea

Sleep Apnea and Sleepiness

A large body of work supports the finding that OSA causes daytime sleepiness.

Objectively measured: MSLT, MWT

Subjectively measured: ESS, SSS

Sleep Apnea and Sleepiness

Multiple Sleep Latency Test (MSLT)

A standardized protocol measuring

average latency to sleep in 4-5 naps > 10 min is “normal”

< 8 min “sleepy”

Average in OSA is <8 minutes

Maintenance of Wakefulness Test (MWT)- Less clear information is available

The Epworth Sleepiness Scale

Sleep Apnea and Sleepiness

Epworth Sleepiness Score –

8 items scored 0-3 = Total of 24 points

Greater than 10 considered to be sleepy

Average 11-16 in OSA in most studies

What Causes the Sleepiness?

OSA is characterized by frequent awakenings and disruption of normal sleep staging. More awake time

Less “deep” sleep

Less REM (dreaming) sleep

Normal Sleep Staging

Sleep Staging in OSA

Cheyne-StokesHypoventilation

RERAHypopnea+ArMix. Apnea+ArObs. Apnea+ArCen. Apnea+Ar

HypopneaMix. Apnea

Obs. ApneaCen. Apnea

11:24 PM 12:16 AM 1:08 AM 2:00 AM 2:52 AM 3:44 AM 4:36 AM 5:28 AM

Respiratory Events

50

60

70

80

90

100

11:24 PM 12:16 AM 1:08 AM 2:00 AM 2:52 AM 3:44 AM 4:36 AM 5:28 AM

SpO2%

What Causes the Sleepiness?

Arousals

Microarousals

Patients may “sleep” for 8 hours but unaware of constant arousals

Other Causes of Sleepiness Hypoxemia (low oxygen)

Some studies have demonstrated that sleepiness is associated with

lowest oxygen level

number of dips in oxygen saturation.

Other Causes the Sleepiness?

Other factors

Interleukin-6 (responds to tissue injury)

TNF-alpha (involved in inflammatory response)

Both elevated in OSA and shown to cause sleepiness

Impairment of Neuropsychological Function

Vigilance

Cognitive function

Memory

Attentional functioning

Learning deficits

Vigilance Constructs

Sustained attention

Divided attention

Measures Reaction Time

Steer Clear

Demonstrated to be impaired in OSA

Associated with AHI

Hypoxemia

Cognitive Function

Includes:

Memory

Learning

Problem solving

All shown to decrease in OSA

Related to disease severity

What causes Neuropsychological Dysfunction in OSA?

Some findings

Loss of grey matter

Decreased cerebral blood flow velocity

Decreased brain blood and tissue oxygenation

Real World Consequences

There is clear evidence that OSA increases risk of crashes in cars! This is likely due to sleepiness and decreased

neuropsychological functioning.

Less evidence in commercial drivers

Given the potential risks: More work needs to be done to

assess the risk of untreated OSA and

accidents in commercial driving/

piloting/navigating.