1. Driver performance in the moments surrounding a microsleep
Transportation Research Part F 11 (2008)
Linda Ng Boyle, Jon Tippin, Amit Paul, Matthew Rizzo Department of Mechanical and Industrial Engineering, College of Medicine, Department of Neurology, University of Iowa, USA
Speaker: Jenny
2008/10/29

2. Agenda
Purpose
Introduction
Method
Results
Discussion

3. Purpose
If OSAS阻塞型睡眠呼吸中止症候群 would impair driving performance during microsleep episodes or not
Hypotheses
driving performance get worse during microsleeps
esp. the longer microsleeps

4. What is OSAS? obstructive sleep apnea syndrome
阻塞型睡眠呼吸中止症候群
$11 billion in crash cost (Sassani et al., 2004)
affects 2-4% of middle-aged adults (Young et al., 1993)
Diagnosis: intermittent airway obstruction, excessive daytime sleepiness, snoring etc
Polysomnograpy (睡眠多項生理檢測)
EEG(腦波圖), EOG(眼電圖)

5. PSG　睡眠多項生理檢查

6. EEG

7. EOG眼電圖
電極位置前視圖

8. Introduction Crashes by driver sleepiness: Lyznicki et al, 1998
40,000 injuries and 1,500 deaths each year in US
McCartt et al., 1996
55% driven while drowsy
23% fallen asleep while driving
Microsleep is a more sensitive indicator of sleepiness.

9. Participants Clinical standard for OSAS diagnosis ESS嗜睡量表: 11.0
PSG睡眠多項生理檢查
API >5 (Apnea-Hypopnea Index,呼吸中止指數)
Each duration of apneas and hypopneas lasts more than 10s.
Airflow reduction, oxygen saturation decrement, EEG arousal

10. 呼吸持續性呼吸道正壓治療 (Co n t i n u o u s positive airway pressure, CPAP)

11. Epworth Sleepiness Scale ESS嗜睡量表
打瞌睡的頻率(0從未，1很少，2一半以上，3幾乎都會)
坐著閱讀書報時
看電視時
在公眾場所安靜的坐著(如在戲院或會議中)
坐車連續超過一小時(不包含自己開車)。
下午可以躺下休息時
坐著與人交談時
沒有喝酒或服感冒藥的情況下，在午餐後安靜坐著時
開車中遇到交通問題而停下數分鐘時
10分以上：白天嗜睡。若白天嗜睡且打呼，可能患有睡眠呼吸中止症

12. Experiment Design Middle-age 12 male + 12 female 14:00 starts
60mins (5-10min warm-up)
Apparatus: driving simulator, EEG, EOG
2-lane highway (55-89 km/h)
3 drive segments: straight & curved road

13. Experiment design 2:1 matched approach (microsleep)
Microsleep: 3-14s during θ activity
MANOVA & univariate ANOVA

14. Results

15. Results

16. Results
Fig. 1. The effect of microsleep duration on lateral controls: (a) SDLP and (b) SDSWA.

17. Results

19. Discussion
Significant differences in driver control were related to occurrence and duration of microsleeps
Low speeds during microsleep episodes
Greater speed variability in drowsy drivers with OSAS (Risser et al., 2000)

20. Discussion Minimum TLC were longer on straight segments.
Driver in real road get more feedback.
Challenge: movement and muscle artifacts may hinder EEG interpretation.
The frequency of alpha and theta bursts typically increase during prolonger driving.

21. Discussion
Decline in alpha+ theta power probably reflects post-event alerting, while microsleep episodes reflect both pre- and post-event EEG changes.
Future studies: cost and benefits of EEG monitoring, how to discriminate safe drivers

22. Conclusion
OSAS impairs driving performance during microsleep episodes.
Degree of deterioration is related to microsleep duration.
It’s getting worse when microsleeps occur on curve road.
Design of countermeasures: drowsy driver detection and alerting systems.