Driver performance in the moments sDriver performance in the moments surrounding a microsleepurrounding a microsleep

Speaker: Jenny 2008/10/29

Transportation Research Part F 11 (2008) 126-136Transportation Research Part F 11 (2008) 126-136

Linda Ng Boyle, Jon Tippin, Amit Paul, Matthew RizzLinda Ng Boyle, Jon Tippin, Amit Paul, Matthew RizzooDepartment of Mechanical and Industrial Engineering, Department of Mechanical and Industrial Engineering, College of Medicine, Department of Neurology, UniverCollege of Medicine, Department of Neurology, University of Iowa, USAsity of Iowa, USA

Agenda

• Purpose

• Introduction

• Method

• Results

• Discussion

Purpose

• If OSAS 阻塞型睡眠呼吸中止症候群 would impair driving performance during microsleep episodes or not

• Hypotheses1. driving performance get worse during microsleeps

2. esp. the longer microsleeps

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 )

PSG 　睡眠多項生理檢查

EEG

EOG 眼電圖• 電極位置前視圖

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.

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

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)

Epworth Sleepiness ScaleESS 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 )1.坐著閱讀書報時2.看電視時3.在公眾場所安靜的坐著 ( 如在戲院或會議中 )

4.坐車連續超過一小時 ( 不包含自己開車 ) 。5.下午可以躺下休息時6.坐著與人交談時7.沒有喝酒或服感冒藥的情況下，在午餐後安靜坐著時8.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

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

Experiment design

• 2:1 matched approach (microsleep)

• Microsleep: 3-14s during θ activity

• MANOVA & univariate ANOVA

Results

Results

Results

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

Results

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)

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.

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

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.