OSA/OSAS Who is Fit to Drive? Stradling JR. Oxford Centre for Respiratory Medicine Churchill Hospital, Oxford

Transcription

1 OSA/OSAS Who is Fit to Drive? Stradling JR. Oxford Centre for Respiratory Medicine Churchill Hospital, Oxford

2 What we hear in the clinic

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4 Cost of road accidents (UK department of transport official figures) Douglas and George Thorax 2002;57:93-4 Fatal accident +Injury 1.25 million Property damage 1, thousand Treating 500 pts for 5 years prevents 1 fatal accident, 75 injury accidents, and 224 property damage accidents. 5.3 million saved, against estimated treatment cost of 0.4 million (12.3 times return on investment!)

5 Sleep Apnoea and Driving uncontrolled treatment data George et al Thorax 2001;56: (similar French data, Chest 1997;112:1561) Driving accidents for 3 years before and 3 years after nasal CPAP (n=210), versus control population. Ontario public record data. Crashes/driver/year Before CPAP After CPAP Controls 1 Controls (p<0.001) Rate remained high in 27 untreated pts Before (113 accidents) After (38 accidents)

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7 Sleep apnoea without sleepiness is not OSAS and does not qualify

8 Assessment of Sleepiness, Vigilance and Performance Relevant to Driving to inform decision making in the clinic Problems:- Why is there such a poor correlation between measures of sleep apnoea and daytime symptoms and performance? Do tests of performance predict real life? Will there ever be a reliable tool to predict performance (and the chance of accidents), either from sleep studies or daytime tests (sleepalyser)?

9 Sleep Studies?? We have no idea what to measure Sleep architecture, microarousals, respiratory variables None of these predict daytime sleepiness or performance well Individual susceptibility to sleep fragmentation Night to night variation in sleep studies is considerable How many nights would be representative? Under what conditions should the sleep be measured? Home or laboratory?

10 Most people with OSA are not sleepy, and most people who are sleepy do not have OSA Young et al. NEJM Questionnaire and PSG to 602 subjects Only obesity, male sex and snoring predicted AHI. This is why OSA and OSAS clearly need separating

11 Correlation between Sleep Study indices (AHI) and symptoms (ESS), both patient and partner. Kingshott et al Thorax 1995;50: OSA patients and their wives. Differences between patient and partner assessment but neither correlated with AHI

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13 Inter-individual variation in susceptibility to sleep deprivation (effect on MWT OSLER, normal subjects) (Grace Robinson, OCRM, unpublished data) Severe deterioration No measurable effect

14 Reproducibility of OSA indices, scatter plot of night 1 versus night 2

15 Large nightto-night variation Chest 2000;118:353-9 (Belgium, AHI>20 for CPAP) 243 subjects with suspected OSA studied with PSG. If AHI <20 (n=142), or >20 and did not want CPAP (n=27) then restudied on subsequent night (total n=169). 27% of those with AHI <20 on the first night had an AHI 20 on the second night 16% of those with AHI 20 on the first night had an AHI <20 on the second night

16 Sleepiness testing?? Subjective Objective Sleepiness/tiredness/exhaustion/fatigue - all different and subject to interpretation. ESS well evaluated. Variation due to denial, personal drive to stay awake. Witness accounts may be subject to other agendas. MSLT, MWT (EEG), MWT (behavioural), driving simulation, cognitive tests Evidence of ability to predict driving crashes

17 Epworth Sleepiness scale. Least sleepy=0 Most sleepy=24

18 Sleepiness testing?? Subjective Objective Sleepiness/tiredness/exhaustion/fatigue - all different and subject to interpretation. ESS well evaluated. Variation due to denial, personal drive to stay awake. Witness accounts may be subject to other agendas. MSLT, MWT (EEG), MWT (behavioural), driving simulation, cognitive tests Evidence of ability to predict driving crashes

19 Correlation between AHI or microarousals and objective tests of sleepiness, MSLT or MWT. Kingshott et al ERJ 1998;12:1264

20 MSLT versus MWT, 258 patients (mixed diagnoses), 17% of one explained by the other. Sangal et al Chest 1992;101:898

21 Murray Johns J Sleep Res 2000;9:5

22 Osler test Variant of MWT. Behavioural endpoint. Failure to tap every 3 seconds (in time with dim flashing light) for 21 seconds. (Mitler et al NEJM 1997;337:755 loss of control can pre-date EEG evidence of sleep) 101 subjects with OSA (>10/hr >4%SaO 2 dips/hr & ESS >10) Mean (SD) 22.6 (11.1), range 1.9 to 40 (max), 5 th /95 th 5.6/40 mins. ESS Mean Osler ESS Mean Osler >4%SaO (dips/h)

23 Osler Test response to treatment In a controlled trial of ncpap, ESS and SF36 showed significant placebo effects, the Osler test did not: Placebo, ; real, minutes, n=101. (6 months later on ncpap, Osler was 40 minutes) Effect sizes ESS SF36 (E&V) Osler Placebo response (n=49) 0.74** 0.93** 0.19 NS Real response (n=52) 2.0*** 2.1*** 0.70 ** cf Poceta et al Chest 1992;101:893 (no control patients) conventional MWT rose, 18 to 32 minutes

24 Driving simulators?? Do they predict real life? Even if they do, should they be used to affect peoples livelihood? Driving simulators? Can they ever be realistic, should a bad result be used to prohibit driving

25 Bad Driving simulator performance Good Normal subjects, influence of alcohol, and effects of OSA Normal subjects given enough alcohol to put them just over the legal limit George et al AJRCCM 1996

26 Oxford Driving Simulator - DADS

27 OSA and driving simulation Start of drive End of drive (30 minutes) OSA Increasing tendency to wander off road Repeated on treatment, 1 month later. No deterioration

28 Placebo controlled trial of ncpap - driving simulator (Hack et al Thorax 2000)

29 Evidence that anything predicts real driving accidents? Conflicting data Larry Findlay, ATS 2000 (abstract only) 28 patients with OSA. Driving records and self reported accidents from last 5 years. 8 patients > 1 accident. Age, gender, miles/yr, AHI, performance on driving simulator. Patients with a crash (8) Patients with no crash (20) Gender 7 males, 1 female 17 males, 3 females Age 56 (SD6) 49 (SD8) AHI 37 (SD34) 52 (SD39) Drive err 0.30 (SD0.21) 0.18 (SD0.13)* Off road 41 (SD50) 17 (SD29)* * P<0.05 Very poor recall of accidents

30 150 patients with?osa, self reported history and performance on Oxford driving simulator. 34 accidents in last 3 years, 56 reported a near miss 51 admitted to nodding off Poor tracking error significantly (P=0.03) associated with near misses little predictive ability at individual patient level ESS significantly associated (P=0.0001) with near misses and nodding off at the wheel Much better at predicting who did not, rather than who did, have an accident

31 448?OSA pts. 40 pts had crashes Accident rate correlated with ESS and AHI No use at an individual patient level (Similar to study of George et al)

32 783?OSA pts and 783 matched controls Insurance records 3 yrs prior to diagnosis for real crash rate Overall crash rates Crashes with injury No correlation with ESS

33 Conclusions The relationship between OSA, sleep deprivation (or fragmentation) and driving performance is immensely complicated with many sequential links between the two. Most of the objective/subjective tests available all measure something, all seem valid, but cannot predict likely crashes in individuals. It is unlikely that subjective, objective or physiological tests will be precise enough to determine fitness to drive, except at either end of the spectrum. Is this much different to epilepsy/cardiovascular disease, diabetes etc?

34 Stradling JR. Driving and Obstructive Sleep Apnoea Thorax 2008;63: As in many other areas of medicine, one simply has to do one s best given the limited evidence. It seems right to assess a patient s likelihood of having a future accident using a composite of several sources of information. These include the patient s own report of sleepiness while driving, a spouse s assessment, any previous accidents due to sleepiness, an assessment of their attitude to the problem (including their stated intention to avoid driving while sleepy), the sleep study itself and, perhaps, objective measures of sleepiness (although we use these tests more to inform and educate rather than as arbitrators of competence to drive an unproven use)."

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