Normally the ferries coming to the Isle of Man run at sensible times, but there is one particular scheduled service that leaves the port of Heysham at 02.15. In the winter, when the only other crossing is 14.15, I seem to find myself on the ‘overnight’ boat far more often than I would like. The boat doesn’t load until at least 01.30, so for a couple of hours I usually try to sleep in the carpark. Cold, rainy and situated next to the nuclear power station, it’s not exactly conducive to any restful sleep. Even if I do doze off I still have that dreadful anticipation of being woken by the port staff to drive onto the car deck.
I’ve learned now to book one of the cabins on the ferry. Head to the customer services desk, collect the key and find the cabin with the beds made up ready. If I’m quick I can kick my shoes off and be asleep before the safety announcement. The journey is just under 4 hours and the arrival in the Isle of Man is accompanied by an announcement and the lights in the cabin coming on. It doesn’t feel like I’ve actually slept at all. After a short drive home, I usually try for more sleep, but it’s not always easy during the day. I usually need a good night’s sleep to recover from my acute sleep deprivation.
As divers we often travel some distance by road, ferry or plane to get to our dive destinations. Travel arrangements can involve early check-ins and sleeping in unfamiliar places. There is considerable research into the effect of sleep deprivation and its effect on behaviour, particularly for in relation to driving. Sleep deprivation has the same hazardous effect as being drunk. Research has shown that being awake for 17-19 hours impairs performance to an extent that is comparable to having a blood alcohol level over the drink driving limit for the UK. As drink-driving has now become socially unacceptable, how many of us are aware that our driving could be as impaired by lack of sleep?
I think back to my days living in London, getting up at 4am to tow the club boat to the South coast, two waves of two dives and some food followed by the drive home. The boat would be stowed away by about 10pm, so the last few hours of towing a rib would have had me well into the fatigue zone. The evidence suggests that performance decline sets in after 16 hours awake, add this to sub-clinical decompression related post-dive tiredness and I think I was in dangerous territory.
How many times though do our trip risk assessments include fatigue? I got up at 5am this morning to collect a group coming in from the ferry. During the summer there is an 03.00 crossing from Liverpool arriving in the Isle of Man at 05.45. If I think I felt tired as I arrived at the ferry terminal – you should have seen the divers we collected! Some of them had managed a little sleep in the airline style seats, but not much. We’ve brought them back to the accommodation and sent them all to bed. We expect to be diving this afternoon, and one of the risks I’m now assessing is how much sleep they haven’t had.
I can’t find any specific research into the impact of fatigue on diving, but I am happy to accept that driving is a reasonably good surrogate activity. Drowsy drivers experience difficulty remembering the last bit of road and slower reaction times. Impaired cognitive and motor performance aren’t good for divers either. We learn about the impairment due to narcosis (with that amazing slide that has several pints of beer on!), but being awake for long periods is going to cause those effects without even stepping in the water. Maybe there are hints about this in our training, we do advise to have a good interval between flying and diving, but there’s nothing explicit regarding sleep deprivation. If you aren’t convinced that this is a problem, perhaps you should know that it’s been estimated that sleep deprivation is implicated in 1 in 5 road accidents. Sleep deprived drivers are much more likely to get angry with other road users and deal poorly with stressful situations (like navigating unfamiliar roads).
Caffeine can help, but only in the short term and not with all the aspects. It can improve alertness and reduce reaction time, but fine motor control isn’t improved even with high doses. So, I could send all the divers to the local coffee shop and insist they top up their espresso quota, but I know that won’t last. Instead, I hope they have their heads down and are napping now. Me? I’m too wide awake and writing columns instead!
Michelle has been scuba diving for nearly 30 years. Drawing on her science background she tackles some bits of marine science. and sometimes has a sideways glance at the people and events that she encounters in the diving world.