Sunday, October 20, 2013

More health issues

It seems that my joy in cutting down the number of apneic events by increasing the pressure that my CPAP machine provides was short lived: true, I had three days with few events at a pressure of 7.5 cmH2O, but then I had four days with high numbers (back into the realm of 20 incidents per hour). As per my instructions, I increased the pressure to 8 cmH2O. After a week, I checked the results and saw that increasing the pressure had made no difference.

Yesterday, I increased the pressure to 9 cmH2O; presumably as a result of trying to adapt to the higher pressure, I slept very badly and this morning I feel lousy. Hopefully I'll get used to the new pressure and get some sleep, although its quality will be an unknown factor.

In my doctoral studies, I was working on what's called the Mann-Whitney U test, which basically checks whether one series of values is significantly different from another series of values. This test is meant for non-standard distributed values which are independent of each other - exactly like the values I get from the CPAP machine. I checked 24 values from Friday nights against 24 values from Saturday nights, and assuming that I did the maths correctly, I can conclude with a confidence level of 95% that I have more apnea on a Friday night than on a Saturday.

The only good thing that I can find to say about my health is that my weight is fast decreasing. Two weeks ago I was surprised to discover that my weight had ballooned from 82 kg to 85 kg; last week it had decreased to 84.3 kg and this morning I weighed only 83.3 kg. At this rate, in another two weeks I will have lost all the extra weight and will be well placed to make some serious losses.

Which leads me back to sleep apnea: shortly my weight will be the same as it was in April when the machine was set up, which means that I should be using the same pressure as then (7 cmH2O). If there is a significant increase in the number of apneic events (without regard to pressure) then there is some other variable which needs to be taken into account. Maybe there is a problem with the machine or the mask ... or maybe me.

As an aside, I note that despite the fact that a sizeable proportion of the adult population suffers from sleep apnea, I have never seen this (or CPAP machines) mentioned in either films or books. So it was a happy moment when I found the following passage in the opening pages of 'Up in the air'  "Once between Denver and Oklahoma City, I nodded off next to a pulmonary specialist who told me when I woke that I had apnea - a tendency to stop breathing while unconscious. The doctor recommended a machine that pushes air through the nostrils while one sleeps to raise the oxygen level in one's blood."

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