Need help with readings...

[iwant2sleep]

Hi all,

I've been having problems with my machine readings. Since becoming a hose head in November, I've not had the data on my machine show any AHI's until two weeks ago. Now I am getting between 3 and 6 per hour, and it's kinda scary. I took my machine to the sleep clinic last week and they said it was nothing to worry about, but were very vague when I asked 'why now?'

I also asked about the pressure support bar chart. Some nights it is coloured all the way up to the top and sometimes only 1/4 the way up the graph. I wanted to know should I be gettnig a full bar chart all the time? If so, why on some nights is it so low? Conversely does a low reading mean that was a 'good night' and my lungs didn't need so much support? Or were they not getting enough due to leaks? Again, vagaries only offered...I've had leaks most nights but only between 7 and 10 litre per min. This I am told, is well within acceptable perameters. Strangley last month I had a week without registering leaks at all but I cannot work out what I did differently (Same mask, same sleeping position)

If you can shed any light on my questions and confusion I'd be very grateful!!

PS I have a Resmed Stellar 100 bipap machine

[tallishbloke]

bipap

Hi
If you are getting an AHI between 3 and 6 / hrs, I would not be concerned. The normal range for AHI for majority of population is up to 5 / hr, so you are very close to the normal range. The fact that you are on a stellar means you are on a BiPAP unit which is a bit sdifferent from CPAP. CPAP deliveres one continuous pressure throughout the breathing cycle (hence the Continuous in CPAP Continuous Positive Aiways Pressure). BiPAP on the other hand gives you 2 distinct pressures - a lower Expiratory (EPAP) pressure when you breathe out and a higher Inspiratory (IPAP) pressure as you breathe in. This also suggests that you have some OHVS (Obesity Hypoventilation Syndrome) not just OSA. People's sleep tends to vary night by night and is dependent upon may factors, not just position and mask - any drugs they are on, how tired they are, any caffeine they have had, just to name but a few factors. This in turn means the pressures delivered is likely to vary (if they are on auto setting).
What is allost more important than having poretty numbers is how it makes you feel. if it imoprives sleep, and you feel alert, refreshed etc etc, then thats what should make you want to keep using the system, not having a good set of numbers.

Good Luck!!
TB

[iwant2sleep]

Thanks for your reply, Unfortunately, it didn't really naswer my question. The information about the differences between CPAP and BIPAP I already knew, and what i am really concerned about - the fluctuations in pressure support and what this indicates - still remains a mystery.

Also, it might not be a good idea to assume that everyone who uses a bipap does so because of breathing difficulties caused by obesity. I am not one of these users. I have a severe curvature of the spine which causes a chest wall deformity. This has become so severe that I am now retaining co2 at night as my diaphragm is distorted and weakened and can no longer support my chest wall muscles.

If anyone else has suggestions why my pressure support fluctuates so, I'd love to hear from you. Having monitored it now for a couple of weeks it is definitely not related to mask leaks. Sometimes my machine shows no leaks at all, but my PS hardly shows up on the monitor.

[tallishbloke]

PS

Hi
Yes, I agree, there are a number of conditions that may require people to use BiPAP machines, only one of which is Obesity Hypoventilation; another being problems with abnormal spinal curvature such as kyphoscoliosis. All these conditions have one thing in common which is that the individual retains excessive amounts of CO2 (known as type 2 respiratory failure) during sleep. It sounds as if your machine is set on an auto-titrating setting, meaning that the pressures are allowed to vary according to requirement, according to what the machine thinks you need. It is quite possible that you will have different pressure requirements night by night, indeed, hour by hour. The pressures required, and thereby delivered will be dependent on a variety of factors including how deep a sleep you are in at any point in time, your position in bed, mask fit, the presence of any medication which could affect the respiratory system or the parts of the brain controlling respiratory function.
Looking at AHI can give you a guide as to the effectiveness of the system, but equally, you should look out for return of symptoms such as increasing lethargy / tiredness, confusion or muzzyness, headaches first thing in the morning, a tremor in your hands.
Cheers