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Wednesday, May 22, 2013
I recently had a sleep study that showed severe sleep fragmentation, mild sleep apnea and hypoventilation. I had the study done because of a preexisting myopathy with resp muscle weakness. My CO2 rose to 52% but my O2 sat only dropped to 91%. But I actually had more apnea and hypoventilation sleeping on my side than on my back. My dr (who is a sleep specialist) was unsure why this was. Do you have any thoughts as to why this is? I do not have large tonsils etc. My dr is recommending bipap because of the myopathy. His theory being it is better to treat sooner than later and also because of extreme fatigue and sleepiness during the day. I am scheduled for another sleep study to titrate the bipap and find out what pressures I need etc. As far as the fragmented sleep, will the bipap help with this? I toss and turn all night almost every night. It has become much worse lately. Is the fragmented sleep caused by the apnea and hypoventilation? Thanks for your time and help.
This is an interesting question and there are many items to address in your story. The main questions you have are why your obstructive sleep apnea (OSA) might be worse when in sleeping on your side (versus your back) and whether or not a Bipap (also known as bilevel pressure support) device might help your sleep. I'll discuss OSA in general first and then attempt to speak to the particulars of your case.
OSA is a common condition, affecting roughly 5% of middle aged adults in America. OSA is a condition where the airway partially or completely collapses during sleep. This results in fragmentation of sleep and, in some individuals, low oxygen level during sleep. The consequences of this condition can be serious and range from a poor quality of life (morning headaches, disabling sleepiness, poor concentration, irritability, etc) to increasing problems with blood pressure control, heart disease and strokes.
Symptoms may include waking up choking or gasping at night, very loud snoring (as you describe), poor and unrefreshing sleep, morning headaches and daytime sleepiness. The typical risk factors for sleep apnea include obesity and craniofacial abnormalities, though having a neuromuscular disease may also lead to sleep apnea if there is weakness of the upper airway muscles.
Usually, OSA tends to be worse when individuals sleep on their backs. This is due to fatty tissue or other upper airway abnormalities (such as having a large tongue or large tonsils) tending to create more collapse when in the supine (back) position as opposed to the lateral (side) position. However, in some individuals, sleep apnea may be worse when on their sides if there are certain factors, such as nasal congestion, involved. Another point to consider is that, in cases where the sleep apnea is mild such as yours, factors such as the amount of time spent in each position (supine and lateral) and the sleep stage seen when in each position, may magnify minor differences and thus the position issue may really be of no significant consequence.
Aside from the OSA, it appears you have significant hypoventilation in sleep (an elevated CO2 level and low normal oxygen saturations). This is likely related to your underlying neuromuscular disease. The hypoventilation in and of itself can contribute to fragmentation of sleep and some of the symptoms of fatigue and sleepiness. It's also important to consider other factors that may influence the quality of your sleep and can lead to fragmented sleep with resulting excessive fatigue and sleepiness. These can range from the environment you sleep in (i.e. too warm, too loud) to other medical problems (i.e. heartburn or breathing problems) to medications you may be taking. However, in your case, it's likely that much of your symptoms are related to your OSA and hypoventilation.
In order to address your problems, treatment should be geared to control both the OSA and hypoventilation. The primary treatment for OSA is the use of a continuous positive pressure airway (CPAP) device, which is very effective at keeping the airway open during sleep. It does this by "pressurizing" the airway to prevent it from collapsing. In a large number of well-done studies, CPAP therapy has been shown to be very effective at improving a number of measures of quality of life, including daytime alertness, improved concentration and improved mood.
In addition, growing data suggest that CPAP may reduce some of the medical consequences associated with sleep apnea. However, in the setting of neuromuscular weakness associated with hypoventilation, CPAP will not treat the hypoventilation and may actually worsen the work associated breathing. In this setting, Bipap is indeed a more appropriate treatment.
Bipap works differently from CPAP in that it provides a higher level of pressure when breathing in than when breathing out and thus supports and rests the breathing muscles during sleep (in addition to keeping the airway open). As a result, it should lead to less fragmented and more restful sleep.
To learn more about sleep apnea or other sleep disorders, please visit the American Academy of Sleep Medicine website. In addition to information, the website contains a list of Sleep Centers across the country so that you may locate one near you. Good luck and here's to good sleep!
Dennis Auckley, MD
Associate Professor of Medicine
School of Medicine
Case Western Reserve University