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Sleep Disorders

CPAP Results



I have been using an APAP machine for a month that has daily readout of the therapy. The data shows that the machine has not reduced my AHI as compared to my sleep study. I asked my sleep doctor why this is and she could not explain it. What can I do to reduce my AHI or find someone who can help?


First, let me say that I’m glad you are getting your obstructive sleep apnea (OSA) treated as this is very important. Before I address your concerns about your ACPAP machine, I’ll briefly discuss OSA in general and speak to the particulars of your case as we go.

OSA is a common condition, affecting roughly 5% of middle aged adults in America. Most individuals with this condition are still not diagnosed and, of those that are diagnosed, many have had it for many years prior to undergoing appropriate testing.

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, poor and unrefreshing sleep, morning headaches and daytime sleepiness. The risk factors for sleep apnea include obesity and craniofacial abnormalities.

OSA is usually diagnosed by a sleep study, where your apnea-hypopnea index (AHI) is determined. The AHI is a measure of the number of times you have trouble breathing per hour of sleep. It is one of the parameters used to assess the severity of your sleep apnea as well as your response to treatment.

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.

There are several mechanisms by which we can assess the adequacy of CPAP therapy on an ongoing basis. Try not to focus on the AHI alone. The most important parameter in your CPAP therapy is whether your SYMPTOMS are improving. If you had sleepiness, is it better? If you had snoring, is it better? Focus on your reason for getting the sleep study in the first place.

The AHI readout from an APAP machine tells a very small part of the overall story. This AHI is much less accurate than the AHI determined on a formal sleep study. Therefore the AHI readout from the machine is only an extremely rough estimation. In general, we don’t use the AHI from an APAP machine as the sole guide to therapy or treatment success. However, if your experiencing symptoms related to your sleep apnea and your AHI is being read as being elevated, then a reassessment is needed. In some cases, an adjustment of the interface may help, though sometimes an in-lab study is required.

You should have the expectation of getting a good nights sleep and relief of your OSA-related symptoms. However, keep in mind that there may be nights when you do not sleep as well as you’d like and that this does not necessarily mean your CPAP is not working. A variety of factors could contribute to problems on any given night, so look for a consistent pattern before you contact your doctor with concerns.

It would probably be a good idea to discuss your case with your Sleep Specialist and make sure you have a good working relationship with him or her.

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Response by:

Troy  Schaffernocker, MD Troy Schaffernocker, MD
Assistant Professor
College of Medicine
The Ohio State University