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Abstract & Commentary
Synopsis: Most women with fibromyalgia have a variant of sleep apnea when carefully tested, and their symptoms improve with CPAP treatment.
Source: Gold AR, et al. Sleep. 2004;27:459-466.
Gold and colleagues hypothesized that disrupted sleep resulting from excessive work of breathing while asleep may contribute to the symptoms of fatigue, bodily pain, heartburn, depression, and insomnia frequently reported by fibromyalgia patients. To evaluate this, they assessed the amount of inspiratory work (negative pressure, or suction) and the amount continuous positive airway pressure (CPAP) necessary to overcome additional work in patients with fibromyalgia and the Upper Airways Resistance Syndrome (UARS), which is believed to be a variant of obstructive sleep apnea. In brief, inspiratory airflow limitation (and excessive work of breathing) is present when an individual continues to try to inhale (generates negative intrathoracic pressure) but cannot move air. With normal breathing, of course, negative intrathoracic pressure generates inspiratory airflow. With sleep-disordered breathing such as sleep apnea or UARS, increasingly negative (stronger) inspiratory pressures (eg, suction) are needed to generate flow, and ultimately cannot produce flow (resulting in frank apnea). To assess inspiratory airflow limitation, airflow is measured with a pneumotachograph, and negative intrathoracic pressure is measured with an esophageal pressure catheter. Gold and colleagues attempted to determine if inspiratory airflow limitation were present by measuring the pressure (suction level) at which the upper airway closed off (Pcrit) during non Rapid Eye Movement (NREM) sleep, and also by measuring how much positive airway pressure it took to provide unrestricted inspiratory airflow during inspiratory efforts.
The study population consisted of 28 fibromyalgia patients and 11 patients with UARS. Fibromyalgia was diagnosed by a rheumatologist in every case. All patients were women. Their average age was mid-40s, and their average Body Mass Index (BMI) was 29 Kg/m2. Half of the FM patients did not snore regularly, and 10 did not snore at all.
In this study, 27 of the 28 patients with fibromyalgia had inspiratory airflow limitation during NREM sleep. 26 had UARS, one had sleep apnea, and only one had no flow limitation. In this group of patients, 90% of their breaths were flow-limited, with an average change in intrathoracic pressure (suction) of -13 cm H20 (normal is -2 to -4 cm H20). It took an average of 7 cm H20 CPAP to eliminate the flow limitation. Arousals from sleep associated with episodes of airway obstruction resulted in alpha intrusion, or alpha delta sleep, the characteristic sleep EEG pattern of patients with fibromyalgia. Very similar findings were seen in the UARS patients. Only one of the fibromyalgia patients did not have inspiratory flow limitation. She did not differ from the other patients in any other way.
Fourteen of the fibromyalgia patients accepted CPAP treatment for sleep-disordered breathing. For this group, there was a 46% improvement in fatigue, and 30% improvement in pain, a 39% improvement in sleep problems, a 23% decrease in functional disability, a 33% decrease in the rheumatology distress index, and a 47% improvement in GI symptoms after 3 weeks of CPAP treatment. 5 of the subjects chose to remain on CPAP after the trial.
Comment by Barbara A. Phillips, MD, MSPH
As internists, we regularly encounter patients who have been diagnosed with or who think they may have fibromyalgia. As a sleep specialist, I frequently encounter these patients, often referred to evaluate the possibility of sleep apnea, but sometimes simply sent in a desperate attempt to explain poor sleep quality and daytime fatigue. This paper suggests that many patients with fibromyalgia have respiratory pathophysiology like that of sleep apneics. In fact, they appeared to be very similar to patients with UARS, which has been thought to be a sleep apnea variant. Since the original description of UARS by Guilleminault,1 sleep specialists have believed that subtle obstructed breathing events could cause some of the symptoms of obstructive sleep apnea (OSA), and that this could account for many of the symptoms seen in the so-called functional somatic syndromes, notably fatigue and body pain. An interesting finding of this paper is that the pattern of alpha-delta sleep was seen in these patients related to arousals resulting from inspiratory airflow resistance.
I discussed these findings with the study’s author, Ave (rhymes with Dave) Gold. I told him I was impressed that he had chosen to work with the fibromyalgia population, which can be difficult. His reply:
"I did my best to ignore their fibromyalgia. I was just interested in treating their UARS. But then one of my referrals came in and told me she was referred by a friend in her FM support group because I had cured’ her friend’s FM. I have studied at least 45 FM patients already and I am still looking for my second without flow limitation. The same is true for all the functional somatic syndrome patients that I have seen clinically. Moreover, if you can treat their SDB (sleep-disordered breathing), you can greatly improve (not cure) their functional symptoms. If you look at the FSS (Functional Somatic Syndrome) literature, however, they do not have a clue. Rheumatologists, Neurologists, GI’s do not emphasize sleep as a cause of the FSS. In short, sleep apnea is the tip of the iceberg when it comes to the clinical effects of SDB. This has become my mission’—doing the work that is needed to enable patients with FSS to get real help. With that, I will get off my soap box! Also . . . FSS patients are not that hard to deal with if you have something to offer."
Wow! This has the potential to change my practice. It’s important to remember that patients can have inspiratory flow limitation and sleep disturbance as a result without having snoring or typical symptoms and signs of sleep apnea. It’s even more important to remember that we may have something to offer these patients!
Dr. Phillips, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington, KY, is Associate Editor of Internal Medicine Alert.