Original ArticleIs portable monitoring accurate in the diagnosis of obstructive sleep apnea syndrome in chronic pulmonary obstructive disease?
Introduction
Obstructive sleep apnea syndrome (OSAS) affects 3–7% of the general population [1]. In a recent population study in São Paulo, Brazil, the prevalence of OSAS was 32.9%, more frequent in men, in age groups above 50 years, and in obese individuals [2].
The association of OSAS and lung diseases, especially chronic obstructive pulmonary disease (COPD), is called the overlap syndrome [3]. Patients affected with overlap syndrome have worse hypoxemia, poor sleep quality, higher risk of pulmonary hypertension in the long-term, and cor pulmonale, which consequently leads to bad prognosis [4], [5], [6]. Some studies have reported the prevalence of overlap syndrome to be between 11% and 22% [4], [5], [7].
Polysomnography (PSG) is considered the golden standard for the diagnosis of OSAS, but has a high-cost and technically complex approach. The use during sleep of portable cardio-respiratory monitoring equipment at home without supervision is an alternative for OSAS diagnosis in patients with high clinical susceptibility [8], [9], [10], [11]. Some studies showed that a specific type of portable monitoring equipment (Stardust II [STD]) was effective for diagnosing OSAS in patients with high clinical probability, and these studies observed a robust correlation, sensitivity, and specificity compared to PSG [10], [12]. A recent publication tested STD in patients with coronary syndrome, showing favorable results in the use of this device (92% sensitivity and 67% specificity) [13]. However, to date, there is not enough scientific evidence to indicate the use of portable devices for the diagnosis of OSAS in patients with co-morbidities, especially lung diseases [8].
Based on these data our goal was to evaluate the accuracy of the STD, compared to PSG, for the diagnosis of OSAS in patients with COPD with high clinical probability of overlap syndrome.
Section snippets
Participants
We selected consecutive patients of both genders, over 40 years of age from the pneumology outpatient clinic of UNIFESP. Patients had been diagnosed with COPD in GOLD’s stages II and III [14], were stable (no COPD exacerbation in the last three months), were using bronchodilators without a dose change during that period, and had symptoms suggestive of OSAS (loud snoring, reported breathing pauses during sleep, and excessive sleepiness). We excluded patients with other sleep-related disorders, a
Results
Seventy-two patients diagnosed with COPD and clinical suspicions of OSAS were recruited and underwent the two nights of the study. PSG was effective in 93% of patients, and portable recordings of 41 volunteers had poor recording quality and were excluded from the analysis. The remaining 26 patients presented good recordings and were included in the final analysis (Fig. 1).
Comparing the demographic, physical examination, gasometry, smoking habits, spirometry, and 6-min walking test data in the
Discussion
OSAS is often associated with COPD. Portable monitoring is validated for use in patients with high clinical probability of OSAS; however, there is no evidence to apply that reasoning in overlap syndrome. Our study found significant recording failures of respiratory events.
The loss rate was approximately 61% considering all recordings, 39% when the recordings were performed at home, and 22% in the laboratory. This loss was very high, and bigger than in the other studies for the diagnosis of OSAS
Conflict of interest
The ICMJE Uniform Disclosure Form for Potential Conflicts of Interest associated with this article can be viewed by clicking on the following link: http://dx.doi.org/10.1016/j.sleep.2012.06.011.
Acknowledgments
We would like to thank Laura Castro, MsC, and Altay Souza, Ph.D., for valuable suggestions and statistical analyses.
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