Body position during sleep influences the frequency of apneas and hypopneas in 50 to 60% of individuals with obstructive sleep apnea (OSA). In such cases, the apnea-hypopnea index (AHI) is increased in the supine posture and lower in the lateral posture. Positional sleep apnea is said to be present when there is a 50% reduction in the AHI during nonsupine sleep. Continuous positive airway pressure (CPAP) is a highly effective form of therapy for OSA. However, acceptance and compliance with CPAP are less than ideal. As an alternative to CPAP, patients with positional sleep apnea may be candidates for therapies that are designed to prevent the supine posture during sleep, ie, positional therapy. However, positional therapy is not likely to relieve symptoms if the AHI in the nonsupine position remains elevated. A more clinically appropriate definition would define positional sleep apnea when the rate of the AHI falls below the diagnostic threshold during sleep in the nonsupine posture. Thus, if positional therapy were totally effective in eliminating sleep in the supine position, the AHI would be normalized and positional therapy alone could be used for treating OSA in these patients.
The prevalence of positional sleep apnea as defined above is not known. Various estimates indicate that positional therapy alone could be used to treat approximately 30 to 50% of all patients with OSAA The studies on which this value is based are relatively small and to our knowledge have only been published in abstract or letter form.
The primary aim of this report is to determine the prevalence of positional OSA defined as a total AHI > 5 with a > 50% reduction in the AHI between the supine and nonsupine postures and an AHI that normalizes (AHI < 5) in the nonsupine position. Secondary aims were to determine if positional sleep apnea as defined above can be diagnosed accurately during a combined diagnostic and CPAP titration study (split-night testing) and to compare anthropomorphic and polysomnographic data between patients who do and do not meet this definition of positional sleep apnea. It is unpleasant feelings when you wake up during night because of lack in oxygen but Canadian Neighbor Pharmacy may help you to change the situation considerably due to the drugs sold by our pharmacy. Command the service and cope with you problems.
The sleep records of consecutive patients referred for overnight polysomnography to rule out OSA at the Veterans Affairs Western New York Healthcare System Sleep Center (VAWNY) from January 8, 2001, to November 12, 2002, and from an Associated Sleep Center (ASC) from March 6, 2003, to August 8, 2003, were reviewed for study. Two hundred sixty-nine patients who underwent all-night diagnostic polysomnography and 57 patients who underwent a combined diagnostic and CPAP titration split-night study from the VAWNY sleep center and 242 patients from the ASC who underwent diagnostic polysomnography alone comprised the sample of records for the study. Patients with split-night studies at the ASC were not included since the way in which the data were collected digitally made it difficult to separate the diagnostic from the therapeutic portion of the study when addressing postural effects. Studies that did not include at least 15 min of data in both the supine and nonsupine postures were excluded from analysis. At both sleep centers, patient demographics were recorded. At the VAWNY, the Ep-worth sleepiness scale and neck circumference were obtained in all patients on the night of the sleep study. The Institutional Review Boards of the VAWNY and the University of Buffalo approved the study.
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Standard overnight polysomnography included recordings of EEG, electro-oculogram, submental and bilateral leg electromyograms, and ECG. Airflow was measured by a nasal pressure transducer (VAWNY: Pro-flo plus; Pro-Tech; Mukiteo, WA; and ASC: Ultima pressure transducer; Braebon; ON, Canada) and respiratory effort by thoracoabdominal piezoelectric belts. Measurement of arterial oxyhemoglobin saturation was performed with a pulse oximeter (VAWNY: Nonin 8600M; Nonin Medical;
Plymouth, MA; and ASC: Nellcor N-200; Nellcor Puritan Bennett; St Louis, MO) with the probe placed on the patient’s finger. All signals were collected and digitized on a computerized polysomnography system (VAWNY: Sandman; Nellcor Puritan Bennett; Ottawa, ON, Canada; and ASC: Rembrandt; Aerosep Corporation; Buffalo, NY).
Body position was confirmed by direct observation of the patient by the technician using a low-light camera. Each technician was responsible for monitoring of one or two sleeping patients. The camera monitors were placed side by side in the control room to allow simultaneous visualization of the patient’s body position. If the technician missed a change in patient posture, the digital recording was backtracked and posture tag was placed (to denote a change in posture) when gross movement artifact was seen on the sleep record. At the VAWNY, a videotape recording of the patient synchronized to the sleep digital recording was obtained in all patients. The scoring technician then rescored the record using the videotape recording to determine the time in each sleep posture. In 10 patients, an epoch-by-epoch comparison of scoring was calculated based on direct observation of the patient by the nighttime technician and a scoring from the videotape record.
Sleep stages were scored in 30-s epochs according to the Rechtschaffen and Kales sleep scoring criteria. Each epoch was analyzed for the number of apneas and hypopneas when an apnea was defined as the absence of airflow for > 10 s. An obstructive apnea was defined as the absence of airflow in the presence of rib cage and/or abdominal excursions, and a central apnea was defined as the absence of both airflow and rib cage and abdominal excursions. Events were scored as hypopneas when a visible reduction in airflow lasting at least 10 s was associated with either a 4% decrease in arterial oxyhemoglobin saturation or when an EEG arousal occurred. An arousal was defined according to the criteria proposed by the Atlas Task Force. The AHI was defined as the number of apneas and hypopneas per hour of sleep. A sleep study finding for OSA was considered positive when the AHI was > 5/h. As recommended by the American Academy of Sleep Medicine task force, the severity of sleep apnea was classified as mild if the AHI ranged from 5 to 15/h, moderate when the range was 15 to 30/h, and severe when the AHI was > 30/h. Each epoch was classified as being either in the supine or nonsupine postures (prone or lateral) and if there was a > 50% reduction in the AHI between the supine and nonsupine postures and the AHI in the nonsupine posture was < 5/h, the patient was identified as having positional sleep apnea. Sleep records were initially scored by a certified sleep technologist and then reviewed by an American Board of Sleep Medicine-certified sleep physician. Patients at the VAWNY are offered split-night studies if their AHI during the initial portion of the study (a minimum of 2 h of recording) was > 40/h or from 20 to 40/h if the patient was coming from a considerable distance.
Descriptive statistics were performed. Data are expressed as mean ± SD. Means were compared using Student t test and Mann-Whitney test when the data were not normally distributed. Proportions were analyzed using x2 analysis with Yates continuity correction or Fisher Exact Test when appropriate.