Joined: Feb 2012
Machine: PR System One REMstar Auto (DS560)
Mask Type: Nasal pillows
Mask Make & Model: ResMed Mirage Swift II
CPAP Pressure: 12.5 - 18.5 cmH20 (auto range)
CPAP Software: SleepyHead
Other Comments: Have diabetes Type II
Location: Illinois, USA
RE: Sleeping in a semi-inclined position
It's widely believed that the severity of sleep apnea is affected by sleeping positions.
Here's one summary of a study that was done:
Quote:Positional vs. Nonpositional Obstructive Sleep Apnea Patients Anthropomorphic, Nocturnal Polysomnographic, and Multiple Sleep Latency Test Data
Arie Oksenberg, PhD; Donald S. Silverberg, MD; Elena Arons, PhD; and Henryk Radwan, MD
The Sleep Disorders Unit, Loewenstein Hospital Rehabilitation Center, Raana, Israel, and the Department of Nephrology, Tel-Aviv Medical Center, Tel-Aviv, Israel
Published in Chest Vol. 112(3), pp 629-639, 1997
In some patients with Obstructive Sleep Apnea (OSA), the severity of their apnea and sleep disturbance as measured by the Respiratory Disturbance Index (RDI) is twice as high or more when sleeping on their backs (the supine position) compared to sleeping on their sides (the lateral position). This is referred to as Positional Sleep Apnea. In contrast, those with less or no change in RDI related to sleeping position are said to have Nonpositional Sleep Apnea.
In Positional patients, the RDI measured in a sleep study depends largely on how much time they spend in the supine vs. lateral positions. Some may even lower their RDI to normal simply by sleeping always on their sides.
Estimates as to the prevalence of such Positional apnea among patients with OSA have varied widely, from 9% to 60%, probably related to the small size of many samples.
This study undertook to draw on a large group of 666 consecutive patients diagnosed with OSA between 1990 and 1995 at the Loewenstein Hospital Sleep Disorders Unit. The purpose was to compare Positional and Nonpositional patients on anthropomorphic measures (measures of body size), nocturnal polysomnography data, and Multiple Sleep Latency Test data.
After eliminating patients younger than 20, obese patients, and borderline ill apneics with RDI's less than 10/hr, they were left with 574 patients. These comprised their study group. All patients had overnight sleep studies in the lab and all those who complained of daytime sleepiness had MSLT's as well. The authors also included four obese patients with an average BMI of 33.6 who refused CPAP and had a sleep study before and after a weight reduction program.
Using the criterion that supine RDI had to be at least twice as high as lateral RDI, they identified 321 patients (56% of the total) as having Positional Apnea, the remaining 253 (44%) having Nonpositional Apnea.
The Positional patients were slightly but significantly younger than the Nonpositional patients (52.9 years vs. 54.9 years, SD=+/-10). The Positional patients were also significantly thinner (BMI 29.4 vs. 31.9, SD=+/-4.1 vs. 4.9). However, the two groups were of virtually identical height and the weight difference between them was only about 14 pounds, with a standard deviation of about 33 pounds, indicating very substantial overlap in weight between the two groups, as with age.
On measures of sleep, the Positional group showed an advantage with greater total sleep time (422 mins vs. 407 mins, SD=+/- 57 vs. 77) so that they slept on average 15 minutes more, again with great overlap between the groups. Positional patients showed greater sleep efficiency (83% vs. 80%, SD=+/- 11% vs. 12%). The Positional patients had less light sleep (stage 1: 5.4% vs. 7.0%; stage 2: 55.0% vs. 61.3%) and more deep sleep (stage 3: 5.2% vs. 4.2%; stage 4: 12.9% vs. 9.7%); to reduce confusion of numbers, I have omitted standard deviations here but they follow the same pattern of substantial overlap. Positional patients had fewer brief arousals of less than 15 seconds duration (159.2 vs. 209.6) but not so with arousals of greater duration which were much less common overall.
There were a number of sleep variables on which the two groups did not differ significantly: sleep latency, REM latency, number of REM periods, duration of REM periods, percentage of REM sleep, and time awake after onset of sleep.
The Positional patients had an advantage on four measures of breathing: the Apnea Index, the Respiratory Disturbance Index, the Minimum Oxygen Saturation during REM, and the Minimum Oxygen Saturation during Non-REM sleep. The Respiratory Disturbance Index or RDI, possibly the most interesting and fundamental variable, was 27.8/hr for Positional patients and 44.0/hr for Nonpositional patients (standard deviations were +/-17.7 and 29.7 respectively, also rather different, suggesting more variability among the Nonpositional patients in severity of sleep apnea.
The MSLT was not used on all patients, so the comparison here was between 194 Positional patients (60.4% of their total) and 175 Nonpositional patients (69.2% of their total), which was a significant difference suggesting more complaints of Excessive Daytime Sleepiness in the Nonpositional group. Other differences between the two groups on measures from this test were of only borderline statistical significance. Neither did the two groups differ on measures of Periodic Leg Movements of Sleep.
Among four categories of increasing severity of RDI, the Positional patients showed no differences in amount of time spent sleeping in the supine position. In the most severe category, with RDI greater than 40, Positional patients comprised a smaller proportion (32%) of the total. Within each category of severity, Positional Apnea was less common among the obese patients (BMI greater than 30) than among the non-obese patients. A nonobese patient was more likely to be Positional than an obese one.
Among the four severely obese patients who opted for a weight loss program rather than CPAP, all succeeded in losing weight, 22 pounds to 72 pounds, a change of 11% to 27% from their initial weights. In all four cases the RDI fell to normal in the lateral sleeping position but remained elevated in the supine position, thereby converting these four initially Non-Positional sleep apneics to Positional patients.
Age was marginally related to Positional sleep apnea, the oldest patients (over 60) having a lower likelihood of being positional (48.6%).
In their discussion of these results, the authors emphasized the high proportion of Positional Sleep Apnea among their large group of OSA patients, and the fact that these Positional patients were younger, weighed less, had less severe breathing abnormalities and better sleep quality than the Nonpositional patients. They stressed the inverse relationship of RDI to Positional sleep apnea and the power of RDI as a predictor of Positionality.
They proposed that Positional patients would be good candidates for positional therapy, whereas severe Nonpositional patients would be candidates for CPAP as treatment of choice. They went further and suggested that patients with Upper Airway Resistance Syndrome, as the mildest form of OSA, would be optimal candidates for Positional therapy, perhaps thereby avoiding the further development of the syndrome with a minimally intrusive treatment measure.
They saw Positionality as a characteristic of Obstructive Sleep Apnea in its earlier, milder stages, and loss of Positional effects as characteristic of later-stage, more severe OSA. From the experience of their four obese patients who lost weight and reduced their lateral RDIs to become Positional, the authors considered this course of the illness reversible with weight loss. Conversely, they suggested that alcohol and sleep deprivation, as factors exacerbating OSA, could convert Positional Sleep Apnea to Nonpositional Sleep Apnea. They noted the parallel relationship of snoring to sleep position but admitted that Positional therapy might not eliminate snoring as effectively as CPAP.
They noted that Positional Sleep Apnea might be considerably less common in a more obese and severely ill population seen in some other clinical settings.
They pointed to a need for anatomical studies of changes in the Upper Airway in supine versus lateral sleeping positions, which might explain the Positionality effect. They mentioned a couple of studies suggesting differences in the anatomical structure of the Upper Airway in Positional patients versus Nonpositional patients, differences generally in the nature of Positional patients having a less restrictive space for the passage of air and a more elliptical shape with a larger diameter from side-to-side, which one might expect to reduce the gravity effect on airway size of the recumbent sleeping position.
They expressed surprise at the limited number of studies carried out on the therapeutic efficacy of positional treatments, and even the rarity of monitoring sleep position in sleep labs, contrary to standards of practice. In some recent reviews, Positional therapy has even gone unmentioned as a treatment for OSA. Perhaps this is because, even sleeping in the lateral position, Positional Sleep Apneics may continue to snore and cause complaints from spouses. Another possible explanation is that positional treatment is not appropriate for the most severely and dangerously ill of Sleep Apneics.
They note that, as patients with non-Positional Sleep Apnea lose weight they may turn into Positional Sleep Apneics who could be effectively treated with positional therapy instead of CPAP, giving hope of eventually dispensing with the CPAP machine. They also mentioned some people finding the sitting position equally effective in improving breathing during sleep.
The actual means of accomplishing Positional therapy may vary. The authors use a tennis ball (or several) sewn into a vertical pocket on the back of a T-shirt to be worn at night. Another investigator used an alarm to wake patients when they lay on their backs. However, a few months after ceasing to use the alarm patients had started to resume supine sleeping a larger proportion of the time.
Study objectives: To compare anthropomorphic, nocturnal polysomnographic (PSG), and multiple sleep latency test (MSLT) data between positional (PP) and nonpositional (NPP) obstructive sleep apnea (OSA) patients.
Design: This is a retrospective analysis of anthropomorphic, PSG, and MSLT data of a large group of OSA patients who underwent a complete PSG evaluation in our sleep disorders unit. The patients were divided in two groups: the PP group, those patients who had a supine respiratory disturbance index (RDI) that was at least two times higher than the lateral RDI, and the NPP group, those patients in whom the RDI in the supine position was less than twice that in the lateral position.
Subjects: From a group of 666 consecutive OSA patients whose conditions were diagnosed in our unit from September 1990 to February 1995, 574 patients met the following criteria and were included in the study: RDI>10; age>20 years, and body mass index (BMI)>20.
Results: Of all 574 patients, 55.9% were found to be positional. No differences in height were observed but weight and BMI were significantly higher in the NPP group, these patients being on the average 6.5 kg heavier than those in the PP group. The PP group was, on average, 2 years younger than the NPP group. Nocturnal sleep quality was better preserved in the PP group. In this group, sleep efficiency and the percentages of deep sleep (stages 3 and 4) were significantly higher while the percentages of light sleep (stages 1 and 2) were significantly lower than in the NPP group. No differences for rapid eye movement (REM) sleep were found. In addition, wakefulness after sleep onset and the number of short arousals (<15 s) were significantly lower in the PP group. Apnea index and total RDI were significantly higher and the minimal arterial oxygen saturation in REM and non-REM sleep was significantly lower in the NPP. No differences in periodic limb movements data were found between the two groups. The average MSLT was significantly shorter in the NPP group. Univariate and multivariate stepwise logistic regression analysis showed that the most dominant variable that correlates with positional dependency in OSA patients is RDI, followed by BMI which also adds a significant contribution to the prediction of positional dependency. Age, although significant, adds only a minor improvement to the prediction of this positional dependency phenomenon. A severe, obese, and older OSA patient is significantly less likely to be positional than a mild-moderate, thin, and young OSA patient. In four obese OSA patients who lost weight, a much more pronounced reduction was seen in the lateral RDI than in the supine RDI, and three of these cases who were previously NPP became PP.
Conclusions: In a large population of OSA patients, most were found to have at least twice as many apneas/hypopneas in the supine than in the lateral position. These so-called "positional patients" are on the average thinner and younger than "nonpositional patients." They had fewer and less severe breathing abnormalities than the NPP group. Consequently their nocturnal sleep quality was better preserved and, according to MSLT data, they were less sleepy during daytime hours. RDI was the most dominant factor that could predict the positional dependency followed by BMI and age. RDI showed a threshold effect, the prevalence of PP in those with severe RDI (RDI≥40) was significantly lower than in those OSA patients with mild-moderate RDI. BMI showed a major significant inverse relationship with positional dependency, while age had only a minor although significant inverse relationship with it. Body position during sleep has a profound effect on the frequency and severity of breathing abnormalities in OSA patients.
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