| LinkExchange Member | Free Home Pages at GeoCities |
| LinkExchange Member | Free Home Pages at GeoCities |
I came upon this article through a posting in the “Great Tennis Ball Debate” of which segments are reproduced as Article #31. A lot of what was being argued there is brought up here, namely the idea that Positional Sleep Apnea is quite common and can be treated simply and inexpensively with Positional therapy without need for CPAP or surgery. Moreover, there is the idea that obese Nonpositional patients who at first would be recommended for CPAP might lose weight, becoming Positional in the process, and susceptible to Positional therapy as a substitute for CPAP.
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), noctural polysomnography data, and Multiple Sleep Latency Test data (see Glossary).
After eliminating patients younger than 20, obese patients, and borderline ill apneics with RDIs 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 MSLTs as well. The authors also included four obese patients with an average BMI of 33.6 (see Glossary) 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, nmber 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 reversable 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.
My own contribution to this debate was an ill-advised early reference to the Tennis Ball Technique as “antiquated and quaint.” This aroused the ire of people who spent much their careers doing research to demonstrate the importance of this Positional phenomenon and the efficacy of this approach to treatment.
Without attempting any complete review of the literature on Positional therapy, not appropriate for this site in any case because much of it is not at all recent, I will admit that a little better understanding of the situation has led me to agree that positional factors and positional therapy have been unjustly neglected. It is often the case in medicine that enthusiasm over a new treatment (like the antidepressant Prozac) will lead doctors to forget about the continuing advantages of earlier treatments (like the tricyclic antidepressants and monoamine oxidase inhibitors). Older treatments are abandoned like fads that have passed in the face of newer fads, and older knowledge is sometimes lost in enthusiasm for new findings.
However, let me confine the rest of my comments here to the findings of this particular study. Here I must raise some criticisms which deter me from declaring Positional Apnea and Positional Therapy the most important aspects of OSA!
First of all, I note the large number of subjects. I have often made the point that very small groups of subjects raise the possibility that meaningful, real, clinical differences cannot be demonstrated on a statistical basis, leaving sometimes a false impression of negative findings rather than a correct impression of inadequate study design. On the other hand, very large numbers of subjects can raise the contrary problem: that small and clinically insignificant differences can be identified as statistically significant and therefore incorrectly considered “important.” I think that problem arises here. I have several times pointed out the high standard deviations compared to the small differences between groups as evidence of great overlap.
This doesn’t invalidate the fact the differences exist, on average, between the groups. But it does make it quite inappropriate for the clinician trying to simplify findings, to form a stereotype, such as that a thin patient must be both mildly ill and positional, or the contrary. This kind of stereotyping can lead to frequent errors in clinical judgment. When I look at the magnitude of differences in BMI and age between the two groups, I wonder whether standing all the Positional and Nonpositional patients in two separate groups would permit an observer tell which was which by visual inspection. Certainly an observer could not go through a mixed group and pick the Positional and Non-Positional patients apart by their weight and age! Perhaps he could do so given the knowledge of their RDIs, but this confounds one measure of severity with what may be another (ie, Positionality).
Furthermore, the authors imply a sanguine attitude towards weight loss that seems quite unjustified. Many people can lose weight for a short time, but almost all put it back on again. Will the sleep clinician who opted for the economical measure of instructing the patient in the Tennis Ball Tecnique be continuing to follow that patient when the weight comes back, the sleep apnea worsens and becomes Nonpositional, the patient retries the Positional therapy on his own and doesn’t realize it’s not working any more, and meanwhile becomes more and more obese, depressed, dimwitted, even incapable of functioning at work or driving safely, and also acquires hypertension and chronic obstrucitve pulmonary disease and brain damage as a result of the uncontrolled OSA previously diagnosed as “mild” and easily managed by sleeping on his side? Catastrophe may eventuate in the form of an auto accident, stroke, heart attack; patients may lose licenses to drive or to practice their livelihood. Perhaps the clinical who administered the Positional therapy, having ascertained improvement, has told the patient to come back if problems recur. Perhaps the patient, experiencing what he viewed as a quick and easy solution with no need for intensive aftercare, or else a treatment which failed, will not come back, nor seek dreaded alternatives elsewhere.
One positive aspect of CPAP is that it forces the patient to remain aware of his condition and the doctor to maintain some contact and responsibility for that patient with periodic follow-up examinations and sleep studies to ascertain that the settings and the machine are still working properly, that the patient is in good physical health, etc. This is an important advantage when dealing with a chronic, progressive, potentially disabling or even fatal illness. It is not appropriate to treat such a disease with a “quick fix” that leaves an impression of favoring intervention of minimal cost, duration, and intrusiveness.
What works wonderfully well today and even next month may not be working many months later, when the patient is out of sight and mind. What is needed here are very long-term studies, with follow-ups ranging into many years, to determine the eventual outcome of this disease. In that context, I suspect, the effect size of a positional interventional may assume the dimensions of a rather small blip in a catastrophic course of events!
WHAT DO YOU THINK ABOUT THIS
ARTICLE AND MY COMMENTS ON IT? CAN YOU RELATE IT TO ANY PERSONAL EXPERIENCES?
If you can add any thoughts or comments, please E-mail me (and mention the article you are commenting on) at
Get your own Free Home Page