Preliminary Study of The Periodic Limb Movement Disorder Following Nasal CPAP:Is it associated with Supine-Sleeping position?

Yang, C K; Clerk, Alex A

Abstract

INTRODUCTION: Periodic limb movement disorder(PLMD) is shown to common in patients with OSA and may become evident or worsened when treated with nasal continuous positive airway pressure(CPAP). Whether this due to improved sleep continuity, adverse nocturnal body positioning, uncovered by CPAP, or due to the CPAP stimulus is still debat-ed. We hypothesized that the increase in PLM activity following CPAP is associated with more supine-sleeping tendencies when being treated with CPAP. In the present work, we compared differences in the PLMD index(PLMI)and sleeping position of patients with sleep disordered breathing before and after CPAP treatment. METHOD: We studied 16 patients(mean age 46yr, 9M, 7F) with OSA(11 patients) or UARS(5 patients) who either had PLMD on intial polysomnogram (baseline PSG) or on nasal CPAP trial(CPAP PSG). All periodic leg movements were scored on anterior tibialis EMG during sleep according to standard criteria(net duration;0.5-5.0 seconds, intervals; 4-90 seconds. 4 consecutive movements). Paired t-tests compared PLMD index (PLMI), PLMD-related arousal index(PLMD-ArI), respiratory disturbance index(RDI), and supine sleeping position spent with baseline PSG and CPAP PSG.
RESULTS
Ten patients(63%) on baseline PSG and fifteen patients(94%) on CPAP PSG had documented PLMD(PLMI> or =5) respectively with significant increase on CPAP PSG(p<0.05). Ten patients showed the emergence(6/10 patients) or substantial worsening(4/10 patients) of PLMD during CPAP trial. Mean CPAP pressure was 7.6+/-1.8cmH2O. PLMI tended to increase from baseline PSG to CPAP PSG, and significantly increase when excluding 2 outlier(baseline PSG,19.0+/-25.8/hr vs CPAP PSG, 29.9+/-12.5/hr, p<0.1). PLMD-ArI showed no significant change, but a significant decrease was detected when excluding 2 outlier(p<0.1). There was no significant sleeping positional difference(supine vs non-supine) on baseline PSG, but significantly more supine position(supine vs no-supine, p<0.05) on CPAP PSG. There was no significant difference in PLMI during supine-sleeping and nonsupine-sleeping position on both of baseline PSG and CPAP PSG. There was also no significant difference in PLMI during supine-sleeping position between baseline PSG and CPAP PSG. With nasal CPAP, there was a highly significant reduction in the RDI(baseline PSG, 14.1+/-21.3/hr vs CPAP PSG, 2.7+/-3.9/hr, p<0.05).
CONCLUSION
This preliminary data confirms previous findings that CPAP is a very effective treatment for OSA, and that PLMD is developed or worsened with treatment by CPAP. This data also indicates that supine-sleeping position is more common when being treated with CPAP. However, there was no clear evidence that supine position is the causal factor of increased PLMD with CPAP. It is, however, suggested that the relative movement limitation induced by CPAP treatment could be a contributory factor of PLMD.