0609 RELATIONSHIP BETWEEN PAIN AND POLYSOMNOGRAPHIC MEASURES IN ADULTS WITH OBSTRUCTIVE SLEEP APNEA

Abstract

Introduction: In severe OSA patients, CPAP therapy reduced pain sensitivity. However, in chronic pain patients, the presence of untreated OSA related to lower pain sensitivity. Also, in pediatric OSA patients, lower SpO2% nadir related to lower need for morphine following adenotonsillectomy. Opposing effects of sleep fragmentation and hypoxemia on pain perception in OSA were proposed. We collected pain measures in adult patients undergoing PSG for suspected OSA. Method(s): On the PSG evening, 49 patients (18-59y.o., 24 women, 27 minorities, no neurological or endocrine conditions) reported pain intensity (PI) and its functional effects (FE) for the preceding 6 months using Chronic Pain Grade Scale (CPGS), and for the preceding 24 hours using Brief Pain Inventory (BPI). A forearm pressure pain threshold (PPTh) was measured in the evening and the following morning. Backward regression was used to predict pain scores from sex, age, BMI, sleep efficiency, awakenings, arousal index, N1%, AHI, SpO2% nadir, time spent below SpO2 90% (TimeO2<90%), and desaturation index. Result(s): Mean AHI=22.9 +/- 32.5. Lower SpO2% nadir predicted lower CPGS-PI (p=0.04), lower CPGS-FE (p=0.008) and lower BPI-PI (p<0.001). Longer TimeO2<90% predicted lower BPI-PI (p=0.02). Higher AHI predicted higher CPGS-FE (p=0.04). Evening PPTh showed greater pain tolerance with increased TimeO2<90% (p=0.04) and increased N1% (p=0.005). Morning PPTh showed greater pain tolerance with lower AHI (p=0.001), higher N1% (p=0.046) and higher arousal index (p=0.02). Conclusion(s): More profound OSA-related oxyhemoglobin desaturation relates to lower long-term and short-term retrospective ratings of pain, and to higher pain tolerance on a psychophysical measure, suggesting pain-blunting effect of hypoxemia. Higher respiratory event frequency relates to higher long-term pain ratings and lower pain tolerance on PPTh, suggesting hyperalgesic effect. However, increased sleep fragmentation, as measured by N1% and arousals, appears to increase pain tolerance in OSA patients.