1022 ANALYSIS OF SLEEP DISORDERED BREATHING AND ALVEOLAR HYPOVENTILATION AMONG OBESE HYPOTHYROID PATIENTS UNDERGOING NOCTURNAL POLYSOMNOGRAPHY

Abstract

Hypothyroidism is associated with depression of hypoxic and hypercapnic ventilatory drives, resulting in alveolar hypoventilation (pCO2>45 torr). There is dearth of studies describing prevalence of hypoventilation in obese hypothyroid patients undergoing nocturnal polysomnography (NPSG). This is a retrospective study of consecutive obese (BMI ≥ 30 kg/m2) adult hypothyroid subjects who underwent NPSG between November 2015 and October 2016. Data collection included demographics, NPSG variables, end-tidal pCO2 (PetCO2), peak CO2, % of total sleep time with PetCO2 >50 torr (pCO2>50), oxygen saturation (SpO2) nadir, average sleep SpO2, comorbidities, and thyroid stimulating hormone (TSH). We used Chi-square test and Wilcoxon’s rank order test for statistical analysis. We identified 53 subjects: 18 with and 35 without alveolar hypoventilation. The demographic variables reported as median (quartile1, quartile3) were: age 58 (47, 68) years, BMI 37.8 (34.1, 44.3), female 66%. The variables which were significantly associated with hypothyroid subjects with alveolar hypoventilation compared to hypothyroid subjects without alveolar hypoventilation were: AHI 40 (19.5,69.7) vs 18.6 (7.7,30) [p=0.038], SpO2 nadir: 79% (73%,83%) vs 86% (80.5%,88.5%) [p=0.018], average sleep SpO2: 92% (90%,94%) vs 95% (94%,96%) [p=0.0076], TSH: 2.7 (1.5,7.9) vs 1.28 (0.04,2.36) [p=0.03], peak CO2: 59.5 (57,62) vs 50 (45,52.5) [p<0.0001] and pCO2>50: 57% (24%,84%) vs 0% (0%,1%) [p<0.0001]. Uncontrolled hypothyroidism was present in 36.4% of the subjects with hypoventilation as compared to 9% of those without hypoventilation, along with a higher percentage of the following comorbidities: hypertension (78% vs 71%), heart failure (39% vs 11%), depression (27% vs 22%) and diabetes (72% vs 31%), with only diabetes being statistically significant [p=0.004]. Adult obese hypothyroid subjects with alveolar hypoventilation have lower average sleep oxygen saturation, lower oxygen saturation nadir, and higher AHI compared to those without hypoventilation. None.