A 45-year-old male presents with persistent hypertension that has been refractory to lifestyle modifications, perindopril and amlodipine. He reports excessive daytime sleepiness, snoring loudly at night, and his spouse has noticed episodes where he seems to stop breathing while asleep. Cardiovascular examination is normal besides obesity with BMI 33. Blood electrolyte levels and renal function are normal. Which of the following would most likely yield positive findings?