Metabolic Impact of Intermittent CPAP

Not Applicable

Completed

Brief Summary: Obstructive sleep apnea is a risk factor for diabetes and cardiovascular disease, by unknown mechanisms. The investigators hypothesize that sleep apnea changes glucose and lipid metabolism during sleep, which over time could lead to diabetes and cardiovascular disease. This study examines metabolic changes during sleep in patients with obstructive sleep apnea. Patients accustomed to continuous positive airway pressure (CPAP) therapy are enrolled to undergo sleep studies, either on CPAP therapy or after withdrawing from CPAP for 3 nights. During sleep, blood samples are obtained so that metabolic function can be compared between sleep apnea and CPAP nights.

Detailed Description: Participants with a history of moderate severe sleep apnea (AHI\>20) will be enrolled if participants meet inclusion/exclusion criteria. Investigators will report to the sleep laboratory on two nights, (1) after continuing their CPAP or (2) after discontinuing CPAP for 3 nights. The order of observation will be randomized. A standard research dinner is provided before each study. IV's are placed so that blood can be sampled at frequent (30 min) intervals throughout the night. In the morning after each study, a glucose tolerance test and endothelial function study (endoPAT) are performed. Serum samples will be analyzed for glucose, insulin, free fatty acids, triglycerides, hormones, and other metabolic biomarkers.

Recruitment & Eligibility

Inclusion Criteria

History of moderate to severe Obstructive sleep apnea (OSA) (AHI or respiratory disturbance index (RDI)> 10).
They must also own a CPAP machine and report the ability to tolerate sleeping with or without CPAP during the night.

Exclusion Criteria

Uncontrolled hypertension with systolic blood pressure >170 or diastolic blood pressure > 110
Congestive heart failure
Use of clonidine or nicotinic acid medication
Diabetes requiring the use of insulin
Known pregnancy, by urine testing in women of child-bearing age
History of falling asleep while driving, near miss
High risk occupation (pilot, commercial driver)
Hemoglobin < 10 g/dL on point of care screening

Arm && Interventions

Group	Intervention	Description
CPAP withdrawal;	CPAP withdrawal	Cessation of established CPAP therapy for 3 nights. CPAP will NOT be worn during this period, and a metabolic sleep study off CPAP is performed in the research laboratory on the third night.

Primary Outcome Measures

Name	Time	Method
Concentration of Plasma Triglycerides (mg/dl)	2 nights, <1 month apart. Data from each night was averaged to report a single value.	We will report the mean for all participants per group (CPAP vs. CPAP withdrawal).
Concentration of Plasma Free Fatty Acids (FFA, mmol/L)	2 nights, <1 month apart. Data from each night was averaged to report a single value.	We will report the mean for all participants per group (CPAP vs. CPAP withdrawal).
Concentration of Plasma Glucose (mg/dl)	2 nights, <1 month apart. Data from each night was averaged to report a single value.	We will report the mean for all participants per group (CPAP vs. CPAP withdrawal).
Concentration of Plasma Insulin (mcU/ml)	2 nights, <1 month apart. Data from each night was averaged to report a single value.	We will report the mean for all participants per group (CPAP vs. CPAP withdrawal).

Secondary Outcome Measures

Name	Time	Method
Oral Glucose Tolerance Test (OGTT)	2 nights, <1 month apart. 5 OGTT values were averaged to a obtain a single value.	We will report the mean of the area under the curve (AUC) during OGTT for all participants per group (CPAP vs. CPAP withdrawal).
Augmentation Index (AI)	2 nights, <1 month apart, 1 measurement each visit	Measured in the morning using Itamar EndoPAT device. Augmentation index is measured once during each visit, and is expressed as a % increase in the pressure waveform during systole. We will report the mean for all participants per group (CPAP vs. CPAP withdrawal).
Reactive Hyperemia Index (RHI)	2 nights, <1 month apart, 1 measurement each visit	Measured in the morning using Itamar EndoPAT device. This will measure the ratio of blood flow after brachial artery occlusion to blood flow prior to brachial artery occlusion. Normal values range from approximately 1 to 3 with higher values being associated with better vascular function. We will report the mean for all participants per group (CPAP vs. CPAP withdrawal).