SAN DIEGO — Two weeks of continuous positive airway pressure significantly reduced the blood pressure of hypertensive obstructive sleep apnea patients in a small randomized controlled trial presented in a poster at the International Conference of the American Thoracic Society.
Dr. Daniel Norman reported that nighttime systolic, mean arterial, and diastolic blood pressure decreased by 6 mm Hg, 5 mm Hg, and 4 mm Hg, respectively, in 18 patients on continuous positive airway pressure (CPAP).
Daytime mean arterial pressure (MAP) and diastolic blood pressure each declined by 3 mm Hg as well. Though the difference was not statistically significant, daytime systolic blood pressure also dropped by about 2 mm Hg.
“This kind of improvement in blood pressure is similar to what you'd see with many hypertensive medications,” Dr. Norman, a fellow in pulmonary and critical care at the University of California, San Diego Medical Center, said at a press briefing.
Based on these reductions, he added, “You would expect to see improvement in morbidity and mortality.”
In contrast, 24-hour ambulatory blood pressure monitoring revealed no significant improvements in the blood pressure of 13 patients treated with supplemental oxygen or of 15 patients on placebo. The investigators adapted the equipment taken home by patients, so that the assigned apparatus looked the same regardless of which therapeutic option was delivered.
Though patients given supplemental oxygen did have better oxygenation saturation, this did not appear to have an impact on blood pressure, according to Dr. Norman and his coinvestigators in the departments of medicine and psychiatry at the university. They speculated that CPAP's ability to improve blood pressure may involve “mechanisms other than improvement of nocturnal oxyhemoglobin saturation.”
After 2 weeks of therapy, both the CPAP and supplemental oxygen groups registered improvements in average nocturnal saturation of oxyhemoglobin (SpO2) and average SpO2 nadir. These values had been similar in all three groups at baseline, but the final SpO2 values for both CPAP and supplemental oxygen patients were higher than those recorded in patients on placebo.
Apnea/hypopnea index (AHI) and oxygen desaturation index (ODI) scores fell in the groups treated with CPAP or supplemental oxygen, but the investigators reported “the magnitude of change was smaller in the oxygen group and not enough to differentiate it from placebo.”
Dr. Norman noted that obstructive sleep apnea is known to increase the risk of hypertension. He also acknowledged that half of the sleep apnea patients offered CPAP find they cannot tolerate it and seek other therapies, such as supplemental oxygen.
The trial doesn't rule out supplemental oxygen, he commented, “but it reaffirms that CPAP remains the gold standard of therapy.”
The patients in the trial ranged from 25 to 65 years of age with a mean body mass index of 29.5–31.5 kg/m
Mean arterial pressure at baseline was 91.2 mm Hg in the placebo group, 94.9 mm Hg in patients treated with oxygen, and 98.1 mm Hg in the CPAP group. Average diastolic blood pressure was 75.6 mm Hg, 76 mm Hg, and 79.6 mm Hg, respectively.