Effect of CPAP on arterial stiffness in severely obese patients with obstructive sleep apnoea.

Background: Obstructive sleep apnoea (OSA) may independently increase cardiovascular risk in obesity. Although there is evidence that arterial stiffness is altered in OSA, knowledge of these effects with continuous positive airway pressure (CPAP) in severe obesity (body mass index (BMI) ≥ 35 kg/m(2)) is limited. This study aimed to explore how arterial stiffness, as measured by the augmentation index (Aix), changed in severely obese patients with OSA who were treated with CPAP and in patients without OSA.
Methods: Forty-two patients with severe obesity-22 with OSA, 20 without OSA-were recruited at baseline and followed-up after a median of 13.5 months. Pulse wave analysis (PWA) was performed using applanation tonometry at the radial artery to measure augmentation index (Aix), augmentation pressure (AP) and subendocardial viability ratio (SEVR). Cardiovascular parameters and body composition were also measured.
Results: There were significant improvements in Aix, AP (both P < 0.001) and SEVR (P = 0.021) in OSA patients on CPAP compared with subjects without OSA. Epworth scores (P < 0.001), systolic (P < 0.001) and mean arterial pressures (P = 0.002) improved with CPAP. Regression showed that CPAP was significantly associated with change in arterial stiffness from baseline. However, patients with OSA on CPAP continued to have increased arterial stiffness (Aix) (P < 0.001), AP (P = 0.028) and reduced SEVR (P = 0.002) relative to non-OSA patients.
Conclusion: Although sleepiness and blood pressure improve with CPAP in severe obesity, CPAP alone is not sufficient to modify PWA measures to levels comparable with non-OSA patients. This supports a need for a multifaceted approach when managing cardiovascular risk in patients with severe obesity and obstructive sleep apnoea receiving CPAP therapy.