Study of the vascular wall by means of functional imaging in patients with sleep apnea
Obstructive sleep apnea (OSA) is a disorder with a high prevalence, which is present in 5 to 10% of the general population, depending on its severity. Untill recently sleepiness during the daytime, fatigue and concentration problems are considered as the most important consequences of the disease. These symptoms are often present and disappear quickly after the start of adequate treatment with CPAP (1). The last decennium it has become clear that sleep apnea, which is characterized by repetitive oxygen desaturation, with inherent reoxygenation, is an important source of oxidative stress and systemic inflammation. More recently these changes have been associated with increasing vascular pathology. Indeed, sleep apnea is associated with hypertension and an increasing cardiovascular morbidity and mortality. The link between severe OSA and cardiovascular burden has been shown convincingly by a very significant reduction of cardiovascular morbidity in patients with adequate nCPAP therapy compared to untreated OSA patients (2). OSA can lead to cardiovascular pathology by an incrase in sympathetic tone, but probably also by complex inflammatory processes
and oxidative stress at the vascular wall (3). Therefore it is extremely important to describe in a very sensitive and adequate manner the changes in the structure of the vascular wall in OSA patients. The structural changes in the larger vessels can only be detected by means of a threedimensional reconstruction. Moreover, it is of interest to calculate the vascular resistance. Only recently, an analysis method has become available which makes it able to calculate resistances in geometries, when boundary conditions like pressure and flow are known. This method is known as 'computational fluid dynamics' or CFD. There is already some experience with biomedical applications of CFD in both the cardiovascular (4) and respiratory field (5). In the current research project we will study patients with different degrees of sleep apnea, before and after adequate treatment, with focus on the structure of the vascular wall, using CFD. The treatments which will be considered are antioxidants and anti-inflammatory drugs compared to CPAP. Also the effect of combination therapies will be evaluated.
1. McMahon, J. P., B. H. Foresman, and R. C. Chisholm. 2003. The influence of CPAP on the neurobehavioral performance of patients with obstructive sleep apnea hypopnea syndrome: a systematic review. WMJ. 102:36-43.
2. Marin, J. M., S. J. Carrizo, E. Vicente, and A. G. Agusti. 2005. Long-term cardiovascular outcomes in men with obstructive sleep apnoea-hypopnoea with or without treatment with continuous positive airway pressure: an observational study. Lancet 365:1046-1053.
3. Lavie, L. 2004. Sleep apnea syndrome, endothelial dysfunction, and cardiovascular morbidity. Sleep 27:1053-1055.
4. Eloot, S., Y. D'Asseler, P. De Bondt, and R. Verdonck. 2005. Combining SPECT medical imaging and computational fluid dynamics for analyzing blood and dialysate flow in hemodialyzers. Int.J Artif.Organs 28:739-749.
5. De Backer, J., O. Vanderveken, W. Vos, A. Devolder, S. Verhulst, J. Verbraecken, P. Parizel, M. Braem, P. Van de Heyning, W. De Backer. 2007. Functional imaging using computational fluid dynamics to predict treatment success of mandibular advancement devices in sleep-disordered breathing. J Biomechanics 40:16: 3708-3714.