The Effect of Continuous Positive Airway Pressure on Total Cerebral Blood Flow in 23 Healthy Awake Volunteers

Continuous Positive Airway Pressure (CPAP) is used as the gold standard treatment for sleep disordered breathing, acting as a pneumatic splint to prevent collapse of the pharyngeal airway. However, the influence that CPAP has on Cerebral Blood Flow (CBF) dynamics is not well understood. This preliminary study investigates the influence of CPAP on total CBF in 23 healthy awake subjects by measuring flow velocity and lumen diameter of the left and right proximal Internal Carotid Arteries (ICA), Vertebral Arteries (VA), and Middle Cerebral Arteries (MCA) using Duplex Color Doppler Ultrasound (US) with and without CPAP at a level of 15 cm H₂O. Transcutaneous Carbon Dioxide (PtcCO2) level, heart rate, Blood Pressure (BP), and oxygen saturation (SaO2) were monitored before and after each test. The preliminary measurements indicate that CPAP results in a decrease of CBF by 17% (p-value < 0.05). The theoretically predicted decrease in CBF from PtcCO2 variation was 6%. The study should be further explored in patients with sleep apnea and various types of cerebrovascular and craniospinal disorders.