{'fraction_non_alphanumeric': 0.036931818181818184, 'fraction_numerical': 0.041666666666666664, 'mean_word_length': 4.362944162436548, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
0647 The Effect of CPAP on the Blood Flow to the Brain: A Preliminary Report


 
 
 We aim to determine the effect of positive airway pressure (PAP) on total cerebral blood flow in a sample of middle-aged to older male patients with obstructive sleep apnea (OSA).
 
 
 
 We evaluated consecutive treatment-naïve male OSA patients with Apnea hypopnea Index (AHI)≥15, from January to November of 2019. We obtained demographic variables, vascular risk factors, the Epworth sleepiness scale (ESS) and the Pittsburgh sleep quality index (PSQI). Brain magnetic resonance imaging (MRI) consisted of high resolution anatomical imaging and velocity encoded phase contrast MRI to measure volumetric blood flow rate to the brain, or the total cerebral blood flow (tCBF), by summation of the flow rate through the two internal carotid and vertebral arteries. Positive airway pressure at various pressures was provided during the MRI, while subjects were awake, starting at 0 cm H20, then 5 cmH20, 10, 15, and 20 cmH20. Each setting was applied for six minutes. Two subjects did not tolerate pressure setting of 20 cmH2O.
 
 
 
 We had a total of 11 participants’ age 40-73 years, 70% Hispanic/Latino background. The average ESS was 8.2±6.0, PSQI=5.7±4.9, and AHI=48.9±25.5. Five of the subjects had hypertension and a quarter had diabetes. In all subjects total CBF monotonically decreased with increasing PAP. The initial decreases in total CBF (PAP from 0 to 5 and 5 to 10) where significantly larger than the decrease in the higher pressure range. In two subjects the total decrease in tCBF was nearly 50%. The average tCBF was 682.3 mL/min at 0 cmH20 and 506.3 ml/min at 20 cmH20.
 
 
 
 Incremental increases in PAP lead to substantial decrease in tCBF during wake. Substantial decrease in tCBF is possibly explained by decreasing end tidal CO2 pressure. The specific physiologic cause and the neurologic impact of prolonged decreased tCBF during CPAP therapy needs to be further investigated.
 
 
 
 Scientific Advisory Committee, Pilot grant, Miller School of Medicine; R21AG056952; R21HL140437; Jazz-Pharmaceutical.
