30 CIENCIAS Cardiovascular Autonomic Regulation, ETCO2 and the Heart Rate Response to the Tilt Table Test in Patients with Orthostatic Intolerance Chronic orthostatic intolerance (COI) is defined by changes in heart rate (HR), blood pressure (BP), respiration, symptoms of cerebral hypoperfusion and sympathetic over-activation. Postural tachycardia syndrome (POTS) is the most common form of COI in young adults and is defned by an orthostatic increase in heart rate (HR) of≥30 bpm in the absence of orthostatic hypotension. However, some patients referred for evaluation of COI symptoms do not meet the orthostatic HR response criterion of POTS despite debilitating symptoms. Such patients are ill defined, posing diagnostic and therapeutic challenges. This study explored the relationship among cardiovascular autonomic control, the orthostatic HR response, EtCO2 and the severity of orthostatic symptoms and fatigue in patients referred for evaluation of COI. Patients (N=108) performed standardized testing protocol for the Autonomic Refex Screen and completed the Composite Autonomic Symptom Score (COMPASS-31) and the Fatigue Severity Scale (FSS). Greater severity of COI was associated with younger age, larger phase IV amplitude in the Valsalva maneuver and lower adrenal barorefex sensitivity. Greater fatigue severity was associated with a larger reduction in ETCO2 during 10 minutes of head-up tilt (HUT) and reduced low-frequency (LF) power of heart rate variability. This study suggests that hemodynamic changes associated with the barorefex response and changes in EtCO2 indicate a stronger association with the severity of orthostatic symptoms and fatigue than the overall orthostatic HR response in patients with COI. Wheeler, C., Pacheco, J.M., Kim, A.C. et al. Cardiovascular Autonomic Regulation, ETCO2 and the Heart Rate Response to the Tilt Table Test in Patients with Orthostatic Intolerance. Appl Psychophysiol Biofeedback 47, 107–119 (2022). https://doi. org/10.1007/s10484-022-09536-4 jannay m. pacheco torres maestría en ciencias con especialidad en neurociencias integradas y aplicadas en neurociencia clínica mentor: dra. marisol camacho y dr. josé r. criado pots autonomic nervious system etco2 hrv valsaba maneuver
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