19 research outputs found
Intracranial Pressure Monitoring in Patients with Fulminant Hepatic Failure Treated with Plasma Exchange and Continuous Hemodiafiltration
Blood flow velocity in the common carotid artery in humans during graded exercise on a treadmill
Velocity of regional blood flow and blood flow in the middle cerebral artery in surgical leg lengthening in patients with congenital and acquired limb shortening
Subdural Intracranial Pressure and Cerebral Haemodynamics During General Anaesthesia for Craniotomy in Patients with Cerebral Aneurysm
Effect of Reverse Trendelenburg Position on Subdural Intracranial Pressure and Cerebral Haemodynamics During General Anaesthesia for Craniotomy in Patients with Supratentorial Cerebral Tumours
Aging blunts hyperventilation-induced hypocapnia and reduction in cerebral blood flow velocity during maximal exercise
Cerebral blood flow (CBF) increases from rest to ∼60% of peak oxygen uptake (VO(2peak)) and thereafter decreases towards baseline due to hyperventilation-induced hypocapnia and subsequent cerebral vasoconstriction. It is unknown what happens to CBF in older adults (OA), who experience a decline in CBF at rest coupled with a blunted ventilatory response during VO(2peak). In 14 OA (71 ± 10 year) and 21 young controls (YA; 23 ± 4 years), we hypothesized that OA would experience less hyperventilation-induced cerebral vasoconstriction and therefore an attenuated reduction in CBF at VO(2peak). Incremental exercise was performed on a cycle ergometer, whilst bilateral middle cerebral artery blood flow velocity (MCA V(mean); transcranial Doppler ultrasound), heart rate (HR; ECG) and end-tidal PCO(2) (P(ET)CO(2)) were monitored continuously. Blood pressure (BP) was monitored intermittently. From rest to 50% of VO(2peak), despite greater elevations in BP in OA, the change in MCA V(mean) was greater in YA compared to OA (28% vs. 15%, respectively; P < 0.0005). In the YA, at intensities >70% of VO(2peak), the hyperventilation-induced declines in both P(ET)CO(2) (14 mmHg (YA) vs. 4 mmHg (OA); P < 0.05) and MCA V(mean) (−21% (YA) vs. −7% (OA); P < 0.0005) were greater in YA compared to OA. Our findings show (1), from rest-to-mild intensity exercise (50% VO(2peak)), elevations in CBF are reduced in OA and (2) age-related declines in hyperventilation during maximal exercise result in less hypocapnic-induced cerebral vasoconstriction