The postural reduction in middle cerebral artery blood velocity is not explained by PaCO2
| Autor: | C. M. Roos, J. J. van Lieshout, Rogier V. Immink, Frank Christian Pott, Per Lav Madsen, Niels H. Secher |
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| Přispěvatelé: | ACS - Amsterdam Cardiovascular Sciences, Anesthesiology, General Internal Medicine |
| Rok vydání: | 2006 |
| Předmět: |
Adult
Middle Cerebral Artery Cardiac output medicine.medical_specialty Supine position Ultrasonography Doppler Transcranial Physiology Posture Physiology (medical) Internal medicine medicine.artery medicine Homeostasis Humans Orthopedics and Sports Medicine Cardiac Output Respiratory system Spectroscopy Near-Infrared Chemistry Public Health Environmental and Occupational Health General Medicine Oxygenation Carbon Dioxide respiratory tract diseases Cerebral blood flow Cerebrovascular Circulation Oxyhemoglobins Anesthesia Middle cerebral artery Cardiology Arterial blood Female medicine.symptom Blood Flow Velocity Vasoconstriction circulatory and respiratory physiology |
| Zdroj: | European journal of applied physiology, 96(5), 609-614. Springer Verlag |
| ISSN: | 1439-6327 1439-6319 |
| DOI: | 10.1007/s00421-006-0136-6 |
| Popis: | In the normocapnic range, middle cerebral artery mean velocity (MCA Vmean) changes ∼ 3.5% per mmHg carbon-dioxide tension in arterial blood (PaCO2) and a decrease in PaCO2 will reduce the cerebral blood flow by vasoconstriction (the CO2 reactivity of the brain). When standing up MCA Vmean and the end-tidal carbon-dioxide tension (PETCO2) decrease, suggesting that PaCO2 contributes to the reduction in MCA Vmean. In a fixed body position, PETCO2 tracks changes in the PaCO2 but when assuming the upright position, cardiac output \((\dot {Q})\) decreases and its distribution over the lung changes, while ventilation \((\dot {V}_{{\rm E}})\) increases suggesting that PETCO2 decreases more than PaCO2. This study evaluated whether the postural reduction in PaCO2 accounts for the postural decline in MCA Vmean. From the supine to the upright position, \(\dot {V}_{{\rm E}},\)\(\dot {Q},\) PETCO2, PaCO2, MCA Vmean, and the near-infrared spectrophotometry determined cerebral tissue oxygenation (CO2Hb) were followed in seven subjects. When standing up, MCA Vmean (from 65.3±3.8 to 54.6±3.3 cm s−1 ; mean ± SEM; P |
| Databáze: | OpenAIRE |
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