Clinical physiology (Oxford, England)
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Comparative Study
Comparison of ultrasound assessment of flow-mediated dilatation in the radial and brachial artery with upper and forearm cuff positions.
In the published literature relating to flow-mediated dilatation (FMD), there are substantial differences between centres in terms of normal FMD amongst healthy subjects. This present study attempts to identify the effect of differing methodologies on FMD. High frequency ultrasound was used to measure blood flow and percentage brachial and radial artery dilatation after reactive hyperaemia induced by forearm or upper arm cuff occlusion in 24 healthy subjects, less than 40 years, without known cardiovascular risk factors. ⋯ The local ischaemia of the brachial artery with a proximal occlusion may explain why the brachial artery dilated more after upper arm occlusion compared with after forearm occlusion. The study has also shown that FMD of the radial artery could be assessed by B-mode ultrasound technique. FMD was greater using the radial artery compared with the brachial artery, suggesting that the radial artery may be a useful way to assess FMD in future clinical studies.
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In the elderly, standing can frequently be accompanied by blood pressure (BP) changes and cerebral symptoms such as dizziness, fall, or even syncope, but this may vary from day-to-day. Therefore, we aimed to investigate the reproducibility of orthostatic responses of cerebral cortical oxygenation and systemic haemodynamics in elderly subjects. In 27 healthy elderly subjects (age 70-84 years), changes in systolic BP (SBP), diastolic BP (DBP), heart rate (HR) and stroke volume (SV) were continuously monitored by Finapres (Finger Arterial Pressure), and changes in oxyhaemoglobin ([O2Hb]) and deoxyhaemoglobin ([HHb]) concentrations were continuously measured over the right frontal cortex by near infrared spectroscopy (NIRS) during supine rest and 10 min of active standing on two separate occasions. ⋯ Cortical oxygenation changes were not accompanied by severe cerebral symptoms. Active standing induced reproducible group-averaged frontal cortical oxygenation declines in healthy elderly subjects, although an intraindividual day-to-day variability was present, possibly related to the variability of orthostatic BP responses. These findings indicate that cerebral autoregulation fails to compensate completely for postural changes in elderly subjects, which might predispose elderly subjects to ischaemic cerebral symptoms.
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When right ventricular (RV) afterload is abnormally increased, it correlates inversely with right ventricular ejection fraction (RVEF). We tested, whether this would be different with normal afterload. Additionally, we investigated whether previous studies on the slope of RV preload recruitable stroke work (SW) relation, which used rather non-physiological measures to change RV preload, could be transferred to more physiological loading conditions. ⋯ In conclusion, (i) RVEF correlates positively with RV afterload when afterload varies within normal range; (ii) the slope of the RV preload recruitable SW relation, which is obtained at steady state under normal loading conditions, is substantially flatter than previously described for dynamic changes of RV preload. With increasing afterload, preload loses its determining effect on RV performance, while afterload becomes more important. This puts earlier assumptions of an afterload independent RV preload recruitable SW relation into question.