Clinical physiology (Oxford, England)
-
Transcranial Doppler (TCD) determined cerebral blood flow velocity and laser Doppler flowmetry (LDF) measured cortical perfusion were simultaneously assessed during hypotensive haemorrhage in 15 anaesthetized rabbits. Systolic (Fsys), diastolic (Fdia) and mean (Fmean) blood flow velocities were recorded into the intracranial internal carotid (ICA) and basilar artery (BA). Resistance (RI = Fsys-Fdia/Fsys) and pulsatility (PI = Fsys-Fdia/Fmean) indices were calculated. ⋯ Pulse pressure (systolic-diastolic pressure) correlated with RI (ICA: r = -0.62, P < 0.001; BA: r = -0.61, P < 0.001) and PI (ICA: r = -0.61, P < 0.001; BA: r = -0.62, P < 0.001). In conclusion, during haemorrhagic shock, TCD correlates with LDF and indicates regional differences in autoregulatory settings. However, Doppler indices do not reflect the changes in cerebral resistances because they are influenced by the changes in pulsatile pressure.
-
Near-infrared spectrophotometry-determined cerebral (ScO2) and muscle oxygen saturations (SmO2) were followed in 15 volunteers during passive 50 degrees head-up-tilt-induced central hypovolaemia, and in nine volunteers during ventilatory manoeuvres affecting arterial carbon dioxide tension. During head-up tilt, mean arterial pressure [MAP, 88 (77-118) to 97 (80-136) mmHg, median and range] and heart rate [HR; 66 (49-77) to 87 (42-132) beats min-1 P < 0.01] increased, but after 22 (1-45) min they declined [to 61 (40-91) mmHg and 69 (38-109) beats min-1, respectively, P = 0.001] and pre-syncopal symptoms developed. Central hypovolaemia was indicated by an increased thoracic electrical impedance, and a decreased cardiac output and central venous oxygen saturation. ⋯ Cardiovascular changes during tilt were not reflected in skin temperature. The ScO2 reflected the maintained autoregulation of cerebral blood flow until the perfusion pressure decreased markedly. In contrast, SmO2 mirrored muscle vasoconstriction early during tilt, and vasodilatation when pre-syncopal symptoms appeared.
-
Comparative Study Clinical Trial Controlled Clinical Trial
Beat-to-beat agreement of non-invasive finger artery and invasive radial artery blood pressure in hypertensive patients taking cardiovascular medication.
The aim of this study was to investigate and quantify the agreement between simultaneous and ipsilateral non-invasive finger artery blood pressure (Finapres) and intra-arterial radial blood pressure among 13 volunteer hypertensive patients, aged 36-71 years and taking cardiovascular medication, during steady-state fluctuation of arterial blood pressure and during an increase in blood pressure induced by static exercise. Eight patients were being treated with beta-blocking agents, eight with calcium antagonists, four with angiotensin-converting enzyme inhibitors, four with diuretics and one with prazosin in combination therapy. Their auscultatory brachial artery blood pressures ranged in systole from 142 to 206 mmHg and in diastole from 88 to 120 mmHg during the treatment. ⋯ In general, neither systolic nor diastolic differences between the methods exceeded the limits of +/- 10 mmHg, and the bias did not significantly increase (P > or = 0.12) during a 10-mmHg increase in arterial blood pressure caused by static exercise. Among three subjects, an increase in bias and poorer agreement was associated with atrial fibrillation and steplike changes in the Finapres output after autocalibration. The results support usage of the Finapres technique to measure beat-to-beat changes of peripheral arterial blood pressure in hypertensive patients taking cardiovascular medication, with a feasible agreement with beat-to-beat radial artery blood pressure.
-
We examined the effect of temperature on digital arterial blood pressure obtained by continuous beat-to-beat non-invasive monitoring with a volume-clamp technique (Finapres). In 10 normal volunteers and 13 patients with symptoms of vasospasm, digital pressure and brachial artery pressure (cuff method) was simultaneously recorded in control conditions at room temperature, during body cooling, finger heating, and truncal heating. In the control condition digital systolic blood pressure was significantly higher (16.1 +/- 14.2 mmHg) than brachial systolic pressure. ⋯ Finger heating reduced systolic augmentation without changing the mean and diastolic blood pressure. Similar changes were also observed in the patients with vasospasm except in one case with a pronounced Raynaud syndrome where digital blood pressure was lower than brachial artery pressure. We conclude that augmentation of finger systolic pressure seems to be dependent on local vasoconstriction of A/V shunts and that finger heating may be a useful procedure to improve the reliability of Finapres readings.
-
Comparative Study
Accuracy and repeatability of a pocket turbine spirometer: comparison with a rolling seal flow-volume spirometer.
The accuracy and repeatability of a recently introduced pocket spirometer (Micro Spirometer; Micro Medical Instruments Ltd, Rochester, UK) was evaluated. FEV1 and FVC values obtained with this instrument were compared with those measured with a rolling-seal flow-volume spirometer (CPI 220 with microcomputer) in 31 patients and 11 healthy volunteers. In the whole material, expressed as mean +/- SD, the pocket spirometer recorded 0.44 +/- 0.23 l (13 +/- 7%) smaller values for FEV1 (P < 0.001) and 0.64 +/- 0.48 l (15 +/- 11%) smaller values for FVC (P < 0.001) than the rolling-seal spirometer. ⋯ It is concluded that the underestimation of FEV1 and FVC of the pocket spirometer was too large and inconsistent for the device to be used interchangeably with conventional spirometers. However, the repeatability of the measurements with the pocket spirometer is close to that reported previously for flow-volume spirometry. Thus the pocket spirometer may be suitable in assessing acute changes of spirometric indices e.g. during provocation tests or during patient follow-up in asthma.