PubMed Health⌕ Search

Biomedical subjects

H G Doll

Publications and source records attributed to H G Doll.

7 recordsLinked to original sources
PubMed1979

Myocardial contractility: non-invasive assessment after cardiac surgery.

The shape of the carotid blood-flow signal in the assessment of myocardial contractility is important. The non-invasive electromagnetic method permits the measurement of the pulsatile carotid flow rate and thus to estimate the maximum blood flow acceleration (max. dF/dt), which is directly related to myocardial contractility. The electromagnetic flowmeter method, routinely used in the superficial arteries of arteriosclerotic patients, has been modified to record the blood flow rate in the carotid artery. Two ECG electrodes on both sides of the common carotid artery record the signal given by a small magnet located above the electrodes. Using this method, we have studied the effects of isoprenaline infusion in a normal subject. In patients after cardiac surgery we measured max. dF/dt in the region of the carotid artery and compared changes in it with parameters obtained by invasive methods such as the cardiac index, and the pulmonary and systemic pressures. The first results of blood flow recordings in the ascending aorta are presented here.

Adult↗
PubMed1978

Non-invasive electromagnetic measurement of the peripheral pulsatile blood flow: experimental study and clinical applications.

The non-invasive electromagnetic blood flowmeter described in this paper allows us to measure pulsatile flow through a limb. The limb is placed in a magnetic field and the blood flow rate induces electromagnetic forces which are detected at the skin surface with ECG electrodes (Faraday's law). A special computer technique is necessary to isolate the signal from artefacts (local ECG, BCG, EMG). In vitro calibration is performed using a circulatory model and in vivo using mongrel dogs. Its validity is assessed by comparing the results with the responses obtained from the invasive electromagnetic flowmeter. Sources of error in the measurement such as blood composition (Na+, K+), haematocrit (45% to 29%), and venous flow are reported here. The results indicate that the method is reliable, easy to utilise and offers a unique non-invasive way of measuring true pulsatile blood flow rate in humans. Various clinical applications are discussed for possible use of the device.

Animals↗
PubMedDate not supplied

A noninvasive electromagnetic flowmeter.

The reliability and reproducibility of peripheral blood flow data obtained by a noninvasive electromagnetic flowmeter were tested using seven male and three female volunteers aged 15-46 years. Each subject was studied under multiple testing conditions in which time, subject's metabolic state, and electrode placement were varied. Each condition was repeated within 1 to 8 weeks to obtain test-retest data. Intraclass reliability coefficients of 0.864-0.998 were obtained on all pulsatile components both within a given measurement sessions and from one day to the next. The size and shape of the waveforms obtained from the data did not significantly differ from one another, thus indicating excellent reproducibility. No significant differences were found between data obtained from the right leg and that obtained from the left. The noninvasive electromagnetic flowmeter was found capable of providing reliable and reproducible data. For data analysis, the second of two consecutive curves seems to be the best choice for clinical assessment.

Adolescent↗