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Biomedical subjects

D E Laughlin

Publications and source records attributed to D E Laughlin.

10 recordsLinked to original sources
PubMed1988

Technical note: in vitro evaluation of an in-line Doppler flow-metering system for carotid artery shunts.

Carotid artery shunts are used extensively during carotid artery surgery to maintain cerebral perfusion. Blood flow through such shunts may be compromised by thrombosis, incorrect placement, or inadvertent clamping of the shunt. Currently, however, no direct method exists to detect poor shunt flow that might precipitate cerebral ischemia. A carotid artery shunt system that continuously monitors blood flow rates has been developed. This system utilizes a Doppler crystal embedded in the wall of a silicone elastomer shunt. The crystal ranges through a "liquid lens" that enables it to be placed without violation of the shunt lumen. Because the crystal is at a fixed angle (45 degrees) to the axis of blood flow and the diameter of the lumen remains constant, a linear relationship should exist between flow rates and the Doppler velocity signal. This hypothesis was tested in vitro using a pulsatile pump and both a starch-water solution and whole blood. Doppler velocity meter readings were compared to timed volume collections over a wide range of flow rates. A direct linear relationship between the Doppler flowmeter and timed volume collections existed, and the system was accurate to within 4.7%. This device may be useful in laboratory studies of carotid shunt dynamics and in clinical practice for early detection of correctable shunt flow abnormalities that could lead to cerebral injury.

Carotid Arteries↗
PubMed1985

Transluminal, subselective measurement of coronary artery blood flow velocity and vasodilator reserve in man.

Assessment of coronary blood flow and the vasodilator reserve capacity of individual coronary arteries in the catheterization laboratory has been hampered by methodologic limitations. We have developed and validated a small Doppler catheter that can subselectively measure phasic coronary blood flow velocity (CBFV). In seven anesthetized calves, CBFV was varied from 0.1 to 5.7 times control CBFV. Changes in mean CBFV measured intraluminally by catheter in the left anterior descending and left circumflex arteries were similar to those measured simultaneously with an epicardial Doppler probe on the surface of the same vessel (n = 85, r = .95, slope = 1.04) and to changes in coronary sinus flow (n = 69, r = .97, slope = 1.06) measured with timed venous collections. Identical maximal coronary reactive hyperemic responses with the catheter present and absent in the artery being studied demonstrated that coronary obstruction by the catheter was minimal. Safety studies in six additional calves demonstrated that the catheter caused small changes in coronary endothelial permeability. Histologic studies revealed no endothelial denudation or thrombus formation. Stable phasic recordings of coronary blood flow velocity have been obtained in 58 of 70 patients studied. One of the 70 patients studied had abrupt coronary occlusion probably related to catheter-induced vasospasm. In 10 normal patients, intracoronary meglumine diatrizoate increased CBFV to 3.5 times that at rest (range 2.8 to 5.0). CBFV rose 5.0-fold after an intravenous infusion of dipyridamole (range 3.8 to 7.0). In each patient, dipyridamole produced greater vasodilation than meglumine diatrizoate. The time- and dose-response characteristics to dipyridamole infusion were heterogeneous, underscoring the advantage of continuous on-line measurement of CBFV in the measurement of vasodilator reserve. This method of measuring CBFV and assessing vasodilator reserve in the catheterization laboratory should facilitate studies of the coronary circulation in man.

Animals↗
PubMed1981

A method for continuously assessing coronary blood flow velocity in the rat.

We have developed a directional pulsed-Doppler system to make blood flow velocity measurements in the coronary arteries of the rat. The probe consists of a 1-mm2 crystal mounted in a 6-mm suction cup, which can be attached by vacuum to the vessel without requiring dissection. Recordings of phasic coronary blood flow velocity (CBV) in the rat indicate that 82 +/- 2% (mean +/- SE) of the area under the CBV recording occurs in diastole. CBV increased during an infusion of dipyridamole and changed in parallel with alterations in left-ventricular pressure. To validate the technique we correlated changes in CBV wih changes in microsphere-measured left-ventricular perfusion (range, 20--780 ml/min x 100 g). These two methods of estimating coronary flow correlated closely (r = 0.93). Measurements of phasic CBV in the rat with this Doppler system should permit a detailed characterization of the coronary circulation in many models of disease that have been developed in the rat.

Animals↗
PubMed1978

"False inhibition" of demand pacemaker due to leakage of fluid into the pacemaker lead socket.

"False inhibition" of a demand pacemaker usually occurs with a microfracture of the lead system resulting in a galvanic potential at the site of the fracture or with sensing of myopotential with exercise. An increase in the slope of the leading half edge of the pulse contour is generally considered diagnostic of lead fracture. We report the case of a patient in whom "false inhibition" at rest and an increase in the slope of the leading half edge of the pulse contour were caused by leakage of fluid into the pacemaker lead socket.

Aged↗