Biomedical subjects

A A Shoukas

Publications and source records attributed to A A Shoukas.

44 records · Page 3Linked to original sources

PubMed1977

End-systolic pressure/volume ratio: a new index of ventricular contractility.

A thesis recently developed from a series of experiments on the isolated canine left ventricle is described. It is claimed that the ventricular presure/volume ratio at end-systole is relatively insensitive to cardiac loading and varies greatly in response to changes in ventricular contractility. The clinical viability of this basic finding rests on the substitution of diameter for volume in this formulation. Diameter can be measured using a noninvasive ultrasonic technique in the clinic. Accordingly, end-systolic pressure/diameter ratio was studied in the isolated preparation and found to be similarly insensitive to loading conditions and sensitive to inotropic interventions. A further analysis of the pressure/diameter ratio in the ventricle of the conscious dog is in progress. In parallel with these studies, use of the pressure/diameter ratio to evaluate contractility in cardiac patients is being tested. The preliminary findings from conscious dogs and clinic patients are briefly discussed.

Animals↗

PubMed1977

Construction of hydraulic cuff occluders for blood vessels.

This report describes the construction technique for a simple and inexpensive cuff occluder for various size blood vessels. The occluder is made from polyvinyl chloride tubing and consist of two main parts, the balloon and catheter section, and the reinforcing back section. The occluders have functioned reliably in chronic dog preparations for up to 3 mo.

Animals↗

PubMed1976

Modification of the flow-generating capability of the canine heart-lung compartment by the carotid sinus baroreceptor reflex.

To quantitatively understand how the carotid sinus baroreceptor reflex modifies the Starling curve (i.e., the aortic flow (AF)-mean right atrial pressure (MRAP) relationship), experiments were performed in closed-chest, naturally breathing, and anesthetized dogs before and after vagotomy. Mean aortic pressure (MAP) was fixed at approximately 100 mm Hg and the pressure in the isolated carotid sinus (ISP) was varied from 75 to 150 mm Hg in steps of 25 mm Hg. At each ISP, MRAP was slowly increased and decreased while measuring AF by a previously implanted electromagnetic flow probe. A family of AF-MRAP relation curves specified at the different ISP's were thus obtained. Third-order polynomials in MRAP and ISP adequately fit these curves. Whether the vagi were intact or cut, there was no significant difference between the AF-MRAP relation curves obtained at an ISP of 75 or 100 mm Hg. However, decreasing ISP from 125 to 100 mm Hg caused a 24% increase in AF, and increasing ISP to 150 mm Hg caused a 15% decrease in AF in the dogs with intact vagus nerves. For the vagotomized dogs, the same decrease or increase in ISP caused a 17% increase or a 21% decrease in AF, respectively. When MAP was allowed to change by the reflex, only insignificant changes in AF occurred. We conclude that the carotid sinus reflex significantly alters the flow-generating ability of the heart-lung compartment by as much as 40% but this becomes clearly observable only if the reflex change in aortic pressure is prevented.

Animals↗

PubMed1975

Pressure-flow and pressure-volume relations in the entire pulmonary vascular bed of the dog determined by two-port analysis.

To quantify the resistance and particularly the capacitance properties of the entire pulmonary vascular bed, isolated perfused lungs of nine dogs were studied. In each dog, with a fixed endotracheal pressure of 5 mm Hg, the arterial pressure-flow and pressure-volume relations were determined while venous pressure was fixed at constant values of 2, 5, and 8 mm Hg. In the same dogs, the venous pressure-flow and pressure-volume relations were also obtained when arterial pressure was fixed at constant values of 15 and 20 mm Hg. The arterial and venous pressure-flow relations could be regarded as linear around the physiological ranges of arterial and venous pressures; however, at very low pressures, these relations became nonlinear. The arterial and venous pressure-volume relations were also approximately linear within the physiological pressure ranges. The mean arterial compliance was 0.1798 ml/mm Hg kg-1 and was independent of venous pressures. The venous compliance values were 0.1236 and 0.0955 ml/mm Hg kg-1 for arterial pressures of 15 and 20 mm Hg, respectively. The sums of the arterial and venous compliances were 0.3034 and 0.2753 ml/mm Hg kg-1 for arterial pressures of 15 and 20 mm Hg, respectively. These values were nearly identical to the mean total compliance, 0.3265 ml/mm Hg kg-1, measured in a separate series of experiments in the same dogs. Therefore, the data obtained in these experiments using two-port analysis techniques represent the compliances and the resistance of the entire pulmonary vascular bed around the normal operating pressures and flows.

Animals↗

PubMed1974