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Biomedical subjects

K Yamakoshi

Publications and source records attributed to K Yamakoshi.

At least 91 records · Page 5Linked to original sources
PubMed1977

Effects of stroke volume and velocity of ejection on end-systolic pressure of canine left ventricle. End-systolic volume clamping.

To study the effects of contraction mode on ventricular end-systolic pressure-volume relationship, we compared the end-systolic pressure of isovolumic contraction with that of ejecting contraction at an identical end-systolic volume. The left ventricle of excised cross-circulated canine hearts was fitted with a water-filled balloon. The balloon was connected to a hydraulic pump that allowed the ventricle to contract to a preset constant end-systolic volume (19-37 ml) from a variable end-diastolic volume. At each of control, enhanced, and depressed levels of contractility, differences of end-systolic pressures of steady state isovolumic and ejecting contractions were evaluated while stroke volume and velocity of ejection were widely varied. The end-systolic pressure in the ejecting contraction tended to decrease by 5-15% from that of the isovolumic beat with increases in either stroke volume to 20-25 ml or peak velocity of ejection to about 800 ml/sec. There was no obvious difference in the results at different levels of contractility. The magnitude of the end-systolic pressure depression due to ejection was, however, relatively small as compared to 4-fold changes in end-systolic pressure due to the changes in contracility. We, therefore, conclude that the ventricular end-systolic pressure-volume relationship is affected slightly by ejection, and that this effect is much smaller than the maximal effect of changing contractility on the end-systolic pressure-volume relationship.

Animals↗
PubMedDate not supplied

Fetal and neonatal cerebral oxygen monitoring with NIRS: theory and practice.

Near infra-red spectroscopy (NIRS) is a comparatively new method for monitoring the oxygenation in blood and tissue in the brain of the fetus and the neonate. Absorption of light in the wavelength range 700-1000 nm through such tissue is measured, which is then used to calculate changes in the concentration of cerebral oxygenated and de-oxygenated haemoglobin (HbO2 and Hb) and hence cerebral blood volume (CBV). Studies carried out on several groups of newborn babies have shown clear changes in HbO, Hb and CBV with hypoxia and bradycardia. These changes may well have implications in the occurrence of hypoxic/ischaemic brain injury. Intra partum NIR measurements on the fetal brain have demonstrated clear changes in HbO2, Hb and CBVm, coinciding with the onset of contractions.

Brain↗