Embolized air collection in the superior vena cava of "upright" sheep.

In 34 studies on six "upright" anesthetized sheep central venous pressure from sites in the upper and lower superior vena cava (SVC) was recorded before, during, and after the injection into a neck vein of 1-ml increments of air every minute for 15 min. After the injection of air, the pressure recorded from the upper site increased significantly. This increase was the result of air collecting in the SVC with a consequent loss or partial loss of the SVC hydrostatic pressure difference. The time of onset and the duration of collection were not influenced by hyper- or hypovolemia nor by 1 kPa positive end-expiratory pressure. The readily identifiable change in the venous pressure in the upper SVC provided an earlier and more reliable warning of these small-volume air emboli than did a Doppler probe directed at the right side of the heart.

The influence of insemination timing and semen characteristics on the efficiency of a donor insemination program.

The analysis of accumulated data from conceptional and nonconceptional ovulatory menstrual cycles of patients undertaking artificial donor insemination has allowed some observations to be made on the practical aspects which may influence the efficiency of the program. The evidence suggests that with the use of preserved semen, accurate timing of insemination is essential, and that days 0 and +1 with respect to the luteinizing hormone surge appear to be advantageous as compared with closely related days. When the numbers of motile spermatozoa which were inseminated over a critical 4-day interval were analyzed, the results also suggested that improved conception rates occurred when larger numbers of active spermatozoa were used. A comparison was made between those patients who had been inseminated on a single occasion and those inseminated on more than one occasion during the periovulatory period. The results obtained from those cycles inseminated on a single occasion were inferior to those obtained from cycles inseminated more than once. Finally, some limited comparison is drawn between the established insemination programs of bovine husbandry and the relatively inefficient human experience. One explanation may lie in the wider spectrum of donor semen desirable for the human programs.