Short Cross Sectional Area Of Venous Pressure Essay

1579 Words Nov 15th, 2016 7 Pages
Our recordings of venous pressure close to zero throughout most of the length of the jugular vein demonstrate that the jugular vein had a minute cross-sectional area, in agreement with the waterfall analogy. We also observed a maintained small lumen in the cranial part of the jugular vein of the anesthetized giraffe, implying that a column of blood may be preserved in this part of the jugular vein. Consistent with this column of blood, there was recorded negative venous pressure at the cranial end of the jugular vein, while pressures in the dominant part approached zero. The pressures measured in our study agree with McCalden et al. (24), who measured a jugular venous pressure of 0 mmHg at the level of the first cervical vertebrae, while Mitchell and Skinner (28) measured a jugular venous pressure of 10 mmHg some 30 cm below the head. In contrast, Hargens et al. (18) reported that pressure decreased from 13 mmHg at the base of the skull to 4 mmHg 30 cm above heart level in sedated giraffes. It is not evident why jugular venous pressure varies so much between studies. The experiment in which one giraffe was supported under the thoracic region suggests that the protocol used for suspension substantially affects the hemodynamic variables, but the key finding of the present study is that jugular venous pressure of the giraffe depends on the position of the neck. Yet, we acknowledge that differences in the reported jugular venous pressures might also reside from differences in…

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