Arterial pressure-flow relations in the awake standing dog
Enrlich, W.; Schrijen, F.V.; Solomon, T.A.; Rodriguez-Lopez, E.; Riley, R.L.
American Journal of Physiology 229(5): 1261-1270
1975
ISSN/ISBN: 0002-9513 PMID: 1200145 Document Number: 93140
The transient circulatory changes following paced heart rate increase are reported from 133 trials with 6 unanesthetized dogs with chronically implanted monitoring devices for heart rate, cardiac output, aortic blood pressure, and mean right atrial pressure. In 62 trials with 2 of the dogs, pulmonary artery, and left ventricular end-diastolic pressure, as well as left ventricular dP/dt were also studied. The sequence of changes in pressures and flows is analysed in terms of probable underlying mechanisms, particularly with respect to the nature of vascular resistances. The rise in aortic pressure and flow during the first 6 s of paced heart rate increase, before arterial stretch receptor reflexes become active, is more consistent with an effective downstream pressure of about 49 mm Hg, presumably at the arteriolar level, than with an effective downstream pressure close to 0 mm Hg at the right atrial level. In the pulmonary circulation where vascular reflex effects are less prominent, the pattern of pulmonary arterial pressure and flow for the entire 30 s of observation is consistent with an effective downstream pressure of 9 mm Hg, presumably at the alveolar or pulmonary arteriolar level, rather than at the level of the left ventricular end-diastolic pressure.