Abstract
Quantitative information about the effects of pulmonary blood volume (Qp) on pulmonary haemodynamics is lacking since Qp changes inevitably with flow. To separate flow-dependent from volume-dependent changes in intravascular pressures we imposed changes in Qp (measured continuously) by altering outflow pressure in seven isolated, blood-perfused rabbit lungs and studied the effects of Qp on the relations between arteriovenous pressure gradient (DeltaP) and blood flow (Q.) under two conditions: flow-dependent volume changes were either permitted or compensated. In the latter circumstances, DeltaP changed more for a given change in Q.. The DeltaP/Q. relations were shifted to smaller DeltaP when Qp was increased. Hence, the calculated flow resistance (R = DeltaP/Q.) decreased with increasing Qp at a given Q.. Assuming constant viscosity, changes in R can be predicted from changes in vessel geometry and thus Qp. We found that R increased less than expected (by a factor of 3-7.5 instead of 9) when Qp was reduced to one-third. This discrepancy may be explained by a change in blood distribution within the lung despite constant Qp and by a change in apparent blood viscosity with Q.. Regardless of these speculations we have shown that Qp determines DeltaP at each flow and thus flow resistance.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
