Effects of embolus size on hemodynamics and gas exchange in canine embolic pulmonary hypertension.
We examined the effects of different-sized glass-bead embolization on pulmonary hemodynamics and gas exchange in 12 intact anesthetized dogs. Pulmonary hemodynamics were evaluated by multipoint pulmonary arterial pressure (Ppa)/cardiac output (Q) plots before and 60 min after sufficient amounts of 100-microns (n = 6 dogs) or 1,000-microns (n = 6 dogs) glass beads to triple baseline Ppa were given and again 20 min after 5 mg/kg hydralazine in all the animals. Gas exchange was assessed using the multiple inert gas elimination technique in each of these experimental conditions. Embolization increased both the extrapolated pressure intercepts (by 6 mmHg) and the slopes (by 5 mmHg.l-1.min.m2) of the linear Ppa/Q plots, together with an 80% angiographic pulmonary vascular obstruction. These changes were not significantly different in the two subgroups of dogs. However, arterial PO2 was most decreased after the 100-microns beads, and arterial PCO2 was most increased after the 1,000-microns beads. Both bead sizes deteriorated the distribution of ventilation (VA)/perfusion (Q) ratios, with development of lung units with higher as well as with lower than normal VA/Q. Only 100-microns beads generated a shunt. Only 1,000-microns beads generated a high VA/Q mode and increased inert gas dead space. Hydralazine increased the shunt and decreased the slope of the Ppa/Q plots after 100-microns beads and had no effect after 1,000-microns beads. We conclude that in embolic pulmonary hypertension, Ppa/Q characteristics are unaffected by embolus size up to 1,000 microns.(ABSTRACT TRUNCATED AT 250 WORDS)
Delcroix
M
M
Laboratory of Cardiovascular and Respiratory Physiology, Erasme University Hospital, Brussels, Belgium.
Mélot
C
C
Vachiéry
J L
JL
Lejeune
P
P
Leeman
M
M
Vanderhoeft
P
P
Naeije
R
R
D000818:Animals; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output; D004285:Dogs; D006339:Heart Rate; D006439:Hemodynamics; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D011651:Pulmonary Artery / Q000000981:diagnostic imaging; D011652:Pulmonary Circulation; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011859:Radiography; D012039:Regional Blood Flow
D002245:Carbon Dioxide; D010100:Oxygen