Pulmonary vascular impedance response to hypoxia in dogs and in minipigs: effects of inhaled nitric oxide. Maggiorini, Marco, Serge Brimioulle, Didier De Canniere, Marion Delcroix, Pierre Wauthy, and Robert Naeije. Laboratory of Cardiovascular and Respiratory Physiology, and Department of Cardiac Surgery, Erasme University Hospital, Brussels, Belgium
APStracts 2:0252A, 1995.
The pig has been reported to present with a stronger hypoxic pulmonary vasoconstriction (HPV) than in many other species, including dogs. We investigated pulmonary artery pressure (Ppa) minus pulmonary artery occluded pressure (Ppao) versus pulmonary blood flow (Q) relationships and pulmonary vascular impedance (PVZ) spectra in 9 minipigs and in 9 weight-matched dogs. The animals were anesthetized, and ventilated in hyperoxia (fraction of inspired O2, FIO2, 0.4) or in hypoxia (FIO2 0.12). PVZ was computed from the Fourier series for Ppa and for Q. In hyperoxia, compared with the dogs at the same Q, the pigs had a higher Ppa (26 + 1 versus 16 + 1 mmHg), a higher first harmonic impedance (Z1), a more negative low frequency phase angle, but no different characteristic impedance (Zc). Hypoxia in the dogs increased (Ppa-Ppao) at all levels of Q studied by an average of 2 mmHg but did not affect Z1 or Zc. Hypoxia in the pigs increased (Ppa -Ppao) at all levels of Q by an average of 13 mmHg, and increased Z1 and Zc. Inhaled nitric oxide (NO) (150 ppm) reversed the hypoxia -induced changes in (Ppa-Ppao):Q plots and in PVZ in the dogs and in the pigs. However, differences in (Ppa-Ppao):Q plots and in PVZ between dogs and pigs in hyperoxia and in hypoxia were not affected by inhaled NO. We conclude 1 degrees that minipigs present with an elevated pulmonary vascular resistance and impedance, in hypoxia more than in hyperoxia and 2 degrees that base line differences in pulmonary hemodynamics between dogs and minipigs are structural rather than functional. 

Received 4 January 1995; accepted in final form 5 June 1995.
APS Manuscript Number A8-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  6 July 1995.