Stimulus-response curve of hypoxic pulmonary vasoconstriction in intact dogs: effects of ASA.

Hypoxic pulmonary vasoconstriction (HPV) has been reported to decrease during severe hypoxia in isolated lungs, but it remains unknown whether this decrease occurs in the intact animal and how it is affected by cyclooxygenase inhibition. We investigated the HPV stimulus-response relationship in eight pentobarbital sodium-anesthetized intact dogs with a naturally occurring response to hypoxia ("responders"). The pulmonary arterial minus wedge pressure difference (Ppa-Ppw) was measured at 11 inspired O2 fraction (FIO2) values between 0.

Increased left atrial pressure inhibits hypoxic pulmonary vasoconstriction.

An increase in left atrial pressure (Pla) has been reported to either inhibit or not affect hypoxic pulmonary vasoconstriction in intact dogs. We investigated mean pulmonary arterial pressure (Ppa)-flow (Q) relationships at low and high fixed Pla and Ppa-Pla relationships at fixed Q in piglets, which are known to present with a stronger hypoxic pulmonary pressor response than dogs. Seven piglets were anesthetized; equipped with balloon catheters in inferior vena cava and left atrium to control Q and Pla, respectively; and ventilated alternatively in hyperoxia [fractional concn of O2 in inspired air (FIO2) 0.

Stimulus-response curves for hypoxic pulmonary vasoconstriction in piglets.

Objective: The aim was to characterise stimulus-response curves for hypoxic pulmonary vasoconstriction and to observe the effects of drugs reputed to enhance it: aspirin (a cyclo-oxygenase inhibitor), and doxapram (a peripheral chemoreceptor agonist).

Methods: Mean pulmonary artery pressure (Ppa) versus fraction of inspired O2 (FIO2) relationships were studied in 18 intact anaesthetised piglets, before and after the intravenous administration, in random order, of either physiological saline, 1 g aspirin, or 20 mg.kg-1 doxapram.

Restored hypoxic pulmonary vasoconstriction by peripheral chemoreceptor agonists in dogs.

Hypoxic stimulation of the peripheral chemoreceptors inhibits hypoxic pulmonary vasoconstriction (HPV). On the other hand, almitrine, a peripheral chemoreceptor agonist, has been reported in some studies to enhance HPV. To further explore this apparent contradiction, we investigated the effects of two different low intravenous doses of almitrine on pulmonary arterial pressure (Ppa) versus cardiac index (Q) plots in 32 pentobarbital-anesthetized dogs ventilated alternatively in hyperoxia (FIO2, 0.