Effects of PGI2 on pattern of breathing in the pig during aortic obstruction

We studied the effects of prostacyclin on pattern in six anaesthetized pigs with aortic obstruction. PGI2 causes a rightward displacement of VT/TI relationship (Hering-Breuer threshold curve) without a corresponding change in inspiratory flow. With airways occluded at the end respiratory level, we analyze how PGI2 affects the central respiratory rhythm in the absence of the phasic lung volume-related vagal loop. Infusion of prostacyclin causes leftward displacement of the TE/TI relationship and an increase in TTOTo correlated with the hypotensive action. The change in the bulbo-pontine pacemaker is caused by a marked increase in TEo and this suggests that PGI2 can modulate the central respiratory rhythm, independently of the blood pressure level.