title: PEEP inhibits hypoxic pulmonary vasoconstriction in dogs.
abstract: The effects of an increase in alveolar pressure on hypoxic pulmonary vasoconstriction (HPV) have been reported variably. We therefore studied the effects of positive end-expiratory pressure (PEEP) on pulmonary hemodynamics in 13 pentobarbital-anesthetized dogs ventilated alternately in hyperoxia [inspired O2 fraction (FIO2) 0.4] and in hypoxia (FIO2 0.1). In this intact animal model, HPV was defined as the gradient between hypoxic and hyperoxic transmural (tm) mean pulmonary arterial pressure [Ppa(tm)] at any level of cardiac index (Q). Ppa(tm)/Q plots were constructed with mean transmural left atrial pressure [Pla(tm)] kept constant at approximately 6 mmHg (n = 5 dogs), and Ppa(tm)/PEEP plots were constructed with Q kept constant approximately 2.8 l.min-1.m-2 and Pla(tm) kept constant approximately 8 mmHg (n = 8 dogs). Q was manipulated using a femoral arteriovenous bypass and a balloon catheter in the inferior vena cava. Pla(tm) was held constant by a balloon catheter placed by left thoracotomy in the left atrium. Increasing PEEP, from 0 to 12 Torr by 2-Torr increments, at constant Q and Pla(tm), increased Ppa(tm) from 14 +/- 1 (SE) to 19 +/- 1 mmHg in hyperoxia but did not affect Ppa(tm) (from 22 +/- 2 to 23 +/- 1 mmHg) in hypoxia. Both hypoxia and PEEP, at constant Pla(tm), increased Ppa(tm) over the whole range of Q studied, from 1 to 5 l/min, but more at the highest than at the lowest Q and without change in extrapolated pressure intercepts. Adding PEEP to hypoxia did not affect Ppa(tm) at all levels of Q.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Laboratory of Cardiovascular and Respiratory Physiology, Erasme University Hospital, Brussels, Belgium.
authors.forename: P
authors.initials: P
authors.lastname: Lejeune
authors.forename: J L
authors.initials: JL
authors.lastname: Vachiery
authors.forename: J M
authors.initials: JM
authors.lastname: De Smet
authors.forename: M
authors.initials: M
authors.lastname: Leeman
authors.forename: S
authors.initials: S
authors.lastname: Brimioulle
authors.forename: M
authors.initials: M
authors.lastname: Delcroix
authors.forename: C
authors.initials: C
authors.lastname: Melot
authors.forename: R
authors.initials: R
authors.lastname: Naeije
mesh_terms: D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D004285:Dogs; D006439:Hemodynamics / Q000502:physiology; D000860:Hypoxia / Q000503:physiopathology*; D010100:Oxygen / Q000097:blood; D011175:Positive-Pressure Respiration; D011652:Pulmonary Circulation / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen