Abstract
In intact, open-chested canine preparations, cardiac output (Q), pulmonary artery pressure (Ppa), pulmonary capillary wedge pressure (PCW), left atrial pressure (Pla), and airway pressure (PA) were measured. In a Zone II condition, pulmonary vascular pressure-flow [(Ppa - PA) - Q] relationships were determined. The mean pressure axis intercept, the average critical pressure (PC), was 15.9mmHg (range 9.4 - 18.1mmHg). These data confirm the presence of a Pc in the intact canine pulmonary vascular bed as has been previously described in isolated canine lung lobes. The presence of a PC>PA should influence Pcw measurements. During small (2–3mmHg) step-wise changes in PA over a range of PA (3–26nmHg) we observed that Pcw accurately reflected Pla at low PA and then diverged sharply. After diverging from Pla, PCW increased as PA increased with an average slope of 0.74 (range 0.61 – 0.86); PCW always exceeded PA. The breakpoint of PCW from Pla did not occur at the boundary between Zone II and Zone III of west but rather, when PA was still substantially less than Pla (mean 7mmHg less). These findings suggest that driving pressure in Zone II is the difference between Ppa and Pc, not Ppa – PA. Since PCW is either Pla or Pc, the Pcw can be taken as the pertinent back pressure to flow under all conditions.
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Sconyers, S., Kest, S., Goldberg, H. et al. 210 PRESENCE OF A PULMONARY VASCULAR “CRITICAL PRESSURE” IN INTACT CANINES: POSSIBLE EFFECT ON CAPILLARY WEDGE PRESSURE MEASUREMENTS. Pediatr Res 19, 145 (1985). https://doi.org/10.1203/00006450-198504000-00240
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DOI: https://doi.org/10.1203/00006450-198504000-00240