Pulmonary wedge catheterization during positive end-expiratory pressure ventilation in the dog

In ten supine anesthetized dogs, recordings of left atrial (LA) and pulmonary-artery wedge (PW) pressures were simultaneously obtained at several levels of positive end-expiratory pressure (PEEP) ventilation with the thorax either open or closed. Lateral roentgenograms were taken to determine the relative vertical positions of the LA and PW catheter tips. When the wedge catheter tip was vertically above the left artrial catheter tip, mean PW followed airway pressure at PEEP of more that 5 cm H20. For PEEP 5 cm H20 or less, and for PW catheter tip positions vertically below the LA catheter tip at all levels of PEEP, mean wedge catheter pressure was close to left atrial pressure. Thus, it appears the LA pressure can best be estimated by PW catheter positions vertically below the left atrium during positive end-expiratory pressure ventilation.