The isolated effects of alterations of lung inflation and transmural pulmonary arterial pressure (pressure difference between intravascular and pleural pressure) on pulmonary arterial blood volume (Vpa) were investigated in anesthetized dogs. Using transvenous phrenic nerve stimulation, changes in transmural pulmonary arterial pressure (Ptm) at a fixed transpulmonary pressure (Ptp) were produced by the Mueller maneuver, and increases in Ptp at relatively constant Ptm by a quasi Valsalva maneuver. Also, both Ptm and Ptp were allowed to change during open airway lung inflation. Vpa was determined during these three maneuvers by multiplying pulmonary blood flow by pulmonary arterial mean transit time obtained by an ether plethysmographic method. During open airway lung inflation, mean (±SD) Ptp increased by 7.2 (±3.7) cmH2O and Ptm by 4.3 (±3.4) cmH2O for a mean increase in Vpa by 26.2 (±10.7) ml. A pulmonary arterial compliance term (ΔVpa/ΔPtm) calculated from the Mueller maneuver was 3.9 ml/cmH2O and an interdependence term (ΔVpa/ΔPtp) calculated from the quasi Valsalva maneuver was 2.5 ml/cmH2O for a 19% increase in lung volume, and 1.2 ml/cmH2O for an increase in lung volume from 19% to 35%. These findings indicate that in normal anesthetized dogs near FRC for a given change in Ptp and Ptm the latter results in a greater increase of Vpa.
ASJC Scopus subject areas
- Physiology (medical)