Regulation of regional perfusion distribution in the lungs. Experimental model and effect of alveolar pressure

An experimental model for studying changes in regional perfusion distribution in the lungs of a dog was described. The right upper lobe was separated in vivo from the rest of the lungs by a balloon catheter and gas exchange of the lobe was artificially done asynchronously with the rest of the lungs by using a gas of interest at a prescheduled aveolar pressure. 99mTc-albumin microsphere was the agent of choice for multiple sequential studies in one dog. Alveolar gas composition reached a plateau after the 4th inflation of the right upper lobe. Effect of alveolar pressure on regional perfusion distribution was studied by using nitrogen and air as exchange gases. Perfusion distribution in the right upper lobe was the least at the maximal alveolar pressure of 14 to 19 cm H2O, while it was the greatest at the tidal maximal alveolar pressure of 1 to-1cm H2O with either gas. Alveolar hyperinflation in a localized lung region due to the increase in regional alveolar pressure reduced regional perfusion distribution.