Resistance of central and peripheral airways measured by a retrograde catheter

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Abstract
Pressure in airways 1.5-2.5 mm internal diameter was measured in open-chested living dogs and in excised lungs from different species with a "retrograde" catheter extending from the lumen through the bronchial wall, parenchyma, and pleura to the manometer. The pressure was used to partition pulmonary flow-resistance (RL) into a peripheral resistance (Rp) between the catheter and alveoli and a central resistance (Re) between the catheter and the trachea. Rp was too small to detect above 80% VC but increased at lower volumes to 15% of RL at 10% of VC. RL increased considerably at low volumes due primarily to an increase in RC. RL increased at high lung volumes,as well, usually due entirely to an increase in Re. The low value of Rp favors equality of gas distribution, but constriction of peripheral airways might affect gas distribution and exchange with little change in RL. Because lung tissue resistance is included in Rp, it must be a negligible component of RL in the dogs studied.