Collateral flow resistance and time constants in dog and horse lungs.
We studied collateral flow resistance in exsanguinated, excised lower lobes and accessory lobes of dog and horse lungs, respectively. A double lumen catheter obstructed a peripheral airway isolating a segment of the lobe. Oxygen flowed into the segment via a rotameter which measured flow (Vcoll) while the inner catheter recorded segment pressure (Ps). Gas delivered into the segment flowed out via collateral channels. Collateral flow resistance was calculated as (Ps - PL)/Vcoll, where PL = static transpulmonary pressure. Rcoll at PL = 20, 10, and 5 cm H2O averaged 0.24, 1.25, and 2.65 cmH2O.ml-1.s, respectively, in the dog, and 4.53, 6.00, and 12.62 cmH2O.ml-1.s in the horse. At a given PL, Rcoll measured during inflation. At constant PL, Rcoll increased with time at PL = 5 and 10 cmH2O, but was not time dependent at PL = 20 cmH2O. At constant PL, Rcoll increased at Vcoll increased. We conclude Rcoll is greater in horses than in dogs and is a function of PL, Ps - PL, and lung volume history in both species.
D000403:Airway Resistance; D000818:Animals; D002417:Cattle; D004283:Dog Diseases / Q000503:physiopathology*; D004285:Dogs; D006734:Horse Diseases / Q000503:physiopathology*; D006736:Horses; D006801:Humans; D008168:Lung / Q000033:anatomy & histology / Q000503:physiopathology*; D008173:Lung Diseases, Obstructive / Q000503:physiopathology / Q000662:veterinary*; D012115:Residual Volume; D012119:Respiration; D013045:Species Specificity; D014109:Total Lung Capacity