Indicator dilution measurements of extravascular water in the lungs

Abstract

A B S T R A C T Multiple indicator dilution studies of the pulmonary circulation were carried out in conscious, resting and exercising, and anesthetized dogs under conditions where there was no pulmonary edema. Labeled red cells, water, and albumin were injected together into the pulmonary artery, and effluent dilution patterns were obtained from the descending thoracic aorta. The product of the mean transit time differences between labeled water and red cells, and the pulmonary water flow was used to estimate extravascular parenchymatous water; and this was expressed as a proportion of the water content of the blood-drained lung at postmortem examination. These estimates of the proportional water content were found to increase with flow, and to approach an asymptotic value. Reconsideration of the flow patterns in capillaries, however, led to the postulate that extravascular water should be calculated, utilizing as the appropriate vascular reference a substance that uniformly labels the water in red cells and plasma, and which is confined to the circulation, rather than a tracer that only labels red cells. The mean transit time of this substance is approximated by the sum of the mean transit times of labeled red cells and albumin, each weighted according to the proportion of the water content of blood present in that phase. The values for lung water content so computed also increased with flow, and appeared to approach an asymptote that corresponded to approximately two-thirds of the wet lung weight. The estimated values for the water space after pentobarbital anesthesia corresponded to the lower values obtained in the resting conscious animals. When the anesthetized animals were also bled, the estimated water space was disproportionately large, in relation to the previous values. These experimental results support the hypothesis that dilutional This work was presented in part at the 51st Annual

Effects of exercise on lung lymph flow in sheep and goats during normoxia and hypoxia.

“…While there is evidence that exercise causes an increase in lymph flow from the limbs (7) and heart (8), there are no published data on the effect of exercise on lung lymph flow. There is, however, indirect evidence in animals (9) and man that exercise with (10, 1 1) or without (12)(13)(14)(15)(16) hypobaric hypoxia causes an increase in extravascular lung water. There are also reports of acute pulmonary edema occurring in man during very vigorous exercise at sea level (17) and during moderate exercise at high altitude (18)(19)(20).…”

Indicator Dilution Measurements of Lung Volumes and Alveolar Air Exchange During Breathing

“…It has been found that in the dog lung, the mean transit time of red cells is 0.3 s shorter than plasma (8). Knowing that xenon is two times more soluble in red cells than plasma (9), the error incurred by assuming that the transit delays 1 and 2 are the same for xenon and indocyanine green, is 0.2 s. Since the average experimental Atier exceeds 20 s- (Tables 11, 111) there will be an underestimation of ZIX-Xe-r of approximately 1.0%o when (r) is indocyanine green.'…”

“…The ventilation equation 8 Graham's law states that the rate of diffusion is proportional to <density 17 assumes a single compartment lung with a uniform VA/Q ratio. Under such circumstances VAXe will be identical to VAco2.…”

Effects of antihistamines on the lung vascular response to histamine in unanesthetized sheep. Diphenhydramine prevention of pulmonary edema and increased permeability.

“…We measured cardiac output and extravascular water during steady-state base-line and experimental periods 10 times in four sheep receiving histamine alone and 21 times in seven sheep receiving diphenhydramine plus histamine according to the protocol described above under "Prevention studies." Measurements were made by indicator dilution techniques, with both ['Cr] -erythrocytes and l"I-albumin as intravascular indicators to avoid errors due to erythrocyte-plasma transit time differences (7,8). Each animal's erythrocytes were labeled by incubating a blood sample for 1 h with ['Cr]sodium chromate at room temperature and washing the cells three times with 0.89% NaCl solution.…”