Pulmonary lymph flow and the uptake of liquid from the lungs of the lamb at the start of breathing

Abstract

1. Lymph from the lungs of lambs and sheep was found to enter both the right lymph duct and the thoracic duct. Right lymph duct flow was collected by constructing a venous sac, the venous tributaries of which were ligated but which the right lymph duct entered; thoracic duct flow was collected by cannulating the duct. Lymph from sites other than the lungs was excluded from the collections.2. Measurements were made of the surface tension characteristics of lung extracts and of the liquid present in foetal lungs. These values were used together with gestational age and crown-rump length to designate the foetal lambs into mature and immature groups.3. Lymph flow from the lungs averaged 0.99 ml./kg body wt./hr in immature foetal lambs, and 1.81 ml./kg/hr in mature foetal lambs before the start of ventilation. Lymph flow from the lungs of spontaneously delivered new-born lambs (mean age 51 hr) averaged 0.86 ml./kg/hr. In adult ewes right lymph duct flow averaged 0.11 ml./kg/hr and total lung lymph flow was estimated indirectly to be 0.33 ml./kg/hr. Calculated rates of protein flow in lung lymph (flow x protein concentration) were greater in foetal lambs than in adult sheep.4. Total thoracic duct flow averaged 2.48 ml./kg/hr in immature foetal lambs, 5.30 ml./kg/hr in mature foetal lambs, 3.65 ml./kg/hr in new-born lambs, and 2.92 ml./kg/hr in adult ewes.5. At the start of ventilation there was an increase in lymph flow from the lungs, which at 15-30 min reached a mean of 6.4 ml./kg/hr in mature lambs and 2.6 ml./kg/hr in immature lambs. At the same time the protein concentration of lymph decreased but the calculated protein flow increased.6. The lungs of foetal lambs weighed more than the lungs of spontaneously delivered new-born lambs, and the difference could be accounted for by liquid which could be aspirated through the trachea of the foetal lamb. On ventilation of the lungs for 2 hr, without first allowing the escape of any lung liquid, lung weight measurements indicated that about 66% of the lung liquid had been taken up in mature lambs and about 50% in immature lambs.7. It was concluded that the rate at which lymph is formed in the lungs is greater per kilogram body weight in foetal than in new-born lambs and greater in them than in ewes. The increase in lymph flow at the start of ventilation could account for the removal of about 40% of the liquid present in the lungs of the mature foetus and about 25% of the liquid in the lungs of the immature foetus.

Ion fluxes across the pulmonary epithelium and the secretion of lung liquid in the foetal lamb

“…Lung liquid was sampled via the tracheal cannula and blood was obtained from the carotid artery. In two experiments, samples of pulmonary lymph were obtained by cannulating the thoracic duct and 329 R. E. OLVER AND L. B. STRANG excluding non-pulmonary sources of lymph as described by Humphreys, Normand, Reynolds & Strang (1967).…”

“…It is difficult to aspirate more than half of that actually present through a tracheostomy, so it is unlikely that more is expelled through the mouth during vaginal delivery and even less is likely to be drained away after Caesarean section. From lung weight and lymph flow measurements, Humphreys et al (1967) showed that much of the liquid is cleared by lymphatics from the interstitial spaces of the lung over a period of 5-6 hr, but it seems likely that it must be displaced from the alveolar spaces much more rapidly, otherwise efficient gas exchange would not be possible. The experiments with cyanide show that when the secretion is stopped, absorption takes place at 5-18 ml./hr, presumably down the gradient of water activity which exists because of the difference in protein concentration between lung liquid and plasma, exerting an osmotic pressure of about 25 mmHg (see Boston, Humphreys, Normand, Reynolds & Strang (1968) for protein osmotic pressure values).…”

Lymph and pulmonary response to isobaric reduction in plasma oncotic pressure in baboons.

“…16 The majority of pulmonary lymph drains to the right lymphatic duct 5 ' 16 '" with some pulmonary lymph draining to the thoracic duct. 12 This was confirmed in two additional baboons in which Evans blue dye was instilled into the trachea. Dye was noted to drain predominantly to the right lymphatics.…”

“…16 Division of the right cervical lymphatic chain and interruption of the right arm lymphatics eliminated these sources of contamination of pulmonary lymph. 12 The right lymph collected in this experiment probably contained some cardiac lymph 12 and thus cannot be considered pure pulmonary lymph. However, it was found to be strikingly different from thoracic duct lymph and thus seems to represent principally pulmonary lymph.…”

Extracellular volume and blood volume in chronically catheterized fetal sheep.

“…4 is part of a gradual trend that begins earlier in gestation and continues after birth until adult values are obtained. During late gestation, the increase in the plasma: interstitial volume ratio might be due to the increase in plasma colloid osmotic pressure with age (Lumbers et al 1991), which would tend to hold fluid in the vascular compartment, and the rise in lymphatic flow with age (Humphries, Normand, Reynolds & Strang, 1967), which would return escaped fluid to the vascular compartment. The effect of the rise in plasma colloid osmotic pressure may be magnified by a fall in capillary permeability to protein with age .…”