Transvascular fluid exchange in the tracheal mucosa

Abstract

The fluid balance of the rabbit tracheal mucosa was investigated with the micropuncture technique and the microsphere method was used for blood flow measurements. Under resting control conditions the blood flow was 0.62 ± 0.41 ml/min · g of tissue; it increased to 3.22 ± 1.55 ml/min · g when the trachea was divided by a midline incision and fixed with two clamps for the micropuncture experiments. The hydrostatic pressure in the early part of the capillary was 28 mm Hg, in the middle part 17 mm Hg, and in the late part 14 mm Hg. The pressure in the dense network of sinusoidal submucosal veins was 12 mm Hg. The interstitial pressure was 3–4 mm Hg. The plasma colloid osmotic pressure, as estimated from protein data, was 21 mm Hg, and that in the interstitium or terminal lymph was 19 mm Hg; thus they were almost identical. This was due to a heavy leakage of protein resulting from the irritation caused by the incision and clamp-fixation and resembled any case of irritation. With a horizontal body posture there is an outwardly directed filtration in all vascular segments. Part of the fluid will form the fluid layer on the tracheal epithelium and the mucus. The rest is drained, together with the proteins, by the richly developed lymphatic system. In an upright body posture, significant resorption will take place via the submucosal venous plexus, with less risk of edema.