Oxygen phosphorescence quenching was used to measure tissue Po2 of lymphatic vessels of 43.6 ± 23.1 μm (mean ± SD) diameter in tissue locations of the rat mesentery classified according to anatomic location. Lymph and adipose tissue Po2 were 20.6 ± 9.1 and 34.1 ± 7.8 mmHg, respectively, with the difference being statistically significant. Rare microlymphatic vessels in connective tissue not surrounded by microvessels had a Po2 of 0.8 ± 0.2 mmHg, whereas the surrounding tissue Po2 was 3.0 ± 3.2 mmHg, with both values being significantly lower than those of adipose tissue. Lower of lymph fluid Po2 relative to the surrounding tissue was also evident in paired measurements of Po2 in the lymphatic vessels and perilymphatic adipose tissue, which was significantly lower than the Po2 in paired adipose tissue. The Po2 of the lymphatic fluid of the mesenteric microlymphatics is consistently lower than that of the surrounding adipose tissue by ∼11 mmHg; therefore, lymph fluid has the lowest Po2 of this tissue. The disparity between lymph and tissue Po2 is attributed to the microlymphatic vessel wall and lymphocyte oxygen consumption.

The vascular wall is a sink for oxygen. The modulation of vessel wall oxygen consumption can substantially impact the amount of oxygen released to the tissue.

Intravenous injection of CO-saturated saline caused vasodilation and improved microvascular hemodynamics in the hamster window chamber model in a dose-dependent manner. These changes were related to increased cardiac output and local cGMP content. These results support the possible use of CO-saturated solutions as a vasodilator in critical conditions.