Effect of high ambient pressure and oxygen tension on organ blood flow in conscious trained rats.

Cardiac output and blood flow to different organs and tissues were investigated in conscious trained rats using radiolabeled microspheres (MS) injected into the left ventricle. Two subsequent MS injections were administered to each rat at normal gas atmosphere and pressure (control) and in one of the following experimental situations: at normal ambient pressure and high partial pressure of O2 (PO2 = 1.0 ATA) (Group 1); an ambient pressure of 5 ATA and high partial pressure of O2 (PO2 = 1.0 ATA) (Group 2); and at ambient pressure of 5 ATA and normal partial pressure of O2 (PO2 = 0.2 ATA). The inert gas was nitrogen. Cardiac output fell in Groups 1 and 2 with high PO2 (P less than 0.05), and was unchanged in Group 3 with normal PO2. Heart rate decreased in Groups 1 (NS) and 2 (P less than 0.01), and was unchanged in Group 3. The arterial pressure remained unchanged while the renal blood flow decreased (P less than 0.05) in all groups. The myocardial blood flow fell (P less than 0.05) in both groups with decreased cardiac output, and was increased by 25% (P less than 0.05) in normoxia (Group 3) with maintained cardiac output. The blood flow to the adrenal glands fell (P less than 0.05) in both groups with high PO2, and increased in the normoxic Group 3 (NS). The blood flow to the splanchnic area fell in all groups. The cerebral blood flow and blood flow to the eyes fell in both groups with high PO2 (P less than 0.05), and were constant in normoxia.