Ventilation, cardiac output and blood respiratory parameters in the carp, Cyprinus carpio, during hyperoxia

Abstract

The specific ventilatory flow rate (V̇w), cardiac output (V̇b) and blood respiratory parameters were determined in the carp ( Cyprinus carpio) during hyperoxia. V̇b changed little during moderate hyperoxia (240–330 Torr) but slightly increased during extreme hyperoxia (430–490 Torr) while V̇w decreased. This means that the ventilation-perfusion ratio considerably decreased during hyperoxia. The CO 2 tension (P CO 2 ) of blood rose, causing a corresponding decrease in blood pH. The O 2 tensions (P O 2 ) of arterial and mixed venous blood increased but remained low (about 40 Torr and 15 Torr, respectively). Consequently, the hemoglobin in the arterial and mixed venous blood was not saturated with O 2 (about 80 and 55%, respectively) even during extreme hyperoxia. This indicates that most of the O 2 which is consumed by the fish remains transported in a combined form during hyperoxia. During hyperoxia, when the decreased V̇w was artificially elevated to the normoxic level, the P O 2 of arterial blood (Pa O 2 ) rose further and the P CO 2 and pH of arterial blood became restored to the normoxic levels. This suggests that the CO 2 retention and the depressed increase in Pa O 2 during hyperoxia are mainly due to the decrease in V̇w in the carp.