Appropriate timing of blood sampling for blood gas analysis in the ventilated rabbit

Arterial and venous blood gas analyses (BGAs) are essential to evaluate devices that measure biological oxygenation. The appropriate timing of blood sampling for BGA after respiratory rate (RR) change in animal experiments has not been reported. This study investigated the appropriate timing of blood sampling for BGA in ventilated rabbits and whether venous samples are an alternative to arterial samples.

Under general anesthesia, 14 rabbits (body weight, 3.02 ± 0.09 kg) were ventilated and their RR was changed (40/min, 30/min, and 20/min). Blood was sampled through cervical arterial and venous catheters. Experiment 1: in seven rabbits, arterial BGA was measured at 0, 0.5, 1, 2, 3, 5, 10, 15, and 20 min after the RR change. Experiment 2: in seven different rabbits, simultaneous arterial and venous BGA were measured at 0, 2, 5, 10, 15, and 20 min after the RR change.

Oxygen partial pressure (PO₂) and saturation (SO₂) of the arterial blood stabilized 0.5 min after the RR changed. In venous BGA, no index stabilized during observation. The arterial and venous values of the carbon dioxide partial pressure (PCO₂) and pH had significant correlations (arterial PCO₂ = 0.9316 × venous PCO₂-4.4425 [r = 0.9178]; arterial pH = 1.0835 × venous pH-0.5795 [r = 0.9453]).

In ventilated rabbits, arterial PO₂ and SO₂ stabilized in 0.5 min. No venous value stabilized after the RR change. Only the PCO₂ and pH of venous samples may be an alternative to arterial samples under the defined formula.