Expel air bubbles from a blood gas sample by gently tapping on the side of the syringe to bring the air bubbles to the top. Then expel them by pressing the plunger. You can place the tip of the syringe to a piece of gauze.
However, you can also expel the air bubbles through a vented tip cap, limiting the risk of blood contact. [1-2]
Effect of air bubbles in a blood gas sampleAir bubbles in blood gas samples may have a bias effect on the pO2 value. Depending on the initial pO2 value of the blood, the pO2 bias on blood gas results will be either positive or negative. The bias is often positive. However, samples with high pO2 values can produce falsely lowered results because of the equilibration with the oxygen in the air bubble. [2-3]
Effects on the patient and healthcare professionalsThe presence of air bubbles in a blood gas sample can lead to wrong diagnosis. This may then result in wrong treatment and prolonged length of stay for the patient.
Additionally, in the process of expelling air bubbles from a blood gas sample into a piece of gauze, an instance of blood exposure creates a risk of contact with potentially infected blood. You risk exposing yourself to blood-borne pathogens when expelling air without using a vented tip cap. 
Expel air bubbles from a blood gas sampleA vented tip cap helps in protecting you from blood exposure after blood collection. The vented tip cap forms a closed system, allowing you to expel any air bubbles and minimizing the risk of blood exposure. The vented tip cap seals the sample to prevent contact with atmospheric air. The tip cap stays on during aspiration of blood into the analyzer so you minimize the risk of blood contact. 
The safePICO arterial blood gas syringe with safeTIPCAP
Easily expel air bubbles from an arterial blood gas sample while limiting the risk of blood contact using the safeTIPCAP on the safePICO syringe. The vented tip cap completely seals the sample immediately after blood collection and stays on during blood gas analysis.