Arterial blood gases (ABGs) are commonly used for estimating the acid-base status, oxygenation and carbon dioxide concentration of unwell patients. However, arterial blood can be difficult to obtain due to weak pulses or patient movement. Due to thicker, muscular and innervated walls, arteries are also more painful to puncture than veins. As such, a venous blood gas (VBG) is an alternative method of estimating pH and other variables.

pH                 7.35–7.45  

pCO2             35–45 torr              4.5–6.0 kPa

pO2                 >79 torr              >10.5 kPa

CO2              23-30 mmol/L  

Base excess/deficit ± 3 mEq/L              ± 2 mmol/L

SO2 >94%