<prompt> Commonest aery for cannulation is -RadialUlnarBrachialCubital  <response>: Answer is a i.e. Radial Aerial puncture and cannulation is performed to measure the Pa02, PaCO2, Sa02 and pH to clarify the acid-base and electrolyte status. Any aery that can be compressed after puncture may be used but not end-aeries; usually the radial preferred, brachial, or femoral - Lee 12e 