Some forums threads suggest another solution to fix the gray out iPhone 4S Wifi issue: placing the iPhone 4S in a refrigerator or freezer for several minutes, for they considered the 4S WiFi issue after iOS 7 update is caused by the heating issues.
An ABG test uses blood drawn from an artery, where the oxygen and carbon dioxide levels can be measured before they enter body tissues. Partial pressure of oxygen (PaO2). This measures the pressure of oxygen dissolved in the blood and how well oxygen is able to move from the airspace of the lungs into the blood.
Doctors can and do use arterial blood sampling but usually only when it is absolutely necessary ie. they need an arterial blood sample for arterial blood gas analysis (ABG) to find out how much oxygen and CO2 is in the arterial blood or when they cannot get venous access (for examples in trauma or otherwise seriously ill patients).