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.
What Is an Arterial Blood Gas Test? An arterial blood gas test, commonly known as an ABG, is performed on blood from an artery. It is used to see how well the lungs are functioning and to determine the effectiveness of respiratory therapies, such as the use of a ventilator, CPAP, BiPAP or oxygen.