1)The AirPort Valve (blue): allows air to enter the blue pigtail to equalize pressure, preventing the tube from suctioning to the stomach lining. It prevents a vacuum effect, protects the stomach lining from damage during suctioning, and ensures continuous decompression. This means we don't use that port to flush with water or pull gastric residual. These small, often overlooked components ensure a strong, safe electrical connection. So, what. What is the blue thing at the end of an ng tube? Nasogastric tubes, commonly referred to as NG tubes, are frequently used in healthcare settings to deliver nutrition, fluids, and medications directly into a patient's stomach.