Which of the following is NOT an acceptable verification method for blindly inserted enteral tubes?

• A. Capnography
• B. pH aspirate
• C. Blue litmus paper
• D. Length measurement of tube

Answer: (C)

When a tube is inserted blindly, you need a method that reliably shows where the tube tip actually is. Capnography detects CO2 and directly indicates if the tip is in the airway, which immediately flags misplacement. Testing the pH of aspirate helps confirm gastric placement because stomach contents are typically acidic, though this can be influenced by medications or feeding and isn’t always possible if you can’t obtain aspirate. Measuring the external length of the tube provides a check of the expected depth but isn’t definitive on its own.

Blue litmus paper, however, isn’t acceptable because it merely indicates whether a solution is acidic or basic without revealing the tube’s location. Gastric contents can be variable in pH due to antacids, proton pump inhibitors, or feeding, and aspirate may not always be obtainable or uncontaminated. This makes blue litmus paper an unreliable, non-specific method for confirming proper enteral tube placement.