Prior to GRV assessment, how much air should be injected into the tube?

• A. 10 mL
• B. 20 mL
• C. 30 mL
• D. 60 mL

Answer: (C)

Prior to measuring gastric residual volume, a moderate air flush is used to help verify the tube’s position and to loosen contents for easier aspiration. Injecting about 30 mL of air provides enough volume to generate a clear gastric auscultation cue (a gurgling or whoosh over the stomach) while also helping to clear the lumen so residual can be measured more accurately. This amount strikes a balance: it’s sufficient to aid assessment and reduce clogging, but not so large as to risk gastric distension or reflux. Too little air may yield an unreliable sign or hinder aspiration, while too much (for example, 60 mL) increases discomfort and potential complications.