Adequacy of different measurement methods in determining nasogastric tube insertion lengths: An observational study

Distance from the tip of the nose to earlobe to xiphisternum is commonly used to determine the length of nasogastric tube to be inserted. However, it is not evidence-based and frequently leads to improper positioning.

This study evaluated four formulae and the distance from the tip of the nose to earlobe to xiphisternum in estimating the internal length of nasogastric tube required for optimal positioning.

Observational Study.

Tertiary hospital in Singapore involving patients from the medical and surgical intensive care units and a neurosurgical ward.

Inclusion criteria were patients who required a nasogastric tube insertion and age > = 21 years old and =<85 years old. Patients who required an orogastric tube insertion or did not require a chest x-ray post nasogastric tube insertion were excluded.

Upon nasogastric tube insertion, the external length of the tube was measured and the corresponding internal length calculated. Several anatomical measurements were taken as required in the formulae below: 1. ((Distance from tip of nose to earlobe to xiphisternum-50 cm)/2) + 50 cm. 2. 29.38 + 4.53*gender+0.34*distance from nose to umbilicus with head flat on bed-0.06*weight (gender = 1 for male, and 0 for female). 3. Distance from xiphisternum to earlobe to nose + 10 cm. 4. Distance from earlobe to xiphisternum to umbilicus-distance from tip of the nose to earlobe. Post insertion chest x-rays were examined to evaluate the position of the nasogastric tube. For those with optimal positioning, the distance from tip of the nose to earlobe to xiphisternum and the four formulae were compared to determine which provided the least difference with the internal length of the nasogastric tube.

Ninety-two participants were recruited. The average age of the cohort was 62.9 years old with 54% being male. Twenty-five had nasogastric tubes in optimal position; 13 had it too short and 54 had it too long. For nasogastric tubes in optimal position, distance from xiphisternum to earlobe to nose + 10 cm provided the best estimate of the internal length. Average difference between the distance from xiphisternum to earlobe to nose + 10 cm and internal length of the nasogastric tubes in optimal position was only 1.8 cm which was by far the least difference compared to other formulae.

This study found distance from xiphisternum to earlobe to nose + 10 cm to provide the best estimate for the internal length of nasogastric tube required. However, even this formula could result in placement that is not optimal due to anatomical differences.