A method for optimal depth of the nasopharyngeal temperature probe: the philtrum to tragus distance

Abstract

BackgroundThe nasopharyngeal temperature probe should be placed in the upper nasopharynx to reflect accurate core temperature. However, there have been no studies conducted to predict parameters for the optimal depth of the nasopharyngeal temperature probe. The purpose of this study was to examine the correlation between the optimal depth to the upper nasopharynx and the distance from the philtrum to the tragus and height.MethodsTwo hundred patients (100 females and 100 males) were enrolled in the study. The distance from the philtrum to the tragus along the facial curvature was measured, and the optimal depth from the nostril to the upper nasopharynx was evaluated using nasendoscopy. The relationships between the optimal depth to the upper nasopharynx and the distance from the philtrum to the tragus and height were examined.ResultsThe distances from the philtrum to the tragus were 14.4 ± 0.5 cm in females and 15.1 ± 0.6 cm in males (P < 0.01). The depths from the nostril to the upper nasopharynx were 9.4 ± 0.6 cm in females and 10.0 ± 0.5 cm in males (P < 0.01). The correlation coefficients between the depth from the nostril to the upper nasopharynx and the distance to the tragus from the philtrum were 0.43 in females and 0.41 in males (P < 0.01). However, there were very weak correlations and no correlations between height and the depth from the nostril to the upper nasopharynx in females and males, respectively.ConclusionsThe depth from the nostril to the upper nasopharynx is correlated weakly with the distance from the philtrum to the tragus. Although the distance from the philtrum to the tragus is not a good predicting parameter for the optimal depth of nasopharyngeal temperature probe placement, subtraction of 5 cm from the distance is helpful to estimate the optimal depth of the nasopharyngeal temperature probe.

Optimal Insertion Depth for Nasal Mid-Turbinate and Nasopharyngeal Swabs

“…The 9.40 (SD, 0.64) cm mean insertion depth to the posterior nasopharyngeal wall in our study is in accordance with an earlier study measuring the insertion depth for a nasopharyngeal temperature probe [ 16 ]. Previously published guidelines described a similar insertion depth between 9 and 10 cm [ 6 ], while several instruction-for-use manuals underestimate the depth down to as little as 4 cm [ 5 , 7 , 8 , 9 ].…”

Variability in instructions for performance of nasopharyngeal swabs across Canada in the era of COVID-19 – what type of swab is actually being performed?

“…Minimal data has been published regarding the depth of the nasopharynx. A study by Lim and Lee (21) from Korea demonstrated in a series of 200 individuals that the average distance from nostril to nasopharynx surface was 9.4 ± 0.6cm in females and 10.0 ± 0.5 cm in males. They also found that the average distance from philtrum to tragus (akin to measuring nostril to ear distance) in the same set of patients was 14.4 ± 0.5 cm in females and 15.1 ± 0.6 cm in males.…”

Variability in instructions for performance of nasopharyngeal swabs across Canada in the era of COVID-19 – what type of swab is actually being performed?

“…Minimal data has been published regarding the depth of the nasopharynx. A study by Lim and Lee [ 32 ] from Korea demonstrated in a series of 200 individuals that the average distance from nostril to nasopharynx surface was 9.4 ± 0.6 cm in females and 10.0 ± 0.5 cm in males. They also found that the average distance from philtrum to tragus (akin to measuring nostril to ear distance) in the same set of patients was 14.4 ± 0.5 cm in females and 15.1 ± 0.6 cm in males.…”