Axillary and tympanic membrane temperature recording in the preterm neonate: a comparative study


Judi Bailey, Special Care Baby Unit, Queen Mary’s Hospital, Sidcup, Kent DA14 6LT, UK.


Axillary and tympanic membrane temperature recording in the preterm neonate: a comparative study

Study aims. The aim of this study is to compare axillary temperature recordings with those of the tympanic membrane, in healthy preterm neonates, to ascertain whether there is any significant difference between the two recordings, in particular in relation to postnatal age, and if so to evaluate the clinical implications.

Rationale. Immature thermoregulatory mechanisms, and small body size, mean preterm neonates are prone to temperature maintenance problems, and thermal stress is associated with increased morbidity and mortality. In order to ensure minimal handling, the ideal method of temperature recording would be rapid, painless and reproducible, and accurately reflect core temperature, whilst considering safety, comfort, ease of procedure and cost effectiveness. Recording of the tympanic membrane temperature is rapid and noninvasive, however, the accuracy of this method in preterm neonates has not been established.

Study design. A comparative descriptive design was used, to describe differences in the recorded temperature in healthy preterm neonates, of gestational age of 27–37 weeks, related to temperature recording method. A second comparison was undertaken to establish difference in mean temperature recordings dependant on postnatal age of the baby in days. The sample included all babies fitting the selection criteria, admitted to the Neonatal Unit during the study period. Following approval by the local research ethics committee tympanic membrane and axillary temperatures were recorded consecutively for 7 days (n=154), using the Genius Model 3000A tympanic thermometer and a glass and mercury thermometer.

Results. A t-test demonstrated a statistically significant difference between the recordings (P < 0·05), tympanic membrane recordings being higher. However, analysis of variance indicated that this difference was not associated with postnatal age, and thus the presence of vernix in the auditory canal (P > 0·05). The findings were not, however, deemed clinically significant in that no change in care or treatment resulted from differences in temperature recordings.

Conclusions. Whilst the findings cannot be applied to sick preterm neonate, it was concluded that tympanic membrane temperature recordings in healthy preterm neonates are safe, accurate, easy, and comfortable for the baby, and appropriate with this client group provided staff are trained in the technique.