Body temperature mapping in critically ill newborn infants nursed under radiant warmers during intensive care.

OBJECTIVE: The objectives of this study were to assess (i) the agreement between servo-control temperature (Tfeedback) and rectal temperature (Tre) and (ii) the distribution of regional skin temperatures (Tsk) of neonates nursed under a radiant warmer (RW) in a neonatal intensive care unit. STUDY DESIGN: An observational study of 13 neonates nursed under a RW device set to servo-control mode (Tfeedback set-point: 36.5 °C) who were monitored for Tfeedback, Tre and Tsk at six sites for a period of 105 min. RESULTS: Mean bias for Tfeedback relative to Tre was +0.01 °C, but 95% limits of agreement were ±0.99 °C, and only 66% of Tfeedback values were within the acceptable limits determined a priori (±0.5 °C). Tfeedback was maintained within a range of 1.4 °C (35.9 to 37.3 °C), whereas the range observed for regional skin temperatures spanned from 9.5 °C (27.3 to 36.8 °C; foot) to 4.8 °C (33.1 to 37.9 °C; chest). CONCLUSION: Although Tfeedback is maintained within narrow limits, the level of agreement with Tre is poor. In addition, large fluctuations in regional skin temperatures occur with a consistent caudal-to-rostral temperature gradient, irrespective of Tfeedback.

Precise mimicking of exercise hyperpnea to investigate the oxygen cost of breathing.

The oxygen cost of exercise hyperpnea (V˙(O2 RM)) has been quantified using a variety of techniques with inconsistent findings. Between-study variation relates to poor control of breathing patterns and lung mechanics. We developed a methodology allowing precise matching of exercising WOB in order to estimate V˙(O2 RM). Thirteen healthy young subjects (7 male) completed an incremental cycle exercise test, familiarization and experimental days where exercise hyperpnea was mimicked. On experimental days, feedback of exercise flow, volume and the respiratory pressures were provided while end-tidal CO2 was kept at exercise levels during each 5-min trial. Minute ventilation levels between 50 and 100% maximum were mimicked 3-5 times. The r(2) between exercise and mimic trails was 0.99 for frequency, tidal volume and minute ventilation; 0.86 for esophageal pressure swings and 0.93 for WOB. The coefficient of variation for (V˙(O2) averaged 4.3, 4.4 and 5.7% for 50, 75 and 100% ventilation trials. When WOB and other respiratory parameters are tightly controlled, the V˙(O2 RM) can be consistently estimated.

Accidental overheating of a newborn under an infant radiant warmer: a lesson for future use.

A fully functional radiant warmer induced rapid and continuous increases in regional skin temperatures, heart rate, mean arterial blood pressure and respiratory rate in a newborn patient without corrective action. We report this case of passive overheating to create awareness of the risks associated with regulating radiant heat output based upon a single servo-controlled temperature.