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Assessment of whole body and regional evaporative heat loss coefficients in very premature infants using a thermal mannequin: Influence of air velocity
Author(s) -
Belghazi Khalid,
Elabbassi Elmountacer Billah,
Tourneux Pierre,
Libert JeanPierre
Publication year - 2005
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1862074
Subject(s) - natural convection , forced convection , relative humidity , body surface , airflow , evaporative cooler , thermal , mechanics , convection , air velocity , humidity , thermodynamics , materials science , environmental science , physics , mathematics , geometry
In human adults, experimental assessment of the evaporative heat loss coefficient ( h e ) requires a fully wetted skin surface area implying exposure to severe heat stress. For ethical reasons, this type of experimental situation is impossible to perform on neonates. The aim of the present study was to assess h e values in clinical situations for the body as a whole and for the different body segments, in particular, in natural and forced convection and using an anthropomorphic, sweating, thermal mannequin to represent a very small premature neonate (body mass 900 g). Skin hydration (i.e., simulated sweating) was performed by two electronic pumping systems, providing a steady adjustable flow of water to the mannequin surface. Experiments were carried out in a closed‐incubator heated to air temperatures of 33 °C and 36 °C, with air velocities ( V a ) ranging from 0.01 to 0.7 ms − 1 , and with four levels of air relative humidity (40, 50, 60, and 80%). For the body as a whole, h e = 7 Wm − 2mb − 1in natural convection, whereas in forced convection h e was 11.7, 12.4, and 14.1 Wm − 2mb − 1for air velocities of 0.2, 0.4, and 0.7 ms − 1 , respectively. As far as local h e is concerned, our results showed that the relative values of regional water loss in forced convection differ greatly from those observed under still air conditions. Thus, increasing air velocity enhances the heterogeneity in regional skin cooling, which may contribute to the neonate's thermal discomfort.