A gradient-layer calorimeter for measurement of energy expenditure of infants.

We have developed and validated a gradient-layer calorimeter for direct measurement of energy expenditure of preterm infants. Infant calorimeters must be operated and tested differently from adult calorimeters, because the calorimeter must be warmed during operation to limit heat loss from the infant, the calorimeter wall temperature (which is selected on the basis of the infant's maturity) must be precisely controlled, and energy expenditure (heat output) is typically < 10 W. We calibrated our calorimeter by varying the heat produced by a dry source (manikin or light bulb) with airflow (n = 42) and without airflow (n = 8) at various water jacket temperatures (n = 7) and by a wet source (combustion of ethyl alcohol) with airflow (n = 9). With no air moving, qc = 0.740 Vc + 0.029 Twj-0.697, where qc (W) is the estimated output of the heat source measured by the calorimeter, Vc (mV) is the gradient-layer voltage of the calorimeter, and Twj (degree C) is the temperature of the water jacket surrounding the walls of the device. From this equation and enthalpy calculations, the slope and intercept of the regression line relating the estimated heat production to the actual heat produced from alcohol combustion are 1.029 +/- 0.046 and -0.549 +/- 0.484 (SE), respectively. The slope is not significantly different from unity, and the intercept is not significantly different from zero. Thus we can accurately estimate the energy expenditure of preterm infants from the equations describing our calorimeter, and we can accurately resolve the total heat output into a dry (nonevaporative) component and a wet (evaporative) component.

[The school child carrying heavy burdens]. / Das Schulkind als Lastenträger.

In 163 Viennese pupils in standard 1 to 8, the weight of the schoolbag, the bodyweight and the ratio of these two parameters were examined in order to describe the amount of burden carried by those children. The results were: 1. The weight of the schoolbag war 4.0 kg (range 1 to 9 kg). 2. The pupils carried a schoolbag weighing on the average 10%, in standard 2 about 15% and in standard 8 about 6% of their bodyweight. 3. In every 6th pupil, the weight of the schoolbag constituted more than 15% of the bodyweight. 4. In analogy to pupils in standard 2, adults with a body weight of 70 kg would have to carry a weight of up to 17.5 kg to their working place. 5. While pupils have to carry a burden between 10 and 25% of their bodyweight, adults were carrying only between 1 and 10% of their bodyweight to work. We conclude that pupils are carrying daily a heavy burden in form of a schoolbag and adults apparently don't care about it.