Jon K. Moon

Sleep Organization and Energy Expenditure of Breast-Fed and Formula-Fed Infants

Sleep organization of infants may be influenced by differences in nutrient intakes from human milk and formula. Because sleep/awake and sleep stage patterns affect energy expenditure, we hypothesized that differences in sleep organization between breast-fed and formula-fed infants might account in part for differences in energy expenditure between feeding groups. Sleep stages and cycling of 4-mo-old breast-fed (n = 10) formula-fed (n = 10) infants were studied with simultaneous measurements of energy expenditure. EEG, electrooculogram, body movement by triaxial accelerometry, heart rate, and oxygen saturation were monitored during an overnight sleep session. Sleep stages, nonrapid eye movement (NREM), and rapid eye movement (REM) were determined. Behavioral observations were recorded by video tape and by a technologist. Oxygen consumption and carbon dioxide production were measured with an indirect calorimeter. Total number and duration of sleep cycles, REM latency, number of NREM and REM epochs, and duration of NREM epochs did not differ between feeding groups. Sleep latency was shorter (p <0.05) and duration of REM epochs longer (p <0.01) in the formula-fed group. Formula-fed infants spent a higher percentage of sleep time in REM compared with the breast-fed infants (42 versus 34%) (p <0.003). Conversely, breast-fed infants spent a higher percentage of sleep time in NREM sleep and their heart rates during sleep were lower (114 versus 126 bpm; p <0.01). Energy expenditure during REM sleep was 13.0 ± 4.4% higher than during NREM sleep (p <0.001). Nonetheless, total energy expenditure during REM and NREM sleep did not differ statistically between feeding groups, even though nocturnal sleep organization was affected by infant feeding mode and contributed to the measured variability in energy expenditure observed during sleep.

Energy requirements from infancy to adulthood

To investigate how age and body composition affect energy requirements, the sedentary daily expenditure (SDE) and basal metabolic rate (BMR) of 101 infants, 82 girls, and 27 adults were measured. Energy expenditure was scaled for differences in body size to test the effects of age and body fatness. A power function was superior to linear models. For all subjects, WT0.63 (where WT is weight) or FFM0.63 (where FFM is fat-free mass) explained 94% of the variability in BMR, and WT0.70 or FFM0.70 explained 97% of the variability in SDE. The effects of height and fat mass (kg or % body wt) on BMR and SDE scaled for weight or fat-free mass were age dependent. Best-fitted exponents relating BMR or SDE to body size differed between children (0.40-0.52) and infants (1.04-1.30) (P = 0.001). Human energy requirements from infancy to adulthood appear to be a power, not a linear, function of body weight and composition.

Energy Expenditure: Measurement of Human Metabolism

This paper was focused on the human energy expenditure and metabolism. Since EE ends up as heat, direct or indirect physiological calorimetry was used to measure heat lost. For indirect calorimetry, metabolic carts, portable calorimeters and whole-room indirect calorimeters were used. Physical activity and heart rate monitoring were conducted.

Comparison of Centrifugal and Roller Pump Hemolysis Rates at Low Flow

We compared in vitro rates of hemolysis for a recently developed centrifugal pump with a conventional roller pump (10-10-00; Stöckert, Munich, Germany). Flow rates of 0.3 L/min and 1 L/min and a pressure of 200 mm Hg were chosen to simulate conditions during neonatal extracorporeal membrane oxygenation (ECMO). There was no significant difference in hemolysis rates between centrifugal and roller pumps (p = 0.57) nor between high and low flow (p = 0.86). The centrifugal pump caused no more blood trauma than the roller pump at the low-flow/high-pressure conditions required for neonatal ECMO. The Nikkiso pump is superior to roller pumps in size and priming volume (25 ml) and may permit development of a smaller and simpler ECMO system.

Smart phones are useful for food intake and physical activity surveys

Current self-report methods of recording food intake and Physical Activity (PA) are cumbersome and inaccurate. Food and activity surveys implemented on a smart phone will allow for immediate entry, data transfer to a researcher, and feedback to the user. Ten subjects followed a script, representative of one day, to enter food intake and PA on a smart phone. In the follow-up report, all subjects were interested in using the tested program to compare food intake with PA to predict weight gain and loss.

Pre-term infant volume measurements by acoustic plethysmography

An acoustic plethysmograph has been developed to provide routine total body volume measurements of pre-term (1.5-3.0 kg) infants. It operates near 50 Hz and is excited by band-limited 25 Hz span noise. Excitation, measurement, analysis, and environment are computer controlled for greater accuracy, speed, and objectivity in volume determinations. Performance tests produced volume measurements with a mean per cent error (+/- SD) of 0.77 +/- 0.66% for two phantoms with volumes of 2880 and 2130 cm3. Ten, one-minute volume measurements were obtained for 14 infants over a 20 to 30 min period. Their mean density was 1.061 +/- 0.028 g cm-3 and their weight ranged from 1294 to 2025 g.

Data upload capability of 3G mobile phones

Mobile phones are becoming an important platform to measure free-living energy balance and to support weight management therapies. Sensor data, camera images and user input are needed by clinicians and researchers in close to real time. We assessed upload (reverse link) data transport rates for 2007–2008 model mobile phones on two major US wireless systems. Even the slowest phone (EVDO Rev 0) reliably uploaded 40 MB of data in less than 1 h. More than 95% of file uploads were successful in tests that simulated normal phone use over 3 d. Practical bandwidth and data currency from typical smart phones will likely keep pace with the data needs of energy balance studies and weight management therapy.

Centrifugal pumps may have lower hemolysis rates than roller pumps at low flow

Rates of hemolysis in bovine blood were measured by 4-h in vitro tests with a centrifugal pump and conventional roller pump. Flow rates of 0.3 L/min and 1 L/min and pressure of 200 mmHg were chosen to simulate conditions during neonatal extracorporeal oxygenation. There were no significant differences in index of hemolysis between pumps or flow rates. The overall hemolysis index for both pumps was 20 mg/100L. Low blood trauma recorded for the centrifugal pump confirms that it would be suitable for use in extracorporeal oxygenation.

Prediction of oxygen consumption rates from heart interval mean and variance

Heart interval mean and variance were compared as predictors of waking oxygen consumption rate in 20 adult subjects. Correlations between O/sub 2/ consumption and mean heart intervals were significantly better than heart interval variance during both sedentary (P=0.01) and active (P<0.001) periods.

Improving temporal accuracy of human metabolic chambers for dynamic metabolic studies

Metabolic chambers are powerful tools for assessing human energy expenditure, providing flexibility and comfort for the subjects in a near free-living environment. However, the flexibility offered by the large living room size creates challenges in the assessment of dynamic human metabolic signals—such as those generated during high-intensity interval training and short-term involuntary physical activities—with sufficient temporal accuracy. Therefore, this paper presents methods to improve the temporal accuracy of metabolic chambers. The proposed methods include 1) adopting a shortest possible step size, here one minute, to compute the finite derivative terms for the metabolic rate calculation, and 2) applying a robust noise reduction method—total variation denoising—to minimize the large noise generated by the short derivative term whilst preserving the transient edges of the dynamic metabolic signals. Validated against 24-hour gas infusion tests, the proposed method reconstructs dynamic metabolic signals with the best temporal accuracy among state-of-the-art approaches, achieving a root mean square error of 0.27 kcal/min (18.8 J/s), while maintaining a low cumulative error in 24-hour total energy expenditure of less than 45 kcal/day (188280 J/day). When applied to a human exercise session, the proposed methods also show the best performance in terms of recovering the dynamics of exercise energy expenditure. Overall, the proposed methods improve the temporal resolution of the chamber system, enabling metabolic studies involving dynamic signals such as short interval exercises to carry out the metabolic chambers.