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Light-emitting diode phototherapy treatment for jaundice of the preterm infant presents adverse effects, such as discomfort, changes in metabolism, and overheating. This study quantified the body heat exchanges between the environment and a simulated preterm infant requiring phototherapy treatment in a closed incubator. Phototherapy treatment increased the mean incubator roof temperature by 2.9 °C (p 0.001) and the incubator air temperature by 1 °C (p 0.001). Analytical calorimetry was used to calculate the additional energy received during phototherapy and thus deduce the optimal incubator air temperature for ensuring thermoneutrality and preventing hyperthermia. The optimal air temperature settings inside the incubator during phototherapy were - 0.51 to - 1.25 °C lower than references, for preterm infant weighing 500 to 2000 g.Conclusion: Phototherapy treatment for jaundice of the preterm infant increased the incubator air temperature. To prevent overheating in the preterm during phototherapy, new curves for optimal air temperature settings inside the incubator were calculated with analytic calorimetry. What is Known •Phototherapy treatment is the first-line treatment for jaundice in the preterm infant. •Phototherapy treatment increases the risk of overheating. What is New •The heat transfers and risk of overheating were quantified using a thermal manikin during phototherapy treatment. •Phototherapy treatment increased the incubator roof temperature and heat transfers. •New incubator's air temperature settings during phototherapy treatment were calculated with analytical calorimetry for preterm infant weighing 500-2000 g.

Although cell phones and electronic devices are now integral parts of modern life (especially for young people), the radiofrequency electromagnetic field (RF-EMF) emitted by these devices is a potential health hazard. The effects of RF-EMFs have been assessed in various fields, including epidemiology and neurology. However, there are few published data on the possible effects of RF-EMFs on immune cells; this is surprising, given the importance of the immune system’s role in defending the body against infections and cancer. To assess whether chronic RF-EMF exposure has harmful effects on the immune system in juvenile rats, rats were exposed or not to 900MHz RF-EMF 23h/day during 5 weeks. Hematological, cytometric and bacteriological assays were used to probe differences between exposed and non-exposed tissues. Exposure of rats to 900 MHz RF-EMF was associated with differences in the innate immune system and even more marked in the adaptive immune system. An analysis of the intestinal microbiota revealed dysbiosis, with an over-representation of Enterococcus, Clostridium and Bacteroides spp. Enterococcus was found to have translocated into the spleen in 67% exposed rats. Exposure to a 900 MHz RF-EMF appeared to alter the immune system (and particularly the adaptive immune system) directly or via intestinal dysbiosis.

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Communication technologies based on radiofrequency (RF) propagation bring great benefits to our daily life. However, their rapid expansion raises concerns about possible impacts on public health. At intensity levels below the threshold to produce thermal effects, RF exposure has also recently been reported to elicit biological effects, resembling reactions to cold. The objective of the present study was to investigate the effects of non-thermal RF on body temperature in mice and the related mechanisms. 3-months-old C57BL/6 J mice were exposed to a continuous RF signal at 900 MHz, 20 ± 5 V.m−1 for 7 consecutive days, twice per day during the light phase, for one hour each time. The SAR was 0.16 ± 0.10 W.kg−1. We showed that body temperature patterns in mice change synchronously with the RF exposure periods. Average body temperature in the light phase in the exposed group was higher than in the control group. The expression of the TRPM8 gene was not affected by RF in trigeminal ganglia. Furthermore, the injection of a TRPM8 antagonist did not induce a temperature decrease in exposed mice, as this was the case for sham-controls. These findings indicate that 900 MHz RF exposure at non-thermal level produce a physiological effect on body temperature in mice. However, the involvement of TRPM8 receptors in the mechanism by which RF induced changes in body temperature of mice which remains to be further explored. It must then be assessed if this effect is extrapolable to man, and if this could lead to consequences on health.

Objective Electrohypersensitive people attribute various symptoms to exposure of radiofrequency electromagnetic fields (RF-EMF); sleep disturbance is the most frequently cited. However, laboratory experiments have yielded conflicting results regarding sleep alterations. Our hypothesis was that exposure to RF-EMF alone would lead to slight or non-significant effects but that co-exposure to RF-EMFs and other environmental constraints (such as noise) would lead to significant effects. Methods 3-week-old male Wistar rats (4 groups, n = 12 per group) were exposed for 5 weeks to continuous RF-EMF (900 MHz, 1.8 V/m, SAR = 30 mW/kg) in the presence or absence of high-level noise (87.5 dB, 50–20000 Hz) during the rest period. After 5 weeks of exposure, sleep (24 h recording), food and water intakes, and body weight were recorded with or without RF-EMF and/or noise. At the end of this recording period, sleep was scored during the 1 h resttime in the absence of noise and of RF-EMF exposure. Results Exposure to RF-EMF and/or noise was associated with body weight gain, with hyperphagia in the noise-only and RF-EMF + noise groups and hypophagia in the RF-EMF-only group. Sleep parameters recording over 24 h highlighted a higher frequency of active wakefulness in the RF-EMF-only group and a lower non-rapid eye movement/rapid eye movement sleep ratio during the active period in the noise-only group. There were no differences in sleep duration in either group. During the 1-h, constraint-free sleep recording, sleep rebound was observed in the noise-only group but not in the RF-EMF-only and RF-EMF + noise groups. Conclusion Our study showed effects of RF-EMF, regardless of whether or not the animals were also exposed to noise. However, the RF-EMF + noise group presented no exacerbation of those effects. Our results did not support the hypothesis whereby the effects of RF-EMF on physiological functions studied are only visible in animals exposed to both noise and RF-EMF.

Newborns are prone to hypothermia immediately following birth. Hypothermia is associated with increased morbidity and mortality rates. We sought to assess the thermal environment and metabolic costs associated with exposure to various situations in the delivery room when skin-to-skin care (SSC) has to be curtailed. Environmental variables (air temperature: Ta; relative humidity: RH; radiative temperature: Tr; and air convection velocity) were recorded during sequences reproducing SSC, in the maternity unit’s various rooms (“passive environments”) and in incubators (“active environments”). Analytical calorimetry was then used to calculate the body heat loss (BHL) from these data. The analysis of 1280 measurements of Ta, RH, Tr, and air convection velocity in SSC, passive and active environments revealed that (i) the thermohygrometric environment during SSC was optimal (Ta: 32.7 ± 3.2 °C; RH: 50.9 ± 5.6%), (ii) BHL rose when SSC had to be interrupted, and (iii) the use of a radiant incubator prevented hypothermia and reduced dry BHL but not humid BHL (9.4 ± 1.5 kcal/kg/h; p < .001), relative to SSC (5.8 ± 2.0 kcal/kg/h; p < .001). The newborn infant’s thermohygrometric environment is optimal during SSC in the delivery room. When SSC was interrupted, Ta and RH always decreased, and BHL increased in all passive environments.

Objective To determine whether perinatal smoking exposure is associated with gastroesophageal reflux (GER)-related changes in sleep-wakefulness states in neonates. Study design Thirty-one neonates, referred for the investigation of suspected GER, were recruited and underwent multichannel impedance–pH monitoring and synchronized 8- to 12-hour polysomnography. The infants' exposure to tobacco smoke was estimated by means of a urine cotinine assay. The total number, frequency (h−1), and mean duration (minutes) of GER-pH (reflux events detected by the pH electrode only) and GER-imp (reflux events with bolus movement detected by impedance) events were determined. Intergroup differences (smoking-exposed group vs nonexposed group) were probed with nonparametric, unpaired Mann–Whitney U tests. A χ2 test was used to assess a possible intergroup difference in bolus retrograde migration during GER-imp events. Results According to the urine cotinine assay, 21 of the 31 neonates had been exposed to cigarette smoke during the perinatal period. The number (and frequency) of GER-imp was significantly greater (P = .016) in the exposed group (29 [0-90]) than in the nonexposed group (12 [2-35]). Migration of the esophageal bolus from the distal segment to the most proximal segment was significantly more frequent (P = .016) in the exposed group (83% of GER) than in the nonexposed group (41%). The GER pattern associated with smoking exposure was particularly obvious during Rapid eye movement sleep. Conclusions The more frequent occurrence and greater proximal migration of GER-imp in the smoking-exposed group (especially during rapid eye movement sleep) may have clinical relevance. Smoking exposure is a preventable risk factor for limiting the occurrence of GER in neonates.

Low-birth-weight (LBW) neonates are nursed in closed incubators to prevent transcutaneous water loss. The RH's impact on the optimal incubator air temperature setting has not been studied.On the basis of a clinical cohort study, we modelled all the ambient parameters influencing body heat losses and gains. The algorithm quantifies the change in RH on the air temperature, to maintain optimal thermal conditions in the incubator.Twenty-three neonates (gestational age (GA): 30.0 [28.9-31.6] weeks) were included. A 20% increase and a 20% decrease in the RH induced a change in air temperature of between -1.51 and +1.85°C for a simulated 650g neonate (GA: 26 weeks), between -1.66 and +1.87°C for a 1000g neonate (GA: 31 weeks), and between -1.77 and +1.97°C for a 2000g neonate (GA: 33 weeks) (p0.001). According to regression analyses, the optimal incubator air temperature=a+b relative humidity +c age +d weight (p0.001).We have developed new mathematical equations for calculating the optimal temperature for the incubator air as a function of the latter's relative humidity. The software constitutes a decision support tool for improving patient care in routine clinical practice.

Although sleep is of paramount importance for preterm neonates, care of the latter in a neonatal intensive care unit does not favour sleep. Given that several studies in adults have described a 'vegetative preparedness to sleep' (in which distal skin vasodilation before lights-out promotes rapid sleep onset), we looked at whether or not this process operates in preterm neonates. Sleep propensity was assessed in terms of the duration of a spontaneous episode of wakefulness (W). Skin temperatures at six body sites (the abdomen, pectoral region, eye, hand, thigh and foot) were measured (using infrared thermography) during nocturnal polysomnography in 29 9-day-old preterm neonates (postmenstrual age: 209 ± 9 days). We then determined whether the duration of the W episode depended upon the local skin temperatures measured at the start, during and end of the episode. The W episode was shorter when distal skin temperatures (thigh, hand and foot) and the pectoral temperature were higher at the end of the episode (i.e. at sleep onset). The relationship with the duration of the W episode was not significant for temperatures measured at the start of the W episode. We observed gradual distal vasodilation at the pectoral region, the thigh, hand and foot (i.e. affecting most of the body's skin surface) during W episodes. Our results constitute initial evidence to show that distal vasodilation may have a key role in facilitating sleep onset in very preterm neonates.

Noise is an environmental factor that has been associated with metabolic and sleep disorders. Sleep is a vital function, since it underpins physiologic processes and cognitive recovery and development. However, the effects of chronic noise exposure on the developing organism are still subject to debate.The objective of the present study was to assess the effects of subchronic, high-level noise exposure on sleep, apnea, and homeostasis in juvenile rats.Twenty-four 3-wk-old male Wistar rats were exposed to noise [[Formula: see text], [Formula: see text]] for 5 wk and 2 d during the 12-h rest period. Data on sleep stages, food and water intake, apnea, and body and organ weight were recorded.Five weeks of high-level noise exposure were associated with hyperphagia ([Formula: see text]), body weight gain ([Formula: see text]), a heavier thymus ([Formula: see text]), and heavier adrenal glands ([Formula: see text]). A sleep analysis highlighted microstructural differences in the active period: in particular, the mean daily amount of rapid eye movement (REM) sleep as a proportion of total sleep time (TST) was higher. The mean daily amount of non-REM (NREM) sleep was lower in the exposed group, meaning that the intergroup difference in the TST was not significant. During a 1-h, noise-free plethysmographic recording during the rest period, the mean total amount of active wakefulness (AW) was lower in the exposed group (by 9.1 min), whereas the mean duration of an episode of REM sleep was higher (by 1.8 min), and the TST was higher (by 10.7 min).Subchronic exposure of juvenile rats to high-intensity noise during the rest period was associated with some small but significant sleep disturbances, greater food and water intakes, greater body weight gain, and greater thymus and adrenal gland weights. The main effects of noise exposure on sleep were also observed in the 1-h plethysmography session after 5 wk of exposure. https://doi.org/10.1289/EHP4045.

Mathematical models of body heat exchanges can be used to define the thermal limits needed to protect premature neonates nursed in incubators against thermal stress–stress that can have potentially devastating impairments on neurological development and body growth. Predictive models can help caregivers to keep a neonate’s body temperature within the normal range and to solve problems that arise during intensive care, such as the risk of hyperthermia during phototherapy, the risk of hypothermia during transport from one clinical centre to another, and the use of a plastic bag to reduce skin water loss and body dehydration. Here, we review the strengths and limitations of models used to predict the risk of thermal stress, with a focus on uncertainties in the algorithms governing heat transfers between the neonate’s skin and the complicated thermal environment encountered in incubators. We describe attempts to reduce the large number of empirical assumptions and uncertainties in this field, and suggest ways of more accurately modelling optimal thermal conditions for neonates nursed in closed incubators.

Radiant heat loss is high in low-birth-weight (LBW) neonates. Double-wall or single-wall incubators with an additional double-wall roof panel that can be removed during phototherapy are used to reduce Radiant heat loss. There are no data on how the incubators should be used when this second roof panel is removed. The aim of the study was to assess the heat exchanges in LBW neonates in a single-wall incubator with and without an additional roof panel. To determine the optimal thermoneutral incubator air temperature. Influence of the additional double-wall roof was assessed by using a thermal mannequin simulating a LBW neonate. Then, we calculated the optimal incubator air temperature from a cohort of human LBW neonate in the absence of the additional roof panel. Twenty-three LBW neonates (birth weight: 750-1800g; gestational age: 28-32 weeks) were included. With the additional roof panel, R was lower but convective and evaporative skin heat losses were greater. This difference can be overcome by increasing the incubator air temperature by 0.15-0.20°C. The benefit of an additional roof panel was cancelled out by greater body heat losses through other routes. Understanding the heat transfers between the neonate and the environment is essential for optimizing incubators.

The perinatal period is characterized by developmental stages with high sensitivity to environmental factors. Among the risk factors, maternal High-Fat Diet (HFD) consumption and early-life pesticide exposure can induce metabolic disorders at adulthood. We established the effects of perigestational exposure to Chlorpyrifos (CPF) and/or HFD on respiratory parameters, sleep apnea and diaphragm contractility in adult rats. Four groups of female rats were exposed starting from 4 months before gestation till the end of lactation period to CPF (1 mg/kg/day vs. vehicle) with or without HFD. Sleep apnea and respiratory parameters were measured by whole-body plethysmography in male offspring at postnatal day 60. Then diaphragm strips were dissected for the measurement of contractility, acetylcholinesterase (AChE) activity, and gene expression. The perigestational exposure to CPF and/or HFD increased the sleep apnea index but decreased the respiratory frequency. The twitch tension and the fatigability index were also increased, associated with reduced AChE activity and elevated mRNA expression of AChE, ryanodine receptor, and myosin heavy chain isoforms. Therefore, the perigestational exposure to either CPF and/or HFD could program the risks for altered ventilatory parameters and diaphragm contractility in young adult offspring despite the lack of direct contact to CPF and/or HFD.

Objective Prior to sleep onset in human adults, distal body temperatures change progressively from wakefulness levels (low skin temperatures and a high core temperature) to sleep levels (high skin temperatures and a low core temperature) due to distal skin vasodilation and greater body cooling. It is not known whether this sleep preparedness exists in preterm neonates, even though sleep has a key role in neonatal health and neurodevelopment. The present study's objectives were to determine whether sleep preparedness (as observed in adults) can be evidenced in preterm neonates, and to assess repercussions on thermal stress. Methods During a 12-h night-time polysomnography session, skin temperatures (recorded with an infrared camera), sleep, and wakefulness episodes were measured in 18 nine-day-old preterm neonates. Results Fifteen wakefulness episodes were considered. Our results highlighted significant pre-sleep distal skin vasodilation (mainly at the foot: an increase of 0.38 °C in the 20 min preceding sleep onset) for the first time in preterm neonates. This vasodilation occurred even though (1) most factors known to influence pre-sleep vasodilation in adults were not present in these neonates, and (2) the neonates were nursed in a nearly constant thermal environment. The vasodilatation-related increase in body heat loss corresponded to a 0.15°C/h fall in mean body temperature (calculated using partitional calorimetry). Conclusion Compensation for this body heat loss and the maintenance of body homeothermia would require a 4% increase in metabolic heat production. In neonates, this type of energy expenditure cannot be maintained for a long period of time.

Objectif Chez l’adulte, il existe une phase de preparation au sommeil entre la veille (caracterisee par des niveaux faibles de temperature (T) cutanee et eleve de T interne) et le sommeil (T cutanee elevee et T interne faible). Cette phase transitoire se caracterise par une vasodilatation cutanee, a l’origine de pertes de chaleur corporelle et d’une diminution de la T interne. Notre objectif a ete de determiner si des evolutions similaires de T corporelles existaient chez le nouveau-ne premature (∼1,3 kg) et d’en calculer l’impact sur le bilan energetique, tres fragile pour ces enfants. Methodes Les T cutanees ont ete mesurees par thermographie infra-rouge, pendant un enregistrement PSG de 12 hrs (20 h–8 h) chez 18 nouveaux-nes prematures (en incubateur ferme) au 9e jour de vie. L’evolution temporelle des T avant endormissement a ete analysee. Resultats Au total, 15 episodes de veille repondaient aux criteres de selection (eveil et endormissement spontanes, duree > 12 min). Nos resultats mettent en evidence pour la premiere fois une vasodilatation cutanee principalement au niveau du pied (+0,38 °C, p = 0,008) pendant les 20 min qui precedent l’endormissement. Cette vasodilatation induit une perte de chaleur corporelle de 0,15 °C.h-1 (T corporelle moyenne). Conclusion La vasodilatation existe chez le nouveau-ne premature, bien que la plupart des facteurs connus chez l’adulte pour la favoriser n’existent pas chez ces enfants qui sont de plus maintenus dans un environnement quasi-constant. La compensation d’une telle perte de chaleur represente une augmentation de 4 % de la production de chaleur metabolique.

Dietary exposure to the organophosphorothionate pesticide chlorpyrifos (CPF) has been linked to dysbiosis of the gut microbiota. We therefore sought to investigate whether (i) CPF’s impact extends to the intestinal barrier and (ii) the prebiotic inulin could prevent such an effect. In vitro models mimicking the intestinal environment (the SHIME®) and the intestinal mucosa (Caco-2/TC7 cells) were exposed to CPF. After the SHIME® had been exposed to CPF and/or inulin, we assessed the system’s bacterial and metabolic profiles. Extracts from the SHIME®’s colon reactors were then transferred to Caco-2/TC7 cultures, and epithelial barrier integrity and function were assessed. We found that inulin co-treatment partially reversed CPF-induced dysbiosis and increased short-chain fatty acid production in the SHIME®. Furthermore, co-treatment impacted tight junction gene expression and inhibited pro-inflammatory signaling in the Caco-2/TC7 intestinal cell line. Whereas, an isolated in vitro assessment of CPF and inulin effects provides useful information on the mechanism of dysbiosis, combining two in vitro models increases the in vivo relevance.

The efficacy and safety of three polyethylene bags commonly used to prevent hypothermia in premature infants was assessed.To simulate transfer from the delivery room to a secondary care unit, a thermally stable, bonneted mannequin (skin temperature: 34.4 °C) was placed in a climate chamber under different conditions: with a radiant warmer, with various polyethylene bags (open on one side, closed by a draw-string at the neck, or a "life support pouch" with several access points) or without a bag.With the radiant warmer turned on, the mean reduction in heat loss from the nude mannequin was 50.8 ± 1.7% (p 0.0001, vs. warmer off). The mean reduction in heat loss (vs. no bag) was 55.0 ± 0.9% for the drawstring bag, 49.0 ± 2.2% for the standard bag (p = 0.0001), and 48.1 ± 0.7% for the life support pouch (p = 0.006). When a radiant warmer + polyethylene bag were used, heat stress (body temperature: 38 °C) and severe hyperthermia (40 °C) occurred after 11 and 34 min, respectively.Caution must be taken when using a radiant warmer and polyethylene bag with a premature infant. Heat stress can occur in only 11 min. Continuous body temperature monitoring is therefore required.

AIM We currently lack a suitable gold-standard method for implementation on modern equipment to assess peripheral chemoreceptor sensitivity. The aim of the present study was to develop an accurate and reproducible method for assessing peripheral chemoreceptors sensitivity in sleeping preterm neonates. METHODS A poikilocapnic hypoxic test was performed twice during rapid eye movement sleep (REM sleep) and non-rapid eye movement sleep (nonREM sleep). The infant breathed hypoxic gas (15% O2 ) for 60 s. The ventilatory response to hypoxia was assessed by comparing minute ventilation during the control period (21% O2 ) with successive 4-cycles sequences during hypoxia. We detected the first statistically significant increase in minute ventilation and recorded the corresponding response time. RESULTS During normoxia, minute ventilation was higher during REM sleep than in nonREM sleep (428.1 mL · min-1 · kg-1 [307.7-633.6]; 388.8 mL · min-1 · kg-1 [264.7-608.0], respectively; P = 0.001). After hypoxia, minute ventilation increased in both REM and nonREM sleep. The response was significantly higher in REM than in nonREM (25.3% [10.8-80.0] and 16.8% [7.5-33.2], respectively; P = 0.005). The intraclass correlation coefficients for all respiratory parameters were above 0.90. CONCLUSION We have developed a highly reliable method for assessing peripheral chemoreceptors sensitivity at the response time to hypoxia. In the future, researchers could use this method to assess the involvement of peripheral chemoreceptors in infants who experience chronic hypoxia (e.g. in bronchopulmonary dysplasia and recurrent apnea).

Bowel dilatation occurs proximal to an obstruction and predisposes to intestinal dysmotility. The present study sought to determine whether or not changes in smooth muscle contractility and the thickness of the proximal, dilated bowel wall can be reversed following relief of the obstruction.Three groups of seven male Wistar rats were studied. In 8-week-old animals in a control group and a sham-operated group, a small segment of bowel (designated as R1 for controls and R2 for shams) was resected 5.0 cm from the cecum. In the third (operated) group, a narrow, isoperistaltic intestinal loop was created proximal to an end-to-end anastomosis of the ileum in 4-week-old animals. When these animals were 6 weeks old, the loop was re-anastomosed to the distal small bowel (after resection of the loop's distal portion, referred to as R3). Two weeks later, a small segment of bowel was resected proximal to the anastomosis (R4). We evaluated the thickness of the smooth muscle layers and the in vitro contractile responses of circular smooth muscle ileal strips (R1-R4) to electrical stimulation and pharmacological stimulation (with KCl, acetylcholine (ACh), substance P, N(G)-nitro-l-arginine methyl ester (L-NAME) and histamine).The amplitudes of contraction in response to electrical and Ach-mediated stimulation were higher for R3 than for R4 (P0.001), R1 and R2 (both P0.05). Compared with R1 and R2, the smooth muscle layer was three times as thick in R3 (P0.001) and 2.5 times as thick in R4 (P0.01).Our study provides evidence of the possible recovery of intestinal motility (in response to neurotransmitters involved in gut function) after the relief of an obstruction. If ileal motility can conceivably return to normal values, conservative surgical procedures in pediatric patients should be preferred (in order to leave a sufficient length of bowel and avoid short bowel syndrome).

Etat de l’art La temperature cutanee moyenne (Tsk) est une donnee fondamentale dans la quantification des differents echanges de chaleur entre l’enfant, plus particulierement premature et son environnement. L’utilisation d’une camera infrarouge (IR) permet d’obtenir des mesures de Tsk, alors appelee TskIR, qui sont a la fois tres precises, non invasives et qui n’impactent pas l’environnement de l’enfant. Or, le cout et la duree du traitement des images de cette technique ne permettent pas de l’appliquer en pratique clinique. La methode alternative proposee est de calculer TskIR a partir de deux temperatures cutanees locales, sushepatique (Thep) et peripherique (Tperiph), mesurees en routine clinique a l’aide de sondes thermiques.

Background: The thermal environment surrounding neonates in closed incubators can be regulated via two different modes: skin servocontrol mode (SSC) and air temperature control mode (ATC). These produce different patterns of incubator air and infant body temperatures. Objective: To assess the effects of incubator control mode on clinical outcomes of low-birth-weight-infants during the first days of life and at hospital discharge. Methods: 52 low-birth-weight neonates were nursed over ten days in closed incubators functioning either with SSC mode (n = 29), or with ATC mode (n = 23). Results: The anthropomorphic characteristics of the two groups of neonates were homogenous (gestational age = 29.4 ± 1.4 vs. 29.9 ± 1.2 weeks and birthweight = 1214 ± 347 vs. 1263 ±292 gin the SSC-group and the ATC-group, respectively) and the caregiving (energy and fluid intakes, ventilator assistance and drug administration) did not differ statistically. Daily means of incubator air temperature were similar in the SSC and the ATC-group, however, the SSC mode resulted in more variable incubator air temperature but more stable skin abdominal temperature whereas the reverse was found when using the ATC mode. Those differences had no impact on the body weight of the neonates or their clinical outcomes at hospital discharge which were not statistically different. Conclusion: The clinical outcomes do not differ depending on the incubator control mode after the first ten days of life and at hospital discharge.

Background Prenatal/postnatal exposure to insecticides has been linked to developmental disorders in adulthood. Chlorpyrifos (CPF) is a widely used organophosphorus acetylcholinesterase (AChE)-inhibiting insecticide. The present study established whether prenatal and postnatal exposure to CPF is associated with intestinal motor dysfunction in adult rats. Methods Three groups of pregnant rats were exposed to either CPF (1 or 5 mg/kg/day; the CPF1 and CPF5 groups) or vehicle (the control group) by gavage from gestational day 1 until weaning. At weaning, the pups were separated from their dams and individually gavaged (with the same dose) until postnatal day 60. We then measured in vivo intestinal transit and the in vitro contractile responses of ileal smooth muscle strips to electrical field stimulation. Expression of inducible nitric oxide synthase (iNOS) in the ileum was determined using qRT-PCR and immunoblots. Morphometry and AChE assays were also performed. Key Results At adulthood, the mean body mass was lower in the CPF1 and CPF5 groups than in controls. CPF5 exposure was associated with weaker in vitro contraction of ileal muscle strips, which was reversed by adding the NOS inhibitor (L-NAME). There was no significant intergroup difference in the mean in vivo transit time. Exposure to CPF was associated with greater iNOS expression, lower AChE activity and reduced circular and longitudinal smooth muscle thickness. Conclusions & Inferences Prenatal and postnatal exposure to CPF in the rat is associated with weaker contraction of ileal longitudinal smooth muscle via a nitrergic mechanism with increased iNOS expression.

Objective: We aimed to determine whether in utero exposure to smoking may influence the activity and dynamics of cardiac autonomic control in preterm infants. We hypothesized that cardiac autonomic control is altered in preterm infants exposed prenatally to smoking and that these effects may vary as a function of the sleep state. Methods: We studied healthy, preterm neonates born to mothers who had smoked throughout pregnancy but not since birth ( n =16). In utero -exposed neonates were matched with control preterm neonates born to non-smoking mothers ( n =18). Cardiac autonomic control was monitored as a function of the sleep state by assessing heart rate variability with both linear and non-linear methods. Results: Preterm neonates with in utero exposure to smoking displayed alterations (relative to control neonates) in short-term cardiac autonomic control in all sleep states. These alterations included low vagal activity, elevated sympathetic activity, and low complexity and adaptability in heart rate control dynamics. Conclusions: Our results constitute direct evidence that cardiac autonomic activity and control are altered in sleeping preterm infants exposed to smoking in utero . Significance: These alterations may place the affected infants at a higher risk of neurological and cardiovascular complications, which could conceivably persist throughout childhood and adulthood.

The presence of pesticide residues in food is a public health problem. Exposure to these substances in daily life could have serious effects on the intestine-the first organ to come into contact with food contaminants. The present study investigated the impact of a low dose (1 mg/day in oil) of the pesticide chlorpyrifos (CPF) on the community structure, diversity and metabolic response of the human gut microbiota using the SHIME (R) model (six reactors, representing the different parts of the gastrointestinal tract). The last three reactors (representing the colon) were inoculated with a mixture of feces from human adults. Three time points were studied: immediately before the first dose of CPF, and then after 15 and 30 days of CPF-oil administration. By using conventional bacterial culture and molecular biology methods, we showed that CPF in oil can affect the gut microbiota. It had the greatest effects on counts of culturable bacteria (with an increase in Enterobacteria, Bacteroides spp. and clostridia counts, and a decrease in bifidobacterial counts) and fermentative activity, which were colon-segment-dependent. Our results suggest that: (i) CPF in oil treatment affects the gut microbiota (although there was some discordance between the culture-dependent and culture-independent analyses); (ii) the changes are "SHIME (R)-compartment" specific; and (iii) the changes are associated with minor alterations in the production of short-chain fatty acids and lactate.

Objectives Peripheral chemoreceptor (PC) are crucial for the development and protection of sleeping preterm neonates and play an important role in the chemical regulation of ventilation. However, only few old studies have investigated the impact of sleep state on their activity. The hypoxic test allows to assess PC sensitivity and to estimate their ability to adapt the ventilation to diverse stimulations (apnea, fall of PaO2..). The aim of the present study was to assess the impact of sleep state on the hypoxic ventilatory response (HVR) in preterm infants by using a reproducible method that evaluates with precision the ventilatory response following hypoxia onset. Materials and methods The hypoxic test was performed on 23 healthy preterm neonates (post conceptual age: 36.4±1.1 weeks) during active (AS) and quiet sleep (QS) determined according to neurophysiological criteria. PC sensitivity was determined as the first statistically significant increase in minute ventilation (VE) after hypoxia onset (15% O2). Results VE during the control period was significantly higher in AS (455.7±51.6 mL.min1. kg1) as compared to QS (387.9±25.3 mL.min1.kg1) (p=0.001). VE increase during hypoxia was greater in AS than in QS (28.1 % and 16.8 % respectively; p=0.005) No sleep difference was found for the response time. Conclusions The present study supports the effect of sleep state on resting ventilation. It also suggests an impact on the hypoxic ventilatory response, which emphasis the fragility of preterm infants during QS.

Resume Objectifs Les nouveau-nes prematures doivent etre eleves en incubateur ferme dans des conditions thermohygrometriques adaptees afin d’augmenter leur chance de survie et de reduire la duree d’hospitalisation. Actuellement, ces conditions dites « de thermoneutralite » ne prennent pas en compte l’ensemble des parametres thermiques intervenant dans le refroidissement de l’enfant. L’objectif du projet, realise dans le cadre de l’ANR TecSan, etait de concevoir et valider un logiciel de calcul complet de la thermoneutralite dans les incubateurs fermes pour nouveau-nes. Methodes Le logiciel Pretherm®, base sur l’equation du bilan thermique, considere l’ensemble des pertes de chaleur des enfants et est concu en tenant compte de criteres physiologiques et morphologiques specifiques a ce type de population. Resultats Le logiciel permet d’evaluer, chaque jour, la temperature et l’humidite optimales de l’air auxquelles doivent etre eleves les enfants quelle que soit leur veture (couche associee ou non a un bonnet de tete et un cocon), leur poids de naissance et leur âge postnatal. Les temperatures d’air critiques au-dela desquelles le risque d’hyper- ou d’hypothermie moderee peut apparaitre dans l’heure d’exposition sont egalement definies. Conclusion Le logiciel concu apporte une aide technique aux soins en guidant la decision therapeutique des cliniciens, ce qui devrait ameliorer la prise en charge precoce de ces enfants a haut risque de deficiences fonctionnelles des la naissance. Une validation de la performance de ce logiciel basee sur une analyse des criteres medicaux et physiologiques caracterisant les fonctions vitales de l’enfant est en cours.

Objective The assessments of the internal (IR) and external (ER) rotator muscle strength of the shoulder are often studied from a hand held accessory gripped. In these conditions, even if the wrist is in alignment with the radius, it is not possible to eliminate any compensatory movements of the wrist during maximal contractions of the shoulder muscle rotators. The objective of this study was to investigate the movements of the wrist in flexion/extension during an isokinetic assessment of the strength of shoulder rotators. Material/patients and methods Twenty-two healthy participants were explored. Participant previously installed in a seated position, the shoulder test was performed for IR and ER in concentric (CON) and eccentric (ECC) modes on each shoulder (dominant: D; non-dominant: ND), at 60°/s and 180°/s using an isokinetic dynamometer and an electronic goniometer fixed on the wrist. Data acquisition was recorded continuously and calculated with an analysis software. Results No significant difference founded in wrist mobility depending on muscle groups (IR or ER) and laterality (D or ND) whereas dominant PT was higher at all velocity for ER (in CON and ECC modes) and for IR ECC. No significant correlation between the movements of the wrist and the strength parameters was shown. However, the wrist movements were greater in the concentric modality (P Discussion, conclusion These results highlight compensation strategies of the wrist during isokinetic assessment of the shoulder depending on modality of contraction with a locking strategy in ECC mode, and angular velocity selected. To conclude, isokinetic assessment is to evaluate the muscle potential of an isolated joint by limiting the compensation, but it is important to focus on the surrounding joints due to the fact that the human body is a set of interacting segments with interconnected influences.

In closed incubators, radiative heat loss (R) which is assessed from the mean radiant temperature \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ (\overline{T}_{r} ) $$\end{document} accounts for 40–60% of the neonate’s total heat loss. In the absence of a benchmark method to calculate \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document}—often considered to be the same as the air incubator temperature—errors could have a considerable impact on the thermal management of neonates. We compared \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document} using two conventional methods (measurement with a black-globe thermometer and a radiative “view factor” approach) and two methods based on nude thermal manikins (a simple, schematic design from Wheldon and a multisegment, anthropometric device developed in our laboratory). By taking the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document} estimations for each method, we calculated metabolic heat production values by partitional calorimetry and then compared them with the values calculated from \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}_{{{\text{O}}_{ 2} }} $$\end{document} and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}_{{{\text{CO}}_{ 2} }} $$\end{document} measured in 13 preterm neonates. Comparisons between the calculated and measured metabolic heat production values showed that the two conventional methods and Wheldon’s manikin underestimated R, whereas when using the anthropomorphic thermal manikin, the simulated versus clinical difference was not statistically significant. In conclusion, there is a need for a safety standard for measuring \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document} in a closed incubator. This standard should also make available estimating equations for all avenues of the neonate’s heat exchange considering the metabolic heat production and the modifying influence of the thermal insulation provided by the diaper and by the mattress. Although thermal manikins appear to be particularly appropriate for measuring \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{T}_{r} $$\end{document}, the current lack of standardized procedures limits their widespread use.

Summary Given the liver’s importance in controlling metabolic homeostasis in mammals, we sought to establish (i) whether the thermal status of this organ was involved in the link between sleep, thermoregulation and food intake and (ii) how the hypothalamic structures affect the functional interactions between processes involved in regulation of the body’s energy balance. In 10 freely moving rats, the liver was heated artificially to and maintained at set-point temperatures of 39.5, 40.0 and 40.5 °C for 4 h. Each animal’s feeding activity, cortical temperature and brown adipose tissue (TBAT) temperature were measured continuously. Sleep organization and wakefulness were scored from electroencephalograms. Each animal served as its own control. Heating the liver induced a decrease in food intake and TBAT, corresponding to the development of a hypometabolic hypothermic status. The total amounts of wakefulness and rapid eye movement sleep fell, whereas the total amount of slow wave sleep increased accordingly. Our findings show that the liver is involved significantly in the body’s thermodynamic equilibrium. The organ’s thermal status can induce well-coordinated behavioural and autonomic adaptive responses involved in the control of food intake and in the maintenance of body homeothermia. Our study provides indirect evidence of the existence of hepatic thermosensors afferent to feeding and sleeping hypothalamic integrating centres that can be stimulated by physiological increases in liver temperature.

Summary The aim of the present study was to investigate the impact of gastro-oesophageal acid reflux on sleep in neonates and, reciprocally, the influence of wakefulness (W) and sleep stages on the characteristics of the reflux (including the retrograde bolus migration of oesophageal acid contents). The pH and multichannel intraluminal impedance were measured during nocturnal polysomnography in 25 infants hospitalised for suspicion of gastro-oesophageal reflux. Two groups were constituted according to whether or not the infants displayed gastro-oesophageal reflux (i.e. a reflux group and a control group). There were no differences between the reflux and control groups in terms of sleep duration, sleep structure and sleep state change frequency. Vigilance states significantly influenced the gastro-oesophageal reflux pattern: the occurrence of gastro-oesophageal reflux episodes was greater during W (59 ± 32%) and active sleep (AS; 35 ± 30%) than during quiet sleep (QS; 6 ± 11%), whereas the mean duration of gastro-oesophageal reflux episodes was higher in QS than in W and AS. The percentage of retrograde bolus migrations of distal oesophageal acid content was significantly higher in AS (62 ± 26%) than in W (42 ± 26%) and QS (4.5 ± 9%). In neonates, gastro-oesophageal reflux occurred more frequently during W, whereas the physiological changes associated with sleep state increase the physiopathological impact of the gastro-oesophageal reflux. The duration of oesophagus–acid contact was greater during sleep; AS facilitated the retrograde migration of oesophageal acid content, and QS was characterised by the risk of prolonged acid mucosal contact.

Wrapping low-birth-weight neonates in a plastic bag prevents body heat loss. A bonnet can also be used, since large amounts of heat can be lost from the head region, but may provide too much thermal insulation, thus increasing the risk of overheating. We assessed the time required to reach warning body temperature ( t38°C), heat stroke ( t40°C), or extreme value ( t43°C) in a mathematical model that involved calculating various local body heat losses. Simulated heat exchanges were based on body surface temperature distribution measured in preterm neonates exposed to 33°C air temperature (relative air humidity: 35%; air velocity: 38°Cranged between 75 and 287, t40°Cbetween 185 and 549, and t43°Cbetween 287 and 702 min. When this increase was accompanied by a fall in skin temperature, overheating risk was accentuated (37 ≤ t38°C≤ 45; 99 ≤ t40°C≤117; 169 ≤ t43°C≤ 194 min). Thus plastic bag and bonnet may result in hyperthermia but only when metabolic heat production rises while skin temperature falls (impeding body heat losses), as can sometimes happen with fever.

We present here a new, dedicated mechanical device for monitoring quick-release movements of the wrist. The ergometer was designed to easily assess musculotendinous properties during wrist flexion. Maximal voluntary contractions (MVC) and quick-release (QR) movements during wrist flexion were performed on 14 subjects. A validation of the ergometer, using a test-retest methodology, was performed to assess its reliability and sensitivity. The device has been technically and biomechanically validated in a range of situations, including inertia measurement (mean inertia was found 0.0119+/-0.0012 N m s(2) rad(-1)) and appearance of the unloading reflex. Our results indicate that the device provides highly reliable, sensitive evaluation of wrist muscle stiffness (intraclass correlation coefficient for inertia, maximal voluntary contraction and stiffness index were 0.873, 0.994 and 0.930, respectively). Its portability facilitates measurement of the influence of repetitive, occupational activity on the musculotendinous complex of the wrist flexors.

The aim of the present study was to validate the measurement of metabolic heat production using partitional calorimetry (PC) in preterm neonates exposed to a near-thermoneutral environment in an incubator. In order to reduce experimental uncertainty (due to the different variables involved in the calculation of body heat exchanges between the infant and the environment), the mean radiant temperature and the heat transfer coefficients for convection, radiation and evaporation were measured using a multisegment, anthropometric thermal mannequin which represents a small-for-gestational-age neonate (body surface area: 0.150 m2; simulated birth weight: 1500 g). The metabolic heat production calculated by PC was compared with the results of indirect respiratory calorimetry, which is rarely done in clinical setting since this method interferes with the neonate's environment and requires a high degree of technical preparedness. The oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured in 20 preterm neonates exposed to thermoneutral (32.3 degrees C) and to slightly cool environments (30.2 degrees C). The mean skin temperature was measured by infrared thermography. The measurements were made during well-established periods of active and quiet sleep. Metabolic heat production was assessed by weighting each value of VO2 and VCO2 by the duration of the sleep stages. Our results showed that there was no significant difference between the two methods in terms of their estimation of metabolic activity at thermoneutrality (mean overall difference: 0.34 kJ h(-1) kg(-1)) and in the cool environment (0.26 kJ h(-1) kg(-1)). We observed significant interneonate variability. Partitional calorimetry enabled the prediction of body growth with a daily error of less than 5.3 g (2.38 kJ h(-1) kg(-1)) for all the neonates at thermoneutrality and for 85% of the subjects (3.03 kJ h(-1) kg(-1)) in the cool environment. Despite this limitation, we demonstrate here that PC provides reliable information for calculating the energy expenditure of individual preterm neonates on the basis of standard environmental input variables. We suggest that the technique can be advantageously used to assess the energy expenditure and normal growth of these infants.

Objective: We assessed the relationship between a high-fat (HF) diet and central apnea during rapid eye movement and non-rapid eye movement sleep stages by recording ventilatory parameters in 28 non-obese rats in which insulin resistance had been induced by an HF diet. We also studied whether metformin (an anti-hyperglycemic drug frequently used to treat insulin resistance) could reverse sleep apnea or prevent its occurrence in this experimental paradigm. Research Methods and Procedures: Rats were fed with a standard diet (10 rats), an HF diet (8 rats), or an HF diet concomitantly with metformin treatment (10 rats). Each animal was instrumented for electroencephalographic and electromyographic recording. After 3 weeks, ventilatory parameters during sleep were recorded with a body plethysmograph. All rats were treated with metformin for 1 week, after which time the ventilatory measurements were measured again. Results: Our results showed that the three groups of animals did not differ in terms of body growth over the entire experimental period. The HF diet did not modify sleep structure or minute ventilation in the different sleep stages. A great increase (+266 ± 48%) in central apnea frequency was observed in insulin-resistant rats. This was explained by an increase in both post-sigh (+195 ± 35%) and spontaneous apnea (+437 ± 65%) in the different sleep stages. These increases were suppressed by metformin treatment. Discussion: Insulin resistance induced by the HF diet could be the promoter of sleep apnea in non-obese rats. Metformin is an efficient curative and preventive treatment for sleep apnea, suggesting that insulin resistance modifies the ventilatory drive independently of obesity.

Background: It is well known that severe lung impairment in cystic fibrosis (CF) may compromise respiratory muscle function at rest. Even though patients with CF and severe obstructive lung disease exhibit an abnormal breathing pattern during exercise (due to expiratory flow limitation), patients with CF and normal lung function reportedly have a normal breathing pattern. Objectives: The aim of the study was to assess the precise characteristics of the ventilatory pattern adopted during exercise by children with CF and mild to moderate lung disease. Methods: Nine children diagnosed as having mild to moderate CF and 9 healthy children with a similar age distribution participated in this study. Both groups performed a continuous incremental cycling protocol. Breathing and timing components were assessed during exercise. Results: Differences in the breathing pattern between children with CF and controls during exercise are illustrated in Hey plot which described a rapid shallow breathing pattern in children with CF. During exercise, children with CF showed a significantly lower mean inspiratory flow than healthy children (p < 0.001), whereas the mean expiratory flow was higher (p < 0.001). Children with CF also showed a significant increase in the end-tidal carbon dioxide pressure, which may indicate the emergence of hypercapnia. Conclusions: During exercise, children with CF (even those not suffering from advanced disease) showed signs of rapid, shallow breathing and an increase in the ventilatory response. This was essentially due to an increase in the mean inspiratory flow, which in turn suggests an expiratory flow limitation. The children were also predisposed to hypercapnia.

Objective: The aim of the present study was to test the thermoregulatory feeding control hypothesis in sleeping, premature infants. Research Methods and Procedures: In premature infants, the energy supply from food intake is crucial for (in order of importance): organ operation, body homeothermia, and optimal growth. The Himms-Hagen model of thermoregulatory feeding control involving activation of heat production by brown adipose tissue (BAT) was formulated on the basis of work in (awake) rats. This hypothesis has also been put forward for the human neonate, which can also use BAT to produce metabolic heat. According to the model, feeding episodes occur during a transient increase in body temperature. Feeding is initiated by a dip in blood glucose concentration after sugar uptake by activated BAT. Results: In 14 neonates (bottle-fed on demand), food intake always took place during an increase in skin temperature (+0.19 ± 0.21 °C). Awakening occurred 18 ± 17 minutes after the minimum skin temperature level had been reached. When feeding time was imposed, feeding was not necessarily situated during an increase in skin temperature, and the sleep duration after food intake increased significantly (+43%). This could be considered as an adaptive response to the short-term sleep deprivation and/or stress elicited by an imposed feeding rhythm. Discussion: The validity of the model supports the use of on-demand feeding in neonatal care units, in accordance with the infant's physiological body temperature oscillations.

To assess the various heat exchanges with the environment a multisegment, anthropometric, thermal mannequin representing a neonate with a birth weight of 900g has been designed. The mannequin simulates not only dry heat loss (radiative+ conductive +convective body heat exchanges) but also the evaporative skin water loss which can be encountered in low-birth-weight neonates. The model was placed in the supine or prone position in a closed incubator (air temperature, 33°C; relative air humidity, 50%; air velocity below 0.1ms−1). Experiments were performed with the mannequin either naked or wrapped in a flexible, plastic bag (with the head exposed) used to prevent excessive body water loss at delivery and during the following hours About 30% of the model's total surface was wetted with water. Our results demonstrated that body position does not modify dry and evaporative heat losses, whatever the experimental conditions. The plastic bag acts rapidly and reduces total heat loss by 30% to 34%, primarily through a reduction in evaporative water loss (between 5.4 and 6.7gkg−1h−1). When the bag is present, the uncovered surface of the head accounts for about 50% of the total heat loss. This simple and inexpensive solution can be used to prevent thermal stress and dehydration in very small premature neonates.

Resume Les pertes de chaleur des nouveau-nes prematures avec leur environnement restent tres difficiles a mesurer en raison de la morphologie de l’enfant. Pour resoudre ce probleme, des mannequins thermoregules ayant les dimensions anthropometriques de nouveau-nes ont ete developpes. Le but de ce travail est de montrer les applications biomedicales de ces modeles en decrivant deux etudes, l’une sur la relation entre le stress thermique et la position de couchage dans la Mort Subite du Nourrisson (MSN) et l’autre sur l’evaluation des dispositifs de rechauffement en chirurgie neonatale. Un mannequin simulant les dimensions anthropometriques d’un nouveau-ne de 1400 g a ete developpe. Dans la premiere etude, il etait couche sur le dos ou sur le ventre dans un incubateur ferme a des temperatures d’air comprises entre 25 °C et 37 °C. Les resultats ont montre que les pertes de chaleur sont independantes de la position de couchage. Ceci refute l’hypothese selon laquelle la position de couchage sur le ventre peut provoquer un stress thermique expliquant une mortalite plus grande. Dans la seconde etude, le mannequin couche sur le dos etait place dans des conditions simulant un champ operatoire. L’efficacite d’un matelas chauffant associe ou non a un systeme de rechauffement convectif de type Bair Hugger ® a ete testee (temperature d’air comprises entre 20 °C et 30 °C). Les resultats ont montre l’efficacite du Bair Hugger ® . L’association du Bair Hugger ® soufflant un air a 38 °C et du matelas chauffant a 39 °C montre qu’il serait alors possible de reduire la temperature de l’air de la salle de chirurgie de 27 °C a 20 °C, afin d’ameliorer le confort thermique des intervenants sans desequilibrer de facon importante le bilan thermique de l’enfant.

Resume Chez le nouveau-ne premature, la prise alimentaire qui permet l’apport energetique indispensable au fonctionnement des organes, au maintien de la temperature corporelle et a la croissance, a ete peu etudiee. L’existence d’un controle thermometabolique de la prise alimentaire (hypothese de Himms-Hagen) a ete argumentee chez le rat et transposee au nouveau-ne humain qui possede egalement du tissu adipeux brun, organe thermogenique implique dans ce controle. Dans ce modele, la prise alimentaire est integree a un episode d’augmentation de la temperature corporelle. Le debut du repas est initie par l’hypoglycemie transitoire liee au captage important du glucose circulant par le tissu adipeux brun active. L’objectif de cette etude est de valider ce modele du controle de la prise alimentaire chez le nouveau-ne premature et d’en definir les caracteristiques. Chez 14 nouveau-nes alimentes par biberon en rythme libre, l’episode de prise alimentaire se situe durant la phase ascendante de temperature cutanee inguinale (+0,19 ± 0,21 °C). Le reveil se produit 18 ± 17 minutes apres le niveau minimal de temperature cutanee. Au contraire en rythme impose, la prise alimentaire n'intervient pas dans une phase ascendante de temperature corporelle et la duree de sommeil qui suit l'episode alimentaire est augmentee significativement (+43 %). Cette reponse pourrait etre consideree comme une adaptation a la courte periode de privation de sommeil et/ou au stress genere par le biberon impose. La validation de ce modele suggere que les nouveau-nes en incubateur devraient etre alimentes a la demande pour repondre au mieux aux variations physiologiques de la temperature.

Keeping premature newborns warm is crucial for their survival. Their ability to prevent excessive heat loss to the environment and to control their body temperature is limited. The risk of hypothermia is particularly important for low-birth-weight newborns with a large body surface area in relation to their mass of heat-producing tissues. The present study was performed to assess the body heat loss difference between small and large body-size premature newborns using two anthropomorphic thermal manikins of premature newborns of 900 g and 1,800 g (respective body surface areas of 0.086 and 0.150 m2). The dry heat loss from the six body segments of the small manikin (S) was measured and compared with that of the large manikin (L). The two manikins were exposed to five different environmental temperatures ranging between 29 and 35 degrees C in a single-walled, air-heated closed incubator. The magnitudes of heat loss decreased significantly by 20.4% between the two manikins [small manikin 110.1 (44.3) W/m2 vs large manikin 87.6 (25.8) W/m2, mean values with one standard deviation]. The results obtained from the comparison of the heat loss measures from the two manikins confirm the fact that the heat loss increases with an increase in the ratio of the body surface area to body mass. The thermal manikin appears to provide an accurate method for the assessment of thermal conditions in neonatal care.

Body temperature interacts with respiratory control, but it is unclear what sites or mechanisms mediate those interactions. We hypothesized that warm and cool thermal conditions affect the decrease in ventilation (VE) seen during the hyperoxic test (HT), a breathing response believed to reflect the strength of the peripheral chemoreceptor drive. A breath-by-breath analysis during a 30 s HT was performed in eight premature neonates (postconceptional age: 36 +/- 1 weeks) under neutral, warm, and cool thermal conditions. Quiet sleep (QS) and active sleep (AS) were scored by neurophysiological criteria. The VE fall was higher in AS than in QS, and warm and cool conditions significantly enhanced the response only in AS (-24.2 +/- 6.0, -39.1 +/- 9.1, and -37.5 +/- 14.1% in neutral, warm, and cool conditions, respectively). Central control mechanisms of the respiratory chemoreflex may explain the increase in peripheral chemoreceptor drive during AS in response to thermal challenges, which may produce increased breathing instability leading to apnea in early life.

Objectif Chez l’adulte, l’endormissement est favorise par une vasodilatation cutanee peripherique, notamment au niveau des pieds. Notre objectif est de determiner si une telle vasodilatation est observee chez le nouveau-ne premature, et si elle favorise l’endormissement (apprecie par la duree des episodes de veille intra-sommeil). Methodes Trente enfants prematures ont ete etudies (20-8 h a j9 de vie, terme : 208 ± 8 j, poids naissance : 1,3 ± 0,3 kg). Dix temperatures cutanees locales (thermographie infrarouge, abdomen Tabdo, pectoral, cernes, mains, pieds, cuisses) ont ete relevees pour 118 episodes de veille intra-sommeil spontanee (VIS ; debut, fin, toutes les 5 min pendant VIS). Les regressions entre la duree de VIS et les temperatures ont ete analysees. Resultats La duree de l’episode de VIS est d’autant plus courte que les temperatures cutanees distales (mains, pieds, cuisses) mesurees a la fin de VIS sont elevees et proches de Tabdo, et qu’elles augmentent pendant VIS, se rapprochant de Tabdo et refletant une vasodilatation distale. Conclusion Nos resultats mettent en evidence pour la premiere fois chez des nouveau-nes prematures de 9 jours que les temperatures cutanees distales jouent un role essentiel dans l’induction du sommeil du nouveau-ne : plus la vasodilatation est marquee, plus la VIS est courte. Ceci est particulierement important au regard du role essentiel du sommeil pour le developpement et la sante de ces prematures.

Some studies have shown that people living near a mobile phone base station may report sleep disturbances and discomfort. Using a rat model, we have previously shown that chronic exposure to a low-intensity radiofrequency electromagnetic field (RF-EMF) was associated with paradoxical sleep fragmentation and unusually greater vasomotor tone in the tail without any difference of central temperature at air temperature (Ta) of 31°C. Thus, in the present study, we tested the hypothesis that sleep disturbances are due to thermal discomfort induced by RF-EMF, since the lower skin temperature might be accompanied by a change in thermal preference. In this study, the animal was free to choose Ta value (thermal preference), included in the rat’s thermoneutral zone. Within this range, homeothermia can be maintained by controlling changes in peripheral vasomotor tone and by modulating wakefulness and sleep stage distribution. The present study aimed at assessing the changes in thermal preference and sleep stage distribution in 18 young male Wistar rats.