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ABSTRACT: AIMS: Very Low-birth-weight (VLBW) neonates require regular nursing procedures with frequent opening of the incubator resulting in a decrease in incubator air temperature. This study was designed to assess changes in the thermal status of VLBW neonates according to the type of nursing care and incubator openings. METHODS: Thirty-one VLBW neonates (mean gestational age: 28.7±0.3 weeks of gestation) were included. Over a 10-day period, each opening of the incubator was recorded together with details about caregiving. Body temperature was recorded continuously and door opening and closing events were recorded by a video camera. RESULTS: This study analysed 1,798 caregiving procedures with mean durations ranging from 6.2±2.1 to 88.5±33.4 min. Abdominal skin temperature decreased by up to 1.08°C/h for procedures such as tracheal intubation (p<0.01). The temperature decrease was strongly correlated with the type of procedure (p<0.01), incubator opening (p<0.01) and procedure duration (p<0.01). The procedure duration accounted for only 10% of the abdominal skin temperature change (p<0.01). CONCLUSIONS: For VLBW neonates nursed in skin temperature servo-control incubators, the decrease in abdominal skin temperature during caregiving was correlated with the type of procedure, incubator opening modalities and procedure duration. These parameters should be considered to optimize the thermal management of VLBW neonates. ©2012 The Author(s)/Acta Paediatrica ©2012 Foundation Acta Paediatrica.
Acta Paediatrica 11/2012; · 2.07 Impact Factor
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ABSTRACT: Tobacco smoking is still a common habit during pregnancy and is the most important preventable cause of many adverse perinatal outcomes. Prenatal smoking exposure can produce direct actions of nicotine in the fetus with the disruption of body and brain development, and actions on the maternal-fetal unit by causing repeated episodes of hypoxia and exposure to many toxic smoke products (such as carbon monoxide). Specifically, nicotine through binding to nicotinic acetylcholine receptors have ubiquitous effects and can affect carotid chemoreception development through structural, functional and neuroregulatory alterations of the neural circuits involved in the chemoafferent pathway, as well as by interfering with the postnatal resetting of the carotid bodies. Reduced carotid body chemosensitivity and tonic activity have thus been reported by the majority of the human and animal studies. This review focuses on the effects of perinatal exposure to tobacco smoke and nicotine on carotid chemoreceptor function during the developmental period. A description of the effects of smoking and nicotine on the control of breathing related to carotid body activity, and of the possible physiopathological mechanisms at the origin of these disturbances is presented.
Respiratory Physiology & Neurobiology 06/2012; · 2.24 Impact Factor
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ABSTRACT: Even though ventilatory support for preterm infants has improved over the past few decades, about 30% of intubated preterm infants fail an extubation attempt. There are still no simple standards to determine the optimal extubation time for those infants.
To identify factors related to extubation success or failure in preterm infants less than 32 weeks of gestation (WG).
Retrospective study including 162 newborns less than 32 WG, requiring mechanical ventilation within the first 24h of life. Successful extubation was defined as no need for reintubation for any reason at least 7 days after the first extubation attempt.
Forty-one infants failed extubation (25.3%); 149 infants (92%) had mechanical ventilation in their first 30min of life. These infants had a lower gestational age (p<0.001) and a lower birth weight (p=0.003). They required a higher FiO(2) (p<0.001) and maximum inspiratory pressure (p=0.002). The infants who failed extubation had a lower pH (p=0.001) and hematocrit (p=0.032), and a higher PCO(2) (p=0.003).
As previously described, a low gestational age is a major factor predicting the extubation failure. However, our data suggests that ventilator settings and blood gas should also be considered when attempting extubation, following written guidelines.
Archives de Pédiatrie 08/2009; 16(9):1219-24. · 0.30 Impact Factor
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ABSTRACT: The newborn's energy expenditure is used in order of priority for: (i) basic metabolism; (ii) body temperature regulation and (iii) body growth. Thermal regulation is an important part of energy expenditure, especially for low birth-weight infants or preterm newborns. The heat exchanges with the environment are greater in the infant than in the adult, explaining the increased risk of body hypo- or hyperthermia. The newborn infant is a homeotherm, but over a long period of time, he cannot maintain the thermal processes. Further developments are expected to improve the infant's thermal environment, with assessment of the various heat exchange mechanisms by conduction, convection, radiation and evaporation. The quantification of the respective parts of these exchanges would improve nursing care through clinical procedures or equipment used to ensure the control of the optimal thermohygrometric conditions in incubators, especially when the likelihood of excessive body cooling is high. The present review focuses on the various body heat exchange mechanisms, the thermoregulation processes of the newborn, and their implications in clinical usage and limitations in the neonatal intensive care unit.
Archives de Pédiatrie 05/2009; 16(7):1057-62. · 0.30 Impact Factor
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ABSTRACT: In neonates, it is often assumed that ventilatory control and heat stress interact. Thus the two factors have been implicated in various pathologies (apnoea, sudden infant death syndrome). However, little is known about the mechanisms of this interaction, and the influence of sleep is still debated. This study aimed at determining the influence of warm exposure on the decrease in ventilation during a hyperoxic test (HT), which is considered to be a measure of peripheral chemoreceptor activity. The test was performed in active (AS) and quiet sleep (QS) in 12 neonates exposed to thermoneutral or warm environments. The HT consisted of 30 s of inspired, 100% O(2). The ventilatory response was assessed in terms of a response time, defined as the time elapsing between HT onset and the first significant change in V(E). Our results show that, in both thermal conditions, the fall in V(E) was higher in AS than in QS. Warm exposure significantly enhanced the ventilatory response in AS (-27.5 +/- 8.7% vs. -38.3 +/- 8.8%, P < 0.01) but not in QS. A thermometabolic drive or inputs from thermoreceptors could be involved in the reinforcement of peripheral chemoreceptor activity in AS in warmer environments, which could contribute to an increasing risk of apnoea in neonates with altered chemoreceptor function. Since hypothalamic structures are involved in thermoregulatory, sleep processes and (probably) in respiratory control, it could well be the principal site where this interaction occurs.
Neurophysiologie Clinique/Clinical Neurophysiology 09/2003; 33(4):196-202. · 1.98 Impact Factor
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ABSTRACT: In order to assess the specific sympathetic reactivity in premature infants at term, we designed a study to evaluate the peripheral vasomotor response of such infants when exposed to auditory challenges. Testing was performed in 29 premature neonates at term in both quiet and active sleep during a morning session. Two types of noises were used (click and continuous tones) at three frequencies (250, 1,000 and 6,000 Hz) and at three intensities (60, 85 and 110 dBA). Vasomotor response was studied by analyzing with Mathlab software the variability of the plethysmographic wave of the oxymetric pulse. No behavioral awakening was observed in response to any stimulation. When a tachycardia or a bradycardia reaction to the stimuli was observed, all neonates responded with a vasoconstriction. The global mean of the vasoconstrictive response was 18.45%. The overall ANOVA on the vasomotor response revealed significant effects for sleep stages (t: 1.98; p < 0.05), for frequency (t: 3.3; p < 0.001) and for intensity of noise (t: 3.01; p < 0.03) but no significant response with heart rate variability. From these results, we could conclude that the assessment of the vasomotor response is a very sensitive procedure to determine the reactivity of the autonomic nervous system in neonates, and could be used to study such vegetative responses in other stressful situations with good accuracy.
Biology of the Neonate 02/2002; 82(1):9-16. · 1.90 Impact Factor
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ABSTRACT: The influence of incubator air humidity (via passive humidification through use of a water reservoir or via active humidification to 2 and 4 kPa) on sleep and behavioural changes was investigated in 13 neonates. The thermal environment of the incubator was servocontrolled via an interactive device tracking the skin temperature changes of the neonates. Using this servocontrolled skin temperature derivative heating programme, it is believed that an increase in air moisture content (reducing evaporative skin cooling) can be counterbalanced by a fall in neutral air temperature, so as to keep the body thermally constant. This procedure permits the experimental evaluation of the specific effect of air humidity on the thermal equilibrium air temperature and the thermal comfort of neonates without eliciting thermoregulatory mechanisms. Under the experimental conditions, in order to keep body temperature stable an increase in water vapour partial pressure from 1.72 (water reservoir) to 3.99 kPa (produced by a nebulizer) is counterbalanced by a decrease in air temperature of 1.49 degrees C. Within this humidity range, the air temperature must be lowered by 0.05 degrees C when the vapour pressure is increased by 0.08 kPa. The magnitude of this deviation depends on the humidity range and is probably a result of changes in the wetted skin area. Conclusion: When body temperature is kept constant, changes in air humidity do not modify sleep, body motility and respiratory and heart rates in neonates.
Acta Paediatrica 10/2001; 90(9):998-1003. · 2.07 Impact Factor
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ABSTRACT: A dramatic decrease of sudden infant death syndrome (SIDS) has been noted following the issuance of recommendations to adopt the supine sleeping position for infants. It has been suggested that the increased risk could be related to heat stress associated with body position. In the present study, the dry heat losses of small-for-gestational-age newborns nude or clothed were assessed and compared to see whether there is a difference in the ability to lose heat between the prone and supine positions. An anthropomorphic thermal mannequin was exposed to six environmental temperatures, ranging between 25 and 37 degrees C, in a single-walled, air-heated incubator. The magnitudes of heat losses did not significantly differ between the two body positions for the nude (supine 103.46 +/- 29.67 vs. prone 85.78 +/- 34.91 W/m(2)) and clothed mannequin (supine 59.35 +/- 21.51 vs. prone 63.17 +/- 23.06 W/m(2)). With regard to dry heat exchanges recorded under steady-state conditions, the results show that there is no association between body position and body overheating.
Journal of Applied Physiology 08/2001; 91(1):51-6. · 3.75 Impact Factor
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ABSTRACT: Although thermoregulation and sleep exhibit gender differences in adults, the question is still debated in neonates. The aim of this study was to examine the relationship between gender-related sleep differences and cool defence mechanisms in neonates. Sleep and thermoregulation were recorded in healthy preterm neonates (21 boys and 17 girls, 37 +/- 2 weeks post-conceptional age) exposed to thermoneutral and cool conditions. Sleep was analysed for continuity and structure. Although the cool exposure did not strongly impair body homeothermia, sleep was altered but without any significant gender difference. However, when data recorded under each of the thermal conditions were pooled, some gender differences emerged: boys slept less, with more wakefulness after sleep onset, more active sleep and less quiet sleep than girls. In contrast to sleep architecture, most of the sleep continuity parameters exhibited greater variability in boys than in girls. This variability may bias the statistical analyses and probably explains the varying conclusions reported in the literature regarding gender-specific sleep-related differences.
Journal of Sleep Research 10/2000; 9(3):249-54. · 3.16 Impact Factor
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ABSTRACT: The responses of the thermoregulatory effectors vary greatly among neonates. Therefore, we assume that a small decrease in air temperature from thermoneutrality induces various thermoregulatory responses within neonates that represent an energy cost due to the cold defence processes. To determine the importance of this variability in nursing, 26 neonates were explored at thermoneutrality and in a cool environment (-1.5 degrees C from thermoneutrality) similar to that which occurs currently in clinical procedure. Oxygen consumption (VO2), oesophageal and skin temperatures, as well as sleep parameters were recorded continuously in both conditions. Analysis of all of the data from all of the neonates revealed that the cool exposure induced thermal and sleep disturbances, but VO2 did not increase and was not negatively correlated to body temperature (as might be expected). Analyses of individual data showed large variability in body temperature regulation: the neonates could be assigned to one of three groups according to the direction of the individual slopes of VO2 versus oesophageal or skin temperature. The groups also differed according to the sleep changes recorded in the cool condition. The results show that the definition of thermoneutrality should be revised by incorporating non only changes in the body temperature, but also the sleep disturbances (increased wakefulness and active sleep, decreased quiet sleep), which are criteria that are more sensitive to mild cool exposure. Thermoneutrality should be defined for each individual, since the results stress that the variability does not help to predict a general pattern of thermoregulatory responses in cool-exposed neonates.
Arbeitsphysiologie 05/2000; 81(6):455-62. · 2.15 Impact Factor
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ABSTRACT: The levels of benzo[a]pyrene were monitored for blood DNA-benzo[a]pyrene adducts in 17 workers from a plant producing carbon electrodes, with high exposure to benzo[a]pyrene (575-902-1149 ng m(-3)). Two different techniques, a 32P-postlabelling method and a competitive immunoassay using polyclonal antibodies obtained from rabbits immunised with DNA modified by benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide were used. For each worker, urinary 1-hydroxypyrene, a potential indicator of exposure to polycyclic aromatic hydrocarbons, was measured. The effect of tobacco by urinary cotinine measurement was also considered. The postlabelling and immunoassay detection limits for DNA-benzo[a]pyrene adducts were respectively 0.15 and 10 fmol 50 microg(-1) of DNA. The results obtained by the two methods demonstrated a good detection of DNA-benzo[a]pyrene adducts, but no direct relationship between the quantity of adducts and the concentration of benzo[a]pyrene in air-borne was noted in the studied plant. The levels of DNA-benzo[a]pyrene adducts obtained by immunoassay were significantly higher than those obtained by the 32P-postlabelling (P < 0.001). For several workers, variations due to professional or non professional factors must be taken into account in interpreting the results. In conclusion, the two methods used proved very efficient in determining DNA-benzo[a]pyrene adducts, and may be useful in monitoring human exposure to known and previously unidentified environmental genotoxic agents.
Human & Experimental Toxicology 05/1999; 18(5):314-21. · 1.77 Impact Factor
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ABSTRACT: The present study aimed at testing in human neonates whether the thermal acclimation could reduce the sleep disturbances induced by brief cool exposure. Six neonates were exposed in incubator to a standardised cool thermal load of 75 h duration. The results show an increase of the metabolic heat production (VO2: +25% reaching 5.68 ml/min per kg) during cool acclimation which is not associated with a reduction of the sleep modifications observed on the first cool exposure: the increase of active sleep (+15%, +2 min) and the decrease of quiet sleep (-15%, -11 min) persist and wakefulness after sleep onset increases (+12%, +10 min). In conclusion, there is no sleep adaptation as cool acclimation progressed.
Neuroscience Letters 04/1998; 245(1):25-8. · 2.11 Impact Factor
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ABSTRACT: In the first days of life, the daily evaporative loss from premature neonates can reach up to 20% of body mass. Such loss can be reduced by increasing the air humidity inside the incubator. Neither passive humidification nor open loop systems allow high humidity rates to be maintained or easily controlled: at 34 degrees C, the maximum levels vary with the system from 40% to 77% of relative humidity. The skin evaporative exchanges between the neonate and the environment are directly proportional to the water vapour partial pressure difference between the neonate's skin and the air. An active closed loop system has been designed, which permits reliable and accurate control of humidity according to the water vapour partial pressure set, between 1 and 6 kPa, in an air temperature range of 28-39 degrees C. It is characterised by variations of about 0.05 kPa around the set value and a maximum humidification speed of 0.25 kPa min-1. The algorithm is based on optimal control and the dynamic programming principles. Test results place this active system above usual systems for its power, precision and adaptability. It is an exploitable tool in fundamental and clinical research, to precisely study the humidity effects on neonatal comfort and thermo-regulation evolution.
Medical & Biological Engineering & Computing 04/1998; 36(2):241-5. · 1.88 Impact Factor
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ABSTRACT: Sleep processes and body temperature regulation of neonates are never taken into account in the evaluation of nutrients, although these functions are implicated in the regulation of energy metabolism and are influenced by the nutritional state and its metabolic consequences. Medium-chain triglycerides (MCT) are currently used in paediatric units during the first weeks of because they are considered to be a rapid source of energy, easy to assimilate for growing premature infants, whose digestive function is immature. However, no study has described the thermic effect of these nutrients on body temperature regulation and sleep. The present study aimed at analysing the influence of three feeding formulas with different content of MCT on sleep processes and on thermoregulation of neonates fed until desired intake was reached. Whatever the thermal conditions (thermal equilibrium or cool environment), the MCT-fed groups had higher body temperatures and than groups fed without MCT, for whom total sleep time was reduced at thermal equilibrium. In this group, the large amount of quiet sleep seems to favour a strategy of conserving energy. Higher energy expenditure in MCT-fed groups is not harmful to growth rate since nutritional efficiency is even better reflected by a larger body mass gain. The thermic effect of MCT contributes to lessening the vulnerability of neonates exposed to low incubator temperatures.
Journal of Sleep Research 04/1998; 7(1):31-9. · 3.16 Impact Factor
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ABSTRACT: Placenta constitutes a vital organ of exchange between mother and foetus. In addition to this favourable effect for foetal development, placenta indirectly may allow transfer of several maternal blood xenobiotics. Human placenta and umbilical cord blood are interesting models for investigating maternal environment and the metabolism, the bioactivation and the transfer of carcinogens such as polycyclic aromatic hydrocarbons. We used them to assess the effect of a woman's smoking on the foetus. Few studies cover this subject. In pregnant women who have continued to smoke, benzo[a]pyrene compound of cigarette smoke is metabolically activated to diol-epoxide derivative: benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide, ultimate carcinogen (BPDE-I). This derivative is covalently fixed on DNA and gives BPDE-I-DNA adducts. By a competitive immunoassay technique, we determined BDPE-I-DNA adducts in 20 samples of placenta and umbilical cord blood from women who smoked (n = 15) and who did not (n = 10). Tobacco consumption was checked by urinary cotinine determination. In the group of smokers levels of adducts were found in 13 specimens of placenta (from 10 to 60 fmol/50 micrograms of DNA) and 12 umbilical cord blood (from 10 to 22.15 fmol/50 micrograms of DNA) samples. These results indicate that a mother's tobacco consumption is linked to the accumulation of BPDE-I-DNA adducts in the placenta, which are seen in smaller quantities in the umbilical cord blood, probably because of the metabolic capacity of the placenta and the transfer of B[a]P from the mother to the foetus.
Human & Experimental Toxicology 01/1998; 16(12):716-21. · 1.77 Impact Factor
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Pflugers Archiv-European Journal of Physiology. 01/1998; 435(4):R34-R34.
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ABSTRACT: A new heating unit (servocontrolled skin temperature derivative system) has been designed to control the thermal environment in closed incubators. This type of control acts to attain and closely maintain a thermal equilibrium between a neonate's skin temperature and the environment. The present study aims to discover if thermal equilibrium is located within a thermoneutral range defined from oxygen consumption VO2 and body temperature, and whether it is more appropriate to define an optimal thermal environment. As regards VO2 and body temperature, results show that the air temperature reached at thermal equilibrium fulfils the definition of thermoneutrality. According to these criteria, a small decrease (1:5 degrees C) from thermal equilibrium also provides a near thermoneutral environment to the neonate but induces sleep disturbances and an increase in body movements. These two additional parameters delineate a narrower thermoneutral zone than does minimal metabolic rate because VO2 can stay constant even when air and body temperatures decrease. The results suggest that thermal equilibrium might be assimilated with a thermal comfort zone.
Medical & Biological Engineering & Computing 10/1997; 35(5):516-20. · 1.88 Impact Factor
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ABSTRACT: Defining a thermoneutral environment remains difficult because thermoneutrality depends on both physical and physiological factors. A servocontrolled skin temperature derivative (SCS) heating device has been designed to control the thermal environment in closed incubators without the necessity of setting an air or skin reference temperature. The thermal environment obtained with the SCS program is controlled only by the neonate's skin temperature changes. For each neonate, the program allows the attainment of a specific individual thermal equilibrium (Teq). Although the mean value of the thermal equilibrium level measured on 29 neonates does not differ significantly from the neutral air temperature defined from the charts of other researchers, individual values of Teq differed greatly among neonates of similar birthweight and postnatal age. When compared with on/off heating programs, the SCS system permits greater quiet sleep occurrence and seems to provide an optimal thermal environment. The results suggest that the skin temperature derivative heating program takes into account both the ambient and physiological factors affecting body temperature regulation of each neonate.
Medical & Biological Engineering & Computing 10/1997; 35(5):521-7. · 1.88 Impact Factor
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ABSTRACT: Low-birth-weight neonates should be nursed at thermoneutrality inside incubators. Thermoneutrality control is essential to enhance body growth and to reduce neonatal illnesses and mortality. Guidelines have been published to provide the thermoneutral range, but the recommendations did not always take into account all ambient and physiological parameters influencing thermoneutrality. In most marketed incubators, the heat supply is controlled through convective air flow (closed incubators) or through radiant power density (radiant warmer beds). The heating unit (on/off cycling or adjustable proportional control) is activated by an error signal calculated from the difference between a controlled temperature and a reference value preset by the clinician. The controlled variable can be either the incubator air or the skin temperature of the anterior abdominal region of the neonate. The neonate's size, thermal properties of the mattress and of incubator walls, air temperature and humidity, air velocity, incubator wall temperatures all influence the heat exchanges between the neonate and the surroundings, and, consequently, modify the obtention of thermoneutrality. Moreover, studies of the physiological mechanisms by which the neonate regulates body heat storage suggest that metabolic rate, behavior, vigilance level, nursing care, and heater control processes should also be taken into account. Little attention has been paid to these factors, and incubator performances are often disappointing. This article reviews the different factors that modify thermoneutral condition. An attempt is made to suggest new ways to design equipment incorporating these factors in algorithms controlling heater processes in order to reach the optimal thermal environment in which the neonate should be nursed.
Critical Reviews in Biomedical Engineering 01/1997; 25(4-5):287-370.
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ABSTRACT: Brain capillary perfusion was evaluated in the different states of the wake-sleep cycle-quiet wakefulness (QW), quiet sleep (QS), and active sleep (AS)-in rats. The extent of the perfused capillary network was determined by intravascular distribution of a fluorescent marker. Evans blue (EB); it remained unchanged across the three behavioral conditions, QW, QS, and AS. The anatomical network was assessed by alkaline phosphatase (AP) endothelial staining, which is known to underestimate the number of existing capillaries. The resulting number of AP profiles were, therefore, significantly lower than the number of EB profiles, but the percentage of AP-stained capillaries that were perfused (96%) was also unchanged across the behavioral conditions. The results indicate that no capillary recruitment accompanies the wake-sleep cycle. Capillary surface area is a relevant factor in determining exchanges across the blood-brain barrier. In the absence of capillary recruitment (relative constancy of the surface area), the CBF changes during sleep should preferentially affect flow-limited with respect to diffusion-limited transport.
Journal of Cerebral Blood Flow & Metabolism 12/1996; 16(6):1312-8. · 5.01 Impact Factor
