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Biomedical subjects

A Leke

Publications and source records attributed to A Leke.

10 recordsLinked to original sources
PubMed2001

Influence of incubator humidity on sleep and behaviour of neonates kept at stable body temperature.

UNLABELLED: 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.

Body Temperature↗
PubMed2001

Assessment of dry heat exchanges in newborns: influence of body position and clothing in SIDS.

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.

Body Temperature Regulation↗
PubMed2001

[Neonatal deafness screening with the evoked otoacoustic emissions technique. Study of 320 newborns at the neonatal resuscitation service of the Amiens neonatal care unit].

Between January 1997 and June 1999, we screened for hearing loss using evoked otoacoustic emissions in 320 newborns in the neonate intensive care unit at the Amiens University Hospital. The purpose of this study was to search for correlations between deafness and one of the hearing loss risk factors identified by the Joint Committee on Infant Screening. Three risk factors were found to be significant: craniofacial abnormalities, low birth weight (less than 1500 g) and a familial history of hearing loss. Unfortunately a large proportion of the infants were lost to follow-up. Evoked otoacoustic emission provide an excellent screening technique for hearing loss in newborns. Such screening implies however the creation of networks to assure patient follow-up.

Deafness↗
PubMed2000

Interindividual differences in the thermoregulatory response to cool exposure in sleeping neonates.

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.

Body Temperature↗
PubMed2000

Gender-related sleep differences in neonates in thermoneutral and cool environments.

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.

Body Temperature Regulation↗
PubMed2000

The hyperoxic test in infants reinvestigated.

The hyperoxic test (HT) examines peripheral chemoreceptor function (PCF) by measuring the decrease in ventilation (V E) after 100% O(2) inhalation. A 30-s HT has been previously used in infants with calculation of the ventilatory response (VR) as the mean percentage change in V E during HT as compared with normoxia. However, it has been shown that during hyperoxia V E rises secondarily after the initial drop because of loss of PCF. We hypothesized that the mean V E change over a 30-s HT may underestimate the strength of PCF and may be poorly reproducible. We performed breath-by-breath analysis during 30-s HTs, calculating VR at the response time (RT) defined as the time from HT onset to the first significant HT-related change in V E. Eighteen infants (postnatal age, 21 +/- 4 d) underwent two HTs (quiet sleep, face mask attached to a pneumotachograph, and inspired and expired O(2) and CO(2) fractions measured using mass spectrometry). V E, VT, and VT/TI decreases at the RT were significantly greater than the corresponding means (-21 +/- 7 versus -15 +/- 7%, -21 +/- 8 versus -13 +/- 8%, and -22 +/- 11 versus -17 +/- 11%, respectively). Intra-individual coefficients of variation of V E, VT and VT/TI were significantly smaller when RT values were considered rather than means. We conclude that calculation of the VR to HT at RT improves assessment of PCF and enhances HT reproducibility in infants.

Breath Tests↗
PubMed1998

Sleep modifications during cool acclimation in human neonates.

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.

Acclimatization↗
PubMed1998

Effects of medium- and long-chain triglycerides on sleep and thermoregulatory processes in neonates.

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.

Body Mass Index↗
PubMed1997

Human recombinant growth hormone increases small bowel lengthening after massive small bowel resection in piglets.

BACKGROUND/PURPOSE: Dramatic improvement in small bowel lengthening and in weight gain has been demonstrated in newborn rats treated with human growth hormone (GH) after massive small bowel resection. The aim of this study was to confirm these results in another animal model and to specify the part food intake plays in small bowel lengthening induced by GH. METHODS: Twenty-five piglets underwent laparotomy at day 28 of life. Intestinal length was measured under general anesthesia, and animals had an 80% resection of small bowel, leaving a similar length of jejunum and ileon. There were no perioperative deaths. One animal died 3 days after surgery. Animals were assigned to five groups: (1) S (n = 4): sham, mere laparotomy; (2) GH-S (n = 4): sham and GH treatment (0.1 IU/kg/d subcutaneously); (3) R (n = 7): intestinal resection; (4) GH-R (n = 6); and (5) GH-R AdL (n = 4): intestinal resection and GH treatment. S, GH-R, and GH-R AdL had a free diet; GH-S and GH-R were pair-fed with S and R, respectively. Animals were killed 28 days later. RESULTS: Weight gain was not different in the two nonresected groups (S, 144 +/- 6% of initial weight; GH-S, 150 +/- 3%) and was significantly higher than in the resected groups (R, 67 +/- 28%; GH-R, 74 +/- 16%; GH-R AdL, 55 +/- 16%; NS). GH did not enhance small bowel lengthening in the nonresected groups; S, 41.9 +/- 23% and GH-S, 36.9 +/- 9%, in sharp contrast with the resected groups; R, 28 +/- 9 cm versus GH-R, 96 +/- 39 cm (P = .0008) and versus GH-R AdL, 89 +/- 41 cm (P = .003). Compared with initial length, the increase was R, 16.2 +/- 5%; GH-R, 56.5 +/- 24%; GH-R AdL, 51 +/- 25%. Villus height and diameter, average number of mitosis per field, intestinal muscular layer, wall thickness, and crypt ratio were higher in resected groups than in unresected ones, with no difference observed between resected groups. CONCLUSIONS: GH improves the postoperative intestinal adaptation process after massive small bowel resection in newborn piglets in terms of small bowel lengthening. In contrast to rats, GH did not improve weight gain. In addition, no difference was observed whether animals were on a free or a controlled diet.

Adaptation, Physiological↗