Biomedical subjects

Stéphane Delanaud

Publications and source records attributed to Stéphane Delanaud.

9 recordsLinked to original sources

PubMed2006

Breathing pattern adopted by children with cystic fibrosis with mild to moderate pulmonary impairment during exercise.

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.

Adolescent↗

PubMed2006

A new, transportable ergometer for the measurement of musculotendinous stiffness during wrist flexion.

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.

Adult↗

PubMed2006

Effect of high-fat diet and metformin treatment on ventilation and sleep apnea in non-obese rats.

We investigated the effect of insulin resistance on ventilation and the incidence of sleep apnea in non-obese rats and determined whether metformin could change ventilation and occurrence of sleep apneas. Five groups of rats were studied: (1) standard chow; (2) high-fat groups, with 1 with metformin; (2) had type 2 diabetes induced by streptozotocin, with 1 with metformin. Compared to standard rats, ventilatory parameters remained unchanged in the high-fat fed diet as well as in diabetic rats. However, their oxygen consumption was reduced (p<or=0.01). They had a lower ventilatory response to CO2 challenge (p<or=0.01), and their sleep apnea scores increased markedly (p<or=0.001). These results suggest that insulin resistance could impair the ventilation control. Metformin treatment, known to reduce insulin resistance, got sleep apnea scores back to their basic levels, reinforcing the idea that insulin resistance is a major factor in the occurrence of apneas in this rat model.

Analysis of Variance↗

PubMed2006

Thermoregulatory control of feeding and sleep in premature infants.

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 degrees 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.

Adipose Tissue, Brown↗

PubMed2004

Effects of warm and cool thermal conditions on ventilatory responses to hyperoxic test in neonates.

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.

Body Temperature↗

PubMed2004

Assessment of the efficiency of warming devices during neonatal surgery.

This study assessed the relative efficiency of different warming devices (surgical sheets covering the body and a tubegauze on the head, forced-air warming, warming mattress) commonly used to prevent body hypothermia during neonatal surgery. Dry heat losses were measured from a thermal manikin, which simulated a low-birth-weight neonate of 1,800 g. The manikin's surface temperatures (35.8 degrees C) corresponded to those of neonates nursed in closed incubators. Experiments were performed in a climatic chamber at an ambient temperature of 30 degrees C, as commonly found in operating theatres. The supine manikin was naked or covered with operative sheets with a 5x5 cm aperture over the abdomen. Its head could be covered by a tube-gauze. Additional warming was provided by conduction through a warming mattress (surface temperature, 39 degrees C) and/or by convection (Bair Hugger, forced-air temperature 38 degrees C). Covering the manikin with surgical sheets decreased the dry heat loss by 10.4 W. Additional forced-air warming was more efficient than the warming mattress to reduce the total dry heat loss (6.8 W vs 2.1 W). Heat losses were reduced by 7.9 W when combining the warming mattress and Bair Hugger. The heat loss from the head of the covered manikin was reduced from 4.5 W to 3.9 W when the head was covered with the tubegauze. Our data indicate that forced-air warming is more effective than conductive warming in preventing neonatal hypothermia during abdominal operations.

Abdomen↗

PubMed2004

Dry heat loss in incubator: comparison of two premature newborn sized manikins.

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 Size↗

PubMed2003

Liver temperature during sleep.

STUDY OBJECTIVE: The liver, like brown adipose tissue, is an important source of nonshivering thermogenesis. We tested the hypothesis that the thermal state of the liver is preserved during slow wave sleep but deteriorates during paradoxical sleep. METHODS: Twelve adult male Wistar rats were equipped with electrodes and thermistor probes--which measured cortical (Tco), interscapular brown adipose tissue (Tibat), and liver (Tl) temperatures--for thermal and sleep studies. Six rats were exposed to thermoneutral (24 degrees C) and 6 to low (9 degrees C) ambient temperature. Isolated paradoxical sleep episodes preceded and followed by more than 3 minutes of wakefulness or slow wave sleep were analyzed. The Tco, Tibat, and Tl levels were also assessed during the slow wave sleep that preceded each isolated paradoxical sleep episode. RESULTS: During slow wave sleep, the Tibat and Tl were clearly higher in rats exposed to the cold than in those exposed to the thermoneutral condition (< 1 degrees C). During paradoxical sleep, however, these 2 temperatures decreased in rats exposed to the cold condition, and the changes observed for Tco were completely inversed. CONCLUSIONS: These results support the hypothesis that the thermal state in the liver of rats deteriorates during paradoxical sleep and suggest that nonshivering thermogenesis in the liver contributes to the defense of global thermal homeostasis in the sleeping endothermic organism, especially during slow wave sleep.

Animals↗

PubMed2002

Head insulation and heat loss in naked and clothed newborns using a thermal mannequin.

In newborns, large amounts of heat are lost from the head, due to its high skin surface area. Insulating the head (for example, with a hat or bonnet) can be a simple and effective method of reducing dry heat loss. In the present study, we evaluated the safety aspects of insulating the head of low-birth-weight naked or clothed newborns by using a heated mannequin that simulates a low-birth-weight newborn. Experimental conditions (comprising a nude and three clothed setups) were performed in a closed incubator at three different air temperatures (29 degrees C, 32 degrees C, and 34 degrees C) and with and without the head being covered with a bonnet in each case, i.e., 24 experimental conditions in all. The study shows that added clothing elements and insulating the head decreases the total heat loss of the mannequin as a whole. As regards the dry heat exchange from the head, wearing a bonnet decreases the local heat loss by an average of 18.9% in all clothed and thermal conditions. This phenomenon could be at the origin of brain overheating in heavily dressed newborns, when unrestricted heat loss is limited to the face only. Our results suggest that--apart from accidental hypothermia-in order to achieve thermal equilibrium of the body, it is preferable to leave the head unprotected and to increase the level of clothing insulation over the rest of the body.

Body Temperature Regulation↗