Quantitative Imaging of Regional Aerosol Deposition, Lung Ventilation and Morphology by Synchrotron Radiation CT.

To understand the determinants of inhaled aerosol particle distribution and targeting in the lung, knowledge of regional deposition, lung morphology and regional ventilation, is crucial. No single imaging modality allows the acquisition of all such data together. Here we assessed the feasibility of dual-energy synchrotron radiation imaging to this end in anesthetized rabbits; both in normal lung (n = 6) and following methacholine (MCH)-induced bronchoconstriction (n = 6), a model of asthma. We used K-edge subtraction CT (KES) imaging to quantitatively map the regional deposition of iodine-containing aerosol particles. Morphological and regional ventilation images were obtained, followed by quantitative regional iodine deposition maps, after 5 and 10 minutes of aerosol administration. Iodine deposition was markedly inhomogeneous both in normal lung and after induced bronchoconstrition. Deposition was significantly reduced in the MCH group at both time points, with a strong dependency on inspiratory flow in both conditions (R2 = 0.71; p < 0.0001). We demonstrate for the first time, the feasibility of KES CT for quantitative imaging of lung deposition of aerosol particles, regional ventilation and morphology. Since these are among the main factors determining lung aerosol deposition, we expect this imaging approach to bring new contributions to the understanding of lung aerosol delivery, targeting, and ultimately biological efficacy.

[Noise level in the NICU: Impact of monitoring equipment]. / Nuisances sonores en réanimation néonatale : impact d'un outil de monitorage.

BACKGROUND: The sound level in the neonatal intensive care unit (NICU) may induce adverse effects for neonates, their family, and the staff. This study evaluated the sound level in a NICU before and after the implementation of an educational program. MATERIAL AND METHODS: A baseline audit determined the most exposed area of the NICU and the most exposed periods over 24 h. Then an educational program started, including sound level measurement methods, side effects for neonates, results from the baseline audit, and new visual monitoring equipment (SoundEar®). Sound levels were measured before, 1, 2, and 3 months after starting the educational program and the use of SoundEar®. The NICU staff was blind to the periods of sound level measurements. RESULTS: The base noise level was high, especially near the central part of the NICU and during transmission time (mean Leq: 60.6±3.6dB(A); sound peaks: 94.8±6.8dB(A)). A decrease in the sound level (P<0.001) was found 1 and 2, but not 3 months after starting the educational program. It remained high compared to the guidelines. CONCLUSION: Human activity was responsible for most of the sound level. An educational program was effective in reducing the sound level, but did not reach the guideline's target. The continuous use of sound-monitoring equipment after starting the project reduced the sound level for 2 months, but no longer. Therefore, a continuous educational program about the sound level in the NICU including feedback monitoring every 2-3 months should be encouraged.

A mean body temperature of 37°C for incubated preterm infants is associated with lower energy costs in the first 11 days of life.

AIM: This randomised trial compared the energy costs of providing incubated preterm infants born before 32 weeks of gestation with homeothermia using either air temperature control (ATC) or skin servocontrol (SSC). METHODS: We studied 38 incubated preterm infants for the first 11 days of life, calculating the frequency of hypothermia (<36.0°C), hyperthermia (>37.5°C) and thermal challenge, together with energy costs, based on a change in incubator air temperature of 2°C above or below thermoneutrality. RESULTS: The daily mean incubator air temperature was higher in ATC than SSC (p < 0.05) for the first 6 days, and the mean body temperature was higher in ATC (37.0 ± 0.03°C) than SSC (36.8 ± 0.02; p < 0.01) over the whole study period. The frequency of moderate hyperthermia was higher in ATC (p < 0.001), whereas warm and cold thermal challenges were higher in SSC (p < 0.001). The two groups did not differ in terms of energy costs. The time to recover birthweight was shorter in ATC (p < 0.05). CONCLUSION: In incubators using ATC, a body temperature of 37°C was associated with lower energy costs and greater weight gain at 11 days of life for preterm infants. Future studies should test SSC shielded abdominal skin temperature set to 37°C.

Impact of nursing care on temperature environment in preterm newborns nursed in closed convective incubators.

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.

Variations in incubator temperature and humidity management: a survey of current practice.

AIM: To describe and assess routine procedures and practices for incubator temperature and humidity management in France in 2009. METHODS: A questionnaire was sent to all the 186 neonatal care units in France. RESULTS: The questionnaire return rate was 86%. Seventy-five per cent of the units preferred skin servo-control to air temperature control in routine practice. Air temperature control was mainly used for infants with a gestational age of more than 28 weeks and aged over 7 days of life. In general, thermal management decisions did not depend on the infant's age but were based on a protocol applied specifically by each unit. All units humidified the incubator air, but there was a large difference between the lowest and highest reported humidity values (45% and 100% assumed to be a maximal value, respectively). More than 65% of the units used a fixed humidity value, rather than a variable, protocol-derived value. CONCLUSION: We observed large variations in incubator temperature and humidity management approaches from one neonatal care unit to another. There is a need for more evidence to better inform practice. A task force should be formed to guide clinical practice.

[Heat exchanges and thermoregulation in the neonate]. / Echanges thermiques et thermorégulation chez le nouveau-né.

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.