Rationale:The technique used to provide continuous positive airway pressure (CPAP) to the newborn may influence lung function and breathing efficiency. Objectives: To compare differences in gas exchange physiology and lung injury resulting from treatment of respiratory distress with either bubble or constant pressure CPAP and to determine if the applied flow influences short-term outcomes. What This Study Adds to the FieldIn an ovine model of preterm lung disease, treatment with bubble CPAP immediately after birth enhances gas exchange, lung mechanics, gas mixing efficiency, and lung volume compared with constant pressure CPAP.in New York, where B-CPAP has been a cornerstone of clinical treatment practice since the 1970s. Despite the lengthy period over which B-CPAP has been used, surprisingly little is known about the importance or relevance of the bubble component of the CPAP treatment.During B-CPAP, the expiratory limb of the CPAP circuit vents through an underwater seal. The resulting bubbles create pressure oscillations that are transmitted back to the airway opening. The noisy nature of the pressure waveform delivered to the airway opening generates broadband frequency composition and oscillatory pressure amplitudes that are in the order of 4 cm H 2 O around the mean pressure. Although this noisy component may contribute to gas mixing in a similar fashion to mechanisms present during high-frequency oscillatory ventilation (4), only two previous studies have examined the effect of B-CPAP on gas exchange. Lee and colleagues (4) randomized a group of infants ready for extubation to receive either B-CPAP or ventilator-derived (constant pressure) CPAP (CP-CPAP) for a period of 15 minutes before crossover to the alternative treatment. Although there were no differences in Pa CO 2 between B-CPAP and CP-CPAP groups, the babies treated with B-CPAP had lower respiratory rates and lower minute volumes, suggesting more efficient ventilation. More recently, Morley and colleagues reported a crossover study of clinically stable infants treated with CPAP in the neonatal intensive care unit (5). They found no differences in transcutaneous measurements of arterial CO 2 or in oxygen saturation between CPAP with and without bubbles over the brief 30-minute study epochs. Both studies tested the effect of B-CPAP on clinically stable infants in the recovery stage of neonatal respiratory illness, and focused predominantly on the concept that the bubble component was likely to influence CO 2 clearance.
Sixty two infants ,28 weeks were occlusively wrapped and randomised to radiant warmer or incubator transport to the neonatal unit. Median axillary temperature on arrival was 36.8˚C in both groups. Target temperatures (36.5-37.5˚C) were achieved in 60% of the incubator group compared to 75% in the warmer group (not statistically significant). While powered to detect a 35% difference between warming devices, a more modest difference is not excluded. L ow admission temperature in preterm infants is an important predictor of mortality and morbidity. Strategies to avoid hypothermia immediately after birth include methods of reducing heat loss (for example, plastic wrap), and using an external heat source. 1In this study we wished to minimize heat loss after birth using plastic wrap and compare two heat sources (radiant warmer and incubator) with regard to core temperature on admission. According to the null hypothesis, use of a radiant warmer and occlusive wrap would be no more likely to achieve desired admission temperatures than an incubator and occlusive wrap. METHODSInfants 23-27 weeks gestation admitted to the neonatal unit were eligible provided there was no suspected congenital infection, major congenital abnormality or open skin defect. Following delivery the infant was placed on a radiant warmer and wrapped with occlusive polyethylene (NeoWrap, Fisher & Paykel Healthcare, Auckland, New Zealand). The infant (undried) was placed on the radiant warmer (heater output 100%) in the middle of the sheet and the sides closed over the limbs and trunk. The head was not wrapped or covered. Resuscitation was consistent with current American Heart Association guidelines. Ambient temperatures in delivery suite, theatre and the neonatal unit were maintained at 25˚C.Once stable, infants were moved from delivery or theatre to the neonatal unit, a 5-7 min trip. Infants were transported (wrapped) on either a radiant warmer (Fisher & Paykel CosyCot) with power source or in an incubator (Caleo, Drager, Biolab, Auckland, New Zealand) with power supply; all received mask CPAP. Heater output of the warmer was 100% throughout and incubator air temperature was set at 39˚C and was 39˚C at the start of the transfer. Portholes were open to provide CPAP. Skin servocontrol was not used before arrival to the nursery.In the nursery infants were weighed (wrapped) and placed on a warmer. Axillary temperatures were measured immediately with digital electronic thermometers (Becton Dickinson, Auckland, New Zealand) and skin servocontrol commenced.Primary outcome was the proportion with axillary temperature in the target range of 36.5-37.5˚C.2 3 Secondary outcomes were interference with resuscitation, skin infection or 5 day course of antibiotics in the first week, respiratory support requirements, length of stay, chronic lung disease, necrotising enterocolitis, severe intraventricular haemorrhage, retinopathy of prematurity and death. Sample size was determined from a separate pilot study; 43% of 21 infants ,1000 g transported either by warmer or...
The objectives of this research were to; develop a validated mathematical model of the premature neonatal lung. A description of the multi-compartmental, branched airway model of the neonatal lung is presented and shown to compare well with existing in-vivo data from the literature. The model described will be used in engineering practice to assess the design of conventional and emerging forms of continuous positive airway pressure (CPAP) devices in treating respiratory distress syndrome (RDS) in premature neonates.
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