High amplitude bubble continuous positive airway pressure decreases lung injury in rats with ventilator-induced lung injury.

BACKGROUND: Bubble continuous positive airway pressure (BCPAP) has been used in neonates with respiratory distress for decades; however, the optimal setting for BCPAP circuits remains unknown. This study compared the gas exchange efficiency and lung protection efficacy between conventional and high-amplitude BCPAP devices. METHODS: We compared gas exchange, lung volume, and pulmonary inflammation severity among rats with ventilator-induced lung injury (VILI) that were treated with conventional BCPAP (BCPAP with an expiratory limb at 0°), high-amplitude BCPAP (BCPAP with an expiratory limb at 135°), or spontaneous breathing (SB). After mechanical ventilation for 90 minutes, the rats were randomly divided into four groups: a control group (euthanized immediately; n = 3), an SB group (n = 8), and two BCPAP groups that received BCPAP with the expiratory limb at either 0° (n = 8) or 135° (n = 7) for 90 minutes. RESULTS: The high-amplitude BCPAP group exhibited significantly lower alveolar protein, lung volume, and Interleukin-6 (IL-6) levels than did the SB group. The high-amplitude BCPAP group exhibited significantly lower IL-6 levels than did the conventional BCPAP group. The two BCPAP groups demonstrated no difference in gas exchange efficiency. CONCLUSION: High-amplitude BCPAP reduced lung inflammation and alveolar overdistension in rats with VILI after mechanical ventilation was ceased. Thus high-amplitude BCPAP may offer a superior lung protective effect than conventional BCPAP.

[Effects of different salinity levels on nitrification processes in sediments of Minjiang River Estuary, China]. / 不同盐度对闽江河口沉积物硝化作用的影响.

Two estuary wetlands in Minjiang River, Shanyutan and Daoqingzhou, were selected as the research objects. Wetland sediments were collected to examine the effects of different salinity levels on nitrification processes in the wetland with a culture experiment. The results showed that the nitrification rate of sediment in Minjiang River estuary wetland was generally low. The highest nitrification rate of sediment in the Shanyutan wetland was 0.193 mg·kg-1·d-1, while that in the Daoqingzhou wetland did not exceed 0.050 mg·kg-1·d-1. In the low salinity level (5), the decrease of nitrification rate was attributed to the restraint of nitrifying bacteria activities. The nitrification rate slightly increased with the increases of salinity (10), but was still lower than the initial value. This would be owed to the fact that the inhibitory effect of salinity on the activities of aerobic bacteria was strengthened, which reduced the rate of NH4+-N production, and thus resulted in a decrease of the contribution of aerobic ammonification bacteria to the apparent nitrification rate. There were regional variations in the responses of sediment nitrifying activity to salinity. In saltwater wetland (Shanyutan wetland), the adaptability of microbes in sediment to salinity was stronger, so that the nitrification activity in high salinity conditions was still higher. While in the freshwater wetland (Daoqingzhou wetland), the adaptability of the sediment to the salinity change was relatively lower, with a lower nitrification activity of the sediment in high salinity than in middle salinity. Acidic condition was the main reason for the low nitrification in the sediments of Minjiang estuary wetland. The nitrification rate and nitrification activity of the two wetlands increased first and then decreased with the duration of the culture experiment, which was driven by combined effects of initial NH4+-N concentration, oxygen content and denitrifying.

Pulmonary Hypoplasia Induced by Oligohydramnios: Findings from Animal Models and a Population-Based Study.

Pulmonary hypoplasia is a substantial cause of death in newborn infants, and oligohydramnios is one of the most commonly associated abnormalities. Lung growth is influenced by physical factors such as the intrauterine space, lung liquid volume and pressure, and fetal breathing movements. During lung development, the main physical force experienced by the lungs is stretching induced by breathing movements and the lung fluid in the airspaces. Oligohydramnios reduces the intrathoracic cavity size, thus disrupting fetal lung growth and leading to pulmonary hypoplasia. The exact mechanism by which oligohydramnios alters the respiratory system structure and the effect of oligohydramnios on long-term respiratory outcomes remain unknown. In this review, we summarize the effects of oligohydramnios on lung development, discuss the mechanisms of oligohydramnios-induced pulmonary hypoplasia identified in various animal studies, and describe the long-term respiratory outcomes in childhood of oligohydramnios-exposed fetuses reported by a population-based study.

Bubble CPAP Support after Discontinuation of Mechanical Ventilation Protects Rat Lungs with Ventilator-Induced Lung Injury.

BACKGROUND: Bubble continuous positive airway pressure (BCPAP) has been used in neonates with respiratory distress for decades, but its lung-protective effect and underlying mechanism has not been investigated. OBJECTIVES: To test the hypothesis that BCPAP use after extubation decreases lung injury and that alterations to lung nitric oxide synthase (NOS) 3 expression may be one of the underlying mechanisms. METHODS: We compared gas exchange, lung injury severity, and lung NOS expression among rats with ventilator-induced lung injury (VILI) treated with either BCPAP or spontaneous breathing. After high tidal volume ventilation for 30 min, the rats were randomly divided to three groups: a control group underwent spontaneous breathing (n = 7), and two BCPAP groups were treated with the bubble technique with either a 2.5-mm-diameter (n = 7) or a 5.5-mm-diameter (n = 7) expiratory limb for 2 h. RESULTS: The bubble technique (2.5 and 5.5 mm diameter combined) resulted in a significantly higher PaO2, decreased alveolar protein levels (1.01 vs. 1.43 mg/kg, p < 0.05), a lower lung injury score (3.87 vs. 4.86, p < 0.05), and decreased NOS3 expression (1.99 vs. 3.32, p < 0.05) compared to spontaneous breathing in the control group. BCPAP with a 2.5-mm-diameter and with a 5.5-mm-diameter expiratory limb was not different with regard to gas exchange, alveolar protein levels, and lung injury scores, but there was a trend for lower NOS3 expression in the 5.5-mm group (1.41 vs. 2.56, p = 0.052). CONCLUSIONS: BCPAP decreases lung injury in rats with VILI after stopping mechanical ventilation. Attenuation of lung NOS3 expression may be one of the underlying mechanisms.

Influence of changing the diameter of the bubble generator bottle and expiratory limb on bubble CPAP: an in vitro study.

BACKGROUND: The noisy component of bubble continuous positive airway pressure (CPAP) is thought to contribute to breathing efficiency and lung volume recruitment, mainly because of stochastic resonance. The magnitude and frequency of the superimposed noise are vital to this process. We wanted to evaluate the in vitro effect of changing various parameters of the bubble CPAP circuit regarding the magnitude and frequency of pressure oscillations transmitted to the lung model. METHODS: In a bubble CPAP lung model, we immersed different sizes (3.0∼12.5 mm) of the expiratory limb of the CPAP circuit into different depths under water (2.0∼10.0 cm) and used various diameters (2.9∼9.0 cm) of bubble generator bottles. We also varied the compliance of the model lung. We measured the changes in mean, magnitude, and frequency of pressure oscillations transmitted to the lung model at three different flow rates (namely 4, 8, and 12L/minute). RESULTS: Increasing the size and submergence depth of the expiratory limb of a CPAP circuit and decreasing the diameter of the bubble generator bottle intensified the magnitude but diminished the frequency of noise transmitted to the lung model. Decreasing compliance of the lung model intensified both the magnitude and frequency content of pressure oscillations in the model lung. CONCLUSION: The size and submergence depth of an expiratory limb of a CPAP circuit, the diameter of the bubble generator bottle, and the compliance of the model lung all influence the magnitude and frequency of the transmitted pressure waveform. Therefore, these factors may affect lung volume recruitment and breathing efficiency in bubble CPAP.