Colloidal gas aphron (CGA) based foam cement system
PETROLEUM EXPLORATION AND DEVELOPMENT
Authors: Velayati, Arian; Roostaei, Morteza; Rasoolimanesh, Rasool; Soleymani, Mohammad; Fattahpour, Vahidoddin
Abstract
To solve the problems such as high denstiy, foam instability, low compressive strength, high porosity and poor durability associated with conventional foam cements, a novel colloidal gas aphron (CGA) based foam cement system was investigated and tested for properties. CGA is used in a base slurry as the foam component and the recipe was optimized with hollow sphere and micro-silica in terms of particle size distribution (PSD). Porosity, permeability, strength, brittleness, elasticity, free water content, foam stability and density tests on the CGA based foam cement system were carried out to evaluate the performance of the system. According to the experiment results, at the foam proportion of 10%, the cement density was reduced to 1 040 kg/m(3), and stable microfoam net structure not significantly affected by high temperature and high pressure was formed in the cement system. The optimal CGA based foam cement has a free water content of 0%, porosity of 24%, permeability of 0.7x10(-3) mu m(2), low elasticity modulus, high Poisson's ratio, and reasonable compressive strength, and is more elastic and flexible with capability to tolerate regional stresses.
Prediction of extubation success using the diaphragmatic electromyograph results in ventilated neonates
JOURNAL OF PERINATAL MEDICINE
Authors: Hunt, Katie A.; Hunt, Ian; Ali, Kamal; Dassios, Theodore; Greenough, Anne
Abstract
Objectives: Extubation failure is common in infants and associated with complications. Methods: A prospective study was undertaken of preterm and term born infants. Diaphragm electromyogram (EMG) was measured transcutaneously for 15-60 min prior to extubation. The EMG results were related to tidal volume (Tve) to calculate the neuroventilatory efficiency (NVE). Receiver operating characteristic curves (ROC) were constructed and areas under the ROCs (AUROC) calculated. Results: Seventy-two infants, median gestational age 28 (range 23-42) weeks were included; 15 (21%) failed extubation. Infants successfully extubated were more mature at birth (p=0.001), of greater corrected gestational age (CGA) at extubation (p<0.001) and heavier birth weight (p=0.005) than those who failed extubation. The amplitude and area under the curve of the diaphragm EMG were not significantly different between those who were and were not successfully extubated. Those successfully extubated required a significantly lower inspired oxygen and had higher expiratory tidal volumes (Tve) and NVE. The CGA and Tve had AUROCs of 0.83. A CGA of >29.6 weeks had the highest combined sensitivity (86%) and specificity (80%) in predicting extubation success. Conclusions: Although NVE differed significantly between those who did and did not successfully extubate, CGA was the best predictor of extubation success.