Detecting unilateral phrenic paralysis by acoustic respiratory analysis

The consequences of phrenic nerve paralysis vary from a considerable reduction in respiratory function to an apparently normal state. Acoustic analysis of lung sound intensity (LSI) could be an indirect non-invasive measurement of respiratory muscle function, comparing activity on the two sides of the thoracic cage. Lung sounds and airflow were recorded in ten males with unilateral phrenic paralysis and ten healthy subjects (5 men/5 women), during progressive increasing airflow maneuvers. Subjects were in sitting position and two acoustic sensors were placed on their back, on the left and right sides. LSI was determined from 1.2 to 2.4 L/s between 70 and 2000 Hz. LSI was significantly greater on the normal (19.3±4.0 dB) than the affected (5.7±3.5 dB) side in all patients (p = 0.0002), differences ranging from 9.9 to 21.3 dB (13.5±3.5 dB). In the healthy subjects, the LSI was similar on both left (15.1±6.3 dB) and right (17.4±5.7 dB) sides (p = 0.2730), differences ranging from 0.4 to 4.6 dB (2.3±1.6 dB). There was a positive linear relationship between the LSI and the airflow, with clear differences between the slope of patients (about 5 dB/L/s) and healthy subjects (about 10 dB/L/s). Furthermore, the LSI from the affected side of patients was close to the background noise level, at low airflows. As the airflow increases, the LSI from the affected side did also increase, but never reached the levels seen in healthy subjects. Moreover, the difference in LSI between healthy and paralyzed sides was higher in patients with lower FEV1 (%). The acoustic analysis of LSI is a relevant non-invasive technique to assess respiratory function. This method could reinforce the reliability of the diagnosis of unilateral phrenic paralysis, as well as the monitoring of these patients.Peer ReviewedPostprint (published version

A simplified approach to determine the activation energies of uncatalyzed and catalyzed combustion of soot

Catalyst screening tests for soot oxidation is usually performed in semi-batch mode under a temperature ramp-up. Due to the complexity of soot combustion process, generally the activation energy data are not reported. Rather, the catalyst performances are compared on the basis of temperatures required to achieve a certain conversion. In this study, the Redhead method [Vacuum, 12 (1963) 203] of activation energy determination for temperature programmed desorption processes was adopted for soot combustion processes. The method was applied to extract loose contact activation energies of catalytic oxidation of soot over pure and 1 wt.% Pt/oxide. The oxides investigated in this study are SiO2, gamma-Al2O3, TiO2, ZrO2, CeO2 and La2O3. The dry air activity of pure oxides was screened by thermo-gravimetric analysis (TGA) while the activity tests on Pt/oxide catalysts were performed in a home built temperature programmed oxidation (TPO) set-up. The activation energies for soot oxidation determined for these catalysts by a differential method, by an integral method and by Redhead method indicated that the Redhead method provides reasonable estimates of activation energies from peak temperature data of the temperature programmed experiments such as TGA or TPO. Comparison of the activation energies determined as such revealed little difference in the soot combustion activities of the oxides in the presence of Pt in dry air atmosphere

A novel catalyst for diesel soot oxidation

In this study, cobalt and lead based mixed oxide catalysts were tested for their soot oxidation ability. In addition to a mixed oxide formerly marketed as ceramic paint, a home made set was also prepared by incipient wetness impregnation of a cobalt oxide powder with a lead acetate solution and subsequent calcination. The materials investigated in this study were shown to decrease the peak combustion temperature of home made soot from 500 to 385 degrees C in air. Soot oxidation tests under inert (N-2) atmospheres revealed that the oxidation took place by using the lattice oxygen of the catalyst. Reaction temperature could be further decreased when these mixed oxide catalysts were impregnated with platinum. An optimum platinum loading was determined as 0.5 wt% based on the peak combustion temperature of the soot. The role of Pt was to assist the oxygen transfer from the gas phase to the lattice. It was observed that NO2 is a better oxidizing agent as compared to air whereas NO had hardly any activity against soot oxidation reaction. When the mixed oxide catalyst was impregnated with platinum, the peak combustion temperature was measured as 310 degrees C in the presence of NO, and air. The catalyst's unique performance was in terms of the rate of soot oxidation. Under the experimental conditions studied here, the soot oxidation was so facile that the oxygen in the gas phase was completely depleted. This stream of oxygen depleted and CO enriched gas phase can be used to reduce NO, in the presence of a downstream or a co-catalyst. (0 2005 Elsevier B.V. All rights reserved