BackgroundThe impulse oscillometry is increasingly used for assessing the oscillatory mechanics of the respiratory system. The within-breath behaviour of the oscillatory mechanics in chronic obstructive pulmonary disease (COPD) is a well-known physiological feature. The purpose of this study was to develop a new approach for assessing this feature using impulse oscillometry.MethodsThe oscillatory mechanics were assessed by a commercially available impulse oscillometry device. The respiratory system resistance (Rrs) and reactance (Xrs) were measured during tidal breathing in patients with COPD (n=39) and healthy subjects (n=5). Selected data, the Rrs at 5 Hz (R5), Rrs at 20 Hz (R20), Xrs at 5 Hz (X5), and resonant frequency of Xrs (Fres) every 0.2 s, were extracted from the device. These data were divided into eight time fractions during the respiratory cycle to form averaged respiratory phases.ResultsThe time courses of the R5 and X5 were notably dependent on the respiratory cycles in patients with COPD, while there was little such dependency in healthy subjects. Irrespective of respiratory phase, R5 and Fres increased, and X5 fell to a more negative level in patients with COPD in a severity-dependent fashion. The increase in the R5 and negative level in the X5 were more prominent in the middle of the expiratory phase. The severity dependence in the R20 was relatively small compared with that in the R5.ConclusionsThe results of this study suggest that impulse oscillometry can assess the within-breath behaviour of the oscillatory mechanics with high temporal resolution, which may be helpful for evaluating the severity of COPD. Further studies are needed to reveal which biomarkers obtained with this approach would be suitable for evaluating the airway obstruction.

A series of amine-specific reagents based on the benzaldehyde reactive group have been synthesized, characterized, and used to study beef heart cytochrome c oxidase reconstituted in phospholipid bilayers. The series contained three classes of reagents: lipid-soluble phosphodiesters having a single hydrocarbon chain, phospholipid analogues, and a water-soluble benzaldehyde. All reagents were either radiolabeled or spin-labeled or both. The Schiff bases formed by these benzaldehydes with amines were found to be reversible until the addition of the reducing agent sodium cyanoborohydride, whereas attachment of lipid-derived aliphatic aldehydes was not readily reversible in the absence of the reducing agent. The benzaldehyde group provides a convenient method of controlling and delaying permanent attachment to integral membrane proteins until after the reconstitution steps. This ensures that the lipid analogues are located properly to identify amine groups at the lipid-protein interface rather than reacting indiscriminately with amines of the hydrophilic domains of the protein. The benzaldehyde lipid labels attach to cytochrome c oxidase with high efficiency. Typically, 20% of the amount of lipid label present was covalently attached to the protein, and the number of moles of label incorporated per mole of protein ranged from 1 to 6, depending on the molar ratios of label, lipid, and protein. The efficiency of labeling by the water-soluble benzaldehyde was much less than that observed for any of the lipid labels because of dilution effects, but equivalent levels of incorporation were achieved by increasing the label concentration. Electron spin resonance spectra of a nitroxide-containing phospholipid analogue covalently attached to reconstituted cytochrome c oxidase exhibited a large motion-restricted component, which is characteristic of spin-labeled lipids in contact with the hydrophobic surfaces of membrane proteins. The line shape and splittings were similar for covalently attached label and label free to diffuse and contact the protein molecules in the bilayer, providing independent evidence that the coupling occurs at the protein-lipid interface. The distribution of the benzaldehyde reagents attached to the polypeptide components of cytochrome c oxidase was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The labeling pattern observed for the lipid analogues was not affected by the presence of the nitroxide moiety on the acyl chains but was dependent on the molar ratio of labeling reagent to protein.(ABSTRACT TRUNCATED AT 400 WORDS)

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Respiratory impedance measured by the forced oscillation technique (FOT) can be contaminated by artifacts such as coughing, vocalization, swallowing or leaks at the mouthpiece. We present a novel technique to detect these artifacts using multilevel discrete wavelet transforms. FOT was performed with artifacts introduced during separate 60 s recordings at known times in 10 healthy subjects. Brief glottal closures were generated phonetically and confirmed by nasopharyngoscopic imaging of the glottis. Artifacts were detected using Daubechies wavelets by applying a threshold to squared detail coefficients from the wavelet transforms of both pressure and flow signals. Sensitivity and specificity were compared over a range of thresholds for different level squared detail coefficients. Coughs could be identified using 1st level detail (cd1) coefficients of pressure achieving 96% sensitivity and 100% specificity while swallowing could be identified using cd2 thresholds of pressure with 95% sensitivity and 97% specificity. Male vocalizations could be identified using cd1 coefficients with 88% sensitivity and 100% specificity. For leaks at the mouthpiece, cd3 thresholds of flow could identify these events with 98% sensitivity and 99% specificity. Thus, this method provided an accurate, easy, and automated technique for detecting and removing artifacts from measurements of respiratory impedance using FOT.

Corresponding author's email: kurosawa-thk@umin.ac.jpAirway resistance is lung volume dependent. The bronchi are supported by the radial traction of the surrounding lung tissue, and their caliber is increased as the lung expands. The high resistance should be observed at low lung volume such as residual volume (RV) while the low at the high lung voume such as total lung capacity (TLC). In patients with ventilatory uneveness or high airway resistance such as chronic obstructive pulmonary disease (COPD), the dependency could be prominent especially at the lower lung volume near RV. To assess these physiological and pathophysiological properties, a new method was designed. Instead of airway resistance, respiratory system resistance (Rrs) was measured with forced oscillation technique using a commertially available machine (MostGraph-01, Chest MI co. ltd., Tokyo, Japan). Impulse oscillatory signals at the intervals of 0.25 second were applied to obtain Rrs properties against oscillatory frequency ranged from 5 to 35 Hz. Because the Rrs curves were possible to be obtaied in every 0.25 second, those were serially lined up along time axis, resulted in 3 dimensional imaging pattern of Rrs. Using this machine, simple quasi-static measurements were performed in healthy volunteers. The subjects were advised to expirate slowly at the approximate flow rate of 0.2L/min from TLC to RV. All the subjects showed the minimum Rrs at TLC and the maximum at RV, which clearly showed lung volume dependent Rrs changes. The dependency was mild in the healthy younger subjects compared to the older, that possibly reflected less inhomogenous ventilatory mechanics in the younger subjects. Because this was very simple, easy, and non-invasive way, the future application can be widely expected as a very useful physiological tool in such a situation to screen the early COPD or very mild asthma. Lung volume dependent changes of Rrs propertiesThis abstract is funded by: None Am J Respir Crit Care Med