The study of the amplitude of respiratory muscle mechanomyographic (MMG) signals could be useful in clinical practice as an alternative non-invasive technique to assess respiratory muscle strength. ...The MMG signal is stochastic in nature, and its amplitude is usually estimated by means of the average rectified value (ARV) or the root mean square (RMS) of the signal. Both parameters can be used to estimate MMG activity, as they correlate well with muscle force. These estimations are, however, greatly affected by the presence of structured impulsive noise that overlaps in frequency with the MMG signal. In this paper, we present a method for assessing muscle activity based on the Lempel–Ziv algorithm: the Multistate Lempel–Ziv (MLZ) index. The behaviour of the MLZ index was tested with synthesised signals, with various amplitude distributions and degrees of complexity, and with recorded diaphragm MMG signals. We found that this index, like the ARV and RMS parameters, is positively correlated with changes in amplitude of the diaphragm MMG components, but is less affected by components that have non-random behaviour (like structured impulsive noise). Therefore, the MLZ index could provide more information to assess the MMG–force relationship.
Peer Reviewed
Bacillus Calmette-Guerin (BCG) is an attenuated bacterial vaccine used to protect against
(
) in regions where infections are highly prevalent. BCG is currently delivered by the intradermal route, ...but alternative routes of administration are of great interest, including intrapulmonary delivery to more closely mimic respiratory
infection. In this study, mice subjected to pulmonary delivery of green fluorescent protein–tagged strains of virulent (
) and attenuated (BCG) mycobacteria were studied to better characterize infected lung cell subsets. Profound differences in dissemination patterns were detected between
and BCG, with a strong tendency of
to disseminate from alveolar macrophages (AMs) to other myeloid subsets, mainly neutrophils and recruited macrophages. BCG mostly remained in AMs, which promoted their activation. These preactivated macrophages were highly efficient in containing
bacilli upon challenge and disrupting early bacterial dissemination, which suggests a potential mechanism of protection associated with pulmonary BCG vaccination. Respiratory BCG also protected mice against a lethal
challenge, suggesting that BCG-induced innate activation could confer heterologous protection against respiratory pathogens different from
. BCG drove long-term activation of AMs, even after vaccine clearance, and these AMs reacted efficiently upon subsequent challenge. These results suggest the generation of a trained innate memory-like response in AMs induced by pulmonary BCG vaccination.
