Ultrasound in obstructive lung diseases: the effect of airway obstruction on diaphragm kinetics. A short pictorial essay

The ultrasound study of the chest is showing a continuous development. This technique could be helpful in managing several chest diseases, but it is limited to the acoustic windows provided by intercostal spaces and by the inability to study healthy lung parenchyma and all intra-parenchymal diseases such as chronic obstructive lung disease (COPD), because the interaction between ventilated lung and ultrasound generates only artifacts. Currently, there are few applications of ultrasound that are useful in COPD, with recent studies providing some innovation potentially useful in clinical practice. The similarity of the trend between the time/volume curve of spirometry and the M-mode representation of diaphragm during forced breath allowed to identify the M-mode Index of Obstruction (MIO), an index obtained from the ratio between forced diaphragmatic excursion in the first second (FEDE1, cm) and the maximal expiratory diaphragmatic excursion (EDEMax, cm). MIO has shown a linear correlation with the ratio between forced expiratory volume in the first second (FEV1) and vital capacity (VC), used in spirometry to identify airways obstruction. The value of MIO seems to be lower in patients affected by airways obstruction as showed by a recent study. The technique is easy to learn and fast to perform and the analysis could be provided with any ultrasound machine equipped with M-mode. In conclusion, these findings, if confirmed by other studies, could suggest a new add-on screening tool for obstructive lung diseases, in particular COPD, that could be performed during a routine abdominal ultrasound exam.