Transthoracic sonographic assessment of B-line scores during ascent to altitude among healthy trekkers

Hand-Held Ultrasound of the Lung: A Systematic Review

BACKGROUND

The ultrasound examination is a surface technique with an accurate diagnosis of pathological processes adjacent to the pleural line. The purpose of the study was to evaluate the role of hand-held ultrasound devices (visual stethoscopes) in the diagnosis of peripheral lung disease.

METHODS

We conducted a systematic search of literature comparing the diagnostic accuracy of truly hand-held ultrasound devices compared to conventional high-end ultrasound devices, chest X-rays, thoracic CT (computer tomography), or physical examinations to diagnose peripheral lung lesions. ScienceDirect, PubMed, and PubMed Central bibliographic databases were searched within a time limit of 15 years.

RESULTS

The applied search strategy retrieved 439 studies after removing duplicates; 34 were selected for full-text review, and 15 articles met all inclusion criteria and were included in the analysis. When comparing hand-held ultrasound devices to chest X-rays, negative predictive values were above 90%, while positive predictive values tended to be lower (from 35% to 75.8%). Hand-held ultrasound reached a correlation of 0.99 as associated with conventional ultrasound with a Bland-Altman bias close to zero.

CONCLUSIONS

Being accessible, radiation-free, and comparatively easy to decontaminate, hand-held ultrasound devices could represent a reliable tool for evaluating peripheral lung diseases. This method can be successfully employed as an alternative to repeated X-ray examinations for peripheral lung disease monitoring.

Low activation threshold of juxtapulmonary capillary (J) receptors of the lung

Respiratory reflexes arising from stimulating juxtapulmonary capillary (J) receptors by increasing doses of phenyl diguanide (PDG) were examined in 18 spontaneously breathing cats. In 60% an immediate and four-fold increase in breathing frequency (fR) was produced by doses as small as 5.1 ±  μg/kg (range: 3.5-7.5) thus establishing that a significant increase in fR is produced by J receptors by stimulating them with minimal or threshold doses of PDG. In response to similar minimal doses of PDG J receptor afferent activity increased accompanied by acceleration of breathing rate. The response to supra threshold doses was either an apnoea followed by rapid shallow breathing (rsb) or to an apnoea preceded by rsb or only to rsb. Respiratory excursions counted from high-speed run records of intrapleural pressure revealed that the apnoeic response obtained in some cases was a phase of high-frequency breathing and not its suspension. These findings using a chemical stimulus demonstrate that J receptors, with some variability, have a very low threshold for stimulation resulting in notable respiratory acceleration. Thus their afferent output could increase significantly at low intensities of their physiological stimuli such as rise in cardiac output and incipient pulmonary congestion that are generated with mild exercise, to give rise to augmented breathing which is consequently seen.