The vulnerable air-tissue interface: Summary of ultrasound related bioeffects on lung and their implications for the use of different imaging modes and applications beyond

Abstract

Introduction: Lung tissue is sensitive to mechanical stress. Animal studies showed induction of pulmonary capillary hemorrhage (PCH) in lung in the diagnostic regime at intensities. Therefore, this work summarizes novel findings regarding the interaction of ultrasound at the alveolar epithelium-gas interface. Method: Literature research related to ultrasound bio-effects on lung was carried out. Furthermore, recent studies reporting thresholds of PCH induction depending on imaging mode and duration will be discussed. Results: Ventilated lung tissue is more vulnerable to mechanical forces than solid tissue. From peak negative pressure below 1.5 MPa the likelihood of PCH induction increases with exposure time. Such PCH is asymptomatic but can falsify the diagnostic outcome. The causes remain still unknown but is not related to cavitation or thermal effects. The extent of PCH in lung is depending of physiological beside acoustic parameters. The extend of PCH is, therefore, not entirely predictable. In addition, observational studies on humans could not confirm the findings as investigated on pathological level on animal models. Conclusion: The vulnerability of lung should become aware in the lung ultrasound community. Current recommendations for output limitations given by AIUM and EFSUMB should be followed and only increased for diagnostics needs.