Expanding the Role of Critical Care Ultrasound

The overarching aim of this thesis was to contribute to the ongoing refinement and implementation of critical care ultrasound, in particular lung ultrasound. Critical care ultrasound is widely accepted and increasingly used, but effective implementation is hampered by inconsistencies in training, competency definitions, and organizational support. Many skills currently labelled as ‘basic’ are not easily mastered, exposing a gap between expert-defined frameworks and the realities of education and clinical practice. Classification of skills as basic or advanced should consider not only technical ease but also the frequency with which relevant pathologies are encountered. This distinction is well-established in cardiac ultrasound but remains poorly defined in other domains, contributing to lack of standardization in curricula and certification. A global survey confirmed large variability in use and experience: some applications, like lung ultrasound or vascular access, are frequently used, while others, such as advanced cardiac or neurocritical ultrasound, are not fully implemented. Barriers include lack of training, formal certification, and institutional infrastructure, with use often dependent on motivated individuals. Effective implementation requires addressing both facilitators and barriers while communicating the benefits for clinicians and patients. Standardization of and access to training remain limited. Short, targeted training can achieve competency in lung ultrasound image interpretation, even in those without prior experience. Competency can be defined across four domains: indication, acquisition, interpretation, and clinical decision-making. Digital channels can partially address all domains, increasing accessibility and scalability worldwide while focusing in-person training on acquisition techniques. Acquisition training remains a challenge, particularly in resource-limited settings, and future research should evaluate practical approaches to overcome this. A holistic strategy integrating individual training with system-level support is necessary, including institutional initiatives such as dedicated image archiving and supervision systems to enhance training and implementation. Coordinated efforts across departments and professional societies are essential to create an environment where critical care ultrasound use becomes standard, effective, and sustainable. This thesis also explores the evolving role of lung ultrasound in critically ill patients and its potential impact on patient outcomes. Lung ultrasound can guide the setting and titration of positive end-expiratory pressure in mechanically ventilated patients, identifying lung conditions and assessing the response to interventions to support tailored ventilation strategies. Parenchymal changes, particularly in posterior lung regions, frequently occur even in patients without primary lung disease, likely due to immobility and gravitational forces, though the clinical relevance of these changes remains uncertain. Anterior lung ultrasound reliably predicts gas-exchange improvement in prone COVID-19 patients, emphasizing how lung morphology influences the response to ventilation strategies and supporting phenotypic approaches to personalizing mechanical ventilation. Correlations between lung ultrasound and systemic biomarkers in COVID-19 are partial: while some serum biomarkers show weak to moderate correlation with ultrasound scores, many do not, reflecting fundamentally different biological signals. Lung ultrasound primarily captures structural and aeration changes, whereas systemic biomarkers reflect broader inflammatory dysregulation. Local biomarkers from the alveolar space may better correspond to ultrasonographic findings, providing a more precise assessment of pulmonary involvement. Lung ultrasound-guided management may also improve patient-centred outcomes, as demonstrated by the CONFIDENCE study, a randomized trial investigating ultrasound-guided deresuscitation in invasively ventilated patients, bridging diagnostic validation and clinical outcomes. This thesis underscores the importance of continued research into the impact of critical care ultrasound, and in particular lung ultrasound, on patient outcomes. However, it is important to recognize that many interventions with clear and robust evidence still face slow or limited implementation. Therefore, combining scientific research with frameworks for effective implementation is essential for adopting critical care practices that can drive meaningful changes in daily clinical practice.