Noninvasive pulmonary monitoring in critical care: role, advances, limitations

Acute respiratory failure is a frequent cause of ICU admission and carries a high mortality rate. Multimodal respiratory monitoring integrating imaging techniques, respiratory mechanics and functional data provides a more comprehensive physiologically grounded assessment of the respiratory status. This review describes recent advances in noninvasive bedside monitoring options that when combined could enable a safer, more personalized management of patients on invasive mechanical ventilation.

Quantitative lung ultrasound can be reliably used at the bedside to quantify and monitor the lung density and guide the ventilatory strategy; a recent expert consensus has defined its technical and clinical applications. While providing information on lung morphology, it needs to be combined with other bedside tools such as tidal hysteresis in pressure-volume loops and/or EIT to individualize ventilatory settings. Muscle ultrasound assessment is used to monitor active patients, mainly to quantify patient effort and predict weaning outcomes. Expired CO 2 kinetics evaluates lung efficiency, with important prognostic implications, and new promising developments may allow to continuously estimate static lung volume and cardiac output.

Multiple noninvasive bedside tools are available for a multimodal assessment of the respiratory system; while each evaluates the patient from a different perspective, their effectiveness is maximized when they are integrated and combined for daily monitoring and clinical assessment.