Assessment of respiratory mechanics during non-invasive ventilation

Despite monitoring of lung mechanics is highly recommended in patients receiving NIV (22), suitable, accurate methods for its measurements are still lacking. Measuring lung mechanics during NIV is particularly challenging because of the presence of spontaneous breathing, reduced patient collaboration, unavoidable leaks, flow and pressure measurements not available at the patient mouth, and possible upper airways reflex and closures in response to applied manoeuvres. The presence of spontaneous breathing requires the estimation of the respiratory muscles activity by oesophageal manometry, that is not suited for clinical practice. Although methods relying on the relaxation of respiratory muscles only in limited portions of the respiratory phase are applied during invasive assisted ventilation, further validations are needed for their application during NIV. The lower sedation levels, the presence of leaks and possible upper airways reflex in response to performed manoeuvres (as the occlusions) limit the possibilities of obtaining reliable results. Recent technologies and approaches, such as FOT, may fill this gap and improve tailoring NIV settings. Further studies are required to evaluate usefulness, applicability and tolerability of such methods and, possibly, also of other new approaches.