Tissue Doppler Ultrasound During Spontaneous Breathing and Non-invasive Ventilation in the Post-extubation Period.

Early weaning from invasive ventilation, in patients admitted to intensive care, is associated with a marked reduction in ventilator-associated pneumonia, length of stay in intensive care unit and hospital, total duration of mechanical ventilation and decrease in overall mortality. Moreover, in case of need of protected extubation, non-invasive ventilation has allowed to prevent re-intubation and decrease hospital mortality compared to the simple administration of oxygen through a facial mask, in particular when applied immediately after extubation. The diaphragmatic tissue doppler imaging (TDI) is an ultrasonographic technique derived from ultrasound evaluation of the heart's motility. It can be easily used on the diaphragm to calculate the speed of muscles displacement that could be associated with patient's respiratory drive. The aim of the study is the evaluation of the diaphragmatic excursion velocity variations using diaphragmatic tissue doppler, measured in venturi mask and non-invasive ventilation in the post-extubation period, in order to compare the diaphragm stress variations during the two different modes. Method Patients after extubation will be randomly submitted to a spontaneous breathing test in venturi mask and in facemask or helmet NIV. Each trial will last 20 minutes. During the last minute of each trial a tissue doppler diaphragm examination will be performed to assess the speed speed of muscle displacement, acceleration and deceleration. Inclusion criteria: invasive mechanical ventilation \> 24h with consequent extubation. Exclusion criteria: refusal to grant consent, pregnancy, age \< 18 years, haemodynamic instability, difficult management of secretions, required inotropic and / or vasoactive drugs at high doses. During the study, vital parameters will be given.