Non-invasive Respiratory Monitoring During SBT

To be eligible, patients had to meet all of the following criteria: 1. Age ≥ 18 years. 2. The presence of ≥ 1 among the following factors to define the high-risk for re-intubation: age older than 65 years; heart failure as the primary indication for mechanical ventilation; moderate to severe chronic obstructive pulmonary disease (COPD); an Acute Physiology and Chronic Health Evaluation II (APACHE II) score higher than 12 on extubation day; body mass index of more than 30; inadequate cough reflex or suctioning \>2 times within 8 hours before extubation; prolonged use of invasive ventilation (≥ 7 days from the first SBT); more than 2 comorbidities categorized based on the Charlson Comorbidity Index. 3. Deemed ready to be weaned from the ventilator, based on the following criteria: (a) invasive mechanical ventilation for more than 48 hours, including at least 12 hours of pressure support ventilation with PEEP ≤ 8 cmH2O and pressure support ≤ 10 cmH2O; (b) Improvement of the condition leading to intubation; (c) patient making inspiratory effort; (d) adequate gas exchange, as indicated by a ratio of partial pressure of arterial oxygen (PaO2) to inspiratory fraction of oxygen (FiO2) ≥ 150 with FiO2 ≤ 40% and arterial pH within normal range (7.30 - 7.50); (e) Glasgow Coma Score higher than 13; (f) a core temperature below 38°C; (g) Richmond agitation and sedation scale between -1 and +1. Eligibility required readiness for scheduled extubation after successfully completing a 30-minute SBT in the pressure-support mode (7 cmH₂O) SBT success was defined by the following criteria \[19\]: (a) adequate gas exchange, as indicated by a ratio of partial pressure of arterial oxygen (PaO2) to inspiratory fraction of oxygen (FiO2) ≥ 150 with FiO2 ≤ 40% and arterial pH within the normal range (7.30 - 7.50); (b) respiratory rate \< 35/min; (c) spontaneous tidal volume higher than 5 ml of predicted body weight (PBW); (d) a ratio of respiratory rate to tidal volume (i.e. the rapid shallow breathing index, RSBI) \< 105/min per liter; (e) systolic blood pressure between 90 and 160 mmHg and heart rate \< 140/min, with or without low doses of vasopressors (\< 0.5 mcg/kg/min). Exclusion criteria were tracheostomy, patients undergoing withdrawal of life-sustaining treatments, known neuromuscular diseases.