The study aims to evaluates if the treatment with HFCWO Via The Vest® Airway Clearance System, in addition to standard care in critically ill patients admitted in the Respiratory Intensive Care Unit for acute respiratory failure or acute on chronic respiratory failure and unable to manage secretions, could primarily prevent the need for bronchoscopy, and secondarily shorten duration of non invasive respiratory therapy, shorten length of stay and reduce mortality.

Inclusion Criteria:

• Diagnosis of acute respiratory failure (ARF) or acute on chronic respiratory failure (including patients having home oxygen therapy, HFNC, NIV) both hypercapnic ARF (PaCO2 > 45 mmHg; PaO2/FiO2 <300) or hypoxaemic (PaCO2 <45 mmHg; PaO2/FiO2 <300);
• Informed consent from patient or legal tutor;
• Accessory respiratory muscles use;
• Respiratory rate above 25 apm;
• Use of non invasive respiratory therapy (NIRT) NIV+/-HFNC or HFNC alone since RICU admission
• Kelly neurological index ≤ 3
• Excessive airway mucus secretion (clinical evaluation asking the patient to cough) and inability to efficiently remove secretions (evaluated with the Cough Peak Flow (CPF) measurement. A CPF under 270 Lpm is highly suggestive of inadequate cough which prevent the patient from adequately manage and remove airway secretions.
• Cough score < 3: in the case of inability to perform CPF measurement due to poor patient collaboration, cough adequacy will be evaluated by a respiratory physiotherapy with a semiquantitative score ("Cough score") based on the measurement of sputum volume produced after coughing three times (1 point: less than 2 mL, 2 points: 2-6 mL, 3 points: more than 6 mL).

Exclusion Criteria:

• Patient unwillingness or incapability to provide informed consent
• Need for subcontinuous NIV(more than 20 hours per day)
• Kelly neurological index >3
• Cardiac arrest
• Severe haemodynamic instability (more than two amines required);
• acute coronary syndrome;
• Psychomotor agitation unresponsive to analgo-sedation (RASS> 1)
• Contraindications to HFCWO use: acute pneumothorax (even if chest drainage is not required ); severe chest wall deformities (pectus excavatum, pectus carinatum or pectus arcuatum); severe obesity (BMI >40 kg/m2); pregnancy; thoracic or abdominal surgery in the six previous weeks
• Nasal swab positivity to Sars-CoV-2
• Need for endotracheal intubation or urgent bronchoscopy for excessive airway mucus