High Frequency Percussive Ventilation in COVID-19 Patients Receiving Oxygen Through High-flow Nasal Cannula

High frequency percussive ventilation (HFPV) is used in patients with underlying pulmonary atelectasis, excessive airway secretions, and respiratory failure. HFPV is a non-continuous form of high-frequency ventilation delivered by a pneumatic device that provides small bursts of sub-physiological tidal breaths at a frequency of 60-600 cycles/minute superimposed on a patient's breathing cycle. The high-frequency breaths create shear forces causing dislodgement of the airway secretions. Furthermore, the HFPV breath cycle has an asymmetrical flow pattern characterized by larger expiratory flow rates, which may propel the airway secretions towards the central airway. In addition, the applied positive pressure recruits the lung units, resulting in a more homogeneous distribution of ventilation and improved gas exchange. In acute care and critical care settings, HFPV intervention is used in a range of patients, from spontaneously breathing patients to those receiving invasive mechanical ventilation where HFPV breaths can be superimposed on a patient's breathing cycle or superimposed on breaths delivered by a mechanical ventilator. The most common indications for HFPV use are reported as removal of excessive bronchial secretions, improving gas exchange, and recruitment of atelectatic lung segments. This study aims to assess the lung physiological response to HFPV in terms of aeration and ventilation distribution in patients with acute respiratory failure due to SARS-CoV-2 infection and requiring high flow oxygen therapy through nasal cannula