Inclusion Criteria: patients with a confirmed diagnosis of COVID-19, through tests based on PCR and chest tomography with suggestive findings, spontaneously ventilating, dependent on supplemental oxygen. The study included patients with: (1) age ≥ 18 years, (2) peripheral oxygen saturation less than 92% under supplemental oxygen administration equal to or greater than 6 L / min through a nasal catheter or reservoir mask; (3) no use of NIV or high-flow nasal catheter; (4) continuous monitoring with pulse oximeter; (5) mental status that allowed to follow the instructions; and (6) able to tolerate PP with minimal assistance.  -  Exclusion Criteria:  hemodynamic instability, severe obesity, or who were unable to tolerate and cooperate with the performance of PP