## 4 Discussion  
The use of respiratory support has been found to be one of the main therapies related to patients diagnosed with COVID-19. We considered the need for invasive ventilatory support as one of the possible outcomes of patients' progress to more severe stages of the disease. This progression is also evident when there is a failure in oxygenation or when there is a worsening in the condition of hypoxemia, even with the use of oxygen support through non-invasive devices [53; 54]. Data related to the use of NIV in different parts of the world indicate that the rate among patients hospitalized with COVID-19 who need this intervention can vary between 2.3 and 33.1% [55; 56; 57; 58], whereas in Brazil, the rate reported was 24.4% among patients admitted to the ICU [59]. The study by [PERSON] et al. [60] demonstrated that using NIV (oxygen mask) helped prevent tracheal intubation in 77% of 39 patients with severe COVID-19 disease admitted to the Cairo University Hospital ICU. This percentage was similar to that reported by [PERSON] et al. [61], where the intubation rate among patients with severe hypoxemia using NIV (oxygen mask or nasal mask) was 13%. In the case of our study, the use of NIV associated with the bubble device contributed to avoiding tracheal intubation in 68.63% of patients admitted to the wards and ICU of three reference hospitals for the treatment of COVID-19 in the state of Bahia, in Brazil. Another point to be evaluated is the presence of comorbidity among subjects affected with COVID-19, because it is considered an essential issue for hospitalization due to the correlation with certain diseases being a risk factor for the susceptibility to progress to a more severe infection condition by SARS-CoV-2 [62; 63]. The study by [PERSON] et al. [64] evaluated the success in using therapy with continuous positive airway pressure (CPAP) provided through a helmet (\"Helmet\") in order to avoid intubation of patients diagnosed with COVID-19 outside the ICU. The presence of concomitant illnesses was one of the risk factors that could lead to failures in using helmets for the provision of CPAP, where these failures implicate the composite result of death or admission to the ICU for intubation [64]. Our study observed that most participants had comorbidities, regardless of whether they needed invasive ventilatory support or not. Thus, even with the presence of a significant predictor for the development of the most severe degree of the disease [65; 66; 67], the use of the bubble device can be a vital alternative to avoid intubation of patients diagnosed with COVID-19 who present comorbidities. Monitoring lung function through blood parameters is one of the main tools in the care of patients diagnosed and hospitalized with COVID-19. Different follow-up studies of patients infected with SARS-CoV-2 have shown that SpO\({}_{2}\) levels <92% have frequently been associated with the need for hospitalization and, as these levels decrease, with the indication of tracheal intubation [68; 69; 70]. In the study by [PERSON] et al. [71], the authors indicate that CPAP use can delay intubation for seven days or 14 days, mainly due to its ability to maintain SpO\({}_{2}\geq\)92%. The work by [PERSON] et al. [72] reports that the use of NIV in patients with acute respiratory failure with a low level of SpO\({}_{2}\) (about 88%) was able to prolong the survival of these individuals, thus avoiding an increase in the number of deaths. Therefore, the use of the device analyzed in this study may be an alternative to maintain the SpO\({}_{2}\) level within ideal values, which may reduce the rate of tracheal intubation among patients affected by COVID-19, which may also be an indication of survival of these individuals. PaO\({}_{2}\) and paCO\({}_{2}\) are essential variables in the follow-up of patients with COVID-19 because pO\({}_{2}\) provides information on the oxygenation status, whereas paCO\({}_{2}\) provides information on the ventilation status (possible conditions of chronic or acute respiratory failure) [73].