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Comparative Efficacy of Aerosolized Particle Filtration by Non-Invasive Ventilation Modalities: Simulation of SARS-CoV-19 Transmission

Introduction: Patients with COVID-19 with severe respiratory disease may require non-invasive ventilation (NIV) devices, and selection should consider the greatest ability to reduce coronavirus-sized particles aerosolization. The objective of this study was to characterize the aerosolization of coronavirus-sized particles using different oxygen delivery systems. Methods: To simulate real-life clinical scenarios, a surrogate head with adult morphology within an airtight containment box reproduced Nasalonly (N) and Nasal/Oral (N/O) Normal Breathing as well as Coughing for six respiratory support devices: SuperNO2VA with and without HEPA filter; High-Flow Nasal Cannula (HFNC); Non-Rebreather; NV-NIV Mask, both single-and dual-limb; and no device. Results: Fit Factor between devices significantly differed (P<0.0001) but not between Normal Breathing and Coughing (P=0.15). SuperNO2VA with HEPA (N) and NV-NIV Mask with single-limb circuit each had significantly larger FF compared to all other devices (P<0.005). SuperNO2VA without HEPA (N), Non-Rebreather, and NV-NIV Mask with dual-limb circuit had no significant differences between FFs (P=1.0). SuperNO2VA with HEPA (N/O), SuperNO2VA without HEPA (N/O), and HFNC had significantly lower FF than other devices (P<0.05). Conclusion: This model demonstrated in NIV settings the most important factor for minimizing particle spread is a strong mask seal. The SuperNO2VA device offered the strongest mask seal among those tested but, remains ineffective at trapping particles during oral breathing or coughing. Use of SuperNO2VA with a surgical mask can be safely used on patients with COVID-19 with no further risk of transmission. Introduction Coronavirus disease 2019 (COVID-19) is a viral respiratory tract infection caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The treatment and management of patients with COVID-19 is not well understood and is continuously evolving [1,2]. While most symptomatic cases are mild and selflimited, upwards of 14% of patients experience severe disease requiring hospitalization and 5% require critical care admission [3]. Of the critically ill, 71-79% require mechanical ventilation and mortality is between 50-61.5% [4-6]. For mechanically ventilated patients, mortality increases to 81% [4]. The pathophysiology of severe respiratory disease in COVID-19 has been likened to a form of Acute Respiratory Distress Syndrome (ARDS) [1]. The mainstay treatment of ARDS revolves around increased inspired oxygen concentration (FiO2), high positive end-expiratory pressure (PEEP), and low-tidal volume ventilation [7]. With the high mortality rates among ventilated patients, it is important to look to non-invasive respiratory support devices capable of improving FiO2 and PEEP, particularly in patients with mild-to-moderate disease. Three non-invasive ventilation (NIV) techniques may be useful for COVID-19: high-flow nasal Am J Biomed Sci & Res American Journal of Biomedical Science & Research Copy@ Steven Harry Cataldo 506 oxygenation (HFNO); NIV via continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP); and high FiO2/ PEEP nasal positive airway pressure (nPAP) via the SuperNO2VATM device (Vyaire Medical, Mettawa IL). HFNO and NIV/CPAP have been used for many years to treat patients with advanced lung disease and hypoxemic respiratory failure. They have demonstrated efficacy in pulmonary edema, acute exacerbations of Chronic Obstructive Pulmonary Disease, and ARDS, as well as decreased rates of extubating failure in patients weaning from mechanical ventilation [8-11]. Increasing FiO2 and PEEP in patients with COVID-19 may slow disease progression and may prevent intubation and mechanical ventilation. The novel SuperNO2VATM device provides high FiO2 and PEEP using wall oxygen through a non-vented, sealed nasal mask [12]. This device demonstrated efficacy in providing positive pressure and decreasing hypoxemia in high-risk patients, making its use a potential first step prior to mechanical ventilation in patients with COVID-19 [13-15]. High-flow and positive pressure devices have thus far been underutilized in the clinical fight against COVID-19 due to fears of aerosolizing the otherwise droplet-contained SARS-CoV-2, thus increasing the risk of transmission [16,17]. These actions are based primarily on previous data analyzing the exhaled air dispersion distances of simulated and non-simulated clinical scenarios using different types of oxygenation devices [18-21]. These studies did not use a size-matched particle generator to mimic coronavirus aerosolization and did not include a surgical mask placed over the “patient’s” mouth and nose, as is becoming common procedure during oxygen therapies in SARS-CoV-2-positive patients [22]. This study is the first to characterize the aerosolization of coronavirus-sized particles using different types of oxygen delivery systems with and without surgical masks, using a simulation of real-life COVID-19 clinical scenarios.

The pathophysiology of severe respiratory disease in  has been likened to a form of Acute Respiratory Distress Syndrome (ARDS) [1]. The mainstay treatment of ARDS revolves around increased inspired oxygen concentration (FiO 2 ), high positive end-expiratory pressure (PEEP), and low-tidal volume ventilation [7]. With the high mortality rates among ventilated patients, it is oxygenation (HFNO); NIV via continuous positive airway pressure (CPAP) or bi-level positive airway pressure (BiPAP); and high FiO 2 / PEEP nasal positive airway pressure (nPAP) via the SuperNO 2 VA™ device (Vyaire Medical, Mettawa IL).
HFNO and NIV/CPAP have been used for many years to treat patients with advanced lung disease and hypoxemic respiratory failure. They have demonstrated efficacy in pulmonary edema, acute exacerbations of Chronic Obstructive Pulmonary Disease, and ARDS, as well as decreased rates of extubating failure in patients weaning from mechanical ventilation [8][9][10][11]. Increasing FiO 2 and PEEP in patients with COVID-19 may slow disease progression and may prevent intubation and mechanical ventilation. The novel SuperNO 2 VA™ device provides high FiO 2 and PEEP using wall oxygen through a non-vented, sealed nasal mask [12]. This device demonstrated efficacy in providing positive pressure and decreasing hypoxemia in high-risk patients, making its use a potential first step prior to mechanical ventilation in patients with COVID-19 [13][14][15].
High-flow and positive pressure devices have thus far been underutilized in the clinical fight against COVID-19 due to fears of aerosolizing the otherwise droplet-contained SARS-CoV-2, thus increasing the risk of transmission [16,17]. These actions are based primarily on previous data analyzing the exhaled air dispersion distances of simulated and non-simulated clinical scenarios using different types of oxygenation devices [18][19][20][21]. These studies did not use a size-matched particle generator to mimic coronavirus aerosolization and did not include a surgical mask placed over the "patient's" mouth and nose, as is becoming common procedure during oxygen therapies in SARS-CoV-2-positive patients [22].
This study is the first to characterize the aerosolization of coronavirus-sized particles using different types of oxygen delivery systems with and without surgical masks, using a simulation of real-life COVID-19 clinical scenarios.  Five difference device setups were tested in defined conditions and breathing scenarios ( Table 1). The SuperNO 2 VA was tested both with and without a HEPA filter (AirLife TM 303HEPA) and at oxygen "Low" and "High" flow rates of 8

Results
Mean FF, representing the estimated efficacy of each setup to contain particles from escaping into the environment are reported for all devices across breathing scenarios and flow settings in Table   2. When no device was attached to the surrogate head, the Coughing test had the lowest FF (4.0), followed by N/O (4.6) and N (6.6) breathing, indicating the poorest control of particle aerosolization.
The NV-NIV Mask had the highest FF rates for Normal Breathing N/O (13.2 single-limb and 7.5 dual-limb) and Coughing (16.0 singlelimb and 9.1 dual-limb), the best particle aerosolization control.     providers must be armed with all available knowledge to use these therapies safely, including the risk for viral particle spread.

Discussion
In this experimental model, compared to no device at all, a standard non-rebreather mask seems to offer some protection from particle spread. This finding is not surprising as a nonrebreather mask forms a barrier seal on the patient's face and likely limits the spread of respiratory droplets, thereby reducing aerosolization. However, a non-rebreather mask when treating patients with COVID-19 often is insufficient to meet the patient's oxygen requirements, even in mild-to-moderate disease states [4].
Use of HFNO and SuperNO 2 VA for N/O breathing resulted in the greatest concentration of viral-like particles detected, represented as the lowest FF, and was worse with increased oxygen flow rates. In fact, greater particle detection was seen even compared with no device at all. For HFNO, this is likely attributed to the high oxygen flows and the non-sealed characteristics of the nasal cannula interface, consistent with previously reported NIV aerosolization data [18][19][20]. In the SuperNO 2 VA, one explanation is that nasopharyngeal positive pressure transmitted to the patient's oropharynx may cause pressurized release during exhalation, This experimental model demonstrates that in the settings in which aerosolized viral spread is a concern and NIV is used, the most important factor for minimizing particle spread is a strong mask seal. The SuperNO 2 VA device offers the strongest mask seal among those respiratory support set ups tested here but remains ineffective at trapping particles during oral breathing or coughing.
Interestingly, no statistical difference in FF occurred between normal breathing compared to SuperNO 2 VA when a surgical mask was used, suggesting it can be safely used on patients with COVID-19 with no further risk of transmission.