Non-invasive Respiratory Support for Patients with Novel Coronavirus Pneumonia: Clinical Efficacy and Reduction in Risk of Infection Transmission
The emergence of the novel coronavirus disease (COVID-19) in Wuhan, China, in December 2019, has posed significant challenges to global healthcare systems. A substantial proportion of patients, approximately 15% to 30%, develop acute respiratory distress syndrome (ARDS) within a short period, necessitating urgent respiratory support. Non-invasive respiratory support systems, including conventional oxygen therapies, non-invasive positive pressure ventilation (NPPV), and high-flow nasal cannula (HFNC), have been widely employed to alleviate respiratory symptoms and improve patient outcomes. However, the efficacy and safety of these methods remain unclear, and their potential to increase aerosol dispersion and disease transmission is particularly controversial. This article comprehensively discusses the clinical efficacy of NPPV and HFNC in treating COVID-19 pneumonia, along with measures to reduce the risk of infection transmission.
Clinical Efficacy of Non-invasive Positive Pressure Ventilation (NPPV)
NPPV has been a cornerstone in managing acute respiratory failure, particularly in reducing the need for tracheal intubation. This reduction theoretically lowers the risk of infection transmission to healthcare workers during intubation and artificial airway management. A retrospective epidemiological study of 99 COVID-19 pneumonia patients in China revealed that NPPV is the most commonly used mechanical ventilation method for acute respiratory failure, with usage rates of 13% for non-invasive and 4% for invasive mechanical ventilation. However, the efficacy of these methods requires further investigation.
Previous studies on NPPV for severe acute respiratory syndrome (SARS) have shown mixed results. Most of these studies are small-sample, single-center retrospective analyses from China, indicating an NPPV failure rate of approximately 20% to 40%. For instance, a study by Cheung et al. involving 20 Hong Kong SARS patients with acute respiratory failure demonstrated that NPPV could prevent tracheal intubation in 70% of cases and significantly reduce ICU stay duration. Similarly, limited data on NPPV for Middle East respiratory syndrome (MERS) suggest a higher failure rate of 60% to 70%, attributed to more severe lung and extra-pulmonary injuries in MERS patients.
Current evidence and clinical guidelines do not recommend NPPV as a first-line treatment for acute hypoxic respiratory failure and pandemic viral illnesses. Therefore, NPPV should not be the primary treatment for COVID-19 pneumonia patients with respiratory failure. However, for strictly selected early-stage patients with mild-to-moderate hypoxic respiratory failure (PaO2/FiO2 >200 mmHg), particularly in settings with limited invasive ventilators, NPPV can be attempted for short periods (1–2 hours). Immediate intubation is recommended if no improvement is observed. Early identification of high-risk factors for NPPV failure, such as shock, metabolic acidosis, multiple organ failure, and severe hypoxemia, can enhance the safety of NPPV treatment. NPPV should be avoided in patients with hemodynamic instability, multiple organ failure, disorders of consciousness, or mucus drainage disorders.
NPPV Aerosol Dispersion and Disease Transmission Risks
NPPV use can lead to aerosol dispersion, increasing the risk of disease transmission. In vitro simulation experiments have shown that NPPV can disperse exhaled aerosols within 1 meter of patients, with the dispersion range expanding with increased air leakage and inspiratory pressure. Consequently, the World Health Organization considers NPPV a significant source of aerosol transmission in patient wards. However, clinical studies on NPPV for SARS did not conclusively demonstrate an increased risk of infection transmission to healthcare workers. In fact, NPPV masks may reduce aerosol exhalation during coughing and talking. Recent studies suggest that NPPV is a low-risk airborne route with good interface fitting. Therefore, the risk of aerosol diffusion and disease transmission during NPPV remains unclear, necessitating strict control of the medical environment and vigilant monitoring of infection risks to healthcare personnel.
Clinical Efficacy of High-Flow Nasal Cannula (HFNC)
HFNC is a relatively new form of non-invasive respiratory support that can deliver a maximum gas flow of 60 to 80 L/min and an FiO2 of 0.21 to 1.0. There is limited clinical data on HFNC for SARS, MERS, or COVID-19, and its efficacy requires further investigation. However, for patients with non-infectious mild-to-moderate hypoxic respiratory failure, HFNC has been shown to reduce the rate of tracheal intubation and mortality compared to conventional oxygen therapy. Therefore, HFNC can be considered for COVID-19 pneumonia patients when hypoxemia cannot be managed with conventional oxygen therapy devices, NPPV is not tolerated, or in specific situations such as mild-to-moderate hypoxemia (100 mmHg ≤ PaO2/FiO2 30 breaths/min, SpO2 <88% to 90%, paradoxical breathing, pH 45 mmHg persist.
Nosocomial Infection Prevention and Control During HFNC Therapy
To mitigate the risk of nosocomial infection during HFNC therapy, several measures are recommended. First, disposable, single-use high-flow nasal plugs and tubing should be used. Patients should be instructed to breathe with their mouths closed as much as possible while wearing surgical masks or oxygen masks. Condensation in the circuit should be promptly cleaned to avoid aerosol production caused by high-flow gas and condensed water entering the nasal cavity, which can stimulate coughing. Recent evidence indicates that the dispersion distance of exhaled gases during HFNC treatment is limited, and the risk of airborne transmission is low. However, loose connections between HFNC and nasal plugs can significantly increase the dispersion distance of exhaled gases (from 172 to 620 mm). Therefore, correct positioning and wearing of high-flow nasal plugs are crucial.
Conclusion
Non-invasive respiratory support systems, including NPPV and HFNC, play a vital role in managing COVID-19 pneumonia patients with acute respiratory failure. While NPPV can reduce the need for tracheal intubation and potentially lower infection transmission risks, its efficacy and safety require further investigation, particularly concerning aerosol dispersion. HFNC offers a promising alternative for patients with mild-to-moderate hypoxemia, but its use must be carefully monitored to ensure patient safety and minimize infection risks. Strict infection control measures, including the use of personal protective equipment, negative-pressure rooms, and proper equipment maintenance, are essential to reduce nosocomial infections during non-invasive respiratory support. Continued research and adherence to clinical guidelines will be critical in optimizing the use of these therapies in the ongoing COVID-19 pandemic.
doi.org/10.1097/CM9.0000000000000761
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