Is CPAP Therapy the Best for COVID Patients: What do We Know?
The past two years have brought unseen challenges for all of us, but especially for medical workers all around the world. The novel coronavirus (SARS-CoV-2) has come out of nowhere and placed a significant strain on the healthcare system. No one has known how to deal with the disease caused by a new virus and its related complications. Intensive care units (ICU) were under hard pressure at the very beginning of the pandemic and became crowded immediately. This led to reconsidering treatment strategies for COVID-19 patients and special attention to respiratory support.
Pulmonary involvement is seen in a vast majority of persons affected by the SARS-CoV-2 virus. It varies from mild pneumonia to severe respiratory failure or acute respiratory distress syndrome (ARDS). Hospital mortality of patients with acute hypoxemic respiratory failure reaches 30% and the number of these patients increased dramatically during the COVID-19 pandemic.
At the beginning of the COVID-19 era, most of these patients have been transferred to ICU and ventilated invasively. Consequently, intensive care units have faced a shortage of equipment as well as human resources thus clinicians and scientists started to search for new, less invasive, and more convenient treatment strategies.
At the beginning of the pandemic non-invasive ventilation (NIV) methods have been poorly described and employed in the management of ARDS because of many controversies. At first, NIV strategies were thought to be associated with a higher risk of virus transmission and for safety reasons were avoided. However, with a separation of high-risk areas and personal protective equipment, the nosocomial spread of coronavirus was reduced. The other NIV-related concern is the generation of large tidal volume which may worsen lung damage and increase the risk for patients to develop self-inflicted lung injury. However, with the appropriate settings, this risk could be minimized, and it should not be a reason to avoid NIV.
Over time number of patients affected by novel coronavirus was steadily growing and a new non-invasive approach towards hypoxemic COVID-19 patients has become a core treatment.
To date, conventional oxygen therapy, high flow nasal oxygenation (HFNO), and continuous positive airway pressure (CPAP) oxygenation are more and more used in COVID-19 patients.
The main goal of these NIV methods is to maintain adequate oxygenation and reduce the need for endotracheal intubation. Despite growing numbers of patients treated non-invasively efficacy and safety of different NIV methods were scarcely described.
A clinical review by Crimi and colleagues discusses the advantages and disadvantages of HFNC compared with other NIV methods. The authors emphasize many clinical benefits of HFNC as its early application may reduce the need for tracheal intubation and treatment escalation.
They also point out an easy-to-fit HFNC interface and an easier setup. However, only CPAP could maintain positive end-expiratory pressure (PEEP) which is important in COVID-19 affected patients with ARDS.
In August 2021, the first results of a clinical trial called RECOVERY-RS were published. RECOVERY-RS is an open-label three-arm randomized controlled trial that has been performed across 48 sites in the UK with the aim to compare the effectiveness of different NIV methods. The biggest non-invasive respiratory support trial compared three commonly used respiratory interventions - CPAP, HFNO therapy, or conventional oxygen therapy. The primary outcome of this trial was mortality and tracheal intubation within 30 days. Over 1200 patients were included in this trial with respiratory failure caused by coronavirus disease.
The results of the RECOVERY-RS trial have shown CPAP superiority over conventional oxygen therapy. The need for intubation and mortality was significantly lower in patients receiving CPAP than in those with conventional oxygen therapy (137/377 (36.3%) vs. 158/356 (44.4%), respectively). Interestingly, HFNO has not shown a significant advantage over conventional oxygenation. These findings support the idea that CPAP could be highly effective in the management of patients with COVID-19 pneumonia and acute hypoxemic respiratory failure.
RECOVERY-RS trial has several limitations. First, the primary outcome was a quite heterogeneous composite of mortality and tracheal intubation within 30 days. Moreover, the decision to intubate patients was based on a personal physician’s opinion and experience which could obviously lead to biased results.
Nevertheless, RECOVERY-RS findings are supported by Sakuraya and his colleagues. They published a meta-analysis of respiratory management in patients with acute hypoxemic respiratory failure. For the very first time, they compared the efficacy of NIV according to ventilation modes with HFNO, conventional oxygen therapy, and invasive mechanical ventilation. The primary outcome of this study was short-term mortality. They have found that CPAP was significantly associated with a lower risk of mortality (risk ratio, 0.55; 95% confidence interval, 0.31 – 0.95).
Authors support the idea that CPAP may be the most effective option as the primary non-invasive respiratory management for patients with de novo acute hypoxemic respiratory failure.
Several devices could be used to deliver CPAP including helmets. Importantly, helmet-based positive pressure ventilation was significantly associated with a lower risk of death and endotracheal intubation compared with conventional oxygen therapy, HFNO, and face mask NIV among patients with acute respiratory failure in a meta-analysis published in JAMA. Most of the study patients used helmet CPAP therapy and this probably contributed to the superiority of helmet-based ventilation in this meta-analysis. Despite helmet-based ventilation drawbacks, such as large interface volume and dead space it remains an important strategy to deliver CPAP and provide higher levels of PEEP.
To sum up, after almost two years of COVID-19 pandemic we still have more questions than answers. Despite a highly effective vaccine against SARS-CoV-2, we are still facing everyday challenges in the management of COVID-19 patients. Respiratory support remains a cornerstone in the treatment strategy with the emphasis on non or less invasive, safe, and effective methods. To date, more and more studies prove the CPAP superiority over other NIV methods in terms of mortality and tracheal intubation. However, more further studies are needed to confirm this evidence.
1. Crimi C, Pierucci P, Renda T, Pisani L, Carlucci A. High-Flow Nasal Cannula and COVID-19: A Clinical Review. Respir Care. Published online September 14, 2022. doi:10.4187/respcare.09056
2. Sakuraya M, Okano H, Masuyama T, Kimata S, Hokari S. Efficacy of Non-Invasive and Invasive Respiratory Managements in Adult Patients with Acute Hypoxaemic Respiratory Failure: A Systematic Review and Network Meta-Analysis. In Review; 2021. doi:10.21203/rs.3.rs-845769/v1
3. Ferreyro BL, Angriman F, Munshi L, et al. Association of Noninvasive Oxygenation Strategies With All-Cause Mortality in Adults With Acute Hypoxemic Respiratory Failure. JAMA. 2020;324(1):1-12. doi:10.1001/jama.2020.9524
4. RECOVERY RS: CPAP vs HFNO vs Conventional Oxygen Therapy in COVID-19. REBEL EM - Emergency Medicine Blog. Published September 13, 2021. Accessed October 25, 2021. https://rebelem.com/recovery-rs-cpap-vs-hfno-vs-conventional-oxygen-therapy-in-covid-19/
5. JC: Non-invasive ventilation for COVID 19 patients. The Recovery RS trial. St Emlyn’s. St.Emlyn’s. Published August 20, 2021. Accessed October 25, 2021. https://www.stemlynsblog.org/jc-non-invasive-ventilation-for-covid-19-patients-the-recovery-rs-trial-st-emlyns/