Non-Invasive Respiratory Support During Covid-19 Pandemic

Acute respiratory failure frequently occurs in severe COVID-19 and requires ventilator support. However, during the first wave of the pandemic, conventional resources for critically ill patients were insufficient in many centers. Therefore, an alternative strategy based on the use of non-invasive respiratory support (NIRS), and especially continuous positive airway pressure (CPAP), have been massively employed, either as a definitive therapy or as a bridge for orotracheal intubation. The results of this strategy have been excellent. If patients are carefully selected and monitored and NIRS is managed by an expert team in an appropriate environment, the vast majority of patients survive, avoiding intubation in most cases, and even decreasing the possibility of a self-inflicted lung injury (SILI). Moreover, there is evidence that with these techniques the risk of aerosolization is low. Nowadays, CPAP is considered the best option for most patients, with BiPAP being especially recommended in those with previous thoracic diseases or chronic hypercapnia. We conclude that NIRS techniques can be used in the initial care of most patients with severe respiratory failure from COVID-19 pneumonia and/or thromboembolism. To achieve the best results, intermediate care units, where specialized respiratory support can be provided, are the most appropriate framework.


Introduction
Since the pandemic was declared in March 2020, severe acute respiratory syndrome due to coronavirus type 2 (SARS-CoV-2) infection has been a critical global health problem. The first cases were reported in late December in Wuhan city, capital of the Hubei Province in China [1]. The disease caused by this infection is known as COVID-19 and has currently produced more than 550,000 deaths in 200 countries despite the great efforts and strict quarantines in most of these countries [2]. Most cases are considered as a mild disease but nearly 14% require hospitalization, mostly for severe mechanical ventilation, but during COVID-19 outbreaks various European groups have adopted a different strategy using noninvasive respiratory support (NIRS), especially with the modality of continuous positive airway pressure (CPAP), either as a definitive therapeutic alternative or as a bridge for orotracheal intubation due to the lack of intensive care beds [7][8][9]. This was due, at least in part, to the fact that healthcare resources for critically ill patients were insufficient during the most acute phases of the pandemic in many countries.
There are several approaches and controversies regarding the management of patients with ARDS secondary to COVID-19 pneumonia. Early mechanical ventilation, which in other pathologies is considered mandatory, has been widely debated as some of the expert's early reports from Italy suggested the existence of different patient phenotypes based on different physiological parameters [10]. Due to the exponential growth of cases requiring intensive care, the health collapse has been evident in many countries. In Barcelona, for instance, during the first pandemic wave (March and April 2020), we faced a dramatic situation with a massive influx of patients in a very short time. A total of more than 2,000 patients with COVID-19 were hospitalized at our center, and more than 150 were admitted to the ICU. The big problem was that practically all the Intensive Care Unit beds were occupied very early by patients with invasive mechanical ventilation, while a relatively high percentage of critically ill patients remained under clinical surveillance outside this unit. Together with the intensive care team, it was decided that pulmonologists would make the first evaluation and initiate treatment of all those critically ill patients. Most of them showed severe desaturation and/or respiratory distress despite the use of a reservoir mask (FIO2 around 85%). Based on initial published evidence [7][8][9], and the fact that many of these patients initially presented elevated spontaneous inspiratory drive with relatively large tidal volumes, and in trying to decrease the possibility of a self-inflicted lung injury (SILI) we decided to manage them in semicritical and even conventional COVID-19 units, initiating NIRS with CPAP, two-level positive airway pressure (BiPAP), or high flow through nasal cannula (HFNC) as the initial approach for severe cases. As other groups worldwide, we rapidly detected that patients with CPAP and supplemental oxygen therapy responded correctly, with orotracheal intubation being avoided in most of them [7][8][9]. In all cases, patients were constantly evaluated to decide if they needed to be transferred to the intensive care unit for invasive mechanical ventilation. These preliminary results confirm our approach and demonstrate that many patients could avoid orotracheal intubation if NIRS is initiated and managed by respiratory medicine and/or intensive care specialists well-trained in the use of these techniques [9]. For this reason, we have decided to prioritize this approach to treat COVID-19 patients with severe respiratory failure. Moreover, solid evidence has progressively emerged supporting the use of CPAP for these patients. In this regard, Radovanovic et al. [7] found that the application of CPAP with the helmet system can be a valid approach for pulmonary support if used in an adequate setting, even with simple monitoring tools. This strategy could optimize the recruitment of unventilated lung regions and improve hypoxemia [7]. Similar conclusions were recently provided by Oranger et al. [8] who conclude that CPAP is feasible in severe COVID-19 patients, with intubation becoming unnecessary, and the patients can also be managed outside a standard critical care setting [8].
Although initial reports published during the early phases of the pandemics suggested that NIRS should be avoided in COVID-19 patients because of the high potential for particle aerosolization and potential contagion of healthcare personnel, the evidence has shown that the risk is low if appropriate precautions are taken.
Therefore, the use of CPAP, BiPAP or HFNC is now considered safe [11,12].
While CPAP is considered as the best option for most patients,