1-year survival rate of SARS-CoV-2 infected patients with acute respiratory distress syndrome based on ventilator types: a multi-center study

To our knowledge, this is the largest study that compares the effect of ventilator type on the outcome of critically ill patients with ARDS due to SARS COV-2 during the pandemics. In mechanically ventilated patients with ARDS due to COVID-19, management with non-ICU sophisticated ventilators was associated with a higher mortality rate compared to standard ICU ventilators. The surge in patients with COVID-19 requiring hospitalization, ICU admission, and ventilator support has posed an unparalleled challenge to physicians, nurses, hospital managers, and healthcare systems. Due to the limitation and shortage of critical care equipment in ICUs, a considerable proportion of patients who need MV are treated with transport ventilators in hospital settings outside the ICU^10,17. However, despite the widespread use of transport ventilators in medical centers, their impact on COVID-19 patients' outcomes is unclear. To address this lack of information, a multi-center, observational study was conducted to evaluate one-year post-COVID-19 survival according to ventilator types among Iranian patients admitted for COVID-19-related ARDS requiring MV during the first wave of the COVID-19 pandemic.

In the current study, the mortality rate was significantly higher in patients supported with transport ventilators compared to patients supported with ICU ventilators. According to multivariate Cox regression analysis, age, opacity score, and the use of transport ventilators were associated with a higher risk of mortality. Our findings suggest that COVID-19 patients with a higher opacity score and GGO or GGO plus crazy paving lesion type had a lower survival rate. GGO is a sign of the early and active stage of the disease that can progress and worsen patients' health, while the appearance of consolidation opacities is a sign of proper activity of the immune system. Moreover, CT scan images showing GGO and GGO with consolidation, combined with COVID-19 pathological findings including hyaline membrane formation and increased inflammatory exudate in the alveolar space, are associated with increased mortality in patients^18,19,20. However, a longer duration of mechanical ventilation (MV) was associated with a lower risk of mortality. Our hypothesis is that patient deaths may lead to a shorter use of mechanical ventilation, whereas a longer MV duration with professional ventilator settings would be safer for the patients. Additionally, this longer duration of MV may have resulted in extubation after the end of virus shedding and/or clinically significant lung inflammation, which is safer²¹. Furthermore, Kaplan–Meier curves from the survival analysis showed that patients supported with ICU ventilators had a significantly higher one-year post-COVID-19 survival rate.

The mortality rate in our study of patients requiring MV is lower than that reported in previous studies^17,22,23. The majority of our patients (72.4%) were admitted to the ICUs, and the differences in mortality rates may be attributed to variations in strict criteria for ICU admission, such as oxygen requirements equal to or greater than 6–8 L/min to achieve a peripheral oxygen saturation of ≥ 90–92%, respiratory failure, shock, acute organ dysfunction, and patients at high risk for clinical deterioration. Moreover, the availability of ICU beds played a role, as non-emergency activities and surgeries in selected hospitals were rapidly reduced from the onset of the outbreak, and the number of ICUs beds for COVID-19 patients was increased^24,25. Additionally, our lower mortality could be partially explained by the comparatively younger average age of our patients²⁶.

Our results showed a significantly lower one-year survival among patients supported by transport ventilators. Transport mechanical ventilator models cannot reflect all the complexities of patient-ventilator interactions over time. Therefore, they do not provide an accurate estimate of pulmonary indices for physicians¹⁶. Moreover, monitoring lung indices during MV and adjusting ventilator settings based on them is crucial for achieving positive outcomes. Since transport ventilators have fewer monitoring capabilities compared to standard ones, this could be another reason for the higher mortality rate associated with these ventilators²⁷. One of the most significant and independent indicators of mortality is mechanical power, which can be inaccurately estimated and lead to inappropriate ventilator support. One the other hand, patients in these scenarios typically have a high respiratory drive and require a higher level of flow, which may not be adequately provided by transport turbine-based ventilators^28,29. This can result in increased agitation and desynchrony, leading to worse outcomes. However, in critical situation such as COVID-19 outbreak, when no ICU ventilators are available, the use of sophisticated turbine-based transport ventilators to treat patients who need MV is inevitable.

During the first wave of the COVID-19 outbreak, when no specific effective treatment against COVID-19 had been introduced, the majority of treatments relied on assisted ventilation, other organ-supportive interventions, and symptomatic anti-inflammatory medications^30,31. Furthermore, at that time, there was limited knowledge about the optimal ventilation methods for these patients, and there was no time for training and learning. Therefore, in such critical situations, having professional operators who are familiar with all types of ventilators becomes crucial for the successful management of ventilator support and the successful weaning of patients from mechanical ventilation, ultimately leading to longer patient survival³².

The large influx of patients requiring mechanical ventilation for ARDS during the COVID-19 pandemic has necessitated the utilization of ventilators from a variety of sources, and healthcare workers should be familiar with these devices and their limitations. Optimization of standard critical care support is the best strategy to improve these patients' survival. The optimum results for the management of ventilator support and weaning from mechanical ventilation have three basic pillars, in which the professional operator is a key determinant (Fig. 3). Certainly, the critical care team in ICUs consisting of intensivists, critical care nurses, and respiratory therapists is more efficient and experienced in using equipment support devices (e.g., ventilators) and managing these patients than other healthcare workers outside of ICUs. Different ventilators have different capabilities, which could be unfamiliar to healthcare workers. Optimizing the target ventilation can depend on the ventilator type and the operator's decision regarding the management of the respiratory system situation. A study by Ferre et al.¹⁷, on ICU-admitted patients with COVID-19-related ARDS showed that the choice of ventilator type (ICU ventilator versus transport ventilator) not only depends on the situation of patients and the type of ventilators but also on the lack of experienced and expert staff who can address the limitations of these transport ventilators. Results of a similar study by Raymonds et al.³³, showed that the mortality risk of ARDS patients was considerably higher in non-university compared with university hospitals. This study emphasized the importance of the trained and skilled physician and professional operator as important factors in mechanical ventilation management.

Triangle of professional operator as a key determinant in mechanical ventilation management.

In order to enhance patient survival, during the shortage of ICU ventilators, clinicians should focus on increasing the optimal use of portable ventilators. This can be achieved through various strategies. Firstly, it is crucial to provide comprehensive training to healthcare professionals regarding different types of ventilators and their usage^34,35,36. This will ensure that clinicians have the necessary knowledge and skills to effectively support patients in critical care settings. Additionally, given the limited understanding of ventilating COVID-19 patients, it is essential to offer guidance on the optimal settings, modes, and strategies for ventilator use^37,38. Emphasizing a low tidal volume strategy and practicing lung-protective ventilation are particularly important for patients with acute respiratory distress syndrome (ARDS), as these approaches have been proven to enhance outcomes while reducing complications associated with ventilator use^39,40. It is also vital to adhere to evidence-based guidelines and protocols to ensure appropriate ventilation support and minimize harm. Regular monitoring and evaluation of patients' response to ventilation, including factors such as oxygenation levels, lung compliance, and other relevant parameters, should be conducted^41,42. Moreover, interdisciplinary collaboration among healthcare teams involving respiratory therapists, critical care specialists, and other knowledgeable professionals is crucial, especially considering the shortage of experienced staff and experts in transport ventilators^41,43. By implementing these measures, clinicians can increase the optimal use of ventilators, ultimately leading to improved patient survival rates.