In patients with COVID-19 who are receiving mechanical ventilation (MV), the use of a protocol for fraction of inspired oxygen (FiO2) adjustment can reduce hyperoxemia and excess oxygen use. A prospective cohort study was conducted in intensive care units (ICUs) in 2 public hospitals in Brazil that were dedicated to the care of patients with COVID-19. Results of the analysis were published in the journal Medicina Intensiva.

Individuals with severe COVID-19–associated pneumonia may require the use of invasive MV because of the development of acute respiratory distress syndrome (ARDS). Invasive MV is a highly effective way in which to increase oxygenation and reverse hypoxemia, even in those with the most severe forms of ARDS. During MV, however, patients are often exposed to a level of FiO2 that is occasionally higher than needed. Exposure to high FiO2 levels can induce pulmonary inflammation due to the excessive production of reactive oxygen.

With the impact of hyperoxemia in patients receiving MV due to ARDS remaining debatable, the researchers sought to evaluate whether a protocol for FiO2 adjustment might reduce hyperoxemia and the use of excessive oxygen in this patient population. Hyperoxemia is defined as “arterial partial pressure of oxygen (PaO2) higher than
100 mmHg.”


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Patients were enrolled in the current study between March 2020 and June 2021. The main variables of interest included the following: (1) prevalence of hyperoxemia on day 1; (2) sustained hyperoxemia on days 1 and 2; and (3) excess oxygen use (ie, FiO2 of >0.6 in patients with hyperoxemia). These variables were compared in the 2 ICUs. One of the ICUs, which followed an FiO2 adjustment protocol based on oxygen saturation (SpO2), was called the conservative-oxygen ICU. The other ICU, which did not follow the FiO2 protocol, was called the control ICU.

A total of 82 participants from the conservative-oxygen ICU and 145 from the control ICU were included in the study. A significantly lower prevalence of hyperoxemia on day 1 was reported in the conservative-oxygen ICU compared with the control ICU (40.2% vs 75.9%, respectively; P <.001). Rates of sustained hyperoxemia were also significantly lower in the conservative-oxygen-ICU group vs the control-ICU group (12.2% vs 49.6%, respectively; P <.001). Further, excess use of oxygen occurred less often in the conservative-oxygen ICU than in the control ICU on day 1 (18.3% vs 52.4%, respectively; P <.001).

Admission to the control ICU was independently associated with hyperoxemia and excess oxygen use. No independent relationship was observed between day 1 hyperoxemia, sustained hyperoxemia, or excess FiO2 use and adverse clinical outcomes.

Limitations of the present study included the fact that patients were not randomized to the groups but, instead, were selected according to the ICU to which they were admitted; thus, confounding variables might have contributed to the results. Further, the study might have had limited power to detect associations between hyperoxemia or excess oxygen use and mortality. Additionally, data were obtained only once — at a standardized time each morning — on the first 2 days of MV.

The researchers concluded that although the results of the current study were not associated with better clinical outcomes, adopting an FiO2 protocol might prove useful in a scenario of depleted oxygen resources, as was observed during the COVID-19 pandemic. 

Reference  

Gomes EP, Reboredo MM, Costa GB, Barros FS, Carvalho EV, Pinheiro BV. Impacts of a fraction of inspired oxygen adjustment protocol in COVID-19 patients under mechanical ventilation: a prospective cohort study. Med Intensiva. Published online May 2, 2022. doi:10.1016/j.medin.2022.04.004