The impact of hyperoxia on outcome of patients treated with noninvasive respiratory support

Objective: As target values are not clear in oxygen therapy, which is one of the most commonly used methods for the treatments of hypoxemic patients, iatrogenic hyperoxia is a very common situation. The results from the recent clinical researches about hyperoxia in the intensive care unit indicates that hyperoxia can be related with worse outcomes than expected in some critically ill patients. According to our literature knowledge there aren't any reports researching the effect of hyperoxia on clinical course of patients who are not treated with invasive mechanical ventilation. In this study, we aimed to determine the effect of hyperoxia on mortality, and length of stay and also possible side effects of hyperoxia on the patients who are treated with oxygen supplementation by non-invasive devices. Material and Methods: One hundred and eighty seven patients who met inclusion criteria, treated in Dokuz Eylul University Medical Intensive Care Unit between January 1st, 2016 to October 31st, 2018 were examined retrospectively. These patients' demographic data, oxygen saturation (SpO2) values for the first 24 hours, APACHE II (Acute Physiology and Chronic Health Evaluation II) scores, whether they needed intubation, if they did how many days they got ventilated, length of stay in intensive care unit and hospital, maximum PaO2 values of the first day, oxygen treatment method of the first 24 hours and the rates of mortality were recorded. Results: Hyperoxemia were determined in 62 of 187 patients who were not treated with invasive mechanic ventilation in the first 24 hours of admission. Hiperoxia frequency in patients with COPD was found statistically low (16% vs. 35%, p<0.008) when the relation was investigated between comorbid situations and hyperoxia. Hospital mortality was found statistically high (51.6% vs. 35.2%, p<0.04) in patients with hyperoxia. When the types of oxygen support therapies were investigated, hyperoxia frequency was found high in patients treated with supplemental oxygen (nasal cannula, oronasal mask, High Flow Oxygen Therapy) than patients treated with NIMV (44.2% vs. 25.5%, p<0.008). When 56 patients who were intubated and treated with invasive mechanical ventilation after the first 24 hours excluded, hyperoxemia was determined in 46 of 131 patients. Hospital mortality was found statistically high in patients with hyperoxemia who were not treated with invasive mechanical ventilation in their hospital duration (41.3% vs 15.3%, p<0.001). Conclusion: We found that hyperoxemia increases the hospital mortality in patients treated with non-invasive respiratory support in our single center, sectional and retrospective study. At the same time, we determined that hyperoxemia frequency was lower in patients with COPD and treated with NIMV. Conservative oxygen therapy strategy can be suggested to decrease the hyperoxia prevalence and mortality rates. The effects of prospectively determined oxygenation targets on clinical results may the subject of another study.