Factors Associated With the Intubation of Patients With Acute Respiratory Failure and Their Impact on Mortality: a Retrospective Cohort Study

Introduction: Severe respiratory failure often requires intubation and invasive mechanical ventilation. Identifying the factors that lead to this need is crucial, but there are few studies on the evolution of these factors from the onset of symptoms to respiratory failure. This study aims to identify risk factors for invasive mechanical ventilation as well as clinical outcomes in patients with acute respiratory failure considering the time from the onset of symptoms to respiratory failure. Methods Retrospective cohort study with patients hospitalized between May 1, 2020 and May 1, 2021. Patients over 18 years of age admitted to Intermediate and Intensive Care Units with positive polymerase chain reaction for SARS-CoV-2, chest computed tomography and inflammatory markers performed within 72 hours of admission were included. Patients with chronic obstructive pulmonary disease using home oxygen, intubation not related to Covid-19, heart failure, previous tracheostomy and hospitalization of less than 24 hours were excluded. The main outcome was to identify the factors that determined tracheal intubation and the evolution of these patients. Results Of the 852 patients treated, 302 were excluded, leaving 550, of which 346 required intubation. Intubated patients had a higher body mass index (p = 0.02), a higher SAPS-3 (p < 0.001) and a shorter time from symptom onset to hospitalization (p < 0.001). Until the eighth day of hospitalization, these patients had higher levels of C-Reactive Protein (p < 0.001), Interleukin-6 (p = 0.003) and D-dimer (p < 0.001). Chest computed tomography scans revealed a larger area of ​​lung injury since admission. In the Cox model, SAPS-3 (HR = 1.028, 95%CI 1.002–1.055, p = 0.038) and time to intubation (HR = 1.118, 95%CI 1.021–1.224, p = 0.016) were independent risk factors for mortality. Patients intubated 15 days after the onset of symptoms had a higher risk of mortality (OR = 2.13, 95% CI 1.07–4.23). At intubation, the average respiratory rate was 27.5 breaths per minute, with 85% of FiO2 and ROX index of 4.37. The use of non-invasive ventilatory support was longer in the quartile with more than 15 days until intubation (median of 5 [3–7] days) and the use of a high-flow nasal cannula was associated with a longer time to decide to intubate (p = 0.002). Conclusion In patients with Covid-19 and acute respiratory failure, later intubation was associated with higher mortality. Non-invasive ventilatory support strategies can be used as long as there is no delay in using an invasive strategy when necessary.